WO1992014307A1 - Method of achieving a closed synchronization loop for two-way communication between a transponder and an interrogator, where different frequencies can be used for the communication between the interrogator and the transponder - Google Patents

Method of achieving a closed synchronization loop for two-way communication between a transponder and an interrogator, where different frequencies can be used for the communication between the interrogator and the transponder Download PDF

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Publication number
WO1992014307A1
WO1992014307A1 PCT/SE1992/000059 SE9200059W WO9214307A1 WO 1992014307 A1 WO1992014307 A1 WO 1992014307A1 SE 9200059 W SE9200059 W SE 9200059W WO 9214307 A1 WO9214307 A1 WO 9214307A1
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WO
WIPO (PCT)
Prior art keywords
interrogator
transponder
frequency
communication
frequencies
Prior art date
Application number
PCT/SE1992/000059
Other languages
French (fr)
Inventor
Bengt Henoch
Linn Zeng
Original Assignee
Bengt Henoch
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 Bengt Henoch filed Critical Bengt Henoch
Publication of WO1992014307A1 publication Critical patent/WO1992014307A1/en

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Classifications

    • 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
    • G01S13/825—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted with exchange of information between interrogator and responder
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/14—Two-way operation using the same type of signal, i.e. duplex
    • H04L5/1469—Two-way operation using the same type of signal, i.e. duplex using time-sharing

