U.S. patent application number 13/552055 was filed with the patent office on 2012-11-08 for transmitting apparatus, receiving apparatus and communication system.
This patent application is currently assigned to Panasonic Corporation. Invention is credited to Suguru FUJITA, Yoshinori KUNIEDA, Masahiro MIMURA, Kazuaki TAKAHASHI, Noriyuki UEKI.
Application Number | 20120281740 13/552055 |
Document ID | / |
Family ID | 37053158 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120281740 |
Kind Code |
A1 |
FUJITA; Suguru ; et
al. |
November 8, 2012 |
TRANSMITTING APPARATUS, RECEIVING APPARATUS AND COMMUNICATION
SYSTEM
Abstract
A transmitting apparatus, receiving apparatus and communication
system are disclosed, and great improvement in an S/N ratio,
preventing an actual throughput from decreasing, and preventing the
number of circuits for synchronizing spread spectrum signals from
increasing can be expected at the receiving apparatus side. The
transmitting apparatus includes a pulse generating circuit, pulse
repetition cycle determining circuit, peak power determining
circuit, and modulator. The pulse generating circuit generates
pulse strings, pulse repetition cycle determining circuit
determines, based on a clock signal, a pulse repetition cycle of
the pulse string generated by the pulse generating circuit. The
peak power determining circuit determines a pulse peak power of the
pulse string. The modulator modulates the pulse string with
transmission data, and then generates a transmission signal.
Inventors: |
FUJITA; Suguru; (Tokyo,
JP) ; MIMURA; Masahiro; (Tokyo, JP) ;
TAKAHASHI; Kazuaki; (Tokyo, JP) ; KUNIEDA;
Yoshinori; (Tokyo, JP) ; UEKI; Noriyuki;
(Tokyo, JP) |
Assignee: |
Panasonic Corporation
Osaka
JP
|
Family ID: |
37053158 |
Appl. No.: |
13/552055 |
Filed: |
July 18, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11908862 |
Sep 17, 2007 |
8254437 |
|
|
PCT/JP2006/304547 |
Mar 9, 2006 |
|
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13552055 |
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Current U.S.
Class: |
375/219 ;
375/295 |
Current CPC
Class: |
H04L 27/02 20130101;
H04L 25/4902 20130101; H04B 1/7174 20130101 |
Class at
Publication: |
375/219 ;
375/295 |
International
Class: |
H04L 27/00 20060101
H04L027/00; H04B 1/38 20060101 H04B001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2005 |
JP |
2005-094252 |
Mar 7, 2006 |
JP |
2006-060854 |
Claims
1. A transmitting apparatus comprising: a pulse generating circuit
that generates a pulse string while differentiating a peak power of
a portion of the pulse string from a peak power of an other portion
of the pulse string; and a modulator that modulates the portion of
pulse string by a first type of data.
2. The transmitting apparatus according to claim 1 wherein, the
modulator modulates the other portion of the pulse string by a
second type of data.
3. The transmitting apparatus according to claim 1 wherein the
pulse generating circuit generates a plurality of pulse strings
while keeping an average transmission power of the pulse string
including the portion and the other portion, constant.
4. The transmitting apparatus according to claim 1 further
comprising: a timer circuit for designating the portion as a
function of a time interval; and wherein, the pulse generating
circuit generates the pulse string while differentiating the peak
power for the portion designated by the timer circuit.
5. The transmitting apparatus according to claim 4 further
comprising; a random timing generating circuit for designating the
portion while changing the interval; and wherein the pulse
generating circuit generates the pulse string while differentiating
the peak power for the portion designated by the random timing
generating circuit.
6. The transmitting apparatus according to claim 2 wherein, the
first type data is a data required to initialize a communication to
another device, and the pulse generating circuit allocates a
greater peak power to the portion of the pulse string than that of
the other portion.
7. The transmitting apparatus according to claim 6 wherein, the
first type of data is a data containing any one of the following
information: (a) a sync information to be used to reproduction of
clock in a receiver; (b) a communication requesting information;
and (c) a device recognizing information.
8. The transmitting apparatus according to claim 1 further
comprising, a receiving unit operable to receive a feedback
information sent from an apparatus to which the first type data has
been sent; and the pulse generating circuit adaptively adjusts
either of the peak power or the portion of the pulse string
according to the feedback information.
9. The transmitting apparatus according to claim 8 wherein, the
feedback information includes a data related to jitter; and wherein
the pulse generating circuit allocates a greater peak power when
the data indicates the greater jitter.
10. The transmitting apparatus according to claim 8 wherein, the
feedback information includes a data related to control either one
of: (a) the peak power; and (b) the interval.
11. A transmitting apparatus comprising: a pulse generating circuit
for generating a pulse string including large pulses and small
pulses, the large pulses having greater pulse peak power than the
small pulses; a pulse repetition cycle determining circuit for
determining (i) a pulse repetition cycle of the pulses in the pulse
string based on a clock signal, and (ii) an interval during which
the large pulses are transmitted according to an information; a
peak power determining circuit for determining the peak power of
the pulses depending to the interval determined; and a modulator
for modulating the pulses in the pulse string with transmission
data including a first data for generating a radio frequency (RF)
transmission signal so that the interval during which the large
pulses are transmitted is controlled based on a type of the
transmission data or a status of the wireless communication path
between the transmitting apparatus and a receiving apparatus
receiving the pulses.
