U.S. patent application number 09/363945 was filed with the patent office on 2001-12-06 for radio frequency identification devices, remote communication devices, wireless communication systems, and methods of indicating operation.
Invention is credited to TROSPER, SCOTT T..
Application Number | 20010048363 09/363945 |
Document ID | / |
Family ID | 23432393 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048363 |
Kind Code |
A1 |
TROSPER, SCOTT T. |
December 6, 2001 |
RADIO FREQUENCY IDENTIFICATION DEVICES, REMOTE COMMUNICATION
DEVICES, WIRELESS COMMUNICATION SYSTEMS, AND METHODS OF INDICATING
OPERATION
Abstract
The present invention provides radio frequency identification
devices, remote communication devices, wireless communication
systems, and methods of indicating operation. According to a first
aspect, a radio frequency identification device includes a
substrate; communication circuitry coupled with the substrate and
configured to receive wireless signals including spurious signals;
and indication circuitry coupled with the communication circuitry
and configured to output an indication signal to indicate reception
of the spurious signals within the communication circuitry. Another
aspect provides a method of indicating operation of a radio
frequency identification device including providing a radio
frequency identification device including communication circuitry
and indication circuitry; receiving wireless signals including
spurious signals using the communication circuitry; and emitting
human perceptible signals using the indication circuitry to
indicate the receiving spurious signals.
Inventors: |
TROSPER, SCOTT T.;
(MERIDIAN, ID) |
Correspondence
Address: |
WELLS ST JOHN ROBERTS GREGORY AND MATKIN
SUITE 1300
601 W FIRST AVENUE
SPOKANE
WA
992013828
|
Family ID: |
23432393 |
Appl. No.: |
09/363945 |
Filed: |
July 29, 1999 |
Current U.S.
Class: |
340/571 |
Current CPC
Class: |
G06K 19/0723 20130101;
G08B 13/1427 20130101; G08B 21/023 20130101; G08B 21/0227
20130101 |
Class at
Publication: |
340/571 |
International
Class: |
G08B 013/14 |
Claims
1. A radio frequency identification device comprising: a substrate;
communication circuitry coupled with the substrate and configured
to receive wireless signals including spurious signals; and
indication circuitry coupled with the communication circuitry and
configured to output an indication signal to indicate reception of
the spurious signals within the communication circuitry.
2. The radio frequency identification device according to claim 1
wherein the indication circuitry is configured to emit a human
perceptible signal to indicate the reception.
3. The radio frequency identification device according to claim 1
wherein the indication circuitry includes a light emitting device
configured to emit a human visible signal to indicate the
reception.
4. The radio frequency identification device according to claim 1
wherein the communication circuitry is configured to periodically
monitor for the reception of wireless signals.
5. The radio frequency identification device according to claim 1
wherein the control circuitry comprises a latch.
6. The radio frequency identification device according to claim 1
wherein the communication circuitry is configured to search for a
pseudo-random sequence of individual received wireless signals.
7. A remote communication device comprising: a substrate;
communication circuitry coupled with the substrate and configured
to receive a wireless signal, to process the wireless signal, and
to assert a first signal during the processing of the wireless
signal; control circuitry coupled with the communication circuitry
and configured to monitor the first signal, and to selectively
generate a second signal responsive to the first signal being
asserted for a predetermined period of time; and indication
circuitry coupled with the control circuitry and configured to
indicate reception of the wireless signal responsive to the second
signal.
8. The remote communication device according to claim 7 wherein the
indication circuitry is configured to emit a human perceptible
signal to indicate the reception.
9. The remote communication device according to claim 7 wherein the
communication circuitry is configured to periodically monitor for
the reception of a wireless signal.
10. The remote communication device according to claim 7 wherein
the indication circuitry is configured to indicate the reception of
the wireless signal including a spurious signal.
11. The remote communication device according to claim 7 wherein
the control circuitry comprises a filter configured to selectively
remove the first signal if it is asserted for less than the
predetermined period of time.
12. The remote communication device according to claim 7 wherein
the communication circuitry comprises radio frequency
identification device circuitry.
13. The remote communication device according to claim 7 wherein
the control circuitry comprises a latch.
14. A radio frequency identification device comprising: a
substrate; communication circuitry coupled with the substrate and
configured to receive wireless signals including spurious signals,
to process at least some of the received wireless signals, and to
assert signals responsive to the processing of the wireless signals
received within the communication circuitry; and indication
circuitry coupled with the communication circuitry and configured
to emit human perceptible signals indicating reception of the
spurious signals responsive to the assertion of the signals by the
communication circuitry.