Definitions

  • the present invention relates to a method of producing
  • Transponders are used as data carriers or as escort memories which can be read during the passage of interrogators or into which inform- ation can be written. Communication is normally effected with electro- magnetic waves of different frequencies, depending on the field of use. These frequencies range from frequencies of 100 kHz to high microwave frequencies, and the applications determine generally the frequency to be used. Generally speaking, low frequencies are used when the distance between transponder and interrogator is short and when miniaturization is desired, while long distances and high data speeds lead to the choice of microwave frequencies.
  • the present invention solves this problem and relates to a method which will enable two-way communication links operating at different frequencies between transponder and interrogator to be integrated and made compatible.
  • the present invention also provides the technical advantage of enabling range to be selected and a minimum number of components to be used.
  • the present invention relates to a method for producing a closed synchronizing loop for two-way communication between a transponder and an interrogator where different frequencies may be used for communication between interrogator and transponder, said method being characterized by effecting communication between interrogator and transponder by sending a clock signal from the interrogator to the transponder and vice versa, for controlling two-way communication between interrogator and transponder; demodulating data at a low frequency, both when communication between interrogator and transponder is effected via micrcowave frequencies and via lower frequencies, by transmitting two or more microwave frequencies from the interrogator in that case when microwave frequencies are used, where a difference frequency constitutes a clock signal of the same frequency as the aforesaid clock signal when communication is effected at said lower frequencies.
  • FIG. 1 is a simple block schematic of an interrogator and a transponder where relatively low freqencies are used;
  • Figure 1 illustrates a communication link which is intended for comparatively low frequencies.
  • the link includes an interrogator 1 and a transponder 2.
  • the interrogator includes a generator 3 which is constructed to generate two frequencies f1 and 1/2 fl, i.e frequencies of 114 kHz and 57 kHz.
  • the link also includes a phase modulator 4 which is intended to modulate the frequency f1 with a phase-shift of 0° /180° according to the data that is to be sent from the interrogator to the transponder.
  • the interrogator also includes a transmission coil 5 which couples the modulated fl-signal and the nonmodulated 1/2 fl-signal to a receiver coil 6 belonging to the transponder 2.
  • the signals received by the transponder are passed to two rectifier bridges, wherein the f1-signal is passed to a first rectifier bridge 8 via a highpass or bandpass filter 7, and the 1/2 fl-signal is passed to a second rectifier bridge, via a l ⁇ wpass or bandpass filter 9.
  • a half-wave rectified f1-signal and a full-wave rectified 1/2 f1signal are thus formed in this way.
  • the thus rectified signals are passed to a D-type flip-flop circuit 13, via respective amplifiers 11, 12.
  • the amplifiers are saturated amplifiers which produce a rectangular-wave output signal.
  • Figures 2 and 3 are voltage-time-diagrams which illustrate three different signals.
  • Figures 3a and 3b show the last mentioned signals down-stream of the amplifier 11.
  • the signal shown in Figure 2c appears on the input of the amplifier 12 and the signal shown in Figure 3c on the output of the amplifier 12.
  • the signal shown in Figure 3a and Figure 3b is applied to the signal input of the flip-flop circuit 12 and the signal s how n Figure 3c applied to the clock input thereof.
  • the flip-flop circuit is trigger by the positive flanks of the clock signal (Fig. 3c).
  • the flip-flop circuit shows a binary "1" for phase position 0° and a binary "0" for phase position 180°. This means that the phase-modulated signal demodulated without using a phase-locked loop to recover the carrier wave frequency.
  • the signal appearing on the output 13 of the flip- flop circuit is sent to data storing and/or data processing circuits, not shown.
  • a non-modulated signal f1 or 1/2 f1 is transmitted and the other of said two signals is switched off in the generator 3.
  • signal f1 is sent from the interrogator
  • the signal received by the transponder will form the transponder clock.
  • the fullwave-rectified f1-signal received in the transponder is coupled to an amplifier 14 and a muliplication circuit 15, this circuit being intended to deliver a sinusoidal signal whose frequency is a whole-number fraction of f1, i.e. 1/2, 2, 4 and so on.
  • the signal from the multiplication circuit 15 is applied to phase modulator 16, which is intended to phase- modulate the signal with a phase shift of 0°/l80°, i.e.
  • the phase modulator is con- trolled by a modulator which functions to modulate the phase modulator with data whose bit length is synchronized with f1, such that each data bit will be an integer number of carrier wave periods.
  • the thus phase-modulated signal is fed back to the transponder coil 6, the transmitted signal being received by a receiver coil 17 in the interrogator.
  • the coil 17 is coupled to a rectifying bridge 18, so as to farm a half-wave-rectified signal.
  • the half-wave-rectified signal is passed to the signal input of a D-type 20 flip-flop circuit, via a saturated amplifier 19 on whose output a square wave appears.
  • a digitalized signal is thus applied to the signal input.
  • a carrier wave and phase reference produced by the generator 3 and digitilized by an amplifier 21 is applied to the clock input of the flip-flop circuit, whereby the demodulated phase-modulation occurs on the output of the flip-flop circuit in the same manner as that described for the flip-flop circuit 12.
  • the described low frequent link may form part of a microwave link.
  • the interrogator coil 5 is replaced with a microwave generator 28 and a microwave antenna 22.
  • the microwave generator 28 is intended to transmit two signals of microwave frequency, which are frequency modulated with the frequencies f1 and 1/2 f1 respectively by means of the earlier mentioned generator 3, one of said two signals being modulated with f1 and the other with 1/2 f1, as illustrated in Figure 6.
  • the transponder coil 6 is replaced with a receiving microwave antenna 23 which includes a mixer diode 24, this diode causing the frequencies f1 and 1/2 f1 to lie after the antenna, said frequencies being applied to the aforesaid filters 7, 9.
  • the coil 6 is also replaced with a reflecting microwave antenna 25, to which a modulator diode 26 is connected. This modulator diode is supplied from the earlier mentioned modulator 16, said modulation occurring as a sideband of the reflected microwave signal.
  • the coil 17 is replaced with a microwave antenna 27 and a homodyne receiver 28, said receiver having two channels for the detection of sidebands of respective microwave carrier waves transmitted from the interrogator.
  • the modulation signal produced by the modulator 16 has the frequency of 1/2 f1 and the transponder receives two non-modulated microwave s with the difference frequency f1
  • methods taught by Swedish Patent Specification No. 8902808-8 are used to generate in the transponder sidebands with mutual amplitude relationships, so as to enable simple sidebands to be demodulated in the interrogator.
  • the modulation signal produced by the modulator 16 has the frequency N x f1, where N is a whole-number fraction, i.e. a fraction between two integers, so-called cross-mixing is applied, which means that incoming sidebands belonging to one carrier wave are mixed with the other carrier wave.
  • the intermediate frequency from the homodyne receiver 28 will then be (N +/- 1) ⁇ f1, zero positions depending on the distance between interrogator and transponder not occurring in the received signal.
  • the homodyne receiver 28 is coupled to the rectifying bridge 18 in the same way as the coil 17.
  • the frequency of one microwave signal is passed from the microwave generator 28 to the homodyne receiver via a conductor 29, this signal serving as a local oscillator.
  • the frequency f1 is applied to the clock input of the flip-flop circuit 20, via a conductor 30.

Abstract

A method of producing a closed synchronization loop for two-way communication between a transponder and an interrogator where different frequencies may be used for communication between interrogator and transponder. The invention is characterized in that communication between interrogator (1) and transponder (2) is accomplished by sending a clock signal from the interrogator to the transponder and vice versa, for controlling two-way communication between interrogator and transponder; in that the demodulation of data is effected at a low frequency, both when communication between interrogator (1) and transponder (2) is effected via microwave frequencies and via lower frequencies, by transmitting two or more microwave frequencies from the interrogator in that case when microwave frequencies are used, wherein a difference frequency constitutes a clock signal of the same frequency as the frequency of the clock signal when said communication is effected at lower frequencies.

