U.S. patent application number 11/915339 was filed with the patent office on 2009-12-10 for method of obtaining single wire transmission line.
Invention is credited to Geir Monsen Vavik.
Application Number | 20090305628 11/915339 |
Document ID | / |
Family ID | 26649210 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090305628 |
Kind Code |
A1 |
Vavik; Geir Monsen |
December 10, 2009 |
Method of obtaining single wire transmission line
Abstract
A method of obtaining single wire transmission line (440)
wherein the use of short wavelengths yields low radiation losses
and wherein transmission line losses are compensated by repeaters
(19, 213-219) at required intervals.
Inventors: |
Vavik; Geir Monsen;
(Jonsvatnet, NO) |
Correspondence
Address: |
GEIR MONSEN VAVIK
OEVRE VIKERAUNET
JONSVATNET
N-7057
NO
|
Family ID: |
26649210 |
Appl. No.: |
11/915339 |
Filed: |
November 23, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/NO2001/000079 |
Mar 1, 2001 |
|
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11915339 |
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Current U.S.
Class: |
455/14 |
Current CPC
Class: |
G06K 19/0723 20130101;
H04B 1/30 20130101; H04W 28/06 20130101; G01S 7/4056 20130101; H04W
64/00 20130101; G01S 13/767 20130101; G01S 13/878 20130101; G01S
2007/4095 20130101 |
Class at
Publication: |
455/14 |
International
Class: |
H04B 3/58 20060101
H04B003/58 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2000 |
NO |
NO 2000 1057 |
Jan 9, 2001 |
NO |
NO 2001 0132 |
Sep 13, 2001 |
WO |
WO/2001/067625 |
Claims
1. A transmission line for short wavelengths and low attenuation,
comprising: A wire (440) acting as a transmission line whereby the
wave due to the short wavelength is kept trapped near the wire and
where transmission line losses are compensated by repeaters (19,
213-219) at required intervals wherein said repeaters allow said
conductive wire to be uninterrupted using coupling arrangements
(141, 142).
2. A transmission line according to claim 1 where coupling between
the transmission line and repeaters (19, 213-219) and connections
points (120, 121, 210-212, 221-222) is performed using electric
(142) and magnetic field (141) coupling arrangement to said
wire.
3. A transmission line according to claim 1 where the repeaters
(19, 213-219) are powered by at least one of inductive (141),
capacitive (142) and resistive (143) methods from the hosting
infrastructure constituted by said wire.
4. A transmission line according to claim 1 where the said
transmission line is bidirectional.
Description
INTRODUCTION
Background
[0001] In a transponder a radio frequency signal is transmitted to
a transponder, which in turn retransmits the signal, often in
modulated form, that is to say with superimposed information from
the transponder. The purpose of a transponder may thereby be partly
to act as a signal repeater, partly exchanging information with the
transponder. Some transponders work indirectly, others directly, in
indirect retransmission, the signal is received and retransmitted
in sequence. Retransmission may be desired to take place in a
frequency band different from the band for received signal. One
example is aircraft transponders for DME. In direct retransmission
the signal is transmitted simultaneously as it is received, in the
same band. Here, the conversion- and modulation-gain of the
transponder is utilised. Examples are RFID TAGs. In the lastly
mentioned case the transponder acts as an amplifier, often with
very small or negative amplification. Such transponders therefore,
serve few applications within the various areas of wireless
communication and radio navigation.
[0002] A transponder is in many cases in addition to retransmission
(up link) also required to receive information (down link) to
identify itself and act on commands. Applications that use
transponders are therefore often named RFID systems (Radio
Frequency IDentification). It is frequently required that the
transponder is portable, lightweight, compact, simple and carries
few components, is inexpensive to manufacture and has several years
of battery life, at the same time as available performance margins
become inadequate, especially with respect to communication range.
At the same time, requirements of large communication bandwidth and
multi channel operation are present. It is often required that
transponders have coherent retransmission, either with respect to
an interrogator or a phase measuring station when the transponder
is to be positioned as well.
[0003] The most commonly used principle for transponders is the
so-called reflective principle. It works with a RF carrier from a
beacon or interrogator received by an antenna, which is coupled to
a high frequency diode that in turn is modulated by the signal, to
be retransmitted to the interrogator by the transponder. Usually
the aim is to achieve phase modulation, which is easily
accomplished by having a diode switching the refection coefficient
in the antenna connection terminals. The resulting modulation will
always be a combination of amplitude modulation and phase
modulation with no significant performance reduction. The
retransmitted (up link) side bands are coherent with the incoming
signal, and the interrogator works by the homodyne principle. To
avoid cancellation between side bands, single side band reception
with side band cancellation is used in the interrogator.
[0004] Reception (down link) in transponders is accomplished with
the mentioned diode or a dedicated diode demodulating the high
frequency signal from the antenna directly, without high frequency
amplification. High frequency amplification is not used, mostly on
account of power consumption. The sensitivity acquired is therefore
limited, but may be well tuned to the transponder dynamics achieved
with the reflective principle.
[0005] The disadvantage with the reflective principle is that the
retransmitted signal level only can be amplified by the help of
antenna gain. Too much antenna gain is unwanted, because high
antenna gain gives too narrow antenna lobes and consequently
pointing errors, and the result may therefore become losses in
stead of gain.
[0006] In a few existing transponders, active amplification is
introduced, that is active high frequency or microwave components,
to achieve this. With conventional technology this comes with high
costs in the form of high power consumption and costly products.
Power consumption becomes high because unconditionally stable
amplifiers are required. Cost becomes high because this, on
microwave frequencies, usually is accomplished with microstrip
technology and expensive circuit board laminates. The amplification
achievable is very limited due to current draw and because it is
difficult to sustain sufficient isolation between transmitter and
receiver in low cost products. This implies that such solutions
preferably must carry separate transmitter and receiver antennas.
Benefits of such solutions are usually not worth the increased
cost, and the majority of such products today therefore have
passive microwave modules, that is just one diode or a transistor
switch. The solutions are likely to require a limiter which serves
to limit the transmitted level below the maximum allowed level
according to the respective code or standard for the application of
the transponder. Limiter and filter may also be required to achieve
necessary suppression of harmonics of the modulation frequency.
Harmonics of the RF carrier are often very difficult to suppress
sufficiently to meet standard requirements. Transponder range for
the transponder solutions mentioned is very limited, because the
outgoing signal amplitude is nearly proportional to the incoming
signal amplitude as a consequence of no or little active high
frequency amplification in the circuit. Such amplifying
transponders therefore have seen few applications within the
various areas of wireless communication and radio navigation
concerned.
[0007] Some known systems concerning interrogation of sensors or
various types of platforms that require a low current, simple
transponder, have effective solutions for down link in the
transponder, while the up link is comprised by one or more
oscillator functions. A significant disadvantage with this solution
is that it will require a crystal oscillator for the transmitter if
the purpose is not served by the poor frequency stability and
calibration otherwise resulting. Such a transponder is not usable
in a homodyne system unless it carries a phase locked loop (PLL)
frequency locked to the interrogator.
[0008] It has been shown that transponders may be realised as
simple, injection locked oscillators. These have specifications
that seriously limit their applications. The injection locked
oscillator is in principle any type of oscillator circuit where
oscillator stability purposely is made dependent on no outside
noise or an injected CW signal (see below) which is closely
equivalent to the oscillator frequency to give frequency locking.
The circuit is compensated for temperature and other types of
instabilities. The frequency spectrum of an injection locked
oscillator unlocked and with no signal in as well as locked to a
signal in, appears as the spectrum of an ordinary oscillator with a
CW carrier. With an in signal and out of lock it will have a
typical, strong phase noise on one side of the carrier frequency.
As mentioned, the largest disadvantage of the injection locked
oscillator is a very narrow lock frequency band and a very low
sensitivity. The advantage is low phase side band noise. There is a
need for a technology, which improves the injection locked
oscillator and expands the applications there of. One example of
injection locked oscillator application is in phased antenna
arrays, but there, as well, the usefulness is limited on account of
narrow locking bandwidth which typically will be some ten
thousandths of the carrier frequency, and in addition a CW signal
is required. (In the following text, the term CW is both used for a
RF carrier, which is either continues or pulsed. This is in line
with the conventional literature, although CW carrier actually is
supposed to mean "continuous wave". Physically speaking, a
continuous wave cannot exist in reality. "Quenched oscillator" is
used meaning an oscillator, which is quenched with a repetitive
function with frequencies from kHz to MHz). It has been shown, see
U.S. Pat. No. 3,705,385, how an injection locked oscillator may be
improved, especially with regard to locking bandwidth, with so
called quenching, that is switching of the oscillator. Still, the
locking bandwidth is narrow, typically some thousandths of the
carrier wave frequency, and still a CW signal is required, often
limited to FM modulated CW, to allow signal repetition to work
satisfactorily. Besides, the locking is heavily dependent on the
signal dynamics and will generally only work for strong CW signals.