15. The radio frequency identification device according to claim 14
wherein the indication circuitry is configured to emit human
visible signals to indicate the reception.
16. The radio frequency identification device according to claim 14
wherein the communication circuitry is configured to periodically
monitor for the reception of wireless signals.
17. The radio frequency identification device according to claim 14
further comprising control circuitry configured to control the
outputting of the human perceptible signals responsive to the
signals from the communication circuitry being asserted for a
predetermined period of time.
18. A wireless communication system comprising: an interrogator
configured to output a forward link wireless signal; and a radio
frequency identification device including: communication circuitry
configured to receive the forward link wireless signal and a
spurious wireless signal; and indication circuitry coupled with the
communication circuitry and configured to indicate reception of the
spurious wireless signal within the communication circuitry.
19. The wireless communication system according to claim 18 wherein
the indication circuitry is configured to emit a human perceptible
signal to indicate the reception.
20. The wireless communication system according to claim 18 wherein
the indication circuitry includes a light emitting device
configured to emit a human visible signal to indicate the
reception.
21. A method of indicating operation of a radio frequency
identification device comprising: providing a radio frequency
identification device including communication circuitry and
indication circuitry; receiving wireless signals including spurious
signals using the communication circuitry; and emitting human
perceptible signals using the indication circuitry to indicate the
receiving spurious signals.
22. The method according to claim 21 wherein the emitting includes
emitting human visible signals.
23. The method according to claim 21 further comprising processing
the wireless signals using the communication circuitry and the
emitting is responsive to the processing.
24. The method according to claim 23 wherein the processing
comprises searching for pseudo-random sequences of the wireless
signals.
25. A method of indicating operation of a radio frequency
identification device comprising: providing a radio frequency
identification device; receiving wireless signals including
spurious signals within the radio frequency identification device;
processing the wireless signals after the receiving using the radio
frequency identification device; and indicating the receiving of
spurious signals using the radio frequency identification
device.
26. The method according to claim 25 wherein the indicating
includes emitting a human perceptible signal.
27. The method according to claim 25 wherein the indicating
includes emitting a human visible signal.
28. The method according to claim 25 wherein the indicating is
responsive to the processing occurring for a predetermined period
of time.
29. The method according to claim 25 wherein the processing
comprises searching for pseudo-random sequences of the wireless
signals.
30. A method of indicating operation of a remote communication
device comprising: providing a remote communication device;
receiving a wireless signal within the remote communication device;
processing the wireless signal after the receiving using the remote
communication device; asserting a signal during the processing
using the remote communication device; and indicating the receiving
using the remote communication device responsive to the asserting
occurring for a predetermined period of time.
31. The method according to claim 30 wherein the indicating
includes emitting a human perceptible signal.
32. The method according to claim 30 wherein the indicating
includes emitting a human visible signal.
33. The method according to claim 30 further comprising
periodically asserting the signal.
34. The method according to claim 30 further comprising filtering
the asserted signal.
35. The method according to claim 30 wherein the receiving includes
receiving the wireless signal including a spurious signal and the
indicating includes indicating the receiving the spurious
signal.
36. The method according to claim 30 wherein the providing includes
providing a radio frequency identification device.
37. A method of indicating operation of a remote communication
device comprising: providing a remote communication device;
receiving a wireless signal within the remote communication device;
asserting a signal to monitor for the presence of the wireless
signal within the remote communication device; processing the
wireless signal using the remote communication device; maintaining
the asserting during the processing; and indicating the maintaining
using the remote communication device.
38. The method according to claim 37 wherein the indicating
includes emitting a human perceptible signal.
39. The method according to claim 37 wherein the indicating
includes emitting a human visible signal.
40. The method according to claim 37 further comprising
periodically asserting the signal.
41. The method according to claim 37 further comprising filtering
the asserted signal.
42. The method according to claim 37 wherein the receiving includes
receiving the wireless signal including a spurious signal and the
indicating includes indicating the receiving the spurious
signal.
43. The method according to claim 37 wherein the providing includes
providing a radio frequency identification device.
44. A method of indicating operation of a wireless communication
system comprising: providing an interrogator and a radio frequency
identification device; outputting a forward link wireless signal
using the interrogator; receiving the forward link wireless signal
within the radio frequency identification device; receiving
spurious wireless signals within the radio frequency identification
device; and indicating the receiving of the spurious wireless
signals using the radio frequency identification device.
