Transponder system

• US 5,305,008 A
• Filed: 09/04/1992
• Issued: 04/19/1994
• Est. Priority Date: 08/12/1991
• Status: Expired due to Term

• Current Assignee: Integrated Silicon Design Pty Ltd. (Thales SA)
• Original Assignee: Integrated Silicon Design Pty Ltd. (Thales SA)
• Inventors: Turner, Leigh H., Cole, Peter H.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US07/941,322
• Time in Patent Office: 592 Days
• Field of Search: 342/44, 342/42, 342/51
• US Class Current: 342/44
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal

Abstract

An identification and telemetry system comprising: a signal responding label including a first antenna for receiving an interrogation signal and for scattering a reply signal, an impedance connected to the first antenna, means for generating the reply signal and means for varying the impedance connected to the first antenna in accordance with the reply signal; and an interrogator comprising a second antenna for transmitting an interrogation signal and for receiving the reply signal, a transmitter connected to the second antenna and including a generator of pulsed radio frequency energy, means for separating the reply signal from the transmitted signal, a receiver connected to the second antenna and means within the receiver for detecting and decoding the reply signal.

Claims

1. A signal responding label for an identification and telemetry system, said label comprising:

a radio frequency antenna for receiving an interrogation signal at an interrogation frequency;

a resonator including an inductance and a capacitance, having a resonant frequency equal to the interrogation frequency and including an impedance connected to said antenna;

a reply generator for generating reply signals;

a rectifier system including a diode for providing at least part of the power required by said reply generator; and

means for varying said impedance in accordance with the reply signal such that a portion of the interrogation signal is scattered by said antenna;

the improvement wherein said resonator produces voltage magnification and the capacitance of said resonator comprises substantially the junction capacitance of the diode so as to optimize said magnification.

2. A signal responding label as claimed in claim 1, wherein said resonator has a pass band width which includes the interrogation signal frequency and frequencies of significant components of the reply signal.

3. A signal responding label as claimed in claim 2, wherein the inductance in said resonator is adjusted such that said resonant frequency occurs at a value of junction capacitance of said diode, said value being voltage dependent, which applies at a desired signal level within the label.

4. A signal responding label as claimed in claim 3, wherein the capacitance of the voltage multiplying resonator comprises the junction capacitance of a plurality of diodes within the rectifier.

5. A signal responding label as claimed in claim 3, wherein the radiation impedance of the radio frequency antenna is matched to the dynamic impedance of the voltage magnifying resonator.

6. A signal responding label as claimed in claim 2, wherein said antenna comprises a magnetic loop having self inductance which provides the inductance forming the voltage magnifying resonator.

7. A signal responding label as claimed in claim 2, wherein said means for varying said impedance comprises a transistor in series with a resistor, said transistor and resitor being proportioned to produce an impedance versus voltage characteristic which matches the output impedance versus voltage characteristic of said rectifier system.

8. A signal responding label for an identification and telemetry system, said label comprising:

a radio frequency antenna for receiving an interrogation signal at an interrogation frequency;

a resonator incorporating a rectifier diode connected to said antenna and having a resonant frequency equal to said interrogation frequency; and

a generator for generating reply signals;

characterised in that said resonator produces voltage magnification and the capacitance of said resonator comprises substantially the junction capacitance of said diode so as to optimize said magnification.

44. A signal responding label as claimed in claim 8 wherein said diode provides at least part of the power required by said reply generator.

9. An interrogator for an identification and telemetry system, said interrogator comprising:

an antenna for transmitting an interrogation signal incorporating amplitude modulated radio frequency energy at an interrogation frequency, said radio frequency energy including a modulation waveform having during a first period a first amplitude and during a second period a second and lesser amplitude;

means connected to said antenna for generating said interrogation signal;

an antenna for receiving from a signal responding label, during said first period, an analog reply signal containing information and forming a complete reply message;

means for separating the interrogation and analog reply signals;

means for converting said separated analog reply signal to a lower frequency band; and

means for processing the separated analog reply signal to extract the label reply information, the improvement wherein the first period is of a length sufficient to receive from the label the complete reply message, and wherein said processing means includes;

means for sampling the converted analog reply signal at a rate sufficient to detect significant components thereof;

means for further converting the sampled values of the lower frequency band signal to digital form;

means for storing the converted sampled values to create a digital record of the analog reply signal received during the first period, said digital record comprising the complete label reply message; and

means for decoding the stored sampled values during the second period to extract said label reply information from said record.