It appears that one has believed it necessary that the carrier
frequency itself had to be locked in order for a number of
transponders to work together without interference. That may have
been a cause for the super-regenerative principle to have been
overlooked for such applications, see below. Another reason is that
it is a far more difficult challenge to make a quenched oscillator
work according to the intention in superregenerative mode than in
injection locked mode, due to added component requirements besides
design challenges. This follows from the fact that
superregenerative function generally occurs or is effective only in
a narrow region of the bias characteristic for the oscillator,
while the injection locked function occurs across a large part of
the remaining characteristic. This is little or not discussed in
publications about SG applications. In addition, the quench
frequency is often injected in such a way that the
superregenerative dynamic range is severely limited, which again
shows how poorly the circuit was analysed. It has not been shown
earlier how unwanted emission of signals and inter- and cross
modulation products should be reduced in order for a quenched
oscillator to work in accordance with standards. Development in
component technology has additionally made it possible to utilize
the superregenerative principle better, with very low power
solutions, to assist innovations using this principle. The
quenched, injection locked (=locked) oscillator has, as explained
herewith, specifications that iimply large limitations with respect
to signal dynamics and bandwidth and further disadvantages like
reliability, that reduce possible applications. This is proven by
the fact that earlier publicised and patent text technologies
having failed to succeed in applications (i.e. see U.S. Pat. No.
3,705,385), which is due to several factors, some of the more
important ones being unreliable frequency locking and narrow useful
information bandwidth in the kilobaud range. Such bandwidth is
mostly rather uninteresting for today's communication technologies.
Additionally, it is not evident from subsequent patents and
publications if anyone made serious attempts to improve the
technology or widen the scope of the use of narrow band, locked
oscillator.
[0009] There is a need for finding alternative solutions to known
transponder technology that uses "on board" oscillator. There is a
need for a transponder technology which achieves to combine
simplicity with existing, reflective transponders with wide
bandwidth, high performance, stability, power efficiency,
production applicability and that in addition allows simple and
cost effective implementations in microwave ASIC (customer
specified integrated circuit) or MMIC (microwave integrated
circuit). There is also a significant need for a new technology
where the performance of transponders exceed minimum requirements
so that margins and production compatibility are increased and to
allow microwave transponder systems to be realised with less
expensive substrate technologies and without the use of micro
strip.
[0010] Common uses of transponders are sensor systems, control
systems, medicine and in RFID systems. An example of the use of
sensor systems is the need to improve existing technology for
surveillance, control and communication in power distribution in
high and low voltage power line distribution systems. An example of
control systems is measuring and actuating tasks in processes, both
in- and outdoor. An example of medical usage is the application of
sonds and sensors in medical scientific research. An example of
RFID usage is given by the need for identifying and communicating
with objects, persons and vehicles on long range. One application
for simple transponders in RFID which include long range, is radio
tagging of animals, where limited range for today's transponders
makes them less suitable and therefore other technologies are used
like pulsed beacons that renders less service per carried energy
unit because continues transmission is required. Long range may be
defined as from ten meters to several kilometres. One widespread
application within RFID is intelligent and unintelligent "tags" for
identification, access pricing and payment etc. Transponders for
different application areas are most likely to use frequencies
between 30 MHz to over 10 GHz. In toll road systems and similar,
microwave bands 2.45 GHz and 5.8 GHz and more are used.
[0011] Nodes in some signalling networks or data communication
networks may be regarded as indirect repeaters. Examples of such
are cellular phones, or mobile systems (i.e. GSM, GPRS, UMTS,
TETRA). If nodes or stations in such systems are to be used for
retransmission, it leads to a significant reduction in information
bandwidth, usually reduces to half. The same applies to nodes in
Wireless LAN, Bluetooth and other wireless data communication
networks. This seems to be the reason for repeating functions
usually not being implemented in the mentioned systems. There is a
significant need for a new system, which is compatible with
existing, and future, wireless network and communication systems
and which is able to repeat signals in both directions. There is
also a need for inexpensive and effective technology in nodes for
such networks, which is also able to perform repeating functions
without reducing bandwidth from the repeating function. In some
cases there will be needs for the transponders to act
intelligently.
[0012] The evolution of radio based, wireless networks for large
bandwidths that is required to use very high frequencies (10-200
GHz) have been hampered by the fact that it is still too expensive
to implement transmitters, receivers and transceivers. Up to now,
it has not been possible to realise a simple transponder with large
dynamics for such frequencies. At the same time, there is a need
for implementation of inexpensive, local wireless networks with
large bandwidths of more than 100 Mbit/s. There is a great need for
a system technology, which allows inexpensive networks in the cm
and mm wavelengths.
[0013] In wire and cable based communication systems the same as
for wireless systems is valid. Line amplifiers are expensive to
realise and often they can amplify the signal in one direction
only. Examples of line amplifiers that are bi-directional are older
type amplifiers for phone lines that exhibit low amplification and
can only be used for low frequencies. Examples of line amplifiers
that have high amplification, but are unidirectional are cable TV
amplifiers used for data communication. For high frequency it has
been possible to make line amplifiers with limited isolation
between the amplifier input and output, with resulting low useful
amplification and therefore applications are very limited. It is
therefore a need for a new principle of amplification of signals
along a signal cable with the help of simple methods implying small
or no modifications to the system.
[0014] Within positioning, radio navigation and distance
measurements, coherency and controlled phase relationships are
desired parameters. An example is hyperbolic positioning systems
where the phase of the measured signal must be determined by clock
regeneration. This puts strict requirements on real time processing
and filtering, and often reduces the update rate of the system. In
many positioning systems for short and medium ranges there is a
need for a transponder technology which will work effectively and
which retransmits signals with known phase. Applications would be
in objects to be positioned or as parts of known infrastructure of
the system to improve the measurement geometry of the system. Until
now, such transponders have been too expensive to make or have not
been realisable. There is also a need for an inexpensive, low power
and effective transponder technology, which may increase the usage
of radio positioning by positioning people, belongings a.s.o. For
recovering purposes there is also a need for an inexpensive and
more efficient and useful technology for transponders.
[0015] In power line surveillance and communication there used to
be a need for series connected amplifiers (line amplifiers) in the
lines or cables to compensate for signal losses. This has been
excessively expensive and may cost tens of thousands of US dollars
per connected unit. It follows that there can be only a small
number of amplifiers along the lines, resulting in a very low
communication bandwidth. Likewise, it is expensive and complicated
to bypass transformers and other infrastructure in the power
network for communication signals. It exists therefore a need for a
new principle of amplification of signals along the power line
network with the aid of simple methods that require minor or no
modifications of existing installations, and which makes it
possible to realise far wider transmission bandwidths and better
flexibility. With known technology it is not possible to have
distributed surveillance along a power line and existing solutions
therefore use expensive, widely spaced installations that use radio
communication. There is therefore a need for a new technology which
integrates all types of surveillance and control in any position in
the power line network, with two way communication along the power
lines.
[0016] In power line surveillance and communication on the
distribution circuits, where data communication is to include so
called access networks for broad band distribution and other
communication with clients, the communication range will be limited
to 100 to 300 meters due to signal losses. Line amplifiers are very
expensive to realise and install and indirect repeaters reduce the
data bandwidth. Consequently it is often difficult to transmit
signals between clients and other units like routers, masters and
hubs. With known technology there exists no solution, which in a
simple and inexpensive way can relay signals without galvanic
coupling passed embedded separations in a power network, i.e. a
transformer station. It exists therefore a need for a new principle
for amplification of signals in electricity networks used as access
data networks employing simple methods requiring small or no
modification of the infrastructure.