45. The method according to claim 44 wherein the indicating
includes emitting a human perceptible signal.
46. The method according to claim 44 wherein the indicating
includes emitting a human visible signal.
47. The method according to claim 44 further comprising processing
the forward link wireless signal and the spurious wireless signal
and the indicating being responsive to the processing.
48. A method of indicating operation of a wireless communication
system comprising: providing an interrogator and a radio frequency
identification device; outputting a forward link wireless signal
using the interrogator; receiving the forward link wireless signal
within the radio frequency identification device; receiving a
spurious wireless signal within the radio frequency identification
device; asserting plural periodic signals to monitor for the
presence of the forward link wireless signal within the radio
frequency identification device; processing the received forward
link wireless signal and the received spurious wireless signal
using the radio frequency identification device after the
respective assertings; maintaining the asserting of an individual
one of the periodic signals during the processing; filtering the
asserted signals to remove asserted signals which are asserted for
less than a predetermined length of time; and emitting a human
visible signal using the radio frequency identification device
indicating the receiving of the spurious wireless signal after the
filtering.
Description
TECHNICAL FIELD
[0001] This invention relates to radio frequency identification
devices, remote communication devices, wireless communication
systems, and methods of indicating operation.
BACKGROUND OF THE INVENTION
[0002] Wireless communication Systems including electronic
identification devices, such as radio frequency identification
devices (RFIDs), are known in the art. Such devices are typically
used for inventory tracking. As large numbers of objects are moved
in inventory, product manufacturing, and merchandising operations,
there is a continuous challenge to accurately monitor the location
and flow of objects. Additionally, there is a continuing goal to
determine the location of objects in an inexpensive and streamlined
manner. One way of tracking objects is with an electronic
identification system.
[0003] One presently available electronic identification system
utilizes a magnetic coupling system. Typically, the devices are
entirely passive (have no power supply), which results in a small
and portable package. However, such identification systems are only
capable of operation over a relatively short range, limited by the
size of a magnetic field used to supply power to the devices and to
communicate with the devices.
[0004] Another type of wireless communication system is an active
wireless electronic identification system. Attention is directed
towards commonly assigned U.S. patent application Ser. No.
08/705,043, filed Aug. 29, 1996, incorporated herein by reference,
and which describes such active systems in detail.
[0005] These systems include integrated circuit devices which
include an active transponder and are intended to be affixed to an
object to be monitored. The devices are capable of receiving and
processing instructions transmitted by an interrogator. A device
receives the instruction, if within range, then processes the
instruction and transmits a response, if appropriate. The
interrogation signal and the responsive signal are typically
radio-frequency (RF) signals produced by an RF transmitter circuit.
Because active devices have their own power sources, such do not
need to be in close proximity to an interrogator or reader to
receive power via magnetic coupling. Therefore, active transponder
devices tend to be more suitable for applications requiring
tracking of a tagged device that may not be in close proximity to
an interrogator. For example, active transponder devices tend to be
more suitable for inventory control or tracking.
[0006] Radio frequency identification devices may be subjected to
undesired signals in the field. For example, various electronic
devices such as radar, microwave ovens, etc. can emit spurious
radio frequency signals into a communication range of a wireless
communication system. The presence of such spurious undesired
signals can result in rapid consumption of power of batteries of
radio frequency identification devices. This degrades available
power of such batteries which could otherwise be used for providing
communication operations.
SUMMARY OF THE INVENTION
[0007] This invention provides radio frequency identification
devices, remote communication devices, wireless communication
systems, and methods of indicating operation.
[0008] One aspect of the present invention provides a wireless
communication system. The wireless communication system includes an
interrogator and a radio frequency identification device. The
interrogator is configured to output a forward link wireless
signal. An exemplary forward link wireless signal includes an
interrogation signal.
[0009] The radio frequency identification device includes
communication circuitry configured to receive the forward link
wireless signal and a spurious wireless signal. The radio frequency
identification device further includes indication circuitry coupled
with the communication circuitry and configured to indicate
reception of the spurious wireless signal within the communication
circuitry.
[0010] Exemplary indication circuitry includes circuitry operable
to emit human perceptible signals. For example, indication
circuitry can include an indicator comprising a light emitting
device to emit a visually perceptible signal to indicate the
reception of spurious wireless signals. Such indication using the
indication circuitry can be subsequently utilized to implement
actions to reduce the presence of spurious wireless signals. Other
aspects are provided in the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Preferred embodiments of the invention are described below
with reference to the following accompanying drawings.
