Method and apparatus for predictably switching diversity antennas on signal dropout

• US 20010046848A1
• Filed: 04/12/2001
• Published: 11/29/2001
• Est. Priority Date: 05/04/1999
• Status: Active Grant

• Current Assignee: Shure Incorporated
• Original Assignee: Shure Incorporated
• Inventors: Kenkel, Mark A.
• Granted Patent: US 6,871,054 B2
• Time in Patent Office: Days
• US Class Current: 455/277.1
• CPC Class Codes: H04B 7/0802 using antenna selection H04B7/0868 takes precedence; antenna beam directivity switching H01Q3/24
• CPC Class Codes: H04B 7/0814 based on current reception conditions, e.g. switching to different antenna when signal level is below threshold
• CPC Class Codes: H04B 7/0831 Compensation of the diversity switching process for non-uniform properties or faulty operations of the switches used in the diversity switching process

Abstract

A low-cost diversity antenna switching system and method is realized by controlling bias voltages on PIN diodes. By increasing the reverse bias voltage impressed upon a PIN diode, an RF signal impressed upon the diode is increasingly attenuated. As the PIN diode is forward biased to conduct in the forward direction, RF attenuation decreases. Two or more PIN diodes are used to increasingly attenuate signals from one antenna as attenuation of signals from another antenna is gradually decreased. The progression of the bias voltages is accomplished using a microprocessor that monitors a received signal strength indicator (RSSI) signal from a radio receiver. The RSSI is used to control which of two antennas are coupled into the receiver by predicting a signal fade.

Claims

1. A diversity receiving apparatus for coupling signals from at least one antenna of at least first and second antennas to a radio receiver, said diversity receiving apparatus comprised of:

a) a first variable, RF signal level attenuator having an input coupled to receive RF signals from said first antenna and having an output coupled to a RF signal summing node;

b) a second variable, RF signal level attenuator having an input coupled to receive RF signals from said second antenna and having an output coupled to said RF signal summing node;

c) at least one variable RF signal level attenuator controller, coupled to at least said first variable attenuator so as to control attenuation levels of said RF signal level attenuators;

whereby RF signals received at said first and second antennas and coupled to said RF summing node can be selectively coupled to said radio receiver by controlling at least said first variable RF signal level attenuator.

2. The diversity receiving apparatus of

claim 1

wherein said first and second variable RF signal level attenuators are PIN diodes.

3. The diversity receiving apparatus of

claim 1

wherein said first and second variable RF signal level attenuators are gallium arsenide field-effect transistors.

4. The diversity receiving apparatus of

claim 1

wherein said first and second variable RF signal level attenuators are bipolar junction transistors.

5. The diversity receiving apparatus of

claim 1

wherein said at least one variable RF signal level attenuator controller is comprised of a reactive network.

6. The diversity receiving apparatus of

claim 1

wherein said at least one variable RF signal level attenuator controller is an R-C circuit.

7. The diversity receiving apparatus of

claim 1

wherein said at least one variable RF signal level attenuator controller includes a microprocessor.

8. The diversity receiving apparatus of

claim 1

further including an RF signal level attenuator controller coupled to said second attenuator.

9. The diversity receiving apparatus of

claim 1

wherein said control voltage source is a microprocessor providing an analog output voltage.

10. The diversity receiving apparatus of

claim 1

wherein said control voltage source includes a microprocessor that monitors historical signal levels from said first antenna, and, when said the average of said historical signal level from said first antenna drops below a predetermined threshold signal level, said microprocessor supplies a control voltage to said first and second reactive networks in order to substantially continuously increase attenuation of the currently received signal delivered to said summing node from said first antenna and to substantially continuously decrease attenuation of the currently received signal delivered to said summing node from said second antenna.

11. The diversity receiving apparatus of

claim 1

wherein said microprocessor includes a microprocessor that acts to de-attenuate signals from said second antenna prior to attenuating signals from said first antenna.

