Micropower RF transponder with superregenerative receiver and RF receiver with sampling mixer

• US 5,630,216 A
• Filed: 09/06/1994
• Issued: 05/13/1997
• Est. Priority Date: 09/06/1994
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: McEwan, Thomas E.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/300,765
• Time in Patent Office: 980 Days
• Field of Search: 455/336, 455/84, 455/313, 455/318-320, 340/825.54, 329/318, 329/323, 329/339, 329/334, 329/344, 375/316, 375/338, 375/339, 375/340, 375/214, 375/15
• US Class Current: 455/215
• CPC Class Codes: H03D 11/04 by means of semiconductor devices having more than two electrodes
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A micropower RF transdponder employs a novel adaptation of the superregenerative receiver wherein the quench oscillator is external to the regenerative transistor. The quench oscillator applies an exponentially decaying waveform rather than the usual sinewave to achieve high sensitivity at microampere current levels. Further improvements include circuit simplifications for antenna coupling, extraction of the detected signal, and a low-voltage bias configuration that allows operation with less than a 1-volt rail voltage. The inventive transponder is expected to operate as long as the battery shelf life.

Claims

1. An RF receiver comprising in combination:

a) an external quench oscillator for generating a series of quench oscillation pulses at a predetermined quench frequency;

b) an RC pulse forming network connected to said quench oscillator for converting said series of quench oscillation pulses into a series of differentiated exponentially damped drive pulses;

c) a self-detecting RF oscillator connected to, and driven by said drive pulses;

d) an antenna, connected to said RF oscillator, for receiving modulated RF signals;

e) an RC signal extraction network, connected to said RF oscillator, for blocking said quench frequency signals and for passing detected RF signals; and

f) a micropower amplifier, connected to said signal extraction network for amplifying said detected RF signals.

2. The RF receiver according to claim 1 wherein the RF oscillator comprises a bipolar transistor.

3. The RF receiver according to claim 1 wherein said oscillator is a Colpitts oscillator.

4. The RF receiver according to claim 3 wherein said Colpitts oscillator conducts on one polarity only of said exponentially damped drive pulses, and includes a transistor.

5. The RF receiver according to claim 3 further including an input coupling network connected between said antenna and said Colpitts oscillator.

6. The RF receiver according to claim 5 further including a logic interface and a data logic circuit for processing said amplified and detected RF signals at the output of said micropower amplifier.

7. The RF receiver according to claim 5 wherein said Colpitts oscillator includes a transistor having a collector, an emitter and a base;

and wherein said input coupling network is connected to said base.

8. The RF receiver according to claim 5 wherein said Colpitts oscillator includes a transistor having a collector, an emitter and a base;

and

wherein said input coupling network is connected to said collector.

9. The RF receiver according to claim 1 wherein said micropower amplifier includes:

a) a self-stabilizing amplifier comprising one or more inverters operated in the linear mode;

b) a power supply pin V_DD ; and

c) a current regulating circuit connected between a power supply and said power supply pin V_DD'"'"' for automatically maintaining said amplifier at a very low current level.

10. The RF receiver according to claim 9 wherein said current regulating circuit includes:

a) a resistor having a very high resistance value connected between said power supply and said power supply pin V_DD ; and

b) a bypass capacitor connected between said power supply pin V_DD and ground.

11. The RF receiver according to claim 9 wherein said current regulating circuit includes a constant current source connected between said power supply and said power supply pin V_DD.

12. The RF receiver according to claim 9 wherein said micropower amplifier further includes a highly resistive feedback path between the output and input of said self-stabilizing amplifier for causing it to operate in a linear mode.

13. An RF receiver comprising in combination:

a) a receive antenna for receiving RF signals;

b) a frequency selecting network, connected to said receive antenna, for determining one or more desired tuning frequencies;

c) a sampling mixer connected to said frequency selecting network and having an average impedance, for periodically sampling said RF signals to obtain a sampled replica of said RF signals;

d) said frequency selecting network acting as an impedance matching network, for providing a matched termination to said antenna and a high impedance output to match said average impedance of said sampling mixer;

e) said frequency selecting network having a relatively long unloaded output period and a long non-conductive sampling interval, whereby said frequency selecting network accumulates and stores energy during said non-conductive sampling interval, and, at the time of sampling, the stored energy is substantially extracted; and

f) a micropower amplifier, connected to said sampling mixer for amplifying said sampled replica signals.

14. The RF receiver according to claim 13 wherein said sampling mixer samples said modulated RF signals at multiples of the sampling frequency, as indicated by the following equation:

space="preserve" listing-type="equation">F(Sig)=F(RF)-nF(LO),

where F(Sig) is the modulated RF signal frequency;

F(RF) is the RF filtering frequency of said frequency selecting network;

n is an integer; and

F(LO) is the sampling frequency set by a local oscillator.

15. The RF receiver according to claim 14 wherein said sampling mixer comprises two Schottky diodes in a common cathode configuration, and wherein a local oscillator gate pulse is fed to the common cathode of said Schottky diodes.

16. The receiver according to claim 15 further including a local oscillator for generating a square wave oscillation signal.

17. The receiver according to claim 16 further including a pulse generator, connected to said local oscillator, for decreasing the rise time of said square wave oscillation signal.

18. The receiver according to claim 17 further including a pulse forming network, connected between said pulse generator and the common cathode of said Schottky diodes for converting said oscillation square wave signal at the output of said pulse generator into a high peak current signal with a fast rise time and an exponentially decaying tail.

19. A transponder comprising in combination:

a) a receive antenna for receiving modulated RF signals;

b) an RF receiver connected to said receive antenna;

c) a data processing network for processing data;

d) an RF transmitter for transmitting processed data over a transmit antenna; and

e) said RF receiver including;

i) an external quench oscillator for generating a series of pulses at a predetermined quench frequency;

ii) a pulse forming network connected to said quench oscillator for converting said series of periodic pulses into a series of exponentially damped drive pulses;

iii) an oscillator connected to, and driven by said drive pulses;

iv) said receive antenna, connected to said oscillator, for receiving said RF signals;

v) a signal extraction network, connected to said oscillator, for blocking said quench frequency signals and for passing detected RF signals; and

vi) a micropower amplifier, connected to said signal extraction network for amplifying said detected RF signals.

20. The transponder according to claim 19 wherein data pulses generated by said receiver are decoded by said data processing network, which provides an acceptance code;

and

wherein said data processing network generates a query and sends such query over said transmit antenna.