[0012] FIG. 1 is an illustrative diagram of an exemplary wireless
communication system.
[0013] FIG. 2 is an isometric view of an exemplary remote
communication device of the wireless communication system shown in
FIG. 1.
[0014] FIG. 3 is a functional block diagram of exemplary internal
circuitry of the remote communication device.
[0015] FIG. 4 is a functional block diagram of exemplary internal
circuitry of a radio frequency processor of the remote
communication device.
[0016] FIG. 5 is a functional block diagram of exemplary control
circuitry and indication circuitry of the remote communication
device.
[0017] FIG. 6 includes graphs which illustrate first operations of
the control circuitry.
[0018] FIG. 7 includes graphs which illustrate second operations of
the control circuitry.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] 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).
[0020] Referring to FIG. 1, a wireless communication system 10 is
illustrated in accordance with one embodiment of the invention.
Wireless communication system 10 includes an interrogator 12 and at
least one remote communication device 14. Typically, numerous
remote communication devices 14 are provided within wireless
communication system 10 although only two such remote communication
devices 14 are illustrated in FIG. 1. The particular number of
remote communication devices 14 which are in communication with
interrogator 12 may change over time.
[0021] A communication range 11 of the illustrated interrogator 12
is shown in FIG. 1. During exemplary object monitoring operations,
more or less remote communication devices 14 can be within
communication range 11 of interrogator 12 as objects or packages
are moved about. Interrogator 12 communicates with remote
communication devices 14 located within communication range 11.
Typically, there is no communication between multiple remote
communication devices 14. Instead, remote communication devices 14
respectively communicate with interrogator 12. As previously
mentioned, multiple remote communication devices 14 are typically
used in the same field of interrogator 12 (i.e., within
communications range 11 of interrogator 12).
[0022] In the described embodiment, wireless communication system
10 is configured as an electronic identification system. Other
configurations of wireless communication system 10 are possible.
Remote communication devices 14 can individually be associated with
respective objects 16, such as packages in inventory. Wireless
communication system 10 can also be used in other applications
including, for example, other identification applications.
[0023] Remote communication devices 14 individually comprise a
wireless identification device in the described configuration.
Other configurations of remote communications devices 14 are
possible. An exemplary wireless identification device is a radio
frequency identification device (RFID). In the depicted
arrangement, remote communication devices 14 individually include
an antenna 18 for wireless or radio frequency transmission by the
respective remote communication device 14. Remote communication
devices 14 further individually include an antenna 20 for wireless
or radio frequency reception by the respective remote communication
device 14. In one embodiment, the antennas 18, 20 are microstrip
antennas.
[0024] Individual remote communication devices 14 transmit and
receive radio frequency communications to and from interrogator 12.
An exemplary interrogator is described in commonly assigned U.S.
patent application Ser. No. 08/907,689, filed Aug. 8, 1997 and
incorporated herein by reference. Preferably, interrogator 12
includes an antenna 13 as well as dedicated transmitting and
receiving circuitry. In one embodiment, such circuitry is
complementary to that implemented within individual remote
communication devices 14.
[0025] Radio frequency identification has emerged as a viable
system for tagging or labeling small to large quantities of objects
16. In the described configuration, interrogator 12 and remote
communication devices 14 communicate via an electromagnetic link,
such as via an RF link (e.g., at microwave frequencies, in one
embodiment), so all transmissions by interrogator 12 are heard
simultaneously by all remote communication devices 14 within
communication range 11.
[0026] Interrogator 12 transmits forward link wireless signals 22
individually comprising an interrogation signal or command via
antenna 13. An exemplary forward link wireless signal 22 includes a
tag identifier, command, and data. The tag identifier can comprise
an identifier to identify one or more of remote communication
devices 14 in some applications. Typically, the remote
communication devices 14 identified within tag identifier process
the respective command and data.
[0027] Remote communication devices 14 within the appropriate
communication range 11 individually receive the incoming
interrogation forward link wireless signal 22 via respective
antennas 20. Upon receiving wireless signal 22, individual ones of
remote communication devices 14 can respond by generating and
transmitting a responsive signal or return link communication
signal 24 via respective antenna 18. The responsive signal 24
typically includes information that uniquely identifies, or labels
the particular remote communication device 14 that is transmitting.
Such may operate to identify a respective object 16 with which the
responding remote communication device 14 is associated. Exemplary
objects 16 include packages in inventory, people, automobiles,
animals, etc.