12. A wireless communication apparatus comprising: a receiving
unit, including a reception status estimating circuit for
estimating a communication quality between another wireless
communication apparatus based on an information received sent from
the another wireless communication apparatus, and a transmitting
unit transmitting a radio frequency (RF) transmission signal
including a pulse string having large pulses and small pulses, the
large pulses having greater pulse peak power than the small pulses,
the transmitting unit including, a pulse repetition cycle
determining circuit for determining a pulse repetition cycle of the
pulse string, a peak power determining circuit for determining the
pulse peak power of the pulses, wherein the pulse repetition cycle
determining circuit and the peak power determining circuit
determine the pulse repetition cycle and the pulse peak power.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/908,862, filed Sep. 17, 2007, which is a
U.S. National Phase Application of PCT International Application
PCT/3P2006/304547, and is incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to transmitting apparatus,
receiving apparatus, and communication systems using wideband
signals such as pulse waveforms.
BACKGROUND ART
[0003] Institute of Electrical and Electronics Engineers having its
headquarter in the US has established IEEE802.11b standard which
typically represents wireless local-area-network (hereinafter
referred to as LAN) devices having been rapidly and widely used. On
top of that, audio-video (hereinafter referred to as AV) devices
and personal computers are connected in wireless manner, so that a
society where seamless networks are established can be predicted.
This background urgently needs a technique embodying a compact and
high-speed wireless data device at an inexpensive cost. A distance
measuring technique employing wireless techniques including
ultrasonic sensors, or millimeter-wave sensors is one of the
applications of the communications using this standard, and this
technique is used in a variety of fields such as preventing a car
collision, monitoring an invader by detecting a human-body. The
application fields will be expanded from now on.
[0004] A wireless method called ultra wide band (hereinafter
referred to as UWB), which employs pulse-like modulating signals,
has drawn attention as one of techniques that can embody a compact
device, high-speed data communication, and highly accurate distance
measuring. The UWB employs a short pulse not greater than 1 (one)
nano-second, and a wide frequency band over several hundreds of MHz
for communication or distance measuring. In the communication, a
repetition frequency of the short pulse is raised, so that one
symbol is assigned to each one of short pulses or a plurality of
short pulses, thereby embodying a high speed communication over
several hundreds of Mbps. In the distance measuring, an arrival
time is measured by using short pulses, so that a distance can be
accurately measured.
[0005] FIG. 9 shows a block diagram illustrating a structure of a
conventional receiving apparatus. Since the UWB employs an
extraordinary short pulse not greater than ins, a capture of a
signal (acquisition) and a synchronization of a signal (tracking)
should be done quickly and accurately. In this conventional
instance, a signal is captured by a technique called synchronous
addition which also suppresses errors in synchronization. A signal
received via a wireless propagating route is deteriorated its
signal-to-noise (S/N) ratio due to adverse effect of attenuation,
noise, and multi-path.
[0006] To overcome this problem, a reception signal is delayed at
known pulse intervals by using plural delay circuits 701A, 701B,
and the delay is added in the form of voltage by using voltage
adding circuit 702 for boosting the signal voltage. A sync pulse is
extracted from this signal by using sync pulse detecting circuit
703. The reception signal is demodulated with this extracted sync
pulse by demodulating circuit 704, thereby obtaining a demodulated
signal (demodulated data). The foregoing structure is disclosed in,
e.g. Unexamined Japanese Patent Publication No. H05-284128.
[0007] Although a description by using drawings is omitted here,
use of a spread spectrum technique allows to a receiving apparatus
to improve the S/N ratio of a signal sent from a transmitting
apparatus due to spectrum gain for reception (demodulation). This
conventional structure is disclosed in, e.g. Unexamined Japanese
Patent Publication No. 2003-143109.
[0008] However, the conventional transmitting apparatus, receiving
apparatus and communication system discussed above sometime
encounter the following problems: Synchronous addition adds not
only a reception signal but also noise power, so that improvement
effect of S/N ratio is lowered. Use of the spread spectrum
technique takes a time for synchronizing spectrum signals, so that
an actual throughput can be lowered. On top of that, a number of
circuits for synchronizing the spectrum signals are needed, which
makes the circuit complicated. As a result, the device becomes
bulky, and the power consumption becomes greater.
DISCLOSURE OF INVENTION
[0009] The present invention aims to provide a transmitting
apparatus, receiving apparatus and communication system which allow
the receiving apparatus to obtain greater S/N improvement effect,
avoid lowering actual throughput, avoid requiring a large number of
circuits for synchronizing spectrum signals, avoid making its
circuit complicated, avoid making the device bulky, and avoid
increasing the power consumption.
[0010] The transmitting apparatus of the present invention includes
a pulse generating circuit, a pulse repetition cycle determining
circuit, a peak power determining circuit, and a modulator. The
pulse generating circuit generates a pulse string. The pulse
repetition cycle determining circuit determines, based on a clock
signal, a pulse repetition cycle of the pulse string generated by
the pulse generating circuit. The peak power detecting circuit
determines a pulse peak power of the pulse string. The modulator
modulates the pulse string with transmission data, thereby
generating a transmission signal.
[0011] The foregoing structure allows the receiving apparatus, i.e.
the communication counterpart, to obtain greater improvement of S/N
ratio, avoid lowering actual throughput, avoid requiring a large
number of circuits for synchronizing spectrum signals, avoid making
its circuit complicated, avoid making the device bulky, and avoid
increasing the power consumption.
[0012] The transmitting apparatus of the present invention can have
a structure in which a pulse repetition cycle and a pulse peak
power are determined such that the cooperative operation of the
pulse repetition cycle determination circuit with the peak power
determination circuit makes an average power of a transmission
signal constant. This structure allows transmitting pulses having a
great peak power while the average transmission power is kept
constant.
[0013] The transmitting apparatus of the present invention can have
a structure in which a transmission signal is formed of at least
two kinds of pulses having different peak powers from each other.