[0017] In communication systems of different kinds, local shadow
zones will easily occur. This is particularly true in mobile
communications as with GSM, GPRS, UMTS, TETRA and more. Here, it
has until now been impractical to realise inexpensive transponders
or repeater systems to amplify the signals in a simple manner and
in such a way fill in coverage holes or shadow zones. Known
technology did not achieve the necessary signal amplification and
one therefore was obliged to install an additional base station to
serve a coverage hole area. Such insufficient coverage therefore
had to be accepted as along roads, within buildings, ships, ferries
and so on. Power lines are found along roads that could function as
carriers or hosts for small transponders and could also power them
as an example with inductive transmission of the moderate energy
required. With known technology, it is neither easy nor cost
effective to couple shielding rooms in buildings, ships a.s.o. to
the outside world to achieve radio coverage. By this reason, there
is a need for a new principle of amplification of signals in
systems for mobile communications with the help of simple and
inexpensive methods that requires little energy. Correspondingly,
there is a great need of a new technology that allows simple signal
repeating or signal amplification for radio applications within
systems and equipment for broadcasting and communication. This is
particularly true for local, geographic areas. In other
communication systems where passive RF technology or low
transmitting power is used, like in RFID tags, the margins often
are small giving communication problems from changing conditions of
various kinds. There is a significant need for an inexpensive,
energy efficient transponder technology that easily can amplify
signals in both directions that as an example could be installed on
or near such a low power device. In this case, it seems logical to
name the transponder a "signal booster". In optical signal
transmission systems there may be a need as well for a new
technology that in the same manner as the super regenerative
principle with radio waves and by loose coupling to an optical
waveguide or other optical medium, amplifies the signals.
SUMMARY OF THE INVENTION
[0018] It is therefore a main object of the present invention to
provide transponders and transponder systems where the known
disadvantages with transponder systems by large are avoided, and
where new and easy to implement applications of transponder systems
is made possible.
[0019] It is further a main object of the present invention to
provide a very universal and at the same time inexpensive and
energy efficient system for repeating RF signals, on a single or
multiple basis, based on a single or a number of super regenerative
transponders that are easy to install and power, and that require
minor or no modification of existing other communication
technologies or infrastructures or equipment, and thus making
wireless and wire bound network systems with quite new signal
ranges, bandwidths, specifications and applications realisable for
existing technologies and infrastructures of communication.
[0020] Another object of the present invention is also to provide
means of realising new types of communication systems based on the
simplicity and high performance of the present invention that
otherwise would not be possible or would be too costly to
realize.
[0021] It is yet another object of the present invention that it
should work for both direct and indirect repetition of signals, one
or two-way communication and for interrogation.
[0022] Another object of the present invention is to function both
when frequency bands for up link and down link are equal as well as
when they are different. It is further an object of the present
invention that it should function both when signal dynamics up link
and down link or in different directions are equal and when they
are different.
THE INVENTION
[0023] Several of the objects of the invention are achieved, in a
first aspect, with a transponder as given in the appended claim 1.
Further, advantageous characteristics are given by the attached
dependent claims.
[0024] Further stated objects, are achieved in a second aspect,
with a transponder system as given in the appended claim 33.
[0025] Further characteristics of the system are given by the
dependent, attached claims.
[0026] The most evident characteristics of the invention are a
simple transponder that exhibits extraordinarily high conversion
gain and the invention with corresponding performance may
retransmit an amplified version of a received signal. The quenched
oscillator shows CW self oscillation during the active part of the
period of a quench signal that controls the oscillator. Locked
oscillator is a special case of quenched oscillator that is
optimised for locking and that has better locking characteristics
than a none quenched, injection locked oscillator. The working
principle in locked condition is equal to that of the injection
locked oscillator, but with the amplification in the oscillator
that occurs before it oscillates during each quenching period
increasing the locking bandwidth substantially. The
none-oscillating, active part of the quench period gives it better
characteristics as an amplifier than that of the injection locked
oscillator. This amplification depends on frequency locking. With
no in signal it has a high frequency CW self-oscillation on a given
frequency during each quench cycle. With no signal in, it is
characterised by having a high frequency spectrum which contains a
decaying comb of subcarriers on each side of the main frequency,
with separations equal to the quench frequency. The phase noise is
also acceptable. With no signal in and locking, the frequency
spectrum looks correspondingly, and the phase noise is still
acceptable. But with signal in near the carrier and without
locking, it will normally exhibit strong phase noise on one side of
the carriers, corresponding to an injection locked oscillator with
similar conditions. The disadvantages of quenched oscillator in
locked condition are that loss of locking and phase noise may
occur. As an amplifier the self-oscillation will always give
interference for signals that do not achieve locking. Quenched,
locked oscillator has some advantageous characteristics. This mode
is easy to realise and will work across a large part of the
oscillator bias characteristic. Because it may be realised with a
high-level oscillator bias, relatively high output power levels are
achievable. Frequency locking increases conversion gain and
implicit amplification, but at the same time severely limits
information bandwidth and modulation types useful. Utilisation of
quenched oscillator that is out of lock in a transponder is not
known. Example of known technology using a special case of quenched
oscillator is U.S. Pat. No. 3,705,385 showing a locked oscillator
where the working principle is depicted by the shown frequency
spectrum (FIG. 11a) including FIG. 11b for "Locked Oscillator
Transmission Spectrum". The ratio between carrier frequency and
quench frequency is in excess of 1e3. These figures also serve to
show that it describes an invention for narrow band applications
suitable for a few kilobauds. It is evident from FIG. 11b that
during the quench cycle the oscillator goes into "uncontrolled
oscillation" which, is the oscillating part of the characteristic
where injection locking occurs.
[0027] There is a need for a new technology that improves the
performance and applicability of the quenched, locked oscillator.
There is also a need for a technology that utilises the quenched
oscillator generally, especially for wide bandwidths.
[0028] The super regenerative oscillator or amplifier is also a
quenched oscillator. But because the super regenerative oscillator
does not have CW self-oscillation, we should regard it as an
independent technology. The super regenerative oscillator working
principle is characterised by not achieving full oscillating
conditions during a quench cycle when it has no in signal. This
implies that it has no CW self-oscillation, but may have diffuse
(broad band) oscillations that necessarily do not reduce quality of
SG amplification. The part of the quench cycle where amplification
is achieved is hereby substantially larger that with the locked
oscillator and may reach 50%. The importance of the improvement of
the duty-cycle is largely neglected in literature and patents.
This, in combination with no present CW self-oscillation to give
ringing or compression, gives the super regenerative oscillator
superb amplification characteristics. It does not have the
interference problems typical of the quenched oscillator with CW
self-oscillation. It is typical of an oscillator operating in
stabile super regenerative mode with no in signal to show a
frequency spectrum with negligible or little systematic noise.
Systematic noise caused by diffuse oscillations, when present, may
occur quite asymmetrically, with spacing equal to quench frequency
and will resemble white noise. Depending on the way SG oscillator
is implemented, the frequency spectrum of the oscillator response
may be symmetrical or asymmetrical and may have distinct lobes or
no lobes. The frequency spectrum response of the SG oscillator
characterises its abilities as amplifier. In known publications and
patents where SG is used for receiving purposes, this fact is not
pointed out or is left neglected. These are among the relationships
that work together to make the SG oscillator a more complex
technology to master, even if the circuit complexity remains very
simple compared to solutions based on super heterodyne principles
which, in many cases are not useful.
[0029] The transfer function of a super regenerative oscillator as
amplifier is independent of frequency or phase locking of a high
frequency CW carrier. Instead of locking bandwidth one may state
bandwidth factor for the SG oscillator. The bandwidth factor is
best served by the definition response bandwidth divided by centre
frequency where the response bandwidth is defined from signal to
noise ratio for a weak signal with a given amplitude and frequency
variable.
[0030] The transponder according to the present invention may be
regarded high frequency wise as a one port giving from large to
extremely large amplification. Thereby it is stated that the signal
path in and out is exactly the same and that only one antenna is
required. Since being a one port, the isolation between input and
output is undefined and may be regarded as infinitely high. The
amplification is only depending on Q-factors in resonant circuits
and on the stability criteria of the active device, and may
therefore become extremely large. The dynamic range is otherwise
only limited by the power limitations of the active component and
by the bandwidth and noise figure of the complete circuit. When it
is realised for large amplification this results in a transponder
according to the invention where the retransmitted signal has
nearly constant amplitude. Generally a received signal will be
retransmitted with or without added modulation. The transponder in
accordance with the present invention may also be modulated for
purposes like interrogation. As a modulator or mixer the
transponder according to the present invention has positive and
exceptionally high conversion gain. It means that a dedicated
limiter to keep transmitted level within requirements of standards
is not required. Maximum range may thereby become from
significantly improved to multiplied as compared to today's
transponders. Because modulation may be generated at low levels,
harmonics within the communication band will be satisfactorily
attenuated to meet rigid requirements in standards without having
to use complex filters. Due to loose coupling between antenna and
transponder and to the coupling otherwise being selective, unwanted
signals in harmonic bands of the communication band will be easy to
attenuate.