[0028] Referring to FIG. 2, remote communication device 14 can be
included in any appropriate packaging or housing 30. Various
methods of manufacturing housings are described in commonly
assigned U.S. patent application Ser. No. 08/800,037, filed Feb.
13, 1997, and incorporated herein by reference. An exemplary
housing 30 includes an ultrasonically welded plastic injection
molded case. Housing 30 is provided about a substrate 31 and at
least some of the circuitry (described below) of remote
communication device 14. Housing 30 can be configured as a case
about substrate 31 to enclose most if not all of the internal
components of remote communication device 14. More specifically,
circuitry of remote communication device 14 is provided upon
substrate 31 in one embodiment. An exemplary substrate 31 is FR4
board. Circuit components of remote communication device 14 may be
attached to substrate 31 using pick-and-place processing
techniques.
[0029] FIG. 2 shows but one embodiment of remote communication
device 14 in the form of a card or badge including housing 30 of
plastic or other suitable material. In one embodiment, a face of
housing 30 has visual identification features such as graphics,
text, information found on identification or credit cards, etc.
(not shown). Housing 30 can also be formed as a miniature housing
encasing the internal circuitry and power supply 16 to define a tag
which can be supported by object 16 (e.g., hung from an object,
affixed to an object, etc.). Other forms of housings 30 are
employed in alternative embodiments.
[0030] In the illustrated embodiment, remote communication device
14 includes communication circuitry 32, a power source 34, control
circuitry 35 and indication circuitry 36. Communication circuitry
32 is defined by a small outline integrated circuit (SOIC) as
described in the above-incorporated patent application Ser. No.
08/705,043, filed Aug. 29, 1996. Exemplary communication circuitry
32 is available from Micron Communications Inc., 3176 S. Denver
Way, Boise, Id. 83705 under the trademark Microstamp Engine (TM)
and having designations MSEM256X10SG, MT59RC256R1FG-5. Other
embodiments of communication circuitry 32 are possible. Power
source 34 is connected to supply power to communication circuitry
32, control circuitry 35 and 17 indication circuitry 36.
[0031] In one embodiment, power source 34 comprises one or more
batteries. Individual batteries 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, a suitable battery 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, power source 34 comprises a series
connected pair of button type cells. In other alternative
embodiments, other types of suitable power source are employed.
Suitable batteries of power source 34 individually include a 3 Volt
battery having designation CR2016 available from Eveready Battery
Co. Two such batteries can be coupled in series for a 6 Volt output
of power source 34 in one embodiment.
[0032] In the described arrangement, communication circuitry 32 is
coupled with substrate 31 and is configured to at least one of
receive wireless signals and communicate wireless signals.
Exemplary received and communicated wireless signals comprise radio
frequency signals as previously described. In one embodiment,
communication circuitry 32 comprises transponder circuitry
configured to output the reply or return link wireless
identification signal 24 responsive to the reception of forward
link wireless interrogation signal 22 generated within interrogator
12.
[0033] Control circuitry 35 is coupled with communication circuitry
32 and indication circuitry 36. In the described embodiment,
indication circuitry 36 includes an indicator 38 to indicate
operation of remote communication device 14. Remote communication
device 14 can be configured such that indication circuitry 36
indicates reception of signals as described below. Indication
circuitry 36 may also be configured to indicate other
operations.
[0034] Exemplary additional indication operations of remote
communication device 12 are described in a commonly assigned U.S.
Patent Application entitled "Radio Frequency Identification
Devices, Wireless Communication Systems, Communication Methods,
Methods of Forming a Radio Frequency Identification Device, Methods
of Testing Wireless Communication Operations, and Methods of
Determining a Communication Range", naming Mark T. Van Horn, David
K. Ovard and Scott T. Trosper as inventors, filed the same day as
the present application, having attorney docket number MI40-187,
and incorporated herein by reference, and in a commonly assigned
U.S. Patent Application entitled "Radio Frequency Identification
Devices, Remote Communication Devices, Identification Systems,
Communication Methods, and Identification Methods", naming Scott T.
Trosper as inventor, filed the same day as the present application,
having attorney docket number MI40-197, and incorporated herein by
reference.