This structure allows an appropriate transmission of signals the
receiving apparatus needs.
[0014] The transmitting apparatus of the present invention can have
a structure, in which the modulator allots at least a part of the
sync information to a pulse having a great peak power. This
structure allows the receiving apparatus to capture the pulse
(acquisition) and hold the sync (tracking) with ease.
[0015] The transmitting apparatus of the present invention can have
a structure, in which the modulator allots a signal, to be used for
measuring a distance, to a pulse having a great peak power. This
structure allows performing not only data communication but also
measuring a distance with ease.
[0016] The transmitting apparatus of the present invention can have
a structure, in which the modulator employs one of pulse position
modulation, pulse phase modulation or pulse amplitude modulation.
This simple structure allows performing a high-speed communication
with short pulses or accurate distance measurement.
[0017] The transmitting apparatus of the present invention can
further include a random number generating circuit for allowing the
peak power determining circuit to determine the pulse peak power
based on the generated ransom number. This structure can avoid a
poor quality of communication such as interference in specific
condition, and implement at least a communication or distance
measurement with pulses having a great peak power.
[0018] The transmitting apparatus of the present invention can
further include a timer circuit, and the peak power determining
circuit determines a pulse peak power based on time intervals
designated by the timer circuit. This structure allows the
receiving apparatus to receive a pulse, having a great peak power,
at given intervals, so that the arrival time of the pulse can be
estimated with ease. As a result, the pulses can be easily caught,
and the sync can be held with ease.
[0019] The transmitting apparatus of the present invention can have
a structure in which at least one of the pulse repetition cycle
determined by the pulse repetition cycle determining circuit or the
pulse peak power determined by the peak power determining circuit
can be changed based on the information received by the receiving
apparatus. This structure allows the transmitting apparatus to
establish an appropriate transmitting condition in response to a
reception status.
[0020] The transmitting apparatus of the present invention can have
a structure in which the information received by the receiving
apparatus is the information indicating a reception status of a
counterpart to which a transmission signal is sent. This structure
allows the transmitting apparatus to establish an appropriate
transmitting condition in response to the reception status of the
counterpart.
[0021] The transmitting apparatus of the present invention can have
a structure in which the information received by the receiving
apparatus is the information from a device other than the
counterpart to which a transmission signal is sent. This structure
allows the transmitting apparatus to optimize a transmitting
condition which can reduce the interference arising to other
devices.
[0022] The receiving apparatus of the present invention includes a
reception pulse signal generating circuit, selecting circuit,
synchronizing circuit, and demodulating circuit. The reception
pulse signal generating circuit reproduces short pulses based on
reception signals, thereby generating reception pulse signals. The
selecting circuit selects pulses based on a magnitude of pulse peak
power of a reception pulse signal. The synchronizing circuit
synchronizes a clock signal with the selected reception pulse
signal, thereby generating a sync output signal. The demodulating
circuit generates a demodulated signal by using the sync output
signal and the reception pulse signal. The foregoing structure
allows substantially improving an S/N ratio with pulses having a
great pulse peak power, preventing the circuit from becoming
complicated, preventing the device from becoming bulky, and
preventing the power consumption from increasing.
[0023] The receiving apparatus of the present invention can have a
structure in which the selecting circuit selects pulses having a
great pulse peak power, and the synchronizing circuit synchronizes
the clock signal with the pulse having a great pulse peak power,
and the demodulating circuit receives and demodulates pulses having
a small pulse peak power. This structure allows capturing pulses
and holding a sync with ease, so that greater improvement of S/N
ratio can be expected, and an actual throughput is not lowered, a
number of spread signal sync circuits are not needed. As a result,
the foregoing structure prevents the circuit from becoming
complicated, and the device from becoming bulky, and the power
consumption from increasing.
[0024] The receiving apparatus of the present invention can have a
structure in which the selecting circuit selects pulses having a
great pulse peak power, and the synchronizing circuit synchronizes
spread signals with the selected pulses having a great pulse peak
power. This structure allows synchronizing the spread signals with
ease, and obtaining a greater improvement of S/N ratio, and an
actual throughput is not lowered, a number of spread signal sync
circuits are not needed. As a result, the foregoing structure
prevents the circuit from becoming complicated, the device from
becoming bulky, and the power consumption from increasing.
[0025] The receiving apparatus of the present invention can further
include a time difference signal generating circuit, a signal
flight distance estimating circuit. The time difference signal
generating circuit generates a time difference signal based on the
time difference between the clock signal and the reception pulse
signal. The signal flight distance estimating circuit estimates the
flight distance based on the time difference signal generated by
the time difference generating circuit. This structure prevents the
circuit from becoming complicated, the device from becoming bulky,
and the power consumption from increasing, and the distance can be
measured with ease.
[0026] The receiving apparatus of the present invention can have a
structure in which the demodulating circuit obtains reception
information of another device, and outputs the information to the
transmitting apparatus. This structure allows conveying a reception
status of the other device to the transmitting apparatus.
[0027] The receiving apparatus of the present invention can have a
structure in which the obtained reception information of another
device is the reception information of a counterpart to which the
transmitting apparatus sends a transmission signal. This structure
allows conveying the reception status of the communication
counterpart to the transmitting apparatus.
[0028] The receiving apparatus of the present invention can have a
structure in which the obtained reception information of another
device is reception information of a device other than the
counterpart to which the transmitting apparatus sends a
transmission signal. This structure allows conveying information,
e.g. about interference arising to another device, to the
transmitting apparatus.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. 1 shows a block diagram illustrating a structure of a
communication system including a transmitting apparatus and a
receiving apparatus in accordance with a first embodiment of the
present invention.