Description

Method of achieving a closed synchronisation loop for two-way communication between a transponder and an interrogator, where different frequencies can be used for the communication between the interrogator and the transponder.
The present invention relates to a method of producing
a closed synchronization loop for two-way communication between a transponder and an interrogator.
Transponders are used as data carriers or as escort memories which can be read during the passage of interrogators or into which inform- ation can be written. Communication is normally effected with electro- magnetic waves of different frequencies, depending on the field of use. These frequencies range from frequencies of 100 kHz to high microwave frequencies, and the applications determine generally the frequency to be used. Generally speaking, low frequencies are used when the distance between transponder and interrogator is short and when miniaturization is desired, while long distances and high data speeds lead to the choice of microwave frequencies.
A characteristic feature of this area of technology is found in the number of different technical solutions that are proposed and in the small degree of compatability between these solutions and the lack of any real possibility of coupling these solutions together. The present invention solves this problem and relates to a method which will enable two-way communication links operating at different frequencies between transponder and interrogator to be integrated and made compatible. The present invention also provides the technical advantage of enabling range to be selected and a minimum number of components to be used.
Accordingly, the present invention relates to a method for producing a closed synchronizing loop for two-way communication between a transponder and an interrogator where different frequencies may be used for communication between interrogator and transponder, said method being characterized by effecting communication between interrogator and transponder by sending a clock signal from the interrogator to the transponder and vice versa, for controlling two-way communication between interrogator and transponder; demodulating data at a low frequency, both when communication between interrogator and transponder is effected via micrcowave frequencies and via lower frequencies, by transmitting two or more microwave frequencies from the interrogator in that case when microwave frequencies are used, where a difference frequency constitutes a clock signal of the same frequency as the aforesaid clock signal when communication is effected at said lower frequencies. The invention will now be described in more detail with reference to an exemplifying embodiment thereof illustrated in the accompanying drawings, in which
- Figure 1 is a simple block schematic of an interrogator and a transponder where relatively low freqencies are used;
- Figures 2 and 3 show signals at certain points in the block schematic of Fig. 1;
- Figures 4 and 5 show respectively part of an interrogator and part of a transponder where microwave freqencies are used; and
- Figure 6 is a freqency diagram.
Figure 1 illustrates a communication link which is intended for comparatively low frequencies. The link includes an interrogator 1 and a transponder 2. The interrogator includes a generator 3 which is constructed to generate two frequencies f1 and 1/2 fl, i.e frequencies of 114 kHz and 57 kHz. The link also includes a phase modulator 4 which is intended to modulate the frequency f1 with a phase-shift of 0° /180° according to the data that is to be sent from the interrogator to the transponder. The interrogator also includes a transmission coil 5 which couples the modulated fl-signal and the nonmodulated 1/2 fl-signal to a receiver coil 6 belonging to the transponder 2. The signals received by the transponder are passed to two rectifier bridges, wherein the f1-signal is passed to a first rectifier bridge 8 via a highpass or bandpass filter 7, and the 1/2 fl-signal is passed to a second rectifier bridge, via a lσwpass or bandpass filter 9. A half-wave rectified f1-signal and a full-wave rectified 1/2 f1signal are thus formed in this way.
The thus rectified signals are passed to a D-type flip-flop circuit 13, via respective amplifiers 11, 12. The amplifiers are saturated amplifiers which produce a rectangular-wave output signal.
Figures 2 and 3 are voltage-time-diagrams which illustrate three different signals. The signal f1 can be designated as f1 = cos(2πf1xt + 0°/180°), Figure 2a showing the signal at phase position 0° and Figure 2b showing the signal at phase position 180°. These signals appear on the input of amplifier 11, the configuration of the signal being, of course, dependent on that data which controls the phase shift in the interrogator and which shall thus be transmitted to the transponder. Figures 3a and 3b show the last mentioned signals down-stream of the amplifier 11.
The signal 1/2 f1 can be designated 1/2 f1 = sin(πf1xt). The signal shown in Figure 2c appears on the input of the amplifier 12 and the signal shown in Figure 3c on the output of the amplifier 12.