[0035] Indication circuitry 36 includes indicator 38 configured to
emit a human perceptible signal to indicate reception of signals
within remote communication device 14 in accordance with a
preferred configuration. In the described embodiment, indicator 38
is configured to visually indicate operation of remote
communication device 14. In particular, indicator 38 can include at
least one light emitting device, such as a light emitting diode
(LED), to emit a visually perceptible signal to humans. Indication
circuitry 36 can also include other indicators 38 for indicating
operation of remote communication device 14. Another exemplary
configuration of indicator 38 includes an audible device, such as a
buzzer. Indicator 38 can have other configurations.
[0036] Preferably, remote communication device 14 is configured
such that indicator 38 of indication circuitry 36 outwardly emits
the human perceptible signal or otherwise indicates operation
outside of housing 30. For example, indicator 38 may extend through
housing 30 as shown and is externally visible. In the depicted
arrangement, housing 30 is provided about substrate 31 and internal
circuitry with indication circuitry 36 at least partially outwardly
exposed as illustrated.
[0037] Referring to FIG. 3, communication circuitry 32 of remote
communication device 14 implemented as a single die in accordance
with the described embodiment includes a radio frequency (RF)
processor 41, a memory 44, and a microprocessor 46. The depicted
radio frequency processor 41 includes a transmitter 40 and a
receiver 42. Microprocessor 46 is coupled to transmitter 40,
receiver 42, and memory 44 as is described in U.S. patent
application Ser. No. 08/705,043. Forward link wireless signals 22
are received within antenna 20 and applied to receiver 42. In one
configuration, transmitter 40 is configured to reply via antenna 18
using backscatter communications. Forward link wireless signals 22
can be specific to individual remote communication devices 14, or
intended to apply to some or all remote communication devices 14
within communication range 11.
[0038] Microprocessor 46 is configured to process the signals
received by receiver 42. Responsive to the content of a received
forward link wireless signal 22, microprocessor 46 can formulate
return link wireless signal 24 which is applied to transmitter 40.
Transmitter 40 operates to output return link wireless signals 24
using antenna 18. As previously described, transmitter 40 may be
configured for backscatter communications. For example, antenna 18
can be configured as a dipole antenna and transmitter 40 can
selectively short halves of the dipole antenna configuration to
selectively reflect a continuous wave signal generated by
interrogator 12.
[0039] Referring to FIG. 4, additional details of radio frequency
processor 41 are described. For example, RF processor 41 of
communication circuitry 32 additionally includes a wake up timer
circuit 43 and a spread spectrum processing circuit 45. In one
embodiment, remote communication devices 14 individually switch
between a "sleep" mode of operation, and a higher power mode of
operation referred to as a "wake" mode. Such switching is utilized
to conserve energy and extend the life of power source 34 during
periods of time when no forward link wireless signals 22 are
received by remote communication devices 14.
[0040] According to one embodiment, switching between the sleep
mode and the wake mode is implemented using the wake up timer
circuitry 43. During ideal operation conditions, remote
communication device 14 enters the sleep mode when no forward link
wireless signals 22 are detected from interrogator 12. Thereafter,
remote communication device 14 monitors for the presence of forward
link wireless signals 22 during the sleep mode.
[0041] In one configuration, wake up timer 43 periodically asserts
a WAKEUP signal every 16 ms using timing circuitry (not shown). The
WAKEUP signal is applied to microprocessor 46 and receiver 42.
Microprocessor 46 monitors for the presence of a forward link
wireless signal 22 via receiver 42 responsive to the WAKEUP signal.
Remote communication device 14 remains in the sleep mode responsive
to no forward link wireless signal 22 being present.
[0042] Alternatively, remote communication device 14 enters a wake
mode responsive to the presence of a forward link wireless signal
22 within receiver 42. The forward link wireless signal 22 is
subsequently analyzed and return link wireless signal 24 (of FIG.
1) may be generated if appropriate. Thereafter, remote
communication device 14 continues to monitor for the presence of
forward link wireless signals 22 (of FIG. 1) and may enter the
sleep mode again to conserve power if none are detected.
[0043] Spread spectrum processing circuit 40 is included in
communication circuitry 32 in the described embodiment. In this
configuration, signals transmitted and received by interrogator 12
and signals transmitted and received by remote communication device
14 are modulated spread spectrum signals. Such modulation
techniques are advantageous where there are multiple users, as is
the case with the preferred radio frequency identification wireless
communication system 10 of the present invention including plural
remote communication devices 14.
[0044] The spread spectrum modulation technique of the illustrated
embodiment is advantageous because the forward link wireless signal
22 and return link wireless signal 24 can be individually
distinguished from other spurious signals (e.g., radar, microwave
ovens, etc.) operating at similar frequencies. The spread spectrum
signals transmitted by interrogator 12 and remote communication
device 14 are pseudo-random and have noise-like properties when
compared with the command or reply signals. The illustrated
embodiment employs direct sequence spread spectrum (DSSS)
modulation. Other modulation schemes or techniques are
possible.