[0030] FIG. 2 shows pulse waveforms transmitted by the transmitting
apparatus and received by the receiving apparatus in accordance
with the first embodiment.
[0031] FIG. 3 shows a block diagram illustrating another structure
of a communication system including a transmitting apparatus and a
receiving apparatus in accordance with the first embodiment of the
present invention.
[0032] FIG. 4 shows a block diagram illustrating a structure of the
transmitting apparatus in accordance with the first embodiment.
[0033] FIG. 5 shows another pulse waveforms transmitted by the
transmitting apparatus and received by the receiving apparatus in
accordance with the first embodiment.
[0034] FIG. 6 shows another pulse waveforms transmitted by the
transmitting apparatus and received by the receiving apparatus in
accordance with the first embodiment.
[0035] FIG. 7 shows a block diagram illustrating a structure of a
communication system including a transmitting apparatus and a
receiving apparatus in accordance with a second embodiment of the
present invention.
[0036] FIG. 8 shows a block diagram illustrating a structure of a
communication system including a transmitting apparatus and a
receiving apparatus in accordance with a third embodiment of the
present invention.
[0037] FIG. 9 shows a block diagram illustrating a structure of a
conventional receiving apparatus.
DESCRIPTION OF REFERENCE MARKS
[0038] 101, 201, 301, 401, 501A, 501B transmitting apparatus [0039]
102, 102A, 102B transmission clock circuit [0040] 103, 103A, 103B
pulse repetition cycle determining circuit [0041] 104, 104A, 104B,
303 peak power determining circuit [0042] 105, 105A, 105B, 304, 315
pulse generating circuit [0043] 106, 106A, 106B, 305 modulator
[0044] 107, 107A, 107B transmission adjusting circuit [0045] 108A,
108B, 108C, 108D band limiting filter [0046] 109A, 109B, 109C, 109D
antenna [0047] 110, 203, 308, 502A, 502B receiving apparatus [0048]
111, 111A, 111B reception adjusting circuit [0049] 112, 112A, 112B,
204, 309 reception pulse signal generating circuit [0050] 113,
113A, 113B, 206, 310 clock reproducing circuit [0051] 114, 114A,
114B synchronizing circuit [0052] 115, 115A, 115B demodulating
circuit [0053] 117 reception clock circuit [0054] 202 sync
information extracting circuit [0055] 205 selecting circuit [0056]
302, 505 transmission data generating circuit [0057] 306 another
device [0058] 307 object to be measured its flight distance [0059]
311 delay correcting circuit [0060] 312 delay-time calculating
circuit [0061] 402 pulse peak power setting circuit [0062] 402A
timer circuit [0063] 402B random timing generating circuit (random
number generating circuit) [0064] 402C switcher [0065] 503A, 503B
reception status estimating circuit [0066] 601A, 601B, 601C, 601D
pulse having a small peak power [0067] 602 no-pulse existing
position [0068] 603 pulse having a great peak power
DESCRIPTION OF PREFERRED EMBODIMENTS
[0069] Exemplary embodiments of the present invention are
demonstrated hereinafter with reference to the accompanying
drawings.
Embodiment 1
[0070] FIG. 1 shows a block diagram illustrating a structure of a
communication system including a transmitting apparatus and a
receiving apparatus in accordance with the first embodiment of the
present invention. The communication system of the present
information includes transmitting apparatus 101 and receiving
apparatus 110. Transmitting apparatus 101 includes transmission
clock circuit 102, pulse repetition cycle determining circuit 103,
peak power determining circuit 104, pulse generating circuit 105,
modulator 106, transmission adjusting circuit 107, and band
limiting filter 108A.
[0071] Transmission clock circuit 102 generates transmission clock
signals. Pulse repetition cycle determining circuit 103 determines
a repetition cycle of pulses. Peak power determining circuit 104
determines a peak power of pulses. Pulse generating circuit 105
generates a pulse string to be transmitted. Modulator 106 modulates
the transmission pulse string by using transmission data.
Transmission adjusting circuit 107 adjusts transmission signals.
Band limiting filter 108A limits a transmission band. Antenna 109A
transmits the transmission signals.
[0072] Operation of the foregoing transmitter is demonstrated
hereinafter with reference to FIG. 1. When pulse generating circuit
105 generates a pulse string to be transmitted, it uses a
transmission clock signal generated by transmission clock circuit
102 as a reference signal. The repetition cycle determined by pulse
repetition cycle determining circuit 103 and the pulse peak power
determined by peak power determining circuit 104 are input to pulse
generating circuit 105. The pulse repetition cycle of the
transmission pulse string and the pulse peak power can be changed
as required.
[0073] The pulse peak power can be determined based on the
magnitude of transmission data information. Material information
includes, e.g. communication requesting information, device
recognizing information, sync information and so on. The pulse peak
power can be also determined in response to the status of a
communication path. The status of a communication path includes,
e.g. intensity or density of multi-path wave.
[0074] In this embodiment, a modulation method is not limited;
however, a multi-path communication method is generally used. For
instance, a pulse position modulation, pulse phase modulation or
pulse amplitude modulation, or pulse-shape modulation can be used.
Pulses having different peak powers are described by taking the
pulse string shown in FIG. 2 as an example. FIG. 2 shows the
waveform of pulses received by the receiving apparatus, which
pulses are sent from the transmitting apparatus of the present
invention.
[0075] In FIG. 2, pulses 601A-601D having small peak powers and
pulses 603 having a great peak power coexist. For instance,
communication requesting information is attached to pulse 603
having a great peak power, and communication information to be
transmitted is attached to pulses 601A-601D having small peak
powers. In this embodiment, a pulse having a great peak power and a
pulse having a small peak power are used for the description
purpose; however, the present invention is not limited to this
instance, and as far as at least two kinds of pulses having
different peak powers are available, the present invention can
work.