[0031] The transponder according to the first aspect of the present
invention makes it easy to accomplish, in a simple manner,
reception of data signals with high sensitivity and low power
consumption. The demodulated, amplitude modulated information
signal will attain a level which is substantially amplified by the
transponder according to the present invention, and the transponder
therefore gives far higher sensitivity as compared to a receiver
using a simple diode front end.
[0032] The transponder according to the present invention makes it
feasible to simplify existing fixed or mobile interrogation systems
that require a large communication zone. The high performance
transmission function allows therefore, a significant reduction in
physical size of especially fixed installations with resulting
environmental benefits. Portable interrogators may become more
compact and more feasible to design.
[0033] With transponders that work according to the super
regenerative principle the initially mentioned transponder problems
are solved. With the new technology both signal amplification,
indirect repetition, transmitting, receiving and interrogation can
be realised cost effectively and efficiently. The super
regenerative transponder is a switched oscillator as well, but
operates in a different mode to injection locked oscillator and
special requirements must be met for it's full potential to be
utilised as in the present invention. But when these conditions are
satisfied, the super regenerative circuit has superior advantages
and cannot in any important area be replaced by injection locked
oscillators. The super regenerative principle is therefore far more
useful for practical purposes. The super regenerative transponder
may in principle work as a one port amplifier with high
amplification and works equally well across a very wide frequency
range which may include a number of signals, as opposed to a locked
quenched oscillator as in U.S. Pat. No. 3,705,385. Locking or
synchronising of quench frequency, when it is called for, is
possible over a far larger dynamic range than the locking of
carrier frequency in locked oscillator types, and means by example
that substantially higher attenuation between transponders in a
chain is allowed. The super regenerative oscillator or transponder
also be regarded as a "sampling oscillator" where the quench
frequency may be regarded as a sampling frequency. The utilisation
of the super regenerative characteristics in this way is new
because such transponders could not be realised at low costs with
other technologies. The super regenerative principle has been
poorly understood and publicised and patented versions of the super
regenerative principle, mainly for reception application, show that
the function is poorly under stood and inadequately implemented.
One example is insufficient descriptions and solutions concerning
the importance of screening and filtering of the quench frequency
to isolate the input of the super regenerative circuit to avoid
harmonics ruining its dynamic range. This is a decisive parameter
in order to fully utilise the super regenerative principle as in
the present invention. In stead it is often stated that the quench
frequency has an upward limit of 1e3 to 1e4 part of the carrier
frequency (centre frequency). The quench frequency has a decisive
influence on the is transponder performance and must often be
chosen as high as possible in accordance with bias and the quench
cycle function. Reverse bias during part of the quench cycle
permits higher quench frequency. The quenching frequency may be
injected at several points in the SG oscillator to achieve desired
characteristics.
[0034] The super regenerative transponder is an oscillator but
without a stable oscillation unlike the injection locked oscillator
types. Its active component may have an input and output which in
many cases results in a two port. But the output is always part of
the feedback loop and affects the phase change in it, and there
fore does not necessarily interfere with the input. SG is the only
known circuit that may be realised with active components in such a
way that extremely high amplification (40 to 100 dB) is achieved
across a wide frequency band and for a number of various signals
while at the same time the output to input isolation does not
affect feasibility. This is in sharp contrast to other technologies
that typically will only achieve a maximum of 20 dB of
amplification. Additionally, it allows low cost implementations and
can be reproduced with large tolerances. The circuit comprises a
signal booster or a direct repeater, but may also work as an
indirect repeater or transmitter-receiver device (transceiver) by
injecting a carrier from en external source while it is likely to
be modulated. The circuit is also characterised by possibly often
being the only feasible way of realising transmitter-receiver
devices (transceivers) at very high frequencies (cm and mm
bands).
[0035] It is known that voltage controlled oscillators (VCO) and
injection locked oscillators can be realised using RC coupled
oscillators. Such oscillators have wide locking bandwidth. It is
until now not shown that super regenerative oscillators may be
realised using RC networks that are without inductors or
resonators. For use in super regenerative transponders this is of
special interest because it may make it feasible to implement super
regenerative transponders in the lower part of the RF spectrum with
great bandwidth factors.
[0036] As an example it is possible to achieve super regenerative
function across typically 10 MHz using a simple super regenerative
oscillator in the frequency range 4-30 MHz where a number of types
of protocols and modulation types for broad band access
communication over power line distribution are used (OFDM, DSSS and
more).
[0037] The present invention may be realised using RC networks
instead of LC, LCR, ceramic, dielectric, plezo or SAW networks in
the SG oscillator. The main application here is in the lower part
of the RF spectrum where great bandwidth factors are required, in
example 1:5. This may be achieved using RC circuits and possibly a
number of oscillators in parallel with overlapping frequency
ranges.
[0038] Further embodiment of the present invention in order to
achieve high quench frequency is to inject primary quench at
several points in the oscillator circuit.
[0039] Examples of numbers that explain the superiority of the
present invention as opposed to applied, known technology in
transponders are passive transponders of the reflective type or
modulated reflector that are likely to show current draws in excess
of one milliampere and conversion gains minus antenna gain of
typically -6 dB. With the present invention the corresponding net
gain may reach 40 to 100 dB depending on bandwidth and quench
frequency with a current draw of less than a milliampere. It is
therefore easily seen that the present invention is revolutionary
for many existing applications and a key to novel uses.
[0040] One reason that quenched oscillator and super regenerative
oscillator have been overlooked for modern applications is likely
to be found in the fact that patents and publications describing
quenched and especially SG oscillator have focused on micropower
applications and presumably have anticipated very short
communication ranges. It appears one has failed to realise that SG
in principle may be used with any level of power as the present
invention is based on. That makes great communications ranges
possible both with single and co-operating transponders. The fact
that SG oscillators spread their energy across a wide frequency
range with potential interference problems has undoubtedly been
seen as a disqualifying characteristic whilst the present invention
either gives solutions to that particular characteristic or makes
use of it.
[0041] Completely independent of in which way the present
inventions second aspect is realised in detail, the principle of
the second aspect may be described as a communication system
comprising one or more transponders of the quenched type. The use
of quenched, possibly super regenerative transponder offers, as
mentioned before, large amplification achievable in an efficient,
simple and low cost manner without the need of isolation between
input and output and allows the transponders to work properly with
small antennas or, in wire bound networks without need of galvanic
coupling to lines or cables. Stray capacitance may often suffice as
a satisfactory link of the coupling of transponders in the present
invention and will be more efficient with higher frequencies. The
use of super regenerative transponder in the present invention
makes large amplification of a signal achievable without the need
for frequency conversion of the signal or the use of directivity.
Regardless, directivity may be used to combat echoes, standing
waves and multipath transmission, for instance in wireless systems
where twodirectional antennas may be used. In wire bases systems
the same is valid and directional couplers may be introduced. The
high amplification and independence of input to output isolation of
the present invention makes it possible with simple realisations of
directional couplers based on loose coupling, usually inductive at
lower frequencies and as transmission line couplers on higher
frequencies. Transponders according to the present invention may
use carrier with double sideband, carrier with singe sideband or
just single sideband. Reception and retransmission in such a manner
is determined by filtering in the transponders and optionally by
modulation in the transponders. Choice of sideband may be used as a
simple means of frequency conversion to optimise a network or adapt
the transponders to existing technologies. Quench frequencies of
the systems that are parts of the present invention for direct
repetition of signals and with several super regenerative
transponders must, with respect to interference comply with
stricter demands on frequency stability than transponders using
indirect signal repetition, that is where the information is
received and retransmitted in sequence. The type of modulation to
be transmitted (FSK, PSK, QPSK and so on) determines how strict the
demands are. A fundamental difference in technical realisation as
opposed to locked oscillators is the absence of the out of lock
conditions with the super regenerative principle, even though the
super regenerative transponder in many cases must have phase
locking on quench frequency. The difference being that the quench
frequency is much lower and that the locking may take place with
much less loop bandwidth and consequently simple circuits
solutions. Injection locked quench oscillator of the RC type,
crystal or ceramic is such a simple solution. The quench frequency
in the transponders may be controlled by a very stable frequency
source in each transponder or frequency and phase locked to a
common signal distributed on the network or locked to each other
(self locking quench generator). Frequency and phase locking of
quench generator will, even with such simple solutions work across
a large dynamic range, as a rule right down to the intrinsic noise
level of the transponder due to implicit high loop gain and
relatively narrow locking bandwidth. The various transponders of
the present invention may be intelligent and may execute other
tasks than just relaying the received signal. The various
transponders may also work as connection nodes of the network that
is to say that the information may be transmitted both directions
through the transponder i.e. with a PC or a sensor platform.
