GB2300318A - Improvements in or relating to transceivers - Google Patents

Improvements in or relating to transceivers Download PDF

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Publication number
GB2300318A
GB2300318A GB8103989A GB8103989A GB2300318A GB 2300318 A GB2300318 A GB 2300318A GB 8103989 A GB8103989 A GB 8103989A GB 8103989 A GB8103989 A GB 8103989A GB 2300318 A GB2300318 A GB 2300318A
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GB
United Kingdom
Prior art keywords
signals
fed
transceiver
pair
mixers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8103989A
Other versions
GB8103989D0 (en
GB2300318B (en
Inventor
Christopher Keith Richardson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Plessey Co Ltd
BAE Systems Defence Systems Ltd
Original Assignee
Plessey Co Ltd
Siemens Plessey Electronic Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Plessey Co Ltd, Siemens Plessey Electronic Systems Ltd filed Critical Plessey Co Ltd
Priority to GB8103989A priority Critical patent/GB2300318B/en
Publication of GB8103989D0 publication Critical patent/GB8103989D0/en
Publication of GB2300318A publication Critical patent/GB2300318A/en
Application granted granted Critical
Publication of GB2300318B publication Critical patent/GB2300318B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/403—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/0008—General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/081—Details of the phase-locked loop provided with an additional controlled phase shifter
    • H03L7/0812—Details of the phase-locked loop provided with an additional controlled phase shifter and where no voltage or current controlled oscillator is used
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
    • H03L7/087—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using at least two phase detectors or a frequency and phase detector in the loop
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/753—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using frequency selective elements, e.g. resonator
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/758—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using a signal generator powered by the interrogation signal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
    • H03D3/28—Modifications of demodulators to reduce effects of temperature variations
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/16—Multiple-frequency-changing
    • H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/30—Circuits for homodyne or synchrodyne receivers

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Transceivers (AREA)

Abstract

A transceiver comprises a pair of multiplicative mixers 1, 2 each having two input ports, aerial means 13 via which received signals are fed to one input port of each mixer of the pair, an oscillator 3 from which signals are fed to the aerial means 13 to provide carrier signals for transmission, a phase modulator 4 via which signals are fed from the oscillator to the other input ports of the mixers of the pair. A pair of low pass filters 6, 7 are fed one from each mixer. Phase quadrature means 5 are connected as shown, or in the aerial connection to mixer 1, and multiplier means 10 multiplies signals fed thereto from the low pass filters 6,7 and feeds via a further low pass filter 11 the phase modulator 4 thereby to control the phase of signals fed from the oscillator 3 to the mixers so that output signals corresponding to modulation carried by the received signals are produced at an output terminal of the transceiver fed from one of the low pass filters 6 of the said pair and so that output signals fed from the other low pass filter 7 of the pair tend to be nullified.