10. An interrogator as claimed in claim 9, wherein the decoding means includes digital filtering, examination of the positions of zero crossings and variation in amplitude between samples for creating tables of waveform descriptors, and the use of those tables to find, within the reply record, the reply bit intervals, the values of individual reply bits, and start of message.

11. An interrogator as claimed in claim 10, wherein the waveform of the label reply is repeated cyclically as long as a relatively high power level of the interrogation signal is received by the label, and wherein reply generating means within the label is arranged to insert a unique data word within the reply signal to indicate the start of message, and the decoding means is arranged to detect, from the record of the cyclically repeated reply waveform, the start of message.

12. An interrogator as claimed in claim 11, wherein decoding is performed adaptively so as not to be affected by variations in the label reply signal caused by variations in the frequency of an oscillator circuit within the signal responding label.

13. An interrogator as claimed in claim 12, wherein the decoding means includes a search for evidence of either frequency or angle modulation within the record of reply waveform, with subsequent decoding steps being dependent upon the result of that search.

14. An interrogator for an identification and telemetry system as claimed in claim 9, wherein shaping of the interrogation signal envelope is such as to have zero amplitude during said second period.

15. An interrogator for an identification and telemetry system, said interrogator comprising:

an antenna for transmitting an interrogation signal including radio frequency energy;

means for generating said interrogation signal connected to said antenna;

an antenna for receiving from a signal responding label an analog reply signal containing information; and

means for separating the interrogation and reply signals;

the improvement wherein said interrogator includes first means for converting a component of the analog reply signal which is in phase with the interrogation signal to a lower frequency band to create a first low-frequency channel;

second means for converting a component of the analog reply signal which is in quadrature with the interrogation signal to a lower frequency band to create a second low-frequency channel;

separate means for extracting said information from each of those channels;

means for comparing the results of said extraction; and

means for choosing between the two extracted results such that one only of them is reported as the result of the interrogation.

16. An interrogator for an identification and telemetry system as claimed in claim 15, including means for detecting, within the reply signals in each of the in-phase and quadrature channels, rapid frequency changes while ignoring slow frequency changes.

17. An interrogator for an identification and telemetry system as claimed in claim 15, wherein the information extracted from the signals in each of the two channels includes an indication of the quality of the label reply or of the extraction process.

18. An interrogator for an identification and telemetry system, said interrogator comprising:

an antenna for transmitting an interrogation signal incorporating amplitude modulated radio frequency energy at an interrogation frequency, said radio frequency energy including a modulation waveform having, during a first period, a first amplitude and, during a second period, a second and lesser amplitude;

means connected to said antenna for generating said interrogation signal;

an antenna for receiving from a signal responding label, during said first period, an analog reply signal containing information and forming a complete reply message;

means for separating the interrogation and said analog reply signals;

means for converting said separated analog reply signal to a lower frequency band; and

means for processing the separated analog reply signal to extract the label reply information, the improvement wherein the first period is of a length sufficient to receive from the label the complete reply message, and wherein said converting and processing means includes;

first means for converting a component of the analog reply signal which is in phase with the interrogation signal to a lower frequency band to create a first base band channel;

second means for converting a component of the analog reply signal which is in quadrature with the interrogation signal to a lower frequency band to create a second base band channel;

separate means for sampling the converted analog reply signals in the first and second base band channels, at a rate sufficient to detect significant frequency components thereof;

means for further converting the sampled values to digital form;

means for storing the converted sampled values to create separate digital records of the in-phase and quadrature components of the analog reply received during the first period; and

means for extracting said information during the second period by separate filtering and decoding of the stored sampled values in each of the two separate digital records;

means for comparing results of said extraction; and

means for choosing between the two extracted results such that one only of them is reported as the result of the interrogation.

19. An interrogator for an identification and telemetry system as claimed in claim 18, wherein the separate stored digital records of the reply signals in the in-phase and quadrature channels are decoded sequentially.

20. An interrogator for an identification and telemetry system as claimed in claim 18, wherein, if the result of decoding the channel first is satisfactory, decoding of the other channel does not proceed and the result of decoding is reported.