[0042] Up link and down link may have different transponder
devices. For one direction it may be necessary to use a different
bandwidth or power range than the other. Two or several
transponders can be combined in one unit.
[0043] A number of transponders in the present invention may be
connected in parallel directly or indirectly to increase dynamic
range or bandwidth or both. The present invention, therefore, has
theoretically very generous limits for achievable bandwidth and
dynamic range and the theoretical values may be closely
approximated by practical solutions.
[0044] The present invention therefore allows the signal repetition
to pass successively through a small or high number of transponders
to achieve long range without loosing useful signal dynamics or
information bandwidth. When, echoes, standing waves or mulitpath is
a problem, as an example for large information bandwidths, it is
possible with the present invention to introduce directional
sensitivity due to the large amplification which, may be utilised
for the different transponders to handle different transmission
directions. The present invention therefore may be designed so that
each repetition device comprises a transponder system for each of
the two transmission directions.
[0045] To achieve a large dynamic range, high sensitivity and large
bandwidth with the super regenerative transponders in the present
invention it is important how the quench signal is injected, both
with regard to where it is injected and how it is filtered. This
may be accomplished in various ways as long as measures are taken
to avoid harmonics of the quench frequency reducing the dynamic
range of the transponder. A specific way of accomplishing this is a
design with a super regenerative circuit having both in and output
where the input is the most sensitive signal terminal and to supply
the quench signal to the output, where the circuit is least
sensitive to incoming signals. One embodiment of such
implementation of the present invention is to supply the quench
signal via bias through a, for the purpose suitable filter and
thereby benefit from the implicit isolation between input and
output present in the amplifying element. In this way improved
dynamic properties are achieved and increased quench frequency may
be used to accommodate wider information bandwidth. This may be
combined with filtering on the high frequency side in order to
remove unwanted, transmitted signals and reduce inter and cross
modulation products. The use of such filtering also improves
properties when a number of transponders operate together in the
same frequency band. Ringing in the high frequency resonant
circuits may be reduced by quench controlled dampening of the
resonant elements provided that constant dampening does not
suffice. In some cases one may, in order to optimise the properties
of the present invention, insert quench control at several levels,
as an example by controlling varactor diodes in the resonant
networks, but in such a way that the dynamic range properties are
not destroyed by harmonic energy from the quench frequency.
Introducing quenching at various levels, as well as several quench
frequencies, is a way of improving the super regenerative
properties, as opposed to corresponding functions in primitive,
simple self quenched super regenerative receivers with known
technology, where unpredictable spurious oscillations may improve
the super regenerative function sporadically. The important task in
this respect is to control the active part of the cycle (duty
cycle) of the super regenerative oscillator and at the same time
during one duty cycle to prevent stabile oscillations, that is to
say that with no signal in there should be no repeated cycles of
the same cycle length or frequency.
[0046] In the opposite case the oscillator will drastically change
characteristics to become a lockable oscillator with a carrier
frequency and sidebands with individual spacing equal to the quench
frequency.
[0047] The super regenerative transponder of the present invention
is a switched or modulated oscillator, but operates in a mode
different to that of an injection locked oscillator and in the
present invention specific conditions are met for its full
potential to become utilised. With no in signal it transmits just
noise where the noise level is mostly determined by the dynamic
range and bandwidth of the super regenerative transponder. Bias and
quenching are matched to make the high frequency oscillator operate
in super regenerative mode. The curve function of the quenching
signal may be matched to this purpose as when it proves efficient
to supply revers bias in the none active part of the quench cycle
to the SG oscillator. This serves to ensure that the circuit works
across a wide frequency range with no "unlock" problems in the
communication channel. When stabilising, locking or both of quench
frequency is called for, this is done on a much lower frequency
than the carrier frequency and the locking may then be performed
using narrow loop bandwidth and inexpensive, simple and reliable
circuits. The present invention may use injection locked quench
oscillator implemented with resonators of the types RC, crystal or
ceramic. Inexpensive implementations are provided using cheap clock
crystals at 32 kHz in overtone circuits for quench frequencies of
32 to typically 288 kHz. For quench frequencies from 200 kHz and
far into MHz ranges, low cost, ceramic resonators or crystals are
available. A simple version of the present invention is where the
quench oscillator is phase and frequency locked by being connected
to the "output" of the super regenerative oscillator, which
contains the synchronising or locking information. This connection
is done through a filter that is likely to be best served by a one
or multi-pole LC filter. This connection line thereby serves both
quenching of the high frequency oscillator and locking of quench
oscillator. However, the circuits for quenching and locking may
also be designed as separate circuits at the expense of some
complexity. A further embodiment of the present invention is the
possibility of using the high frequency oscillator as a quench
oscillator as well, wherein harmonics of the quench frequency may
be reduced with a suitable oscillator circuit solution with or
without using a selective, high Q resonator element for the quench
frequency. For solutions where cost tolerances are larger, more
advanced frequency and phase locking circuits using known
technology may be applied. The super regenerative transponder in
the present invention works, as mentioned, in principle as a one
port amplifier with the ability of very high gains which may be
used to amplify signals in both directions in a chain or in all
directions in a wireless system. The problem of quench noise into
the transponder is solved by shielding and filtering the quench
frequency from the input or the most sensitive part of the super
regenerative circuit to avoid harmonics destroying the dynamic
range. This is an essential embodiment of the present invention in
order to achieve large dynamic range and bandwidth with the use of
the super regenerative principle. Shielding may often be replaced
by making the electronic circuits small and compact in order to
avoid coupling from larger areas or lines. In this way the present
invention accomplishes use of quench frequencies typically 20 to
more the 100 times higher than known technologies that use the
super regenerative principle, mostly for radio receiver
applications. The present invention may in principle be applied to
communication with whichever center frequency. But in practice it
will serve purposes at frequencies from a few MHz and up to the
millimeter wave ranges. The bandwidth of the communication channel
for a specific super regenerative transponder will among other
things depend on the quench frequency and of how high a quench
frequency is required by the bandwidth. In the present invention
high quench frequency is realised in some cases using active
amplifying components with high gains in combination with dampening
of the Q factor of the resonating network of the super regenerative
oscillator. The super regenerative transponder in the present
invention is an oscillator but without a stabile oscillation where
the active element may have an input and an output and in such
cases therefore if a two port. The output is made as a part of the
feed back loop, but without destroying the properties of the SG
oscillator. The present invention permits with modern components to
accomplish very high gains (40 to 100 dB), sensitivity (typically
-90 dBm) and high output level (example +20 dBm) along with wide
bandwidths. Which of these properties the transponders of the
present invention is to contain, is determined by choosing active
components and bias. As with active circuits in general, the
transponder properties and design must, based on known principles,
be chosen with respect to what parameters are the most important.
The dynamics is further determined by a number of transponders or
super regenerative oscillators brought to work together or in
parallel. None of these measures to optimise the properties of the
present invention have significant negative influence on the high
performance/cost ratio.
[0048] The present invention will be able to work as a two-way
signal booster with or without galvanic connection, or as an
amplifier with large and small signal properties that resemble
those of ordinary, one-way, band limited amplifiers. The present
invention will, on high frequencies like mm frequency bands, be
quite easily realisable due to great advances of amplifying
component frequency limits.
[0049] In a communication system as described, the transponder
system of the present invention allows the level on lines or in
radio systems to be kept low and in many cases exempted from
authority licensing requirements by applying a sufficient number of
transponders using sufficiently close spacing.
SHORT DESCRIPTION OF THE FIGURES
[0050] The present invention is described in more detail in the
following with examples and references to the appended drawings,
where
[0051] FIG. 1 shows the block diagram of a typical transponder
system corresponding to known technology comprised by an analogue
and a digital unit;
[0052] FIG. 2 shows a block diagram of an implementation of the
first aspect of the present invention, where the simplest possible
method of retransmission based on the present invention is
shown;
[0053] FIG. 3 shows a block diagram of an implementation where a
separate oscillator signal is introduced in order to improve
control with bandwidth, unwanted radiation and energy consumption
of the transponder;
[0054] FIG. 4 shows a block diagram of another design version where
a detector and amplification for reception (down link) is arranged
and where various levels of reception may be controlled by an
introduced TR switch;
[0055] FIG. 5 shows a block diagram of still another design
version, where the transponder is introduced in a microwave ASIC
due to the simplicity of the microwave technical concept which the
present invention is based upon which again permits simple and low
cost realisation in microwave ASIC or a MMIC;
[0056] FIG. 6 shows a block diagram of an implementation that
diverts from the design version in FIG. 2 in that an antenna is
replaced by a different coupling element as well as a filter in the
signal path to and from the oscillator is shown as a split
bi-directional filter;
[0057] FIG. 7 shows a block diagram illustrating the second aspect
of the invention where a super regenerative transponder works as
part of a network architecture;
[0058] FIG. 8 illustrates the various signal transmission media
that a transponder in a network may be connected to,
[0059] FIG. 9 shows a special design version of a transponder
according to the present invention aimed at co-operating with a
network;
[0060] FIG. 10 shows an application of a number of transponders
together in various ways in connection with network solutions;
[0061] FIG. 11 shows an application of a number of transponders
together in still another embodiment; and
[0062] FIG. 12 shows an example of distribution of transponders
along transmission lines or waveguides to increase capacity of the
line.