The signal shown in Figure 3a and Figure 3b is applied to the signal input of the flip-flop circuit 12 and the signal s how n Figure 3c applied to the clock input thereof. The flip-flop circuit is trigger by the positive flanks of the clock signal (Fig. 3c). The flip-flop circuit shows a binary "1" for phase position 0° and a binary "0" for phase position 180°. This means that the phase-modulated signal demodulated without using a phase-locked loop to recover the carrier wave frequency. The signal appearing on the output 13 of the flip- flop circuit is sent to data storing and/or data processing circuits, not shown.
When transmitting from transponder to interrogator, a non-modulated signal f1 or 1/2 f1 is transmitted and the other of said two signals is switched off in the generator 3. For instance, if signal f1 is sent from the interrogator, the signal received by the transponder will form the transponder clock. The fullwave-rectified f1-signal received in the transponder is coupled to an amplifier 14 and a muliplication circuit 15, this circuit being intended to deliver a sinusoidal signal whose frequency is a whole-number fraction of f1, i.e. 1/2, 2, 4 and so on. The signal from the multiplication circuit 15 is applied to phase modulator 16, which is intended to phase- modulate the signal with a phase shift of 0°/l80°, i.e. in a manner corresponding to that described above. The phase modulator is con- trolled by a modulator which functions to modulate the phase modulator with data whose bit length is synchronized with f1, such that each data bit will be an integer number of carrier wave periods.
The thus phase-modulated signal is fed back to the transponder coil 6, the transmitted signal being received by a receiver coil 17 in the interrogator. The coil 17 is coupled to a rectifying bridge 18, so as to farm a half-wave-rectified signal. The half-wave-rectified signal is passed to the signal input of a D-type 20 flip-flop circuit, via a saturated amplifier 19 on whose output a square wave appears. A digitalized signal is thus applied to the signal input. A carrier wave and phase reference produced by the generator 3 and digitilized by an amplifier 21 is applied to the clock input of the flip-flop circuit, whereby the demodulated phase-modulation occurs on the output of the flip-flop circuit in the same manner as that described for the flip-flop circuit 12. Known possibilities of synchronized filtration and of forming mean values over given time intervals, etc, can be utilized in the receiver of the interrogator, which is afforded by the precise knowledge of the frequency of the return signal and the data-exchange time points. According to the invention, when the frequencies used are subcarrier waves of a carrier wave of micro wave frequency, the described low frequent link may form part of a microwave link.
In this case, the interrogator coil 5 is replaced with a microwave generator 28 and a microwave antenna 22. The microwave generator 28 is intended to transmit two signals of microwave frequency, which are frequency modulated with the frequencies f1 and 1/2 f1 respectively by means of the earlier mentioned generator 3, one of said two signals being modulated with f1 and the other with 1/2 f1, as illustrated in Figure 6.
Further, the transponder coil 6 is replaced with a receiving microwave antenna 23 which includes a mixer diode 24, this diode causing the frequencies f1 and 1/2 f1 to lie after the antenna, said frequencies being applied to the aforesaid filters 7, 9. The coil 6 is also replaced with a reflecting microwave antenna 25, to which a modulator diode 26 is connected. This modulator diode is supplied from the earlier mentioned modulator 16, said modulation occurring as a sideband of the reflected microwave signal.
The coil 17 is replaced with a microwave antenna 27 and a homodyne receiver 28, said receiver having two channels for the detection of sidebands of respective microwave carrier waves transmitted from the interrogator.
When the modulation signal produced by the modulator 16 has the frequency of 1/2 f1 and the transponder receives two non-modulated microwave s with the difference frequency f1, methods taught by Swedish Patent Specification No. 8902808-8 are used to generate in the transponder sidebands with mutual amplitude relationships, so as to enable simple sidebands to be demodulated in the interrogator. When the modulation signal produced by the modulator 16 has the frequency N x f1, where N is a whole-number fraction, i.e. a fraction between two integers, so-called cross-mixing is applied, which means that incoming sidebands belonging to one carrier wave are mixed with the other carrier wave. The intermediate frequency from the homodyne receiver 28 will then be (N +/- 1) × f1, zero positions depending on the distance between interrogator and transponder not occurring in the received signal.
The homodyne receiver 28 is coupled to the rectifying bridge 18 in the same way as the coil 17. The frequency of one microwave signal is passed from the microwave generator 28 to the homodyne receiver via a conductor 29, this signal serving as a local oscillator. The frequency f1 is applied to the clock input of the flip-flop circuit 20, via a conductor 30.
It is thus clear that a link which is compatible to both high and low frequencies can be obtained in the afore described manner, at the same time as a clock signal is sent to the transponder while avoiding the problem of zero setting at the same time.