Description

IMPROVEMENTS IN OR RELATING TO TRANSCEIVERS This invention relates to transceivers and more particularly it relates to transceiver systems including a transponder adapted to receive radio frequency energy from the transceiver the energy received being modulated at the transponder and re-transmitted to the transceiver.
According to the present invention a transceiver comprises a pair of multiplicative mixers each having two input ports, aerial means via which received signals are fed to one input port of each mixer of the pair, an oscillator from which signals are fed to the aerial means to provide carrier signals for transmission, a phase modulator via which signals are fed from the oscillator to the other input ports of the mixers of the pair, a pair of low pass filters fed one from each mixer, phase quadrature means effective for producing a phase quadrature relationship between two of the signals fed from a common source to the mixers of the pair, multiplier means effective for multiplying signals fed thereto from the low pass filters and a further low pass filter via which a signal fram the multiplier means is fed back to the phase modulator thereby to control the phase of signals fed from the oscillator to the mixers so that output signals corresponding to modulation carried by the received signals are produced at an output terminal of the transceiver fed from one of the low pass filters of the said pair and so that output signals fed from the other low pass filter of the pair tend to be nullified.
The phase quadrature means may be arranged to be effective for producing a phase quadrature relationship between the signals fed to the mixers of the pair from the phase modulator.
The phase quadrature means may comprise a 900 phase shift device via which signals from the phase modulator are fed to one of the mixers of the pair.
The aerial means may comprise a transmitter aerial fed from the oscillator and a receiver aerial arranged to feed the mixers of the pair.
Alternatively a single transmit/receive aerial may be used arranged to feed the mixers and arranged to be fed from the oscillator via signal splitter means as described in our co-pending patent application No. 10360/76 for example.
The transceiver may form part of a transceiver system which includes a transponder adapted to receive signals received from the aerial means of the transceiver, the transponder including a modulator operative to modulate the received signals, the signals thus modulated being transmitted to the transceiver which is itself operative to provide an output signal on the said output terminal which corresponds to the modulation transmitted from the transponder.
The transponder may be passive and may comprise aerial means fed via a tuned circuit from a modulating transducer.
The modulating transducer may comprise a capacitor microphone which forms a part of the tuned circuit.
Alternatively the transducer may comprise a crystal microphone coupled to a varactor diode which forms a part of the tuned circuit and which is responsive to signals from the microphone for changing the reasonant frequency of the tune circuit thereby to modulate signals received by the transponder which thereafter are transmitted from the transponder.
The tuned circuit may comprise a transformer via which it is coupled to the aerial means of the transponder.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a generally schematic block diagram of a transceiver system which includes a passive transponder and a transceiver; Figure 2 is a generally schematic circuit diagram of one form of passive transponder; and wherein Figure 3 is a generally schematic circuit diagram of an alternative form of passive transponder.
Referring now to Figure 1 the transceiver of the transceiver system comprises a pair of multiplicative mixers 1 and 2, fed with received signals from a receive aerial 3Q The mixers 1 and 2 are fed with local oscillator signals from an oscillator 3 via a phase modulator 4. The mixer 2 is fed directly from the phase modulator 4 whereas the mixer 1 is fed via a phase quadrature device 5. Output signals from the mixers are fed to a pair of low pass filters 6 and 7 which feed respectively amplifiers 8 and 9. Amplified signals from the low pass filters 6 and 7 are fed to a multiplicative mixer 10 and output signals from the multiplicative mixer 10 are fed back via a further low pass filter 11 to provide a control signal for the phase modulator 4.
