U.S. patent application number 11/851228 was filed with the patent office on 2008-01-03 for wireless communication systems, interrogators and methods of communicating within a wireless communication system.
Invention is credited to Roy Greeff, David K. Ovard.
Application Number | 20080001754 11/851228 |
Document ID | / |
Family ID | 23008858 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001754 |
Kind Code |
A1 |
Ovard; David K. ; et
al. |
January 3, 2008 |
Wireless Communication Systems, Interrogators and Methods of
Communicating Within a Wireless Communication System
Abstract
The present invention relates to wireless communication systems,
interrogators and methods of communicating within a wireless
communication system. One aspect of the present invention provides
a wireless communication system including at least one remote
communication device configured to communicate a return link
wireless signal; an interrogator including: a communication station
configured to receive the return link wireless signal and to
generate a return link communication signal corresponding to the
return link wireless signal; communication circuitry coupled with
the communication station and configured to communicate the return
link communication signal; and a housing remotely located with
respect to the communication station and including circuitry
configured to receive the return link communication signal from the
communication circuitry and to process the return link
communication signal.
Inventors: |
Ovard; David K.; (Meridian,
ID) ; Greeff; Roy; (Boise, ID) |
Correspondence
Address: |
WELLS ST. JOHN P.S.
601 W. FIRST AVENUE, SUITE 1300
SPOKANE
WA
99201
US
|
Family ID: |
23008858 |
Appl. No.: |
11/851228 |
Filed: |
September 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10081256 |
Feb 19, 2002 |
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11851228 |
Sep 6, 2007 |
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09265074 |
Mar 9, 1999 |
6356764 |
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10081256 |
Feb 19, 2002 |
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Current U.S.
Class: |
340/572.1 ;
340/10.1 |
Current CPC
Class: |
G06K 7/0008 20130101;
G06K 7/01 20130101; H04W 8/005 20130101; H04W 84/18 20130101; G06K
7/10356 20130101; G06K 17/0022 20130101 |
Class at
Publication: |
340/572.1 ;
340/010.1 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Claims
1-37. (canceled)
38. A system to track radio frequency identification (RFID) tags,
the system comprising: a plurality of antennas; a plurality of
communication stations, each communication station being
communicatively coupled to one or more of the plurality of
antennas; a plurality of communication circuitry units, each
communication circuitry unit communicatively coupled to a
respective one of the plurality of communication stations; and an
interrogator communicatively coupled to the plurality of
communication circuitry units, the interrogator being remotely
located from the plurality of communication circuitry units and
configured to cause the communication circuitry units to
communicate with the RFID tags.
39. The system of claim 38, wherein the plurality of antennas and
the plurality of communication stations are configured to
communicate via a spread spectrum signal.
40. The system of claim 38, wherein the interrogator comprises one
or more automatic gain control circuits to compare an incoming
signal to a threshold value and adjust a power level.
41. The system of claim 40, wherein the automatic gain control
circuits each includes a variable gain amplifier, a coupler, a
detector, and a loop filter.
42. The system of claim 38, wherein the interrogator is
communicatively coupled to the plurality of communication circuitry
units by coaxial RF cables.
43. A system to track radio frequency identification (RFID) tags,
the system comprising: a plurality of first antennas configured to
transmit forward link wireless communications and a plurality of
second antennas being configured to receive return link wireless
communications; low noise amplifiers communicatively coupled to
respective ones of the plurality of first and second antennas;
automatic gain control circuits communicatively coupled to
respective ones of the low noise amplifiers, the automatic gain
control circuits adjusting at least one electrical characteristic
of a signal received from the low noise amplifiers; and a
processing circuitry communicatively coupled to the automatic gain
control circuits to process signals received from the automatic
gain control circuits.
44. The system of claim 43, wherein the forward link wireless
communications comprise, a spread spectrum signal.
45. The system of claim 43, wherein the return link wireless
communications comprise a spread spectrum signal.
46. The system of claim 43, wherein the plurality of first antennas
and the plurality of second antennas are the same antennas.
47. The system of claim 43, wherein the automatic gain control
circuits and the processing circuitry are housed in a unit separate
from the plurality of first and second antennas and the low noise
amplifiers.
48. The system of claim 47, wherein the unit is remotely located
from the plurality of first and second antennas and the low noise
amplifiers, the unit being communicatively coupled to the low noise
amplifiers by coaxial RF cables.
49. The system of claim 43, wherein the automatic gain control
circuits are configured to compare an incoming signal to a
threshold value.
50. The system of claim 43, wherein the automatic gain control
circuits each includes a variable gain amplifier, a coupler, a
detector, and a loop filter.
51. A method of tracking inventory, the method comprising:
positioning a plurality of transceivers in a first region, each
transceiver comprising one or more antennas communicatively coupled
to a communication station communicatively coupled to communication
circuitry; positioning an interrogator unit remotely from the
plurality of transceivers, the interrogator unit being
communicatively coupled to the plurality of transceivers; and
positioning one or more items having one or more radio frequency
identification (RFID) tags attached thereto in the first region,
the one or more RFID tags being configured to communicate
wirelessly with one or more of the plurality of transceivers,
thereby identifying at least some of the one more RFID tags.
52. The method of claim 51, wherein the plurality of transceivers
are configured to communicate via a spread spectrum signal.
53. The method of claim 51, wherein the interrogator unit comprises
an adjustment circuitry and processing circuitry, the interrogator
unit being housed in a unit separate from the plurality of
transceivers.
