INTERFERENCE AVOIDANCE SUPERREGENERATIVE RECEIVER

• US 3,746,999 A
• Filed: 04/01/1971
• Issued: 07/17/1973
• Est. Priority Date: 04/01/1971
• Status: Expired due to Term

• Current Assignee: Philip Freen
• Original Assignee: Philip Freen
• Inventors: Freen, Philip
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/130,246
• Time in Patent Office: 838 Days
• Field of Search: 325/418,419,428,429 329/170 331/174
• US Class Current: 455/334
• CPC Class Codes: H03D 11/08 by means of semiconductor devices having more than two electrodes

Abstract

The audio output of an essentially conventional superregenerative receiver is rectified and connected back through a resistor to the capacitor of the quench oscillation circuit and to ground across a capacitor and resistor in parallel. This arrangement causes the quench frequency to vary with the detection of audio modulation, and the shift of local quench frequency avoids sustained detection of the incorrect signal. The interference signal may be the quench frequency of a nearby receiver. A capacitor is situated in the feedback circuit to prevent a shift of two receivers to the same, stable condition.

Claims

1. A superregenerative receiver comprising:

a regenerative circuit responsive to input signals and having a quench-frequency-determining circuit;

a modulation detection circuit responsive to signals from the regenerative circuit; and

, quench-frequency-varying feedback circuit means connected to the quench frequency determining circuit for continuously changing the quench frequency of the regenerative circuit in response to detected modulation to eliminate interference from signals in the quench frequency range which when combined with the quench frequency produce a beat frequency in the vicinity of the desired modulation frequency, whereby when a beat frequency in the vicinity of the desired modulation frequency is received, the quench frequency is changed to move the beat frequency away from the desired modulation frequency to prevent response to quenching beat frequencies.

2. The receiver as in claim 1 in which said modulation-detection circuit and said feedback circuit together comprise at least one rectifier and said feedback circuit is connected to feed back rectified signals.

3. The receiver as in claim 2 in which said feedback circuit also comprises a smoothing capacitor connected in parallel with said quench-frequency-determining circuit and a resistor connected in series between said smoothing capacitor and said quench-frequency-determining circuit, said smoothing capacitor being connected past said rectifier so that rectified, smoothed signals are fed back.

4. The circuit as in claim 1 in which said feedback circuit comprises a direct current blocking element which passes alternating current feedback signals.

5. The receiver as in claim 1 in which said quench-frequency-determining circuit comprises a resistor and a capacitor connected in parallel and said feedback circuit is connected to vary the charge on said capacitor.

6. The receiver as in claim 5 in which said modulation-detection circuit and said feedback circuit together comprise at least one rectifier and said feedback circuit is connected to feed back rectified signals.

7. The receiver of claim 1 wherein the feedback circuit is passive.

8. The receiver as in claim 6 in which said feedback circuit comprises a blocking capacitor to block direct current and pass alternating current feedback signals.

9. The receiver as in claim 8 in which said feedback circuit also comprising a smoothing capacitor connected in parallel with said quench-frequency-determining circuit and a resistor connected in series betweeN said smoothing capacitor and said quench-frequency-determining circuit, said smoothing capacitor being connected past said rectifier so that rectified, smoothed signals are fed back.

10. A superregenerative receiver comprising:

a regenerative transistor amplifier having a parallel RC quench-frequency-determining circuit;

a modulation-detection circuit connected to the output of the amplifier;

quench-frequency-varying feedback circuit means having its input connected to the modulation-detection circuit and having its output connected to the quench-frequency-determining circuit for continuously changing the quench frequency of the regenerative circuit in response to detected modulation to eliminate interference from signals in the quench frequency range which when combined with the quench frequency produce a beat frequency in the vicinity of the desired modulation frequency, whereby when a beat frequency in the vicinity of the desired modulation frequency is received, the quench frequency is changed to move the beat frequency away from the desired modulation frequency to prevent response to quenching beat frequencies;

said modulation-detection circuit and feedback circuit together comprising at least one rectifier;

said feedback circuit comprising;

a smoothing capacitor in parallel with the capacitor of the quench-frequency-determining circuit, a resistor and blocking capacitor in series between the smoothing capacitor and the quench-frequency-determining circuit, and said smoothing capacitor being connected between the rectifier and the quench-frequency-determining circuit to smooth rectified signals fed back to the quench-frequency-determining circuit.