[0076] The structure discussed above allows the device, which
receives signals transmitted from transmitting apparatus 101, to
demodulate pulses 603 having great peak powers at a higher S/N
ratio than that of the demodulation of pulses 601A-601D having
small peak powers, so that at least the communication requesting
information can be received even if great noises and multi-path
signals exist in the communication path. Position 602, where no
pulses exist, has a purpose of outputting pulse 603 having a great
peak power while an average transmission power is kept constant. In
other words, position 602 is a time-concerned position where no
pulses are output for this purpose.
[0077] No-pulse existing position 602 can be set either by changing
a cycle of pulses at the cycle determination by pulse repetition
cycle determining circuit 103, or by setting a peak power as small
as nearly 0 (zero) by peak power determining circuit 104. As
discussed above, the pulse repetition cycle determining circuit and
the peak power determining circuit cooperate with each other for
determining the pulse repetition cycle as well as the pulse peak
power so that the average power of transmission signals can be
constant.
[0078] The transmission signal generated by modulator 106 is
adjusted its power by transmission adjusting circuit 107 and also
adjusted its frequency band by band limiting filter 108A before the
signal is transmitted from antenna 109A. Transmission adjusting
circuit 107 can have such a structure as not only adjusts the power
with an amplifier or an attenuator, but also converts the frequency
of the transmission signal into a signal at any frequency band by
using a frequency conversion circuit such as a local oscillator
combined with a mixer and a switch, or an oscillator for direct
conversion.
[0079] Receiving apparatus 110 includes band limiting filter 108B,
reception adjusting circuit 111, reception pulse signal generating
circuit 112, clock reproducing circuit 113, synchronizing circuit
114, and demodulating circuit 115. Band limiting filter 108B
removes unnecessary signals, existing out of the band, from the
signals received by antenna 109B. Reception adjusting circuit 111
adjusts the power of a signal received. Reception pulse signal
generating circuit 112 shapes the pulses of the reception signal.
Clock reproducing circuit 113 extracts sync signals from the
reception pulse signals. Synchronizing circuit 114 generates a sync
output signal having undergone the sync adjustment with the
reception clock signal generated by reception clock circuit 117.
Demodulating circuit 115 outputs a demodulated signal, i.e.
reception data.
[0080] Operation of the foregoing receiving apparatus is
demonstrated hereinafter. A signal caught by antenna 109B is
removed its unnecessary signals existing out of the band by band
limiting filter 108B, then is adjusted its power by reception
adjusting circuit 111. Similar to transmission adjusting circuit
107 discussed previously, reception adjusting circuit 111 not only
adjusts the power but also removes radio-frequency component with
sync detection using a low pass filter (LPF), a local oscillator
and a mixer, an envelop detector, or a correlated template, or
delayed detection using delay-correlation. The reception signal
adjusted by reception adjusting circuit 111 is input to reception
pulse signal generating circuit 112.
[0081] Reception pulse signal generating circuit 112 shapes the
pulses of the reception signal for clock reproduction or
demodulation. Pulse-shaping can be done by, e.g. extracting signal
components by using a comparison circuit or over-sampling, or by
adjusting a pulse width. Circuit 112 outputs a reception pulse
signal, and is supplied to demodulating circuit 115 and clock
reproducing circuit 113, which then extracts a sync signal.
Synchronizing circuit 114 generates a sync output signal having
undergone sync adjustment with a reception clock signal supplied
from reception clock circuit 117. The sync output signal undergoes
demodulation in demodulating circuit 115, which then outputs a
demodulated signal, i.e. reception data.
[0082] During the foregoing operation of receiving apparatus 110,
as it is described in the operation of transmitting apparatus 101,
a reception signal, running through a path where great noises and
great multi-path signals exist, has a low S/N ratio. Thus when
reception adjusting circuit 111 implements a signal detection by
using the comparison circuit, noise components are erroneously
recognized as signal components, or the signal components tend to
be missed because of small difference between a comparison
reference voltage and a noise voltage, so that a reception signal
having many errors can be generated.
[0083] On the other hand, the difference between the comparison
reference signal and the noise voltage can be greater in the pulse
having a great peak power, so that a reception signal having a
fewer errors can be generated. Clock reproducing circuit 113 can
obtain accurate reception data including pulses having small peak
powers by selecting a pulse having a great peak power and making
the pulse as a reference.
[0084] As discussed above, the transmitting apparatus, receiving
apparatus and communication system in accordance with this first
embodiment allow an appropriate change in a pulse repetition cycle
of a transmission signal and in peak powers of respective pulses at
the transmitting apparatus, so that the receiving apparatus can
obtain greater improvement in the S/N ratio, avoid lowering actual
throughput, avoid requiring a large number of circuits for
synchronizing spectrum signals, avoid making its circuit
complicated, allow capturing pulses and holding synchronization
with ease, and embody a compact device as well as a low power
consumption.
[0085] In the foregoing discussion, information attached to the
pulse having a great peak power is not specifically designated.
Hereinafter, however, the case where sync information is attached
to the pulse is described with reference to FIG. 3 which shows a
block diagram illustrating another structure of a communication
system including a transmitting apparatus and a receiving apparatus
in accordance with the first embodiment of the present invention.