[0045] Wireless communication system 10 may be subjected to
spurious wireless signals during communication operations. Such
spurious wireless signals can include radar signals, signals from
microwave ovens, etc. operating at similar frequencies.
Accordingly, during moments in time when remote communication 14 is
operating in the sleep mode, some spurious signals may be received
within the approximate frequency range of communications (e.g., 2.4
GHz) of wireless communication system 10.
[0046] More specifically, once the WAKEUP signal is asserted by
wake up timer 43, microprocessor 46 analyzes wireless signals
received by antenna 20 and receiver 42. Such received wireless
signals can include undesired spurious wireless signals as well as
desired forward link wireless signals 22. Accordingly,
microprocessor 46 processes the received wireless signals to
distinguish spurious wireless signals from forward link wireless
signals 22.
[0047] In the described embodiment, microprocessor 46 searches for
a pseudo-random sequence within the received wireless signals. Wake
up timer circuit 43 asserts the WAKEUP signal during the modulation
processing (e.g., searching for an appropriate pseudo-random
sequence). Signals containing appropriate pseudo-random sequences
comprise forward link wireless signals 22 as identified by
microprocessor 46 while spurious wireless signals will also be
identified and may be discarded. Thereafter, microprocessor 46
processes forward link wireless signals 22 (e.g., processes
identifiers and commands, etc.). Additionally, microprocessor 46
can enter the sleep mode following the detection of spurious
wireless signals. The additional processing of such spurious
signals to determine whether an appropriate pseudo-random sequence
is present consumes additional power thereby depleting power source
34.
[0048] Referring again to FIG. 3, it is beneficial to indicate the
reception of spurious signals within remote communication device 14
which may lead to a shortened life of power source 34. Once it is
realized such spurious signals are present, steps may be taken to
eliminate or minimize the presence of such spurious signals.
[0049] Indication circuitry 36 coupled with communication circuitry
32 is preferably configured to output an indication signal to
indicate reception of such spurious signals within communication
circuitry 32. As previously mentioned, indication circuitry 36 may
be configured to emit a human perceptible signal to indicate the
reception of spurious signals. More specifically, indicator 38
(shown in FIG. 2) can comprise a light-emitting device configured
to emit a signal which is visible to humans to indicate the
reception of spurious signals.
[0050] Communication circuitry 32 periodically monitors for the
reception of wireless signals via antenna 20 and receiver 42. A
periodic assertion of the WAKEUP signal by wake up timer 43
implements such periodic monitoring operations. Microprocessor 46
is configured to process signals outputted from spread spectrum
processing circuitry 45 to determine whether appropriate
pseudo-random sequences are present, and thus whether the received
signals comprise spurious signals or forward link wireless signals
22.
[0051] The WAKEUP signal is asserted during such processing of
received wireless signals. Control circuitry 35 is coupled with
communication circuitry 32 and is configured to monitor the WAKEUP
signal. More specifically, control circuitry 35 generates a control
signal responsive to the WAKEUP signal being asserted for a
predetermined period of time.
[0052] Indication circuitry 36 is coupled with control circuitry 35
and is configured to indicate the reception of wireless signals
using indicator 38 responsive to the control signal being asserted
by control circuitry 35. Such indication by indication circuitry 36
can be utilized to indicate the presence of spurious signals.
[0053] In effect, control circuitry 35 controls the indication by
indication circuitry 36 responsive to the WAKEUP signal from
communication circuitry 32 being asserted for a predetermined
period of time as described in further detail below. Communication
circuitry 32 maintains the assertion of the WAKEUP signal during
the processing of received wireless signals. Indication circuitry
36 indicates maintenance of the WAKEUP signal in the asserted state
following such assertion for a predetermined length of time.
[0054] Referring to FIG. 5, one configuration of control circuitry
35 and indication circuitry 36 is illustrated. The depicted control
circuitry 35 includes a latch 50, plural resistors 52, 54 and
capacitor 56 arranged as shown. Indication circuitry 36 includes a
resistor 62 coupled with indicator 38 in the illustrated
arrangement. Resistor 52 is a 10 k.OMEGA. resistor, resistor 54 is
a 100 k.OMEGA. resistor and capacitor 56 is a 1,000 pF capacitor in
the described configuration of control circuitry 35. Resistor 62 is
a 10 k.OMEGA. potentiometer and indicator 38 is a light emitting
diode (LED) in the depicted configuration of indication circuitry
36.