DETAILED DESCRIPTION
[0063] In FIG. 1 is shown a typical transponder device 18
consisting of an analogue 22 and a digital 23 unit. The analogue
part has an antenna 1 and a radio frequency transponder 24. It is
often designed to include a down link receiver 25 and a wake up
receiver 26 as well as a control unit 25. When the digital part is
included in the transponder device 18 it will consist of an
information unit 28 normally combined with an interface 29. The
transponder device 18 also consists of a power supply most commonly
made up of a battery 170.
[0064] The most important part of the transponder device 18 is the
transponder 24 for up link. The down link information receiver 25
is either a separate part of the transponder device 18 or is partly
integrated with the wake up receiver 26. The digital unit 23
information device 28 identifies the transponder device 18 and the
digital unit may also posses abilities of processing information as
well as perform control of functions in the analogue unit 22
through a control interface 27. The digital unit 23 may also
contain a physical interface 29 towards user, sensors or
actuators.
[0065] In FIG. 2 a block diagram of a transponder 19 according to
the present invention is shown and where a simple method for
retransmission with the help of the present invention is
illustrated. The solution shown for the present invention may be
used both for signal repetition, interrogation and transmission. It
encompasses a bi-directional coupling 2 between antenna 1 and a
band pass filter 3, and a bi-directional coupling 4 leading to an
oscillator 5 that contains separate parts or is integrated in a
circuit which, depends on the requirements of the transponder 19.
This concerns requirements of channel bandwidth, multi-channel
possibilities, unwanted signal sensitivity and radiation within and
outside the communications band as well as choices of antennas.
[0066] The oscillator 5 may in principle contain a random type
oscillator circuit which, again is identical to an unstable
amplifier, and the connection point 30 involves in principle any
point in the oscillator where the necessary coupling of energy in
and out of the oscillator is achieved while maintaining the minimum
Q in the tank of oscillator 5. This gives a super regenerative
amplification which is sufficient for the purpose of which the
transponder is intended. A bias circuit 6 supplies bias to
oscillator 5 that may contain a bipolar or field effect transistor
in transponders from the short wave ranges and all the way up to
the cm and mm wave ranges (microwave). Oscillator 5 will, as a
rule, only consist of one transistor, but may in principle consist
of more, like when special resonating elements is to be used as
resonating element (tank circuit) or it may contain an integrated
circuit, i.e. a MMIC (microwave integrated circuit). The resonating
element may consist of inductance and capacitance in the form of
coil and capacitor, or may exist in the form of band filter, or in
the form of lines, or in the form of ceramic or dielectric
resonating elements. Dielectric resonator is only applicable for
narrow frequency bands, but gives good suppression of unwanted in
and out signals outside the communication channel. As resonating
element, a dielectric antenna may be used as well. For some
multi-channel applications or for very large bandwidths, resonators
with lower Q values must be used, like inductor and capacitance.
The transponder 19 may then experience unwanted in and out signals
outside the communication channel or band. An electronic switch 7
that may be comprised by a diode or transistor has two main
positions. One gives the oscillator 5 oscillation conditions while
the other quenches the oscillating state. The use of such a switch
in connection with an oscillator is called "quenching". The working
principle of the transponder is that the switch 7 never permits the
oscillator 5 to oscillate continuously. This is accomplished
letting the switch 7 alter or alternate bias to oscillator 5, or by
having switch 7 alter or alternate an impedance which is seen by
oscillator 5 (meaning that the impedance is capacitively,
inductively or resistively connected to the high frequency energy.
At the same time, the oscillator 5 will produce a negative
resistance at the connection point 30 and thereby produce high
amplification for the foreign frequency components present at
connection point 30.
[0067] In the following we will accept that the in signal is a
carrier with no modulation. Since the signal path from the
connection point 30 to the antenna 1 is bi-directional it means
that the signal entering the antenna 1 (i.e. an unmodulated carrier
frequency 60), will be retransmitted 61 through the antenna, but
amplified. The retransmitted signal will also be in exact in-phase
with the received signal. If the controlling signal 32 which
controls the switch 7 is of a sufficiently high frequency in
relation to the bandwidth of the filter 3 or of the resonator in
the oscillator 5, the is only signal retransmitted on antenna 1
will be the received signal that arrived on antenna 1, but
amplified. If the mentioned bandwidth is wider than the frequency
that controls the switch 7, the retransmitted signal on antenna 1
will contain two side bands (sub carriers) spaced from the received
signal corresponding to the frequency that controls the switch 7.
If the control signal 32 that controls the switch 7 that in turn
controls oscillator 5 is an alternating current signal with
superimposed information, the signal retransmitted through the
antenna 1 will include two side bands containing this
information.
[0068] The signal that controls the switch 7 comes from a modulator
17. The signal from the modulator may contain information that is
to be transmitted (up link) over the transponder. The modulator 17
is a self-contained module or is an integrated part that may
consist of a processor. The control signal 32 may be filtered
through the filter block 8 which, may prove necessary in order to
reduce harmonics of the fundamental frequency of the modulator
signal 39, that may be an externally supplied information signal 63
for retransmission.
[0069] In FIG. 3 a block diagram is shown with a second example of
the present invention, with a transponder 19 that may be used both
for signal repetition, interrogation and transmission, where
separate modulators 87, 17 are introduced for modulation of
information 65 respectively switching 31, to improve control with
the transponder 19 bandwidth, unwanted radiation and current
consumption. A signal 39 or 67 may be a signal from a separate
oscillator or from a processor or a similar arrangement that is
able to generate a high frequency signal, or it may in less
critical applications be generated as a self oscillation in the
oscillator 5 (self quenching). Separate modulators for information
and switching makes it possible to use a pulse forming network 9
together with the frequency of the signal 39 and the function of
the modulator 17 can control various properties of the transponder
19. The information signal 38 must in the transponder 19 modulate
the oscillator 5 and this may take place in different ways, here
shown by modulating the bias 89. This modulation frequency is
likely to be half or less of the primary quench frequency 32. The
signal 38 becomes the source of two side bands (sub carriers) that
is positioned closer to the carrier than the sub carriers brought
about by the signal 32. The quenched, locked oscillator may in this
way produce good performance as a mixer/modulator, that is to say
retransmission of data from transponder, primarily in a homodyne
system. By giving the primary quench much higher frequency than
secondary (modulation) quench, primary side bands widely spaced
from (radiation in and out) carrier will be mostly attenuated by a
band pass filter in the input/output. The network 9 may alter the
properties of the transponder 19 by modifying the symmetry of the
signal 39. It will sometimes be desired to lower the current draw
and reduce radiation outside the communication channel. An
important property of the transponder 19 of the present invention
is the possibility of using a switching frequency 39 that is much
higher than the highest information frequency 38, typically 10 to
100 times higher. That will ensure that the transponder 19 has wide
bandwidth, meaning multi-channel possibility, tolerance against
temperature drift and other frequency drifting, and ensure that
unwanted signals generated in the oscillator 5 will fall outside
the bandwidth of the resonator in oscillator 5 or in band filter 3
or in antenna 1.
[0070] FIG. 4 shows a block diagram with the third design version
of the transponder according to the present invention, where a
detector 11 is introduced as well as an amplifier 12 for receiving
(down link), where the transponder still can be used both for
signal repetition, interrogation, transmission and reception. This
design version includes also a frequency or level discriminating
amplifier 13 for wake up and the design version also includes a T/R
(transmit/receive) switch.
[0071] Various levels in oscillator 5 for transmission, reception
and wake up may be controlled by the TR switch 14 to control the
gain in oscillator 5 and the current draw of the transponder. This
is done by altering the bias conditions for oscillator 5, possibly
the oscillator characteristic for the control signal 39, possibly
the pulse forming network 9 like altering the symmetry of the
control signal 32. The purpose here is to achieve optimal
conditions for the three mentioned modes in the transponder 19. The
parameters that are to be controlled in this way are
retransmission, unwanted radiation in and out, receiver sensitivity
and current draw for the three mentioned modes and to ensure that
the present invention can work with a battery life that corresponds
to the shelf life of the battery.