The communication system of this embodiment includes transmitting
apparatus 201 and receiving apparatus 203. In FIG. 3, similar
elements to those in FIG. 1 have the same reference marks, and the
descriptions thereof are omitted here. In this case, transmitting
apparatus 201 includes sync information extracting circuit 202, and
receiving apparatus 203 includes selecting circuit 205. Reception
pulse signal generating circuit 204 generates reception pulse
signals by using outputs from reception adjusting circuit 111, and
the reception pulse signals are supplied to selecting circuit 205.
Clock reproducing circuit 206 receives sync pulse signals from
selecting circuit 205, and then reproduces the clock signal.
[0086] In the transmitting apparatus, receiving apparatus and
communication system discussed above, when the sync information is
generated, e.g. as parts of transmission data, the transmission
data input to transmitting apparatus 201 is supplied to sync
information extracting circuit 202 for extracting a timing of the
sync information, and based on this timing, peak power determining
circuit 104 determines a peak power of a pulse. Receiving apparatus
203 includes selecting circuit 205, which selects only the pulse
having a great peak power, and to which pulse the sync information
is attached. Selecting circuit 205 generates a sync pulse signal
for reproducing the clock signal. This structure allows receiving
apparatus 203 to obtain accurate sync timing, so that reception
pulse signals can be sampled at accurate sync timing. As a result,
reception pulse signals having a small S/N ratio can be demodulated
with fewer errors.
[0087] In the foregoing discussion, a clock signal is synchronized
by using a pulse having a great peak power; however, the present
invention is not limited to this instance, and is applicable to the
following case: both of the transmitting apparatus and the
receiving apparatus have a function of spread spectrum
communication, and a start-time position of a spectrum signal is
attached to the pulse having a great peak power, so that a
code-synchronization can be done in a short time.
[0088] In the foregoing discussion, the information specifically
selected such as sync information is attached to the pulse having a
great peak power. However, the structure shown in FIG. 4 allows
attaching the pulse having a great peak power to the peak power
determining circuit regardless of transmission data. FIG. 4 shows a
block diagram illustrating another structure of the transmitting
apparatus in accordance with the first embodiment. In FIG. 4,
similar elements to those in FIG. 1 have the same reference marks
and the descriptions thereof are omitted here. In FIG. 4,
transmitting apparatus 401 includes pulse peak power setting
circuit 402, which sets timing, and based on this timing, peak
power determining circuit 104 attaches the pulse having a great
peak power.
[0089] Pulse peak power setting circuit 402 is, e.g. timer circuit
402A which sets pulses with a great peak power at given intervals,
or random-timing generating circuit 402B which generates random
numbers in a random-number generating circuit, an then sets pulses
having a great peak power at random. For instance when timer
circuit 402A is employed, the receiving apparatus can receive
pulses with a great peak power at given intervals, so that an
arrival time of a pulse can be estimated with ease. As a result,
pulses can be captured (acquisition) and sync can be held
(tracking) with ease. Use of random timing generating circuit 402B
allows the receiving apparatus to avoid canceling out of cyclic
signals by a specific multi-path environment, or to avoid
consistent interference between the cyclic signals and other cyclic
signals generated by another device. As a result, the receiving
apparatus can capture pulses (acquisition) and hold synchronization
(tracking) with fewer errors.
[0090] Here is another method to achieve the foregoing advantages:
first, timer circuit 402A cyclically sends pulses having a great
peak power to the receiving apparatus, and when the receiving
apparatus encounters the multi-path environment or the interference
with another device discussed above, switcher 402C switches over
timer circuit 402a to random-timing generating circuit 402B.
[0091] In the foregoing discussion, both of the transmitting
apparatus and the receiving apparatus include a clock circuit
individually; however, when the transmitting apparatus is placed
closely to the receiving apparatus, a transmission clock circuit
can be used as a reception clock circuit as well.
[0092] In the foregoing discussion, cycles and peak powers of
pulses can be changed in response to the magnitude of communication
information; however, these two factors can be determined in
response to the status of the communication path as discussed
previously. Hereinafter changes in cycles or peak powers of pulses
in response to the communication path status, e.g. intensity or
density of multi-path wave, are demonstrated with reference to
FIGS. 5 and 6, which show another pulse waveform transmitted from
the transmitting apparatus and received by the receiving apparatus.
Transmission signal 801A having undergone OOK (on-off keying)
modulation, and the presence of pulse 802 indicates "1" and no
pulse 802 indicates "0".
[0093] Reception signal 801B is accompanied by multi-path wave 803.
Signal 801C indicates that reception signal 801B undergoes envelope
detection. Signal 801C having undergone the detection is evaluated
with a given threshold 804, and a signal greater than threshold 804
is evaluated as "1" and a signal smaller than threshold 804 is
evaluated as "0". Signal 801D is a binary signal having undergone
A/D conversion, and indicates "1" when a signal over threshold 804
is input, and indicates "0" when a signal lower than threshold 804
is input. Signal 801E is produced in an ideal condition such as
undergoing A/D conversion without multi-path. Comparison between
signals 801D and 801E will find detected timing difference 805.
[0094] This detected timing difference 805 is caused by
interference between symbols due to multi-path wave 803, and thus a
pulse waveform is distorted. Occurrence of timing difference 805
will increase errors in demodulation because jitters increase in
the sync tracking implemented based on signal 801D having undergone
the A/D conversion. When the jitters increase, sync pull-in cannot
be done or the pulled-in sync becomes out of sync, so that
communication quality becomes substantially lowered.