In use of the transceiver signals from the oscillator 3 are amplified in an amplifier 12 and transmitted via a transmit aerial 13 to a passive transponder 14. Signals received by the passive transponder are locally modulated and re-transmitted from a transponder aerial 15. Thus it will be appreciated that signals transmitted from the aerial 13 are at the same frequency as carrier signals received at the aerial 3. The phase modulator 4 is operative to control the phase of the local oscillator signals fed from the oscillator 3 to the mixers 1 and 2, so that output signals are developed at an output terminal 16 of the transceiver, which correspond with the modulation transmitted from the aerial 15 of the passive transponder 14, the output terminal 16 being fed from the low pass filter 6 via the amplifier 8 and a further amplifier 17.
It can be shown that when a maximum output signal is developed on the output terminal 16 the signal fed to the mixer 10 from the amplifier 9 will tend to zero and a d.c. voltage will be produced on an output line 18 from the mixer 10 which is proportional to the phase difference between the signals fed to the mixer 10 and which has a sense indicative of the direction of any phase continuity. Thus the transceiver system operates in a similar manner to a suppressed carrier double side band system wherein cancellation of one side band occurs in the path which includes the low pass filter 7 and the amplifier 9 and wherein the received signal is maximised in the signal path which comprises the low pass filter 6 and the amplifier 8 feeding the output terminal 16.In effect the phase modulator 4 is controlled by means of the signal applied thereto via the line 18 so that the phase change introduced by the signal path between the transmit aerial 13 and the receive aerial 3 is compensated for whereby an undistorted signal is developed at the output terminal 16 which corresponds to the modulation imposed on the received signal and retransmitted by the passive transponder 14. Although most conveniently the transponder 14 may be passive, that is it may be energised by the signal power of the received signal, it may alternatively be an active transponder having its own local power supply.
One form of passive transponder is shown in Figure 2 and it comprises an aerial dipole 19 which is coupled to a tuned circuit 20 and wherein the tune circuit includes a capacitor microphone 21. It will be apparent to those skilled in the art that audio frequency signals received at the microphone 21 will tend to modulate signals received by the dipole 19 which are thereby re-transmitted.
Figure 3 shows an alternative type of passive transponder including a dipole 22 coupled to a tuned ciruit 23 which includes a varactor diode 24 shunted by a crystal microphone 25. In operation of the transponder output signals from the crystal microphone are effective to change the capacitance of the varactor diode 24 and thus the reasonant frequency of the tuned circuit, whereby modulated signals corresponding to the signals received by the microphone 25 are imposed on carrier frequencies received at the aerial 22 and effectively re-transmitted.
Various modifications may be made to the embodiments described without departing from the scope of the invention and for example the phase quadrature device may alternatively be incorporated between the aerial 3 and one of the mixers 1 or 2.
Additionally it is possible to provide a transceiver having a single transmit receive aerial which is coupled to the oscillator and the oscillator 3 and the mixers 1 and 2 via a suitable signal separation or splitter system.
It will be appreciated that by utilising a transceiver according to the present invention wherein direct conversion of received signal modulation is effected by means of the mixers which are fed in quadrature with a local oscillator signal phase locked to the received carrier, cancellation of the relatively large locally transmitted signal is effected which enables the much smaller retransmitted signal from the transponder to be received and demodulated.