11. Apparatus comprising two superregenerative receivers fixedly mounted in close proximity for simultaneous operation, each receiver comprising:

a regenerative circuit responsive to input signals and having a quench-frequency-determining circuit;

a modulation-detection circuit responsive to signals from the regenerative circuit, and;

quench-frequency-varying feedback circuit means connected to the quench-frequency-determining circuit for continuously changing the quench frequency of the regenerative circuit in response to detected modulation to eliminate interference from the quench frequency of the other receiver, which results when the quench frequencies of the two receivers combine to produce a beat frequency in the vicinity of the desired modulation frequency, whereby when a beat frequency in the vicinity of the desired modulation frequency is detected, the quench frequency of the detecting receiver is changed to move the beat frequency away from the desired modulation frequency to prevent response to quenching beat frequencies.

12. The apparatus of claim 11 wherein in each receiver the modulation-detection circuit and the feedback circuit together comprise at least one rectifier and said feedback circuit is connected to feedback rectified signals.

13. The apparatus of claim 12 wherein in each receiver said feedback circuit also comprises a smoothing capacitor connected in parallel with said quench-frequency-determining circuit and a resistor connected in series between said smoothing capacitor and said quench-frequency-determining circuit, said smoothing capacitor being connected past said rectifier so that rectified smoothed signals are fed back.

14. The apparatus of claim 11 wherein in each amplifier the feedback circuit comprises a direct current blocking element which passes alternating current feedback signals whereby the two receivers are prevented from reaching a steady state condition wherein the beat frequency of the two quenching frequencies is being detected as a modulation signal.

15. The apparatus of claim 11 wherein in each receiver, the quench-frequency-determining circuit comprises a resistor and a capacitor connected in parallel and said feedback circuit is connected to vary the charge on said capacitor.

16. The apparatus as in claim 15 wherein in each receiver, tHe modulation-detection circuit and the feedback circuit together comprise at least one rectifier and said feedback circuit is connected to feed back rectified signals.

17. The apparatus of claim 16 wherein in each receiver, said feedback circuit comprises a blocking capacitor to block direct current and pass alternating current feedback signals whereby the two receivers are prevented from reaching a steady state condition wherein the beat frequency of the two quenching frequencies is detected as a modulation signal.

18. The apparatus of claim 17 wherein in each receiver, said feedback circuit also comprises a smoothing capacitor connected in parallel with said quench-frequency-determining circuit and a resistor connected in series between said smoothing capacitor and said quench-frequency-determining circuit, said smoothing capacitor being connected past said rectifier so that rectified, smoothed signals are fed back.

19. Apparatus comprising two superregenerative receivers fixedly mounted in close proximity for simultaneous operation, each receiver comprising:

a regenerative transistor amplifier having a parallel RC quench-frequency-determining circuit;

a modulation-detection circuit connected to the output of the amplifier;

quench-frequency-varying feedback circuit means having its input connected to the modulation-detection circuit and having its output connected to the quench frequency determining circuit for continuously changing the quench frequency of the regenerative amplifier in response to detected modulation to eliminate interference from the quench frequency of the other receiver, which results when the quench frequencies of the two receivers combine to produce a beat frequency in the vicinity of the desired modulation frequency, whereby when a beat frequency in the vicinity of the desired modulation frequency is detected, the quench frequency of the detecting receiver is changed to move the beat frequency away from the desired modulation frequency to prevent response to quenching beat frequencies;

said modulation-detection circuit and feedback circuit together comprising at least one rectifier;

said feedback circuit comprising;

a smoothing capacitor in parallel with the capacitor of the quench-frequency-determining circuit, a resistor and blocking capacitor in series between the smoothing capacitor and the quench-frequency-determining circuit, and said smoothing capacitor being connected between the rectifier and the quench-frequency-determining circuit to smooth rectified signals fed back to the quench-frequency-determining circuit.