54. The method of claim 53, wherein the adjustment circuitry
comprises an automatic gain control circuit configured to compare
an incoming signal to a threshold value.
55. The method of claim 54, wherein the automatic gain control
circuit includes a variable gain amplifier, a coupler, a detector,
and a loop filter.
56. The method of claim 51, wherein the communication station
comprises a low noise amplifier communicatively coupled to one or
more of the one or more antennas to increase a power level of a
received signal.
57. The method of claim 51, wherein the communication circuitry
comprises RF coaxial cable.
Description
TECHNICAL FIELD
[0001] The present invention relates to wireless communication
systems, interrogators and methods of communicating within a
wireless communication system.
BACKGROUND OF THE INVENTION
[0002] Electronic identification systems typically comprise two
devices which are configured to communicate with one another.
Preferred configurations of the electronic identification systems
are operable to provide such communications via a wireless
medium.
[0003] One such configuration is described in U.S. patent
application Ser. No. 08/705,043, filed Aug. 29, 1996, assigned to
the assignee of the present application, and incorporated herein by
reference. This application discloses the use of a radio frequency
(RF) communication system including communication devices. The
disclosed communication devices include an interrogator and a
remote transponder, such as a tag or card. Another example of a
wireless communication system including a backscatter system is
described in U.S. Pat. No. 5,649,296 to MacLellan et al. which is
also incorporated herein by reference.
[0004] Such communication systems can be used in various
applications such as identification applications. The interrogator
is configured to output a polling or interrogation signal which may
comprise a radio frequency signal including a predefined
interrogation code using which the interrogator may address remote
transponders. The remote transponders of such a communication
system are operable to transmit an identification signal responsive
to receiving an appropriate polling or interrogation signal.
[0005] More specifically, the appropriate transponders are
configured to recognize the predefined code. The transponders
receiving the code can subsequently output a particular
identification signal which is associated with the transmitting
transponder. Following transmission of the polling signal, the
interrogator is configured to receive the identification signals
enabling detection of the presence of corresponding
transponders.
[0006] Such communication systems are useable in identification
applications such as inventory or other object monitoring. For
example, a remote identification device can be attached to an
object of interest. Responsive to receiving the appropriate polling
signal, the identification device is equipped to output an
identification signal. Generating the identification signal
identifies the presence or location of the identification device
and the article or object attached thereto.
[0007] It may be desired to communicate with remote communication
devices located at greater distances in particular applications.
Such areas may exceed the range of the communication system.
Typical conventional arrangements require the utilization of
numerous interrogators for communication with the remote
communication devices located in such spaced areas. Alternatively,
the movement of a single interrogator from one area to another is
required.
SUMMARY OF THE INVENTION
[0008] The present invention provides wireless communication
systems, interrogators and methods of communicating within a
wireless communication system.
[0009] According to one aspect of the -present invention, a
wireless communication system comprises at least one remote
communication device configured to communicate a return link
wireless signal. The return link wireless signal comprises a radio
frequency signal in certain aspects of the invention.
[0010] The wireless communication system in some embodiments
includes an interrogator having a communication station,
communication circuitry and a housing. The communication station is
configured to receive the return link wireless signal and to
generate a return link communication signal corresponding to the
return link wireless signal. The communication circuitry is
provided to couple with the communication station and to
communicate the return link communication signal. The housing is
remotely located with respect to the communication station and
includes circuitry configured to receive the return link
communication signal from the communication circuitry and to
process the return link communication signal.
[0011] In one configuration, the housing includes automatic gain
control circuitry configured to adjust the power level of the
return link communication signals. Amplifiers can be provided
within one or both of the interrogator housing and the
communication station to increase the power level of the return
link communication signals. Plural communication stations and
plural communication circuits are coupled with a single
interrogator housing in some embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Preferred embodiments of the invention are described below
with reference to the following accompanying drawings.
[0013] FIG. 1 is a block diagram of an exemplary communication
system according to one embodiment of the present invention.
[0014] FIG. 2 is a front view of a wireless remote communication
device according to one embodiment of the invention.
[0015] FIG. 3 is a front view of an employee badge according to
another embodiment of the invention.
[0016] FIG. 4 is a functional block diagram of a transponder
included in the remote communication device of FIG. 2.
[0017] FIG. 5 is a functional block diagram of one embodiment of a
portion of an interrogator of the invention.
[0018] FIG. 6 is a functional block diagram of one embodiment of an
RF section of the interrogator of FIG. 5.
[0019] FIG. 7 is a functional block diagram of exemplary
communication circuitry shown in FIG. 1.
[0020] FIG. 8 is a functional block diagram of exemplary transmit
circuitry of a communication station shown in FIG. 1.
[0021] FIG. 9 is a functional block diagram of exemplary receive
circuitry of the communication station shown in FIG. 1.
[0022] FIG. 10 is a functional block diagram of exemplary
adjustment circuitry within a housing of the interrogator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] This disclosure of the invention is submitted in furtherance
of the constitutional purposes of the U.S. Patent Laws "to promote
the progress of science and useful arts" (Article 1, Section
8).
[0024] FIG. 1 illustrates a communication system 10 embodying the
invention. Communication system 10 comprises an electronic
identification system in the embodiment described herein.
Communication system 10 may be configured for backscatter
communications as described in detail below. Other communication
protocols are utilized in other embodiments.
[0025] The depicted communication system 10 includes a plurality of
remote communication devices 12 and an interrogator 26. Wireless
(e.g., radio frequency) communications can occur intermediate
remote communication devices 12 and interrogator 26 for use in
identification systems and product monitoring systems as exemplary
applications.