[0072] The working principle of reception of information (down
link) is that a signal 35 that is connected relatively loosely to
the signal path 4, is led by the help of a coupler 95 to a detector
11 (i.e. a Schottky diode) that demodulates the modulated signal
received on the antenna 1 and is amplified by the oscillator 5. The
coupler is 95 may also be introduced at other points in the
oscillator circuit 6 but normally the optimum point will be at the
signal path 4. The detected signal 33 will have relatively large
amplitude but must still be amplified in an amplifier 12 before it
can be utilised in an information unit like a processor. The
amplifier 12 may be realised as a micro power amplifier using known
technology.
[0073] The signal 34 must be amplified, possibly filtered as well
and passed through a hysteresis circuit in the circuit 12 before a
logical level 37 is accomplished to wake up an information unit
[0074] FIG. 5 shows a block diagram of a fourth design version of
the transponder according to the present invention, here shown as
an "analogue unit" 120 where it is introduced in a microwave ASIC
(customer specified integrated circuit) 651 or MMIC (microwave
integrated circuit). The implementation is comprised by either the
radio frequency transponder 120 only or it contains a digital unit
125 as well, a clock oscillator 135 and input and output
terminals.
[0075] The design version is either a part of an ASIC or MMIC 651,
has only two terminals, acts as a negative resistance amplifier
where bias and modulation is fed across the terminals, or it
includes an ASIC or MMIC 651 with three or more terminals for a
desired number of signals, bias supplies and control signals.
Because the present invention is based on a simple, microwave
technical concept, it allows a simple and cost effective
realisation of microwave ASIC 651 in addition to being simple
enough to become realised in a MMIC 651. The antenna 1 may be
external and connected to ASIC or MMIC 651 through the signal path
2 or the antenna 101 may be integrated in ASIC 651 when it is made
for high microwave frequencies in order to ensure an efficient
electrical length within ASIC or MMIC 651.
[0076] Signal and control lines 710 may be connected to pins 715 on
ASIC 651 or be directly connected to a control unit 125 which, may
be an information unit as well.
[0077] FIG. 6 shows an implementation that is fairly similar to the
example shown in FIG. 2, but it is shown that the antenna 1 is
generalised as a coupling element of a more general type. Moreover
is shown a special type filter 3, namely with possibilities for
differing filter characteristics of the two signal paths to achieve
a frequency shifted retransmitted signal.
[0078] To ensure that the transponder oscillator operates in
stabile super regenerative mode and at the same time maintaining
necessary bandwidth and dynamic range one may provide control of
the super regenerative duty cycle (active part of cycle) as well as
oscillations superimposed on the quench frequency. In some cases.
i.e. for higher power levels, fixed or controlled dampening of Q
factor may be used for the same purpose. One way of realising this
is to arrange a filter to reduce overtones (harmonics) of the
quench frequency within the frequency range where the sensitivity
of the transponder is highest. The filter should be arranged either
as part of the oscillator itself or as part of a separate circuit
connected to the oscillator. The filter implies that the super
regenerative duty cycle is increased which, implies an increase of
the transponder dynamic range and bandwidth and at the same time
reducing interference from the quench signal in the output signal
by using the highest possible quench frequency.
[0079] The same advantages may be accomplished by introducing
secondary quenching as oscillations superimposed on the primary
quench signal itself. Secondary quench is introduced at any point
that affects the oscillation conditions of the oscillator.
[0080] A further possibility that offers the same advantageous
function is to use quenching from any type of function generator
within or separate of the transponder that is able to control the
quenching asymmetrically.
[0081] Lastly, the same type of favourable function is accomplished
by two or more super regenerative oscillators or transponders
connected together. This requires that the transponders have common
quenching or is at least synchronised with controlled phase shifts
between the different quench signals. This allows in principle one
hundred percent duty cycle for the transponder.
[0082] FIG. 7 shows a block diagram in connections with the second
aspect of the present invention where the super regenerative
transponder 510 is used as repeater, amplifier or booster,
separately or as part of a network architecture or as an addition
to a network architecture. The transponder may be present in
different versions depending on what type of network or
infrastructure it is being part of. The transponder 510 may be
intelligent and may receive or transmit information through an
interface circuit 317 like PC, sensor or actuator. To enable a
number of transponders to work together without interference, the
quench signal 311 is stabilised with internal or external
synchronisation. Internal synchronising of the quench generator 210
may, if needed be achieved with an internal, very stable reference
212. The quench generator 210 consists of a function generator and
filtering. External synchronising of the frequency source is
achieved by synchronising to an external synchronising signal 31 or
by synchronising to the implicit quench signal 32 of a
corresponding transponder 511 in the network.
[0083] Synchronising of the quench frequency includes the
possibility of synchronising demodulation with the duty cycle of
the signals from a super regenerative transponder. This may be
desired or required for some applications, like when the
information bandwidth is large compared to the quenching frequency.
In other cases band pass filtering in the transponder or
receiver/demodulator receiving from the transponder(s) may take
care of this problem.
[0084] The quench signal or switching signal 311 may be applied to
the oscillator 355 in such a way that it also contributes to
reduction of harmonics from the quench signal 311 on the input 303,
304 of the oscillator 355. The injection 311 may as well be in
connection with bias on a defined output 305, 306 of the oscillator
355 to reduce the interference effect of injection 311 on input
303, 304. The quench line 311 may combine quenching and
synchronising of the quench generator 210 with the help of a
received signal from the oscillator 355. The combined input and
output 303, 304 is connected to a circuit 200 for receiving and
transmission 51 of received high frequency signals 50 that may be
modulated or not modulated by the transponder 510. In order to
attenuate signals in unwanted direction, a direction sensitive
connecting device 223 is used. The transponders in FIG. 7 may be
intelligent, for example by incorporating a processor as mentioned
in the description of the first aspect of the present invention,
enabling them to transmit their own information signals 33, and
they may contain receiver devices with known technology
independently of or together with the super regenerative
oscillator, for example as mentioned earlier. Such a receiver
device may utilise the large gain available from the super
regenerative oscillator. FIG. 7 also shows how amplification of
signals in one direction on a line 92 can be attenuated using a
directional coupler 223 which, may make use of a combination of
capacitances and inductances, transmission line solutions
(microstrip, stripline, lines without substrate) or
circulators.
[0085] FIG. 8 shows, in accordance with FIG. 7, the various media
that the transponders/transponder system according to the present
invention can be used together with, including:
[0086] free space propagation 400 in vacuum, gas, liquids or solid
material with the help of antennas or probes,
[0087] transmission line 410 consisting of a multi-lead electrical
cable or cable like infrastructure,
[0088] transmission line 420 consisting of an open, electric line
or an arrangement corresponding to an open electric line,
transmission line or a line system comprising a wandering wave
antenna line system 430 consisting of on or more wires and where
the transmission is referenced to earth,
[0089] transmission line 440 performing as a wave guide with open
surface, a so called Lecher Wire where, the wave when, having a
short wavelength, is kept trapped near the wire and experiencing
low attenuation,
[0090] transmission line 450 which, is a closed waveguide, and
[0091] transmission line 460 being an optical waveguide.
[0092] Connections to line may be realised as loose couplings with
the help of inductive arrangements 141, capacitive arrangement 142,
resistive arrangement 143 or, a combination of the three as with
transmission lines in the form of microstrip. The coupling
arrangements of the types 141, 142 and 143 may in some cases be
used alone or in combination to power the transponders from the
hosting infrastructure.
[0093] FIG. 9 shows a transponder 512 in accordance with FIGS. 7
and 8, where an output 305, 306 is defined in the oscillator 355
making the port 303, 304 an input or both input and output, while
the port 305, 306 is an output with a higher level and input with
lower sensitivity. To the ports 303, 304 and 305, 306 have
arrangements 221, 222 connected for receiving and transmission of
signals for retransmission 71, 81 of information and or reception
72, 82 and transmission 71, 81 of information and possibly
reception 72, 82 of synchronising/locking 72, 82 and possible
transmission of synchronising/locking 71, 81. The coupling
arrangements 221, 222 may have directional sensitivity in order to
for example achieve a necessary attenuation of echo when it is
required.