Claims

Claims
1. A method of producing a closed synchronization loop for two-way communication between a transponder and an interrogator where different frequencies may be used for comm unication between interrogator and transponder, character i z ed by effecting communication between interrogator (1) and transponder (2) by sending a clock signal from the interrogator to the transponder and vice versa, for controlling two-way communication between interrogator and transponder; demodulating data at a low frequency, both when communication between interrogator (1) and transponder (2) is effected via microwave frequencies and via lower frequencies, by transmitting two or more microwave frequencies from the interrogator in that case when microwave frequencies are used, wherein a difference frequency constitutes a clock signal of the same frequency as the frequency of the clock signal when communication is effected at said lower frequencies.
2. A method according to Claim 1, character i z ed in that when using microwave frequencies, a low-frequency link is included as a so-called subset to the high frequency link operating at the microwave frequency, by causing the low frequency link to operate with subcarrier waves of the high frequency link.
3. A method according to Claim 1 or 2 character i z ed by applying so-called cross-mixing when the modulation signal produced by the modulator (16) in the transponder (2) has the frequency N x f1, where N is a whole-number fraction,
thereby mixing incoming sidebands belonging to one carrier wave with the other carrier wave, whereby an intermediate frequency becomes (N +/- 1) x f1 and no zero positions which are dependent on the distance between interrogator (1) and transponder (2) will occur in the received signal.
PCT/SE1992/000059 1991-02-01 1992-01-30 Method of achieving a closed synchronization loop for two-way communication between a transponder and an interrogator, where different frequencies can be used for the communication between the interrogator and the transponder WO1992014307A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9100323-6 1991-02-01
SE9100323A SE468030B (en) 1991-02-01 1991-02-01 METHOD FOR AUTHORIZING A CLOSE SYNCHRONIZATION PROCESS FOR A DOUBLE-DIRECT COMMUNICATION BETWEEN A TRANSPONDER AND AN INTERROGATOR WHERE DIFFERENT FREQUENCIES MAY BE USED BEFORE COMMUNICATION BETWEEN THE INTERROGATOR AND TRANSPORTER

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997007414A1 (en) * 1995-08-16 1997-02-27 Alfa Laval Agri Ab Antenna system comprising driver circuits for transponder
BE1012370A3 (en) * 1998-12-24 2000-10-03 Abay T S Vehicle identification system
US6952157B1 (en) * 2001-05-31 2005-10-04 Alien Technology Corporation System and method for concurrently addressing multiple radio frequency identification tags from a single reader
WO2018166790A1 (en) * 2017-03-14 2018-09-20 Thales Device for modulating a microwave signal, transponder including such a device, and responder beacon equipped with such a transponder

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3467962A (en) * 1966-12-15 1969-09-16 Sodeteg Object identification system
US4390880A (en) * 1976-09-02 1983-06-28 Stiftelsen Institute For Mikrovagstenknik Vid Tekniska Hogskolan I Stockholm Radio communication system and transmitter and receiver equipment therefor
WO1991003109A1 (en) * 1989-08-23 1991-03-07 Bengt Henoch A method for the contactless transmission of information

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3467962A (en) * 1966-12-15 1969-09-16 Sodeteg Object identification system
US4390880A (en) * 1976-09-02 1983-06-28 Stiftelsen Institute For Mikrovagstenknik Vid Tekniska Hogskolan I Stockholm Radio communication system and transmitter and receiver equipment therefor
WO1991003109A1 (en) * 1989-08-23 1991-03-07 Bengt Henoch A method for the contactless transmission of information

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997007414A1 (en) * 1995-08-16 1997-02-27 Alfa Laval Agri Ab Antenna system comprising driver circuits for transponder
BE1012370A3 (en) * 1998-12-24 2000-10-03 Abay T S Vehicle identification system
US6952157B1 (en) * 2001-05-31 2005-10-04 Alien Technology Corporation System and method for concurrently addressing multiple radio frequency identification tags from a single reader
WO2018166790A1 (en) * 2017-03-14 2018-09-20 Thales Device for modulating a microwave signal, transponder including such a device, and responder beacon equipped with such a transponder
FR3064141A1 (en) * 2017-03-14 2018-09-21 Thales DEVICE FOR MODULATING A HYPERFREQUENCY SIGNAL, TRANSPONDER COMPRISING SUCH A DEVICE, AND ANSWERING BEACON COMPRISING SUCH A TRANSPONDER
US10879846B2 (en) 2017-03-14 2020-12-29 Thales Device for modulating a microwave signal, transponder including such a device, and responder beacon equipped with such a transponder

Also Published As

Publication number Publication date
SE9100323D0 (en) 1991-02-01
SE9100323L (en) 1992-08-02
SE468030B (en) 1992-10-19

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