[0026] Remote communication devices 12 can include radio frequency
identification devices (RFID) or remote intelligent communication
(RIC) devices in the embodiments described herein. Exemplary remote
communication devices 12 are disclosed in U.S. patent application
Ser. No. 08/705,043. Plural remote communication devices 12
typically communicate with interrogator 26.
[0027] In one embodiment, remote communication devices 12
individually comprise a wireless identification device such as the
MicroStamp.TM. integrated circuit available from Micron
Communications, Inc., 3176 S. Denver Way, Boise, Id. 83705. Such a
remote communication device 12 can be referred to as a tag or card
as illustrated and described below.
[0028] Remote communication devices 12 are configured to interface
with interrogator 26 using a wireless medium in one embodiment.
More specifically, communications intermediate remote communication
devices 12 and interrogator 26 occur via an electromagnetic link,
such as a radio frequency link in the described embodiment.
Exemplary communications occur at microwave frequencies. Other
configurations for communication are possible.
[0029] As described in detail below, interrogator 26 is configured
to output forward link communications. Further, interrogator 26 is
operable to receive reply or return link communications from remote
communication devices 12 responsive to the outputting of forward
link communications. In accordance with the above, forward link
communications and return link communications comprise wireless
signals, such as radio frequency signals, in the described
embodiment. Other forms of electromagnetic communication, such as
infrared, acoustic, etc., are possible.
[0030] The depicted configuration of communication system 10
illustrates interrogator 26 communicating with a plurality of
remote communication devices 12 located in a plurality of
corresponding communication a ranges 15, also referred to as read
zones.-. The depicted interrogator 26 includes a housing 14 coupled
with a plurality of communication paths 17 individually positioned
and configured to communicate with remote communication devices 12
located within corresponding communication ranges 15. Communication
paths 17 individually include communication circuitry 106 and a
corresponding communication station 120 in the described
embodiment.
[0031] As described in detail below, housing 14 of interrogator 26
includes circuitry (not shown in FIG. 1) configured to generate a
plurality of forward link communication signals. Such forward link
communication signals are communicated within communication
circuitry 106 of selected communication paths 17 to respective
communication stations 120 having antennas X1, X2 . . . XN. Such
communication stations 120 are configured to emit forward link
wireless signals 27 which correspond to the forward link
communication signals. In addition, communication stations 120 can
individually emit a continuous wave signal during backscatter mode
of operations of communication system 10. Further transmit
operations of interrogator 26 are described in a copending U.S.
patent application filed the same day as the present application,
having the title "Wireless Communication Systems, Interrogators and
Methods of Communicating Within a Wireless Communication System",
assigned to assignee hereof, having attorney docket number
MI40-179, naming David Ovard and Roy Greeff as inventors, and
incorporated herein by reference.
[0032] As illustrated, communication stations 120 are preferably
configured to radiate the forward link wireless signals 27 to
associated remote communication devices 12 within respective
communication ranges 15. Responsive to the reception of forward
link wireless signals 27, individual remote communication devices
12 are operable to reply with return link wireless signals 29.
[0033] Communication stations 120 also include plurai receive
antennas R1, R2 . . . RN which are configured to receive return
link wireless signals 29 from remote communication devices 12.
Communication stations 120 of interrogator 26 preferably
individually include receive circuitry configured to receive the
return link wireless signals 29 and apply return link communication
signals to interrogator housing 14 for processing as described in
detail below. In particular, communication stations 120 generate
return link communication signals corresponding to the received
return link wireless signals. Communication circuits 106
communicate the return link communication signals to interrogator
housing 14.
[0034] FIG. 1 is an illustrative representation of wireless
communication system 10. More specifically, communication ranges 15
may be spread out over a relatively large geographic range. The
wireless communication system 10 of the present invention provides
the advantages of utilizing a single interrogator housing 14 and
associated communication circuitry therein to communicate with
remote communication devices 12 located in plural communication
ranges 15.
[0035] Further, wireless communication system 10 of the present
invention permits a single interrogator housing 14 and associated
circuitry to service multiple communication ranges 15 which may be
located several hundred feet apart or further, or in harsh
environments. For example, one interrogator housing 14 can be
utilized to service read zones or communication ranges 15 within
spaced warehouses. Individual communication ranges 15 may be spaced
from one another at distances which exceed the communication range
of the devices. Additionally, adjacent communication ranges 15 may
overlap in some applications.
[0036] As previously mentioned, individual communication paths 17
include communication circuits 106 and associated communication
stations 120. Communication stations 120 are preferably positioned
to communicate with respective communication ranges 15.
Communication circuits 106 are configured in the depicted
arrangement to communicate forward link communication signals from
interrogator housing 14 to corresponding communication stations
120. Communication circuits 106 are also configured to communicate
return link communication signals received within corresponding
communication stations 120 to interrogator housing 14.
[0037] In the described embodiment, communication circuits 106 are
located outside of interrogator housing 14. In addition,
communication stations 120 are remotely located with respect to
interrogator housing 14. Communication stations 120 are
individually configured to receive forward link communication
signals from interrogator housing 14 via communication circuitry
106 and radiate forward link wireless signals 27 corresponding to
the forward link communications signals using associated antennas
X1, X2 . . . XN.
[0038] Further, communication stations 120 are individually
configured to receive return link wireless signals 29 from remote
communication devices 12 using associated antennas designated R1,
R2 . . . RN. Communication stations 120 output return link
communication signals corresponding to the return link wireless
signals 29 to interrogator housing 14 using respective
communication circuits 106.