Claims (10)

LAIllS
1. A transceiver comprising a pair of multiplicative mixers each having two input ports, aerial means via which received signals are fed to one input port of each mixer of the pair, an oscillator from which signals are fed to the aerial means to provide carrier signals for transmission, a phase modulator via which signals are fed from the oscillator to the other input ports of the mixers of the pair, a pair of low pass filters fed one from each mixer, phase quadrature means effective for producing a phase quadrature relationship between two of the signals fed from a common source to the mixers of the pair, multiplier means effective for multiplying signals fed thereto from the low pass filters and a further low pass filter via which a signal from the multiplier means is fed back to the phase modulator thereby to control the phase of signals fed from the oscillator to the mixers so that output signals corresponding to modulation carried by the received signals are produced at an output terminal of the transceiver fed from one of the low pass filters of the said pair and so that output signals fed from the other low pass filter of the pair tend to be nullified.
2. A transceiver as claimed in claim 1 wherein the phase quadrature means is arranged to be effective for producing a phase quadrature relationship between the signals fed to the mixers of the pair fro the phase modulator.
3. A transceiver as claimed in claim 1 or claim 2 wherein the phase quadrature means comprises a 900 phase shift device via which signals from the phase modulator are fed to one of the mixers of the pair.
4. A transceiver as claimed in any preceding claim wherein the aerial means comprises a transmitter aerial fed from the oscillator and a receiver aerial arranged to feed the mixers of the pair.
5. A transceiver as claimed in claim 1, claim 2 or claim 3 wherein the aerial means is a single transmit/receive aerial arranged to feed the mixers and arranged to be fed from the oscillator via signal splitter means.
6. A transceiver as claimed in any preceding claim and forming part of a transceiver system which includes a transponder adapted to receive signals received from the aerial means of the transceiver, the transponder including a modulator operative to modulate the received signals, the signals thus modulated being transmitted to the transceiver which is itself operative to provide an output signal on the said output terminal which corresponds to the modulation transmitted from the transponder.
7. A transceiver as claimed in claim 6 wherein the transponder is passive and comprises aerial means fed via a tuned circuit from a modulating transducer.
8. A transceiver as claimed in claim 7 wherein the modulating transducer comprises a capacitor microphone which forms a part of the tuned circuit.
9. A transceiver as claimed in claim 7 wherein the transducer comprises a crystal microphone coupled to a varactor diode which forms a part of a tuned circuit and which is responsive to signals from the microphone for changing the reasonant frequency of the tuned circuit thereby to modulate signals received by the transponder which thereafter are transmitted from the transponder.
10. A transceiver system substantially as hereinbefore described with reference to the accompanying drawings.
10. A transceiver as claimed in claim 9 wherein the tuned circuit comprises a transformer via which it is coupled to the aerial means of the transponder.
11. A transceiver substantially as hereinbefore described with reference to the accompanying drawings.
Amendments to the claims have been filed as follows 1. A transceiver system, comprising a transceiver and a remotely located transponder which in use of the system is responsive to carrier signals transmitted from the transceiver for producing a modulated retransmission signal wherein the transceiver comprises a pair of multiplicative mixers each having two input ports, aerial means via which received retransmission signals are fed to one input port of each mixer of the pair, an oscillator which produces local oscillator signals for the mixers and from which signals are fed to the aerial means to provide the carrier signals for transmission, a phase modulator via which the local oscillator signals are fed from the oscillator to the other input ports of the mixers of the pair, a pair of low pass filters fed one from each mixer, phase quadrature means effective for producing a phase quadrature relationship between two of the signals fed from a common source to the mixers of the pair, multiplier means effective for multiplying signals fed thereto from the low pass filters and a further low pass filter via which a signal from the multiplier means is fed back to the phase modulator thereby to control the differential phase between the local oscillator signals fed from the oscillator to the mixers and the carrier signals for transmission so that output signals corresponding to the modulation carried by the received signals are produced at an output terminal of the transceiver fed from one of the low pass filters of the said pair and so that output signals fed from the other low pass filter of the pair tend to be nullified.
2. A transceiver system as claimed in claim 1 wherein the phase quadrature means is arranged to be effective for producing a phase quadrature relationship between the signals fed to the mixers of the pair from the phase modulator.
3. A transceiver system as claimed in claim 1 or claim 2 wherein the phase quadrature means comprises a 900 phase shift device via which signals from the phase modulator are fed to one of the mixers of the pair.
4. A transceiver system as claimed in any preceding claim wherein the aerial means comprises a transmitter aerial fed from the oscillator and a receiver aerial arranged to feed the mixers of the pair.
5. A transceiver system as claimed in claim 1, claim 2 or claim 3 wherein the aerial means is a single transmit/ receive aerial arranged to feed the mixers and arranged to be fed from the oscillator via signal splitter means.
6. A transceiver system as claimed in any preceding claim wherein the transponder is passive and comprises aerial means fed via a tuned circuit from a modulating transducer.
7. A transceiver system as claimed in claim 6 wherein the modulating transducer comprises a capacitor microphone which forms a part of the tuned circuit.
8. A transceiver system as claimed in claim 6 wherein the transducer comprises a crystal microphone coupled to a varactor diode which forms a part of a tuned circuit and which is responsive to signals from the microphone for changing the reasonant frequency of the tuned circuit thereby to modulate signals received by the transponder which thereafter are transmitted from the transponder.
9. A transceiver system as claimed in claim 8 wherein the tuned circuit comprises a transformer via which it is coupled to the aerial means of the tranrponder.
GB8103989A 1981-02-10 1981-02-10 Improvements in or relating to transceivers Expired - Lifetime GB2300318B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8103989A GB2300318B (en) 1981-02-10 1981-02-10 Improvements in or relating to transceivers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8103989A GB2300318B (en) 1981-02-10 1981-02-10 Improvements in or relating to transceivers

Publications (3)