[0094] FIG. 10 shows how a number of transponder units 213 in
accordance with FIGS. 7 and 9, in order to improve dynamic
characteristics of signals in one or more directions 150, 151, may
be connected together in a coupling arrangement 210 with the help
of a common coupling 90 or with the help of separate coupling
arrangements 210, 211, 212 and correspondingly shows how a number
of transponders 214, 215, 216 are arranged to increase bandwidth
and dynamics and may be connected together to a coupling
arrangement 210 with the help of a common coupling 90 or with the
help of separate coupling arrangements 210, 211, 212 and where the
transponders 214, 215, 216 have differing specifications.
[0095] FIG. 11 shows, in accordance with FIGS. 7 and 10, how a
number of transponder units 216, 217, 218 may be connected together
with the help of a common coupling or transmission line 90 allowing
the coupling arrangements 210, 222 to transmit signals 161, 162
between a physical position 221 and signals 171, 172 on a different
physical location 222, for example from one room 221 to another
room.
[0096] FIG. 12 shows one example of how transponders 219 in
accordance with FIG. 7 to 11 can be distributed along transmission
lines or waveguides 91 making these lines suitable for functioning
as transmission medium for substantially higher bandwidths and
greater distances than would otherwise be possible. This structure
will additionally make the transponders 219 capable to work as
intelligent and unintelligent nodes in the derived network
consisting of the lines 91 and the transponder 219 where other
communications infrastructure 121 may be connected to the medium 91
and where communication with transponder 219 may be done on radio
waves with the help of a radio unit 129 with antenna 95 and an
interface to the outside world 60 for one way or two way
communication or interrogation purposes.
[0097] The super regenerative oscillator in the present invention
works in a way so that without signal, during one quench cycle, it
does not reach full oscillation conditions.
[0098] It therefore has no CW self oscillations, but may have
diffuse (broad band) oscillations that necessarily do not reduce
the SG amplifications. The part of the quench cycle where the
amplifications is achieved should be made as close to 50 percent of
the quench cycle as possible. The duty cycle of the present
invention may be increased beyond this with the help of the quench
signal function from or with other arrangements. This, in
conjunction with no CW self oscillations giving ringing or
compression, makes the SG oscillator as "transponder" in the
invention showing superior gain properties. It may be made to give
negligible or no interference problems with CW self oscillations.
Depending on the way the SG oscillation is accomplished in the
present invention, the frequency spectrum of the SG oscillator may
be symmetrical or asymmetrical and may have significant or not
lobes. Depending on the properties that are most essential to
achieve, the present invention usually will get the best
transponder properties when the frequency spectrum consists of
white noise with a symmetrical curve resembling a Gausian
distribution. For example, this is accomplished using a bandpass
filter. The transfer function of the SG oscillator/amplifier in the
present invention is independent of frequency or phase locking of
high frequency CW carrier and makes large information bandwidths
possible.
[0099] When the SG oscillator is used in the present invention as a
transponder it works both as a very efficient mixer/modulator and
as an amplifier (repeater). The mixer properties can be utilised
where the transponder is to be modulated with information from the
transponder or from an interface connected to the transponder. This
will see applications both in radio systems and in wire based
systems. The signal repeating properties of the present invention
may be utilised.
[0100] Parts of the arrangements of the present invention are
useful together with quenched oscillators generally and for locked
oscillators. This applies to system solutions and detail solutions
like band pass filtering, quenching principles, use of more than
one side band system, directional sensitivity and so on.
[0101] With known technology it is possible to make transponders
that frequency transpose or frequency shift the signals to avoid
implementation problems with directional attenuation. Solid state
technologies are making such a big progress that there are
foreseeable possibilities of making sufficiently low cost and low
power transponders in ASIC technology incorporating parts of the
present invention.
[0102] The present invention lends itself easily to low cost, low
current and efficient transponder in positioning systems for short
and middle ranges where it is advisable to avoid computing phase
(clock regeneration) for a transmitted signal. This is valid for
distance measuring as well. It applies both to devices to be
positioned and to the infrastructure of the positioning system, for
example in order to improve geometry or to realise remote
controlled base lines or similar in the system. The present
invention is also well suited as inexpensive transponders to be
carried by persons and objects that have to be positioned or
found.
[0103] Positioning systems work according to one of two main
principles, either by measuring time (phase) or Doppler shift.
There is a third principle as well which, uses homing with the help
of properties of antennas. Time measuring stations have either a
single antenna (one dimensional positioning--radar and distance
measuring) or two or more antennas with a given geometrical
relationship (base line, aperture--two-three dimensional
positioning). Doppler measuring stations measure either with the
help of the velocity of the object or with the help of a
synthetically produced movement of antennas at the measuring
station. The object to be positioned may in some cases be measured
with the help of a passive reflector. By using a transponder in the
object to be positioned, maximum range and measuring capabilities
are improved and it is conceivable to attain known, calibrated
frequency and phase relationship for the signal which, is being
transmitted from the object. This both simplifies and improves
systems for both time and Doppler shift measurement compared to
where the object only has a transmitter (beacon). As opposed to a
solution using beacon, unknown phase variable is avoided and
measurements in both signal directions are possible. This results
in improved or higher update rates, precision and computation of
ambiguity in time or phase measurements. The transponder 19, 219 is
a novel and cost effective way of realising this with the help of
its gain properties and transmission as modulator/mixer. The
invention permits the positioning interrogator to be realised as a
homodyne system. This is advantageous with respect to phase
coherence.
[0104] Additionally, there are two main areas where the present
invention introduces uniquely novel opportunities of solving
positioning problems. One is the improvement and/or facilitation of
geometry for measuring stations, especially mobile or moveable
ones. Another is local coverage for an area being in the shadow of
a positioning system. By transmitting signals to transponders that
are placed in an optimum geometry in order to achieve coverage and
accuracy one can, with the help of the present invention with
transponders 19, 219 enable objects, that are to be positioned,
perceive the transponders as being the base line system or
aperture. The system must calibrate with respect to the different
time delays and geographical positions of the fixed geometry.
[0105] Any positioning system can be inverted. An inverted system
may mean for example that measuring and computing take place at the
object which, is to be positioned. Here, the present invention is
at least of equal interest. The present invention can for example
facilitate geometrical base lines provided as "sleeping" in the
form of transponders 19, 219 according to the present invention in
current areas for positioning services. The positioning object may
then activate the transponders 19, 219 realised according to the
present invention, transmit a measuring signal to them and with the
help of for example phase measurements on a self contained or
assisted basis compute its own position, one, two or three
dimensionally.
[0106] A corresponding application of transponders 19, 219
according to the present invention is when an area which, resides
in shadow of a positioning system, for example as with satellite
navigation with GPS (Global Positioning System), is covered with
transponders that simultaneously can see satellites in orbit and
the object to be positioned. Corresponding to DGPS, a calibration
station may transmit data to the positioning object GPS receiver to
obtain corrections for the anomalous geometry. It thereby becomes
possible to use standard GPS receivers that compute the position
using PRN code or use the GPS signal phase as well. The receiver
must have possibility for external calibration or may have
dedicated software and lookup tables. Transponders according to the
present invention are suited for this application due to the
application of spread spectrum in GPS.
[0107] The present invention facilitates a supposedly novel
opportunity involving both communications and positioning. It
concerns electronic defence (ECM Electronic Counter Measures). Due
to the high performance of the transponders it is possible to
scatter transponders 19, 219 according to the present invention
that make "copies" of radio and radar signals and complicates the
enemy task of positioning the original signals.
[0108] The present invention using SG oscillator is well adapted as
amplifier for modern modulation forms and transfer protocols since
they mainly were designed to coexist with other signals and noise.
They are readily using spread spectrum and spread the information
energy across the frequency or time domain. The phase response of
the present invention using SG oscillator shows a linear phase
response across a wide frequency range.
[0109] Forms of PSK are also used in spread spectrum communication
as with DSSS and FHSS and the present invention lends itself
conveniently to that as well. For multi-tone, multi-carrier
modulation forms as with OFDM, the present invention is also well
suited provided considerations are taken of special requirements of
dynamic range as with OFDM.
[0110] Synchronising of the quench frequency involves the
feasibility of synchronising the demodulation with duty cycle of
the signals from a super regenerative transponder. For some
purposes this will prove required or desired, e.g. when the
information bandwidth is large compared to the quench frequency. In
other cases band pass filtering in the transponder or in
receiver/demodulator receiving the signal from the transponder(s)
will meet the requirements.
[0111] Control of the super regenerative duty cycle and
oscillations superimposed on the quench frequency are measures that
can ensure that the oscillator operates in stabile, super
regenerative mode while the bandwidth and dynamics requirements are
met.
[0112] Large bandwidth factors of the present invention may be
implemented using parallel coupling of a number of super
regenerative oscillators with overlapping or adjacent frequency
ranges.
* * * * *