[0039] Individual ones of communication stations 120 may be located
at varying distances from interrogator housing 14 depending upon a
particular application. Interrogator housing 14, communication
circuits 106 and communication stations 120 are configured to
communicate the forward link communication signals and return link
communication signals intermediate interrogator housing 14 and
respective communication stations 120 regardless of the varying
distances.
[0040] Remote communication devices 12 are individually configured
for wireless communications in one embodiment as described in
detail below. Such remote communication devices 12 receive the
forward link wireless signals 27 and respond with the return link
wireless signals 29 which are received within communication
stations 120.
[0041] In one embodiment, return link wireless signals 29 are
encoded with information that uniquely identifies or labels the
particular device 12 that is transmitting so as to identify any
object, animal or person with which communication device 12 is
associated. More specifically, remote devices 12 are configured to
output an identification signal within return link wireless signals
29 responsive to receiving forward link wireless signals 27.
Interrogator 26 is configured to receive and recognize the
identification signal within the return or return link
communications 29. The identification signal can be utilized to
identify the particular transmitting remote communication device
12.
[0042] Referring to FIG. 2, one embodiment of a remote
communication device 12 is illustrated. The depicted communication
device 12 includes a transponder 16 having a receiver and a
transmitter as described below. Communication device 12 further
includes a power source 18 connected to transponder 16 to supply
operational power to transponder 16. In the illustrated embodiment,
transponder 16 is in the form of an integrated circuit 19. However,
in alternative embodiments, all of the circuitry of transponder 16
is not necessarily included in integrated circuit 19.
[0043] Power source 18 is a thin film battery in the illustrated
embodiment, however, in alternative embodiments, other forms of
power sources can be employed. If the power source 18 is a battery,
the battery can take any suitable form. Preferably, the battery
type will be selected depending on weight, size and life
requirements for a particular application. In one embodiment,
battery 18 is a thin profile button-type cell forming a small, thin
energy cell more commonly utilized in watches and small electronic
devices requiring a thin profile. A conventional button-type cell
has a pair of electrodes, an anode formed by one face and a cathode
formed by an opposite face. In an alternative embodiment, the
battery comprises a series connected pair. of button type
cells.
[0044] Communication device 12 further includes at least one
antenna connected to transponder 16 for wireless transmission and
reception. In the illustrated embodiment, communication device 12
includes at least one receive antenna 44 connected to transponder
16 for radio frequency reception by transponder 16, and at least
one transmit antenna 46 connected to transponder 16 for radio
frequency transmission by transponder 16. The described receive
antenna 44 comprises a loop antenna and the transmit antenna 46
comprises a dipole antenna.
[0045] Remote communication device 12 can be included in any
appropriate housing or packaging. FIG. 2 shows but one example of a
housing in the form of a miniature housing 11 encasing device 12 to
define a tag which can be supported by an object (e.g., hung from
an object, affixed to an object, etc.).
[0046] Referring to FIG. 3, an alternative housing is illustrated.
FIG. 3 shows a housing in the form of a card 13. Card 13 preferably
comprises plastic or other suitable material. Plastic card 13
houses communication device 12 to define an employee identification
badge including the communication device. 12. In one embodiment,
the front face of card 13 has visual identification features such
as an employee photograph or a fingerprint in addition to
identifying text.
[0047] Although two particular types of housings have been
disclosed, the communication device 12 can be included in any
appropriate housing. Communication device 12 is preferably of a
small size that lends itself to applications employing small
housings, such as cards, miniature tags, etc. Larger housings can
also be employed. The communication device 12, provided in any
appropriate housing, can be supported from or attached to an object
in any desired manner.
[0048] FIG. 4 is a high level circuit schematic of an embodiment of
transponder 16 utilized in remote communication devices 12. In the
embodiment shown in FIG. 4, transponder 16 is implemented within a
monolithic integrated circuit 19. In the illustrated embodiment,
integrated circuit 19 comprises a single die, having a size of
209.times.116 mils.sup.2, including a receiver 30, a transmitter
32, a microcontroller or microprocessor 34, a wake up timer and
logic circuit 36, a clock recovery and data recovery circuit 38,
and a bias voltage and current generator 42. Integrated circuit 19
preferably- comprises a small Outline integrated circuit (SOIC)
package. Receiver 30 and transmitter 32 comprise wireless
communication circuitry configured to communicate 4 wireless
signals.
[0049] In one embodiment, communication devices 12 switch between a
"sleep" mode of operation, and higher power modes to conserve
energy and extend battery life during periods of time where no
interrogation signal 27 is received by devices 12, using the wake
up timer and logic circuitry 36.
[0050] In one embodiment, a spread spectrum processing circuit 40
is included in transponder 16. In this embodiment, signals
transmitted and received by interrogator 26 and signals transmitted
and received by communication device 12 are modulated spread
spectrum signals. Many modulation techniques minimize required
transmission bandwidth. However, the spread spectrum modulation
techniques employed in the illustrated embodiment require a
transmission bandwidth that is up to several orders of magnitude
greater than the minimum required signal bandwidth. Although spread
spectrum modulation techniques are bandwidth inefficient in single
user applications, they are advantageous where there are multiple
users, as is the case with the preferred radio frequency
identification communication system 10 of the present
invention.