[0055] Latch 50 comprises a D-type positive edge triggered
flip-flop with clear and preset in the described configuration. A
suitable latch 50 has designation 74HC74 and is available from
Texas Instruments. As shown, a D input pin 2, a preset (PRE) input
pin 4 and a V.sub.DD input pin 14 all of latch 50 are individually
coupled with a V.sub.DD supply of power source 34.
[0056] The WAKEUP signal asserted within communication circuitry 32
is applied to control circuitry 35. A clear (CLR) pin 1 and clock
(CLK) pin 3 of latch 50 are coupled with a pin 2 of communication
circuitry 32 which outputs the WAKEUP signal. The depicted control
circuitry 35 comprises a filter configured to selectively remove
the WAKEUP signal if it is asserted for less than a predetermined
period of time before application to indication circuitry 36.
[0057] The WAKEUP signal is typically asserted for approximately 25
.mu.s in the described embodiment if no wireless signals are
received within receiver 42. The assertion of the WAKEUP signal by
communication for 25 .mu.s circuitry 32 does not inject a rising
edge to latch 50. Thus, the Q output of latch 50 remains in a logic
low state and indicator 38 is not illuminated.
[0058] However, during the reception of wireless signals (e.g.,
forward link wireless signals 22 and spurious wireless signals) the
WAKEUP signal is typically asserted for an extended period of time
corresponding to processing of the received signals using
microprocessor 46. The WAKEUP signal may be asserted for
approximately 0.5 ms-3 ms responsive to a wireless signal being
received via antenna 20 and receiver 42 in the described
embodiment. Such assertion is longer than a predetermined length of
time as determined by resistor 54 and capacitor 56 in the depicted
arrangement and a rising edge is applied to the clock input of
latch 50. Such results in the Q output of latch 50 going to a logic
high state and the illumination of LED indicator 38.
[0059] Accordingly, control circuitry 35 and indication circuitry
36 indicate the presence of wireless signals including spurious
signals within remote communication device 14. Further, control
circuitry 35 operates to selectively filter signals outputted from
communication circuitry 32 which are shorter in duration than a
predetermined length of time.
[0060] Referring to FIG. 6, graphs 70, 74 are depicted which
illustrate the operation of control circuitry 35 wherein no
wireless signals are received within remote communication device
14. Voltage is represented in the vertical direction in graphs 70,
74 and time is represented in the horizontal direction in graphs
70, 74. Graph 70 illustrates the clear (CLR) signal applied to
latch 50 as represented by line 72. Graph 74 represents the clock
(CLK) signal applied to latch 50 as represented by line 76.
[0061] At a moment in time 71 within graph 70, the clear signal is
asserted corresponding to the periodic assertion of the WAKEUP
signal from communication circuitry 32. As illustrated in graph 74,
the clock signal has a slight dip as represented by line 76
corresponding to the assertion of the WAKEUP signal subsequent to
moment in time 71. However, the slight dip at moment in time 71 of
the clock signal is insufficient to provide a positive edge to
trigger latch 50. Accordingly, the Q output of latch 50 stays at a
logic low state and control circuitry 35 operates as a filter.
[0062] Referring to FIG. 7, plural graphs 80, 84 are shown. Voltage
is represented in the vertical direction in graphs 80, 84 and time
is represented in the horizontal direction in graphs 80, 84. The
clear (CLR) signal applied to latch 50 is represented by line 82
and the clock (CLK) signal applied to latch 50 is represented by
line 86. Graphs 80, 84 represent a situation wherein a wireless
signal is received within antenna 20 and receiver 42.
[0063] At a moment in time 81, the WAKEUP signal outputted from
communication circuitry 32 is asserted for an extended length of
time corresponding to processing of the received wireless signal by
microprocessor 46. As represented by line 86, the clock signal
falls below a threshold 83 responsive to the WAKEUP signal being
asserted for at least the predetermined length of time.
[0064] As further represented by line 86, the clock signal dropping
below the threshold 83 is sufficient to provide a rising edge to
the clock input to trigger latch 50. Accordingly, the Q output of
latch 50 goes to a logic high state and the LED indicator 38 is
illuminated within the depicted indication circuitry 36 to indicate
the reception of a wireless signal within remote communication
device 14.
[0065] 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.
* * * * *