21. An interrogator for an identification and telemetry system as claimed in claim 19, wherein the strongest of the two replies in the in-phase and quadrature channels is selected for initial decoding.

22. An interrogator for an identification and telemetry system as claimed in claim 20, wherein decoding for each channel includes an hierarchy of checks for a satisfactory reply, and decoding of one channel is abandoned as soon as it becomes clear that an unsatisfactory reply in that channel has been received.

23. An interrogator for an identification and telemetry system as claimed in claim 22, wherein the time between interrogation pulses depends upon the time taken for decoding of the reply obtained from the previous interrogation pulse.

24. An interrogator for an identification and telemetry system as claimed in claim 18, wherein shaping of the interrogation signal envelope is such as to have zero amplitude during said second period.

25. An interrogator for an identification and telemetry system, said interrogator comprising:

an antenna for transmitting an interrogation signal incorporating amplitude modulated radio frequency energy at an interrogation frequency;

means for generating said interrogation signal connected to said antenna;

an antenna for receiving a complete label reply signal from a signal responding label containing an oscillator;

means for separating the interrogation and reply signals;

means for transmitting the separated reply signal to a receiver; and

means within the receiver for decoding the reply signal;

the improvement wherein;

said radio frequency includes a modulation waveform having, during a first period, a first amplitude and during a second period, a second and lesser amplitude wherein said oscillator is used for forming said reply signal during said first period, and wherein the envelope of the interrogation signal is shaped to allow, during said first period, coherent operation of the oscillator within the label for a period sufficient for the label to transmit at least one complete label reply.

26. An interrogator for an identification and telemetry system as claimed in claim 25, wherein the amplitude and envelope of the interrogation signal is shaped so that the power which is transmitted during the first period of the interrogation signal is the largest possible subject to a need to achieve at least a required repetition rate of interrogations and to satisfy regulations which limit both peak to average power ratio and average power over a specified averaging period.

27. An interrogator for an identification and telemetry system as claimed in claim 25, wherein the amplitude and envelope of the interrogation pulse is shaped to achieve maximum interrogation range having regard to:

dependence of label oscillator frequency upon power level reaching the label;

a need for at least a required repetition rate of interrogations; and

regulations which limit both peak to average power ratio and average power allowed over a specified averaging period.

28. An interrogator for an identification and telemetry system as claimed in claim 27, wherein the amplitude and envelope of the interrogation pulse is shaped to have regard to dependence of the level of transmitter noise in the frequency band used by the label reply signal, which is present in the receiver upon the label oscillator frequency.

29. An interrogator for an identification and telemetry system as claimed in claim 28, wherein shaping of the interrogation signal envelope is such as to have zero amplitude during said second period.

30. An interrogator for an identification and telemetry system, said interrogator comprising:

a transmitter containing means for generating an amplitude modulated radio frequency interrogation signal;

an antenna connected to said transmitter for transmitting the amplitude modulated interrogation signal supplied by the transmitter;

an antenna for receiving, from a signal responding label, a label reply signal;

separation means for effecting coarse separation of said reply signal from said interrogation signal;

a receiver connected to said separation means;

an auxiliary coupling channel to feed a portion of the interrogation signal directly the receiver wherein it is combined with the reply signal emerging from said separation means;

adjustment means for control of the amplitude and phase of the interrogation signal emerging from the auxiliary coupling channel;

measurement means for determining of the amplitude and phase of the combined signal at the interrogation frequency reaching the receiver;

an adaptive control block connected to said measurement means for producing control signals for said adjustment means;

characterised in that said control block operates to optimise performance of the receiver.

35. An interrogator for an identification and telemetry system as claimed in claim 30, wherein said adaptive control block provides information on motion of objects within the field of the interrogator antenna.

36. An interrogator for an identification and telemetry system as claimed in claim 35, wherein said modulation waveform has during a first period a first amplitude and during a second period a second and lesser amplitude, and said information is used to shorten, for fast moving objects, elapsed time between high power periods of the interrogation signal.