[0051] The spread spectrum modulation technique of the illustrated
embodiment is advantageous because the interrogator signal can be
distinguished from other signals (e.g., radar microwave ovens,
etc.) operating at the same frequency. The spread spectrum signals
transmitted by communication device 12 and interrogator 26 are
pseudo random and have noise-like properties when compared with the
digital command or reply. The illustrated embodiment employs direct
sequence spread spectrum (DSSS) modulation.
[0052] In operation, interrogator 26 sends out a command that is
spread a around a certain center frequency (e.g, 2.44 GHz). After
the interrogator transmits the command, and is expecting a
response, the interrogator switches to a continuous wave (CW) mode
for backscatter communications. In the continuous wave mode,
interrogator 26 does not transmit any information. Instead, the
interrogator just transmits a radio frequency continuous wave
signal. In the described embodiment, the continuous wave signal
comprises a radio frequency 2.44 GHz carrier signal. In other
words, the continuous wave signal transmitted by interrogator 26 is
not modulated. After communication device 12 receives the forward
link communication from interrogator 26, communication device 12
processes the command.
[0053] If communication device 12 is operating in a backscatter
mode, device 12 modulates the continuous wave signal providing a
modulated continuous wave signal to communicate return link
communication 29 responsive to reception of forward communication
signal 27. Communication device 12 may modulate the continuous wave
signal according to a subcarrier or modulation signal. Modulation
by device 12 comprises selective reflection of the continuous wave
signal. In particular, device 12 alternately reflects or does not
reflect the continuous wave signal from the interrogator to send
its reply. For example, in the illustrated embodiment, two halves
of a dipole antenna are either shorted together or isolated from
each other to send a reply. Alternatively, communication device 12
can communicate in an active mode.
[0054] The modulated continuous wave signal communicated from
device 12 comprises a carrier component and plural side band
components about the carrier component resulting from the
modulation. More specifically, the modulated continuous wave signal
output from device 12 includes a radio frequency continuous wave
signal having a first frequency (2.44 GHz), also referred to as a
carrier component, and a subcarrier modulation signal having a
different frequency (e.g., 600 kHz) which provides the side band
components. In particular, the side band components are at +/-600
kHz of the carrier component.
[0055] In one embodiment, the clock for transponder 16 is extracted
from the incoming message itself by clock recovery and data
recovery circuitry 38. This clock is recovered from the incoming
message and used for timing for microcontroller 34 and all the
other clock circuitry on the chip and also for deriving the
transmitter carrier or the subcarrier, depending on whether the
transmitter is operating in active mode or backscatter mode.
[0056] In addition to recovering a clock, the clock recovery and
data recovery circuit 38 also performs data recovery on valid
incoming signals. The valid spread spectrum incoming signal is
passed through the spread spectrum processing circuit 40 which
extracts the actual ones and zeros of data from the incoming
signal. More particularly, the spread spectrum processing circuit
40 takes chips from the spread spectrum signal and reduces
individual thirty-one chip sections down to a bit of one or zero,
which is passed to microcontroller 34.
[0057] Microcontroller 34 includes a serial processor, or I/O,
facility that receives the bits from spread spectrum processing
circuit 40. The microcontroller 34 performs further error
correction. More particularly, a modified hamming code is employed,
wherein each eight bits of data is accompanied by five check bits
used by the microcontroller 34 for error correction.
Microcontroller 34 further includes a memory, and after performing
the data correction, microcontroller 34 stores bytes of the data
bits in memory. These bytes contain a command sent by the
interrogator 26. Microcontroller 34 is configured to respond to the
command.
[0058] For example, interrogator 26 may send a command requesting
that any communication device 12 in the field respond with the
device's identification number. Status information can also be
returned to interrogator 26 from remote communication devices 12.
Additionally, remote communication devices 12 may be individually
coupled with a peripheral device and information regarding the
peripheral device may also be communicated.
[0059] Communications from interrogator 26 (i.e., forward link
communications) and devices 12 (i.e., return link communications)
have a similar format. More particularly, the forward and return
communications individually include a calibration period, preamble
and Barker or start code which are followed by actual data in the
described embodiment. The incoming forward link message and
outgoing return preferably also include a check sum or redundancy
code so that transponder 16 or interrogator 26 can confirm receipt
of the entire forward message or return message.
[0060] Communication devices 12 typically include an identification
sequence identifying the particular tag or device 12 sending the
return link signal. Such implements the identification operations
of communication system 10.
[0061] After sending a command, interrogator 26 sends the
unmodulated continuous wave signal. Return link data can be
Differential Phase Shift Key (DPSK) modulated onto the continuous
wave signal using a square wave subcarrier with a frequency of
approximately 600 kHz (e.g., 596.1 kHz in one embodiment). A data 0
corresponds to one phase and data 1 corresponds to another, shifted
180 degrees from the first phase.
[0062] The subcarrier or modulation signal is used to modulate
antenna impedance of transponder 16 and generate the modulated
continuous wave signal. For a simple dipole, a switch between the
two halves of the dipole antenna is opened and closed. When the
switch is closed, the antenna becomes the electrical equivalent of
a single half-wavelength antenna that reflects a portion of the
power being transmitted by the interrogator. When the switch is
open, the antenna becomes the electrical equivalent of two
quarter-wavelength antennas that reflect very little of the power
transmitted by the interrogator. In one embodiment, the dipole
antenna is a printed microstrip half-wavelength dipole antenna.