[0095] As shown in FIG. 6, coexistence of pulse 902 having a great
peak power with the transmission signal will overcome the problem
discussed above. The following embodiment is an instance of this
case: Transmission signal 901A includes pulses 902 having a great
peak power, e.g. once in four times. Similar to the case shown in
FIG. 5, reception signal 901B accompanied by multi-path wave
undergoes the envelope detection. Signal 901C having undergone the
detection is evaluated with threshold 903, which can be greater
than threshold 804 shown in FIG. 5. Signal 901D having undergone
A/D conversion has a fewer number of pulses than signal 801D shown
in FIG. 5, however, its timing difference (shown in the solid line
arrow mark) from signal 901E having no multi-path is smaller than
that (shown in the broken line arrow mark) shown in FIG. 5.
[0096] The foregoing advantage is produced with this reason: Pulse
902 having a great peak power receives less in-between-symbols
interference from the previous pulse, so that it is less affected
by the interference, and the pulse waveform is less distorted. As
discussed above, insertion of pulses having a great peak power to
the reception signal at given intervals allows preventing
communication quality from lowering even in a multi-path
environment, and allows implementing sync pull-in within a short
time as well as accurate sync tracking. The insertion of the pulses
having a great peak power can take place when sync jitters are
evaluated by a reception status estimating circuit and the
evaluated jitters exceed a given threshold value. Plural threshold
values can be prepared for the insertion cycle and the power of
pulses to be inserted, and when jitters are found great, pulses
having a greater power are inserted at a shorter cycle.
Embodiment 2
[0097] FIG. 7 shows a block diagram illustrating a structure of a
communication system including a transmitting apparatus and a
receiving apparatus in accordance with the second embodiment of the
present invention. This second embodiment differs from the first
one in the structure having a distance measuring function in
addition to the communication function. The communication system in
accordance with the second embodiment includes transmitting
apparatus 301 and receiving apparatus 308.
[0098] Similar to the first embodiment, transmitting apparatus 301
transmits pulses having a great peak power mixed with pulses having
a small peak power by using peak power determining circuit 303. In
this case, data for measuring a distance is attached to the pulses
having a great power, and data for communication is attached to the
pulses having a small power. In the following discussion, an
instance, where only the data for measuring a distance is attached
to the pulses having a great power, is described. The present
invention, however, is applicable both to the distance measurement
and the communication by attaching not only the data for measuring
a distance but also attaching information to be used for
communication, e.g. sync data, to the pulses having a great peak
power.
[0099] The data for communication and the data for measuring a
distance are input to transmission data generating circuit 302, and
are output as transmission data, which is then supplied to peak
power determining circuit 303, where a peak power is determined so
as to be timed to both of the foregoing data. The peak power is
input to pulse generating circuit 304, which then outputs pulses
having different peak powers. The two data are input together to
modulator 305, where they are modulated by an appropriate
modulating method into transmission signals, then the signals run
through transmission adjusting circuit 107 and band limiting filter
108A before being transmitted by antenna 109A.
[0100] A communication signal is received by another device 306,
which performs as a communicating device and processes the signal
accordingly. The signal is returned to antenna 109B of receiving
apparatus 308, and runs through band limiting filter 108B,
reception adjusting circuit 111, then is supplied as a reception
signal to reception pulse generating circuit 309. The reception
pulse signal generated by circuit 309 runs through clock
reproducing circuit 310, synchronizing circuit 114, and is supplied
to as a sync output signal to demodulating circuit 115, which then
outputs a demodulated signal (reception data).
[0101] Next, the distance measurement is demonstrated hereinafter.
A signal reflecting from object 307 is used for measuring the
distance to object 307. A signal for measuring the distance is
transmitted from transmitting apparatus 301, and arrives at object
307, then reflects from object 307 and is caught as a reflected
signal by antenna 109B of receiving apparatus 308. Similar to the
communication signal, this reflected signal is output as a
reception pulse signal from reception pulse signal generating
circuit 309; however, it is selected by selecting circuit 205, and
is output as a reception distance measuring signal.
[0102] There are several selecting methods available, e.g. a simple
method is to use a power difference between the reception pulse
signals, or to use a spread code in the data for measuring a
distance and another spread code in the data for communication, or
to estimate an arrival time of the reflected signal of the distance
measurement data based on a transmission time spent by the
transmitting apparatus. Delay-time calculating circuit 312 includes
a time-difference signal generating circuit which generates a
time-difference signal by using a time difference between a clock
signal and a reception pulse signal, and a signal flight distance
estimating circuit which estimates a signal flight distance by
using the time difference signal. A reception measuring signal
selected by selecting circuit 205 is input to delay-time
calculating circuit 312, which calculates a time difference from
the transmission signal for finding a distance, then circuit 312
outputs the distance as a decoded signal (measured distance). In
this case, a signal generated by pulse generating circuit 315 is
adjusted by delay correcting circuit 311 which corrects the delay
time, and then the adjusted signal is used as the transmission
signal.
[0103] As discussed above, the transmitting apparatus, receiving
apparatus and communication system in accordance with the second
embodiment of the present invention appropriately change a pulse
repetition cycle of a transmission signal and the peak powers of
respective pulses for measuring a distance to an object by using a
signal having a great peak power, and implement a communication
with another device by using a signal having a small peak power, so
that this embodiment allows a simple circuit structure to implement
both of communication and distance measurement.
[0104] In the foregoing description, a distance is calculated based
on the time difference between the transmission signal and the
signal reflecting from the object; however, the distance can be
calculated based on the time difference between the transmission
signal and a reply from a communication counterpart provided that a
time duration from the reception to the reply is a known
factor.
Embodiment 3
[0105] FIG. 8 shows a block diagram illustrating a structure of a
communication system including transmitting apparatus and receiving
apparatus in accordance with the third embodiment of the present
invention. This third embodiment differs from the first one in the
transmitting apparatus which, in response to the request from the
receiving apparatus, can adjust at least one of a pulse repetition
cycle or a pulse peak power.