31. An interrogator for an identification and telemetry system, said interrogator comprising:

a transmitter containing means for generating an amplitude modulated radio frequency interrogation signal;

an antenna connected to said transmitter for transmitting the amplitude modulated interrogation signal supplied by the transmitter;

an antenna for receiving, from a signal responding label, a label reply signal;

separation means for effecting coarse separation of said reply signal from said interrogation signal;

a receiver connected to said separation means;

an auxiliary coupling channel to feed a portion of the interrogation signal directly to the receiver wherein it is combined with the reply signal emerging from said separation means;

adjustment means for control of the amplitude and phase of the interrogation signal emerging from the auxiliary coupling channel; and

measurement means for determining of the amplitude and phase of the combined signal at the interrogation frequency reaching the receiver;

the improvement wherein said interrogator includes an adaptive control block connected to said measurement means for producing control signals for said adjustment means, said control block being adapted to minimize direct coupling between said transmitter and receiver so as to optimise performance of the receiver.

32. An interrogator for an identification and telemetry system as claimed in claim 31, wherein the interrogator uses an amplitude modulated interrogation signal and the receiver uses a continuous wave local oscillator signal fed to a mixer which is used in the receiver, so that the signal level at the interrogation frequency reaching the receiver may be estimated by examining mixer output, even when mixers with imperfect isolation between the local oscillator input and mixer output are used.

33. An interrogator for an identification and telemetry system as claimed in claim 31, wherein the pass band of the auxiliary coupling channel is matched in its variation in amplitude and phase, relative to a centre value of the pass band, to corresponding behaviour of unwanted coupling between the transmitter and receiver arising from imperfections in said coarse separation means or from coupling between separate transmitter and receiver antennas.

34. An interrogator for an identification and telemetry system as claimed in claim 33, wherein said matching is achieved by use of broad band components in the antenna and duplexer systems of the interrogator.

37. An interrogator for an identification and telemetry system as claimed in claim 33, wherein shaping of the interrogation signal envelope is such as to have zero amplitude during said second period.

38. An interrogator for an identification and telemetry system, said interrogator comprising:

a transmitter for transmitting an interrogation signal including a modulation waveform having, during a first period a first amplitude and, during a second period a second and lesser amplitude;

a generator for generating radio frequency energy at an interrogation frequency, a local oscillator signal for a receiver and said modulated interrogation signal for said transmitter;

a transmitter antenna connected to said transmitter for transmitting said interrogation signal;

an antenna for receiving from a signal responding label an analog reply signal containing information;

a controllable phase shifter for adjusting relative phase of the reply signal and said local oscillator signal;

an interrogator controller providing control signals to said phase shifter;

means for converting the reply signal to a lower frequency band to create a low-frequency channel;

means for extracting said information from a signal in said low-frequency channel;

means for examining the quality of the extracted information;

characterised in that the interrogator controller is programmed to significantly alter the phase shift provided by said phase shifter whenever the extracted information is judged to be unsatisfactory.

39. An interrogator for an identification and telemetry system as claimed in claim 38, wherein the significant alteration provided by the phase shifter is by an amount of 90 degrees.

40. An interrogator for an identification and telemetry system as claimed in claim 39, wherein the means for extracting said information, includes:

means for sampling the signal in said low frequency channel, at a rate sufficient to detect significant components thereof;

means for converting the sampled values to digital form;

means for storing the converted sampled values to create a digital record of the analog reply signal; and

means, in the time between relatively high power periods of the interrogation waveform, for filtering and decoding the stored sampled values to extract said information from said record.

41. An interrogator for an identification and telemetry system as claimed in claim 40, wherein shaping of the interrogation signal envelope is such as to have zero amplitude during said second period.

42. A signal responding label for an identification and telemetry system, said label comprising:

a radio frequency antenna for receiving an interrogation signal at an interrogation frequency;

a rectifier system containing a diode and providing a dc supply with positive and negative terminals for supplying power to an integrated circuit including a generator for generating a reply signal;

a multiplexer within said generator, inputs of said multiplexer being connectable to said positive or negative terminals for effecting coding of the reply signal;

characterised in that a larger portion of the reply signal is programmed at time of manufacture of the integrated circuit to include a fixed code and a cyclic redundancy check, while the remainder of the reply signal is programmed by means of connections made externally to the integrated circuit to contain a separate and shorter code, and an error correcting code.

43. A signal responding label for an identification and telemetry system as claimed in claim 42, including a voltage magnifying resonator having an inductance and a capacitance and a resonant frequency equal to said interrogation frequency, and wherein the capacitance of said resonator comprises substantially the junction capacitance of said diode.