[0063] Referring to FIG. 5, one embodiment of interrogator housing
14 and the internal circuitry therein is illustrated. The depicted
interrogator housing 14 generally includes a microcontroller 70, a
field programmable gate array (FPGA) 72 and RF section 74. In the
depicted embodiment, microcontroller 70 comprises a MC68340
microcontroller available from Motorola, Inc. FPGA 72 comprises an
XC4028 device available from Xilinx, Inc. Further details of
components 70, 72 and 74 are described below.
[0064] Interrogator housing 14 also includes RAM 76, EPROM 78 and
flash memory 80 coupled with microcontroller 70 in the depicted
embodiment. Microcontroller 70 is configured to access an
applications program from EPROM 78 for controlling the interrogator
26 and interpreting responses from remote communication devices
12.
[0065] The processor of microcontroller 70 is configured to control
communication operations with remote communication devices 12
during normal modes of operation. The applications program can also
include a library of radio frequency identification device
applications or functions. These functions effect radio frequency
communications between interrogator 26 and associated remote
communication devices 12.
[0066] Microcontroller 70 includes circuitry configured to generate
forward link communication signals to be communicated to remote
communication devices 12. Further, microcontroller 70 is also
configured to process return link communication signals received
from remote communication devices 12. Alternatively, an external
processor or computer (not shown) can be coupled with interrogator
26 to process the return link communication signals.
[0067] RF section 74 is configured to implement wireless (e.g.,
radio frequency) communications with remote communication devices
12. DPSK modulation techniques can be utilized for communications
intermediate devices 12 and interrogator 26. RF section 74 can
include downconversion circuitry for generating in-phase (I) and
quadrature (Q) signals which contain the DPSK modulated subcarrier
for application to FPGA 72 during return link communications.
[0068] Analog to digital (A/D) converters 82, 84 provide received
analog RF signals into a digital format for application to FPGA 72.
In particular, analog to digital converters 82, 84 are implemented
intermediate FPGA 72 and RF section 74 for both in-phase (I) and
quadrature (Q) communication lines.
[0069] An additional connection 85 is provided intermediate FPGA 72
and RF section 74 for forward link communication signals. Digital
signals to be communicated from interrogator 26 are Outputted from
FPGA 72 via connection 85 and converted to RF forward link
communication signals by RF section 74. Connection 85 can
additionally be utilized to transmit phase lock loop (PLL)
information and other necessary communication information. During
forward link communications, FPGA 72 is configured- to provide
communication packets received from microcontroller 70 into a
proper format for application to RF section 74 for communication.
FPGA 72 is configured to demodulate return link communications
received from remote communication devices 12 via RF section 74.
FPGA 72 is configured in the described embodiment to perform I and
Q combination operations during receive operations. The described
FPGA 74 further includes delay and multiplication circuitry to
remove the subcarrier. FPGA 74 can also include bit synchronization
circuitry and lock detection circuitry. Data, clock and lock
detection signals generated within FPGA 74 are applied to
microcontroller 70 for processing in the described embodiment.
[0070] Microcontroller 70 is configured to control operations of
interrogator 26 including outputting of forward link communications
and receiving return link communications. EPROM 78 is configured to
store original applications program codes and settings selected for
the particular application of communication system 10. Flash memory
80 is configured to receive software code updates which may be
forwarded to interrogator 26.
[0071] RAM device 76 is configured to store data during operations
of communication system 10. Such data can include information
regarding communications with associated remote communication
devices 12 and status information of interrogator 26 during normal
modes of operation.
[0072] In accordance with the described embodiment, RF section 74
of interrogator housing 14 is coupled with plural communication
circuits 106 as shown in FIG. 1. Microcontroller 70 is configured
to select an appropriate communication circuit 106 to implement
forward link and return link communications with desired remote
communication devices 12 within respective communication ranges 15.
RF section 74 includes switching circuitry configured to
selectively couple one of communication circuits 106 with RF
circuitry within RF section 74 as well as connection 85 and analog
to digital converters 82, 84. Such switching is controlled by
microcontroller 70 depending upon the individual communication
range 15 presently communicating with interrogator 26.
[0073] For example, microcontroller 70 can initially select one of
communication paths 17 to provide communications of interrogator 26
with remote communication devices 12 within the communication range
15 which corresponds to the originally selected path 17.
Thereafter, microcontroller 70 can select another one of
communication paths 17 using switching circuitry of RF section 74
to provide communications of interrogator 26 with remote
communication devices 12 within the communication range 15 which
corresponds to the newly selected path 17.
[0074] Exemplary switching operations of the communication paths 17
can be performed under control of microcontroller 70 after
individual forward link communications to respective communication
paths 17 and corresponding communication ranges 15 occur in one
operational mode. Alternatively, microcontroller 70 can switch
-communication paths 17 after forward link communications and
return link communications occur with a desired communication range
15. Other communication switching protocols can be utilized in
other configurations.
[0075] Referring to FIG. 6, an exemplary configuration of RF
circuitry 74 is illustrated. The depicted RF circuitry 74 includes
a transmit path 86 and a receive path 87. Communication paths 86,
87 are coupled with RF control circuitry 97. Transmit path 86 is
additionally coupled with FPGA 72 shown in FIG. 5 via connection
85. Receive path 87 is coupled with analog to digital converters
82, 84 shown in FIG. S via the I and Q connection lines.
[0076] Forward link communication signals are communicated via path
86 while return link communication signals are communicated via
path 87. In the depicted embodiment, RF section 74 additionally
includes a transmitter 90 and driver amplifier 92 within transmit
data path 86. Receive path 87 includes a receiver 95 and adjustment
circuitry 96 in the described embodiment.