[0106] In FIG. 8, a combination of transmitting apparatus 501A and
receiving apparatus 502A indicates the communication system which
mainly implements the transmission. A combination of transmitting
apparatus 501B and receiving apparatus 502B indicates the
communication system which mainly implements the reception. These
systems are generally similar to the structure shown in the first
embodiment. Transmission clock circuits 102a-102b are similar to
transmission clock circuit 102 of the first embodiment, and pulse
repetition cycle determining circuits 103a-103b are similar to
pulse repetition cycle determining circuit 103. Peak power
determining circuits 104a-104b are similar to peak power
determining circuit 104. Pulse generating circuits 105a-105b are
similar to pulse generating circuit 105.
[0107] Modulators 106a-106b are similar to modulator 106, and
transmission adjusting circuits 107a-107b are similar to circuit
107. Band limiting filters 108c-108d are similar to filters
108a-108b, and antenna 109c-109d are similar to antenna 109a-109b.
Reception adjusting circuits 111a-111b are similar to circuit 111,
and reception pulse signal generating circuit 112a-112b are similar
to circuit 112. Clock reproducing circuits 113a-113b are similar to
circuit 113, and synchronizing circuits 114a-114b are similar to
circuit 114. Demodulating circuit 115a-115b are similar to
demodulating circuit 115.
[0108] The different point is that reception status estimating
circuits 503A and 503B are provided in this third embodiment.
Receiving apparatus 502B receives a signal sent from transmitting
apparatus 501A, and estimates a reception status of an output from
demodulating circuit 115B with reception status estimating circuit
503B, or estimates the reception status based on, e.g. an average
value of changes in phases of sync output signal generated by
synchronizing circuit 114B. In response to the estimated reception
status, receiving apparatus 502 determines its own pulse repetition
cycle and pulse peak power, and then returns these values.
[0109] In the case of returning, an acknowledgement signal
(hereinafter referred to simply as "ACK") is used for continuing
the communication, or a signal is used for informing whether or the
present repetition cycle synchronizes with a pulse peak power. The
information estimated by circuit 503B about setting the pulse peak
power or the pulse repetition cycle is attached to the transmission
data via transmission data generating circuit. Reception status
estimating circuit 503A of receiving apparatus 502A, which receives
the return, obtains the information about reception status of the
communication counterpart, and when the information is, e.g. ACK
signal, the communication is continued with the repetition cycle
and the peak power being kept. When the information contains a
signal notifying receiving apparatus 502A of a reception with a low
power, the repetition cycle is lowered for increasing the pulse
peak power so that receiving apparatus 502B can receive pulses
having a greater peak power. When the information contains a signal
notifying receiving apparatus 502A of a reception with an excessive
power, the peak power is lowered.
[0110] If the data rate to be processed by receiving apparatus 502B
is high, the pulse repetition cycle is increased, and if the data
late is low, the cycle is decreased. The pulse repetition cycle
from transmitting apparatus 501A at its initial stage to receiving
apparatus 502B can be sent based on a predetermined initial value,
or either one of the transmitting apparatus or the receiving
apparatus can change its established value in order to agree with
that of the counterpart.
[0111] As discussed above, the transmitting apparatus, receiving
apparatus, and communication system of the present invention
appropriately change, in response to a reception status of the
communication counterpart, at least one of the pulse repetition
cycle of a transmission signal or a peak power of respective pulses
for the communication. The present invention thus allows tracking
pulses, holding synchronization, downsizing the device, and
lowering the power consumption with a simple circuit structure.
[0112] In the foregoing discussion, reception status estimating
circuit 503A detects a signal supplied from transmitting apparatus
501B, i.e. communication counter part, and obtains the information
about reception status. However, the present invention is not
limited to this instance. For instance, circuit 503A detects
radio-wave supplied from another device which shares the frequency
band with the communication system, and the repetition cycle or the
peak power can be changed not to interfere with the radio-wave.
INDUSTRIAL APPLICABILITY
[0113] A communication system including a transmitting apparatus
and a receiving apparatus of the present invention comprises the
following elements: The transmitting apparatus includes a pulse
generating circuit, pulse repetition cycle determining circuit,
peak power determining circuit, and modulator. The receiving
apparatus includes a reception pulse signal generating circuit,
selecting circuit, synchronizing circuit, and demodulating circuit.
The pulse generating circuit generates pulse strings, and the pulse
repetition cycle determining circuit determines, based on a clock
signal, the pulse repetition cycle of the pulse strings generated
by the pulse generating circuit.
[0114] The peak power determining circuit determines the pulse peak
power of the pulse strings generated by the pulse generating
circuit. The modulator modulates the pulse strings with
transmission data, thereby generating a transmission signal. The
reception pulse signal generating circuit reproduces short pulses
based on a reception signal, thereby generating a reception pulse
signal. The selecting circuit selects pulses based on amounts of
pulse peak powers of the reception pulse signals. The synchronizing
circuit synchronizes a clock signal with the signal selected by the
selecting circuit, thereby generating a sync output signal.
[0115] The demodulating circuit generates a demodulated signal by
using the sync output signal and the reception pulse signal
supplied from the selecting circuit. This structure allows the
receiving apparatus advantageously to obtain greater improvement in
S/N ratio, to prevent an actual throughput from lowering, to
suppress the quantity of spread spectrum sync circuits, to prevent
the circuit from becoming complicated, to prevent the device from
becoming bulky, and to prevent the power consumption from
increasing. The present invention is useful for a transmitting
apparatus, receiving apparatus and communication system using a
wideband signal, e.g. a pulse waveform.
* * * * *