Publication Number Publication Date
GB8103989D0 GB8103989D0 (en) 1996-04-24
GB2300318A true GB2300318A (en) 1996-10-30
GB2300318B GB2300318B (en) 1997-03-19

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GB8103989A Expired - Lifetime GB2300318B (en) 1981-02-10 1981-02-10 Improvements in or relating to transceivers

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0831594A2 (en) * 1996-09-18 1998-03-25 Kipp, Ludwig Frequency cancelling system and method
EP0936571A2 (en) * 1998-02-10 1999-08-18 Sony Corporation IC card, IC card processor and IC card system
WO2000021204A1 (en) * 1998-10-06 2000-04-13 Crosslink, Inc. A system for reducing transmitter cross-talk in receive part of a rf transceiver
WO2001036995A1 (en) * 1999-11-18 2001-05-25 Marconi Data Systems Ltd. Multimode transceiver circuit
WO2002009021A1 (en) * 2000-07-21 2002-01-31 Microcid Sa High sensitivity reader for passive transponders
EP1710727A1 (en) 2005-04-08 2006-10-11 Fujitsu Limited RFID transceiver device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1172975A (en) * 1965-11-23 1969-12-03 Plessey Co Ltd Improvements in or relating to Demodulation Systems
GB1323446A (en) * 1969-12-15 1973-07-18 Ibm Data communication system
GB2052196A (en) * 1979-06-27 1981-01-21 Plessey Co Ltd Demodulators
GB2064271A (en) * 1979-07-06 1981-06-10 Plessey Co Ltd Transceivers

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1172975A (en) * 1965-11-23 1969-12-03 Plessey Co Ltd Improvements in or relating to Demodulation Systems
GB1323446A (en) * 1969-12-15 1973-07-18 Ibm Data communication system
GB2052196A (en) * 1979-06-27 1981-01-21 Plessey Co Ltd Demodulators
GB2064271A (en) * 1979-07-06 1981-06-10 Plessey Co Ltd Transceivers

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0831594A3 (en) * 1996-09-18 2002-05-02 Kipp, Ludwig Frequency cancelling system and method
EP0831594A2 (en) * 1996-09-18 1998-03-25 Kipp, Ludwig Frequency cancelling system and method
EP0936571A2 (en) * 1998-02-10 1999-08-18 Sony Corporation IC card, IC card processor and IC card system
EP0936571A3 (en) * 1998-02-10 2002-08-21 Sony Corporation IC card, IC card processor and IC card system
WO2000021204A1 (en) * 1998-10-06 2000-04-13 Crosslink, Inc. A system for reducing transmitter cross-talk in receive part of a rf transceiver
WO2001036995A1 (en) * 1999-11-18 2001-05-25 Marconi Data Systems Ltd. Multimode transceiver circuit
US6895226B1 (en) 1999-11-18 2005-05-17 Ian J Forster Multimode transceiver circuit
USRE42604E1 (en) 1999-11-18 2011-08-09 Mineral Lassen Llc Multimode transceiver circuit
WO2002009021A1 (en) * 2000-07-21 2002-01-31 Microcid Sa High sensitivity reader for passive transponders
US7014111B2 (en) 2000-07-21 2006-03-21 Mbbs Holding S.A. High sensitivity reader for passive transponders
US7240838B2 (en) 2000-07-21 2007-07-10 Mbbs Holding S.A. Transponder and reader system
EP1710727A1 (en) 2005-04-08 2006-10-11 Fujitsu Limited RFID transceiver device
US7492812B2 (en) * 2005-04-08 2009-02-17 Fujitsu Limited RFID transceiver device
CN1845469B (en) * 2005-04-08 2010-05-05 富士通株式会社 Rfid transceiver device

Also Published As

Publication number Publication date
GB8103989D0 (en) 1996-04-24
GB2300318B (en) 1997-03-19

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Legal Events

Date Code Title Description
730A Proceeding under section 30 patents act 1977
PE20 Patent expired after termination of 20 years

Effective date: 20010209