[0077] Transmitter 90 is configured to implement radio frequency
modulation operations in the described embodiment using the forward
link communication signal previously generated. The modulated
forward link communication signal outputted from transmitter 90 is
applied to driver amplifier 92. Driver amplifier 92 is configured
to increase the power level of the forward link communication
signal. In typical implementations, driver amplifier 92 is
configured to provide a gain of approximately 10-15 dB. Amplifiers
providing more or less gain may be utilized depending upon the
specific application and expected loss within communication
circuitry 106.
[0078] Thereafter, driver amplifier 92 applies the amplified
forward link communication signal to an input of a selected
communication circuit 106 responsive to control from
microcontroller 70 and using RF control 97. In the described
configuration, RF control 97 comprises switching circuitry
configured to selectively couple transmit path 86 and receive path
87 with a selected one (or ones) of communication circuitry 106. RF
control 97 implements the switching operations to selectively
couple communication circuits 106 with transmit path 86 and receive
path 87 responsive to control from microcontroller 70.
[0079] Depending upon the particular application for use of
communication system 10 or location of associated communication
stations 120, communication circuits 106 can be individually
implemented in one of a variety of configurations. Communication
circuits 106 are located outside of interrogator housing 14 and are
coupled with driver amplifier 92 and adjustment circuitry 96 via RF
control 97. Communication circuits 106 are individually configured
to communicate the forward link communication signals and return
link communication signals within the corresponding communication
path 17 intermediate housing 14 and the corresponding communication
station 120.
[0080] In some embodiments, communication circuits 106 individually
comprise coaxial RF cable. Depending upon the distance intermediate
housing 14 and the corresponding communication station 120,
low-loss coaxial RF cable may be utilized. Further, amplifiers
having increased gain may be utilized in addition to the described
amplifiers to increase the power level of the forward link
communication signals and return link communication signals being
communicated within communication circuitry 106. Various
combinations of components can be utilized depending upon the
particular application and associated loss to ensure that the
forward link communication signals and return link communication
signals outputted from communication circuitry 106 are at a power
level sufficiently above the thermal noise.
[0081] Referring to FIG. 7, an alternative configuration of
communication circuitry 106 which may be utilized within individual
communication paths 17 is illustrated. The depicted communication
circuitry 106 includes a plurality of transceivers 108, 109
individually coupled with one of interrogator housing 14 and one of
communication stations 120. Transceivers 108, 109 operate to
communicate forward link communication signals and return link
communication signals intermediate interrogator housing 14 and the
corresponding communication station 120. In an exemplary
configuration, transceivers 108, 109 are configured to communicate
utilizing electromagnetic signals, such as radio frequency signals.
Such signals are preferably communicated outside of the frequency
band of forward link wireless signals 27 and return link wireless
signals 29.
[0082] Referring to FIG. 8, an exemplary embodiment of one of
communication stations 120 is illustrated. The depicted
communication station 120 is coupled with communication circuitry
106. The depicted communication station 120 includes transmit
circuitry 121 and receive circuitry 123. Transmit circuitry 121 is
coupled with the XI antenna 126 and receive circuity 123 is coupled
with the RI antenna 128. One configuration of transmit circuitry
121 is described 44 with reference to FIG. 8, and one configuration
of receive circuitry 123 is described with reference to FIG. 9.
[0083] The depicted transmit circuitry 121 shown in FIG. 8 includes
adjustment circuitry 122, a power amplifier 124 and a potentiometer
137. Forward link communication signals received from communication
circuitry 106 are applied to transmit circuitry 121. Forward link
wireless signals 27 corresponding to the forward link communication
signals are radiated using antenna 126. Return link wireless
signals 29 are received by R1 antenna 128 and applied to receive
circuitry 123. Receive circuitry 123 outputs return link
communication signals corresponding to the return link wireless
signals to communication circuitry 106.
[0084] Referring to transmit operations, forward link communication
signals from communication circuitry 106 are initially applied to
adjustment circuitry 122 within transmit circuitry 121. Adjustment
circuitry 122 is configured to receive the forward link
communication signals from communication circuitry 106 and to
adjust at least one electrical characteristic of the forward link
communication signals. In an exemplary configuration, adjustment
circuitry 120 is configured to adjust the power level of the
forward link communication signal.
[0085] More specifically, the depicted adjustment circuitry 122
comprises automatic gain control (AGC) circuitry. In particular,
the automatic gain control circuitry is configured to monitor the
power of the forward link communication signals, compare the power
with a predetermined threshold value and adjust the power of the
forward link communication signals responsive to the
comparison.
[0086] Adjustment circuitry 122 comprising automatic gain control
circuitry includes a variable gain amplifier 130, a coupler 132, a
detector 134 and a loop filter 136 in an exemplary configuration.
Forward link communication signals received from communication
circuitry 106 are applied to coupler 132. Coupler 132 directs a
portion of the power of the forward link communication signals to
detector 134 which converts the received power into a voltage.
[0087] The converted voltage is directed to loop filter 136. Loop
filter 136 is additionally coupled with a potentiometer 137 in the
described configuration. Potentiometer 137 can be utilized to
provide an adjustable threshold reference voltage. Potentiometer
137 may be varied to fine tune individual communication stations
120 depending upon the distance intermediate the communication
station 120 and interrogator housing 14 (e.g., the threshold
reference voltage can be varied to accommodate varying amounts of
loss intermediate individual communication stations 120 and the
corresponding interrogator housing 14).
[0088] Loop filter 136 compares the received voltage from detector
134 representing the power level of the received forward link
communication signals with the adjustable reference voltage
determined by potentiometer 137. Thereafter, loop filter 136
outputs a control signal to variable gain amplifier 130 to adjust
the power of the forward link communication signals applied to
power amplifier 124 responsive to the comparison.
[0089] Preferably, variable gain amplifier 130 provides forward
link communication signals to power amplifier 124 which have a
substantially constant input power level as determined by
potentiometer 137. Such is preferred to provide linear operation of
power amplifier 124. Power amplifier 124 amplifies the forward link
communication signals. It is preferred to provide forward link
communication signals of approximately 1 mW to power amplifier 124
which comprises a 1 watt amplifier in one embodiment operable to
provide approximately 30 dB of gain.
[0090] The output of power amplifier 124 is applied to the Xi
antenna 126. Preferably, the distance intermediate power amplifier
124 and the XI antenna 126 is minimized. XI antenna 126 is operable
to receive the amplified forward link communication signals 27 from
power amplifier 124 and to radiate forward link wireless signals 27
corresponding to the forward link communication signals. Xi antenna
126 of the corresponding communication station 120 is preferably
positioned to radiate the forward link wireless signals 27 within
at least one of the plurality of communication ranges 15.
[0091] Referring to FIG. 9, details of receive circuitry 123 are
illustrated. Receive circuitry 123 is coupled with communication
circuitry 106 and R1 antenna 128. The illustrated receive circuitry
123 includes a low noise amplifier (LNA) 140 coupled with an
amplifier 142. The R1 antenna 128 is coupled with low noise
amplifier 140. R1 antenna 128 receives return link wireless signals
29 from remote communication devices 12 located within one or more
of communication ranges 15. Antenna 128 outputs return link
communication signals corresponding to the return link wireless
signals 29 to low noise amplifier 140.
[0092] Preferably, the distance intermediate the R1 antenna 128 and
the low noise amplifier 140 is minimized. The low noise amplifier
140 is configured to receive the return link communication signals
and increase the power of the return link communication signals.
Such amplification preferably increases the level of the return
link communication signals to a sufficient degree above the thermal
noise.
[0093] The return link communication signals are thereafter applied
to amplifier 142 which has a gain to further increase the power
level of the return link communication signals. In an exemplary
configuration, amplifiers 140, 142 individually have a gain of
approximately 15 dB. Receive circuitry 123 is merely exemplary and
can be configured to provide more or less gain depending upon the
expected loss within communication circuitry 106. In one
configuration, amplifier 142 also comprises a low noise
amplifier.
[0094] Preferably, receive circuitry 123 and communication
circuitry 106 are configured to provide return link communication
signals to the interrogator housing 14 having a sufficient
signal-to-noise ratio. As previously described, communication
circuitry 106 comprising coaxial RF cable, transceivers or other
configurations communicates the return link communication signals
to interrogator housing 14.
[0095] Referring to FIG. 10, return link communication signals
received within communication station 120 and communicated using
communication circuitry 106 are applied to RF control 97 within
interrogator housing 14. RF control 97 operates to selectively
couple one of communication circuits 106 with receive path 87
responsive to control from microcontroller 70 as described
above.
[0096] Return link communication signals from RF control 97 are
applied to adjustment circuitry 96 within housing 14. Adjustment
circuitry 96 is configured to receive the return link communication
signals from RF control 97 and to adjust at least one electrical
characteristic of the return link communication signals. In an
exemplary configuration, adjustment circuitry 96 is configured to
adjust the power level of the return link communication
signals.
[0097] More specifically, the depicted adjustment circuitry 96
comprises automatic gain control (AGC) circuitry. The automatic
gain control circuitry is configured to monitor the power of the
return link communication signals, compare the power with a
threshold value and adjust the power of the return link
communication signals responsive to the comparison.
[0098] Adjustment circuitry 96 comprising automatic gain control
circuitry includes a variable gain amplifier 150, a coupler 152, a
detector 154 and a loop filter 156. Return link communication
signals received from RF control 97 are applied to variable gain
amplifier 150 which adjusts the power level of the return link
communication signals responsive to control from loop filter 156.
Coupler 152 directs a portion of the power of the return link
communication signals to detector 154 which converts the received
power into a voltage. The converted voltage is directed to loop
filter 156.
[0099] Loop filter 156 compares the received voltage from detector
154 representing the power level of the return link communication
signals with a reference voltage. Thereafter, loop filter 156
outputs a control signal to variable gain amplifier 150 which
adjusts the power of the return link communication signals applied
to receiver 95 responsive to the comparison. Although not shown,
circuitry may be provided to permit adjustment of the reference
voltage of loop filter 156 similar to that of potentiometer 137 of
communication station 120.
[0100] Preferably, variable gain amplifier 150 provides return link
communication signals to receiver 95 which have a substantially
constant or fixed input level. In one embodiment, adjustment
circuitry 96 is configured to output rerun link communication
signals having a power level of approximately 3 dBm. Such is
preferred to avoid saturation of components (e.g., downconversion
circuitry) within receiver 95. The return link communication
signals may be processed by microcontroller 70 or other circuitry
following demodulation of the return link communication
signals.
[0101] In compliance with the statute, the invention has been
described in language more or less specific as to structural and
methodical features. It is to be understood, however, that the
invention is not limited to the specific features shown and
described, since the means herein disclosed comprise preferred
forms of putting the invention into effect. The invention is,
therefore, claimed in any of its forms or modifications within the
proper scope of the appended claims appropriately interpreted in
accordance with the doctrine of equivalents.
* * * * *