12. The diversity receiving apparatus of

claim 1

wherein said predetermined signal level of said signal from said first antenna is a relative signal strength indicator of radio signal strength generated by said radio receiver.

13. The diversity receiving apparatus of

claim 1

wherein said predetermined signal level of said signal from said first antenna is a signal indicating noise levels of audio signals demodulated from RF signals detected by said radio receiver.

14. The diversity receiving apparatus of

claim 1

wherein said RF signal summing node is coupled to a radio receiver input.

15. A diversity receiving apparatus for coupling signals from at least one antenna of at least first and second antennas to a radio receiver, said receiving apparatus comprised of:

a) a first PIN diode having a first terminal thereof coupled to receive RF signals from said first antenna and having a second terminal coupled to an RF signal summing node;

b) a second PIN diode having a first terminal thereof coupled to receive RF signals from said second antenna and having a second terminal coupled to said RF signal summing node, said summing node being coupled to a D.C. voltage source;

c) a first reactive network coupled to said first terminal of said first PIN diode to supply a variable voltage to said a first terminal of said first PIN diode;

d) a second reactive network coupled to said first terminal of said second PIN diode to supply a variable voltage to said first terminal of said second PIN diode;

e) a control voltage source coupled to said first and second reactive networks to supply a voltage to said first and second reactive networks;

whereby signals received at said first and second antennas can be selectively coupled to said radio receiver by controlling at least said first variable attenuator.

16. The diversity receiving apparatus of

claim 15

wherein each said first terminal is an anode.

17. The diversity receiving apparatus of

claim 15

wherein each said first terminal is a cathode.

18. The diversity receiving apparatus of

claim 15

wherein said D.C. voltage source coupled to said summing node is a voltage source substantially equal to zero volts.

19. The diversity receiving apparatus of

claim 15

wherein said D.C. voltage source coupled to said summing node is a voltage source greater than zero volts.

20. The diversity receiving apparatus of

claim 15

wherein said D.C. voltage source coupled to said summing node is a voltage source less than zero volts.

21. The diversity receiving apparatus of

claim 15

wherein said first reactive network coupled to said first terminal of said first PIN is comprised of an R-C network having a predetermined time constant.

22. The diversity receiving apparatus of

claim 15

wherein said second reactive network coupled to said first terminal of said second PIN is comprised of an R-C network having a predetermined time constant.

23. The diversity receiving apparatus of

claim 15

wherein said control voltage source is comprised of a microprocessor.

24. The diversity receiving apparatus of

claim 15

wherein said control voltage source is a microprocessor providing an analog output voltage.

25. The diversity receiving apparatus of

claim 15

wherein said control voltage source includes a microprocessor that monitors historical signal levels from said first antenna, and, when said the average of said historical signal level from said first antenna drops below a predetermined threshold signal level, said microprocessor supplies a control voltage to said first and second reactive networks in order to substantially continuously increase attenuation of the currently received signal delivered to said summing node from said first antenna and to substantially continuously decrease attenuation of the currently received signal delivered to said summing node from said second antenna.

26. The diversity receiving apparatus of

claim 15

wherein said microprocessor includes a microprocessor that de-attenuates signals from said second antenna prior to attenuating signals from said first antenna.

27. The diversity receiving apparatus of

claim 15

wherein said predetermined signal level of said signal from said first antenna is a relative signal strength indicator of radio signal strength generated by said radio receiver.

28. The diversity receiving apparatus of

claim 15

wherein said predetermined signal level of said signal from said first antenna is a signal indicating noise levels of audio signals demodulated from RF signals detected by said radio receiver.

29. The diversity receiving apparatus of

claim 15

wherein said RF signal summing node comprises a radio receiver input.

30. A diversity receiving apparatus for coupling signals from at least one antenna of at least first and second antennas to a radio receiver, said diversity receiving apparatus comprised of:

a) a first variable, RF signal level attenuator having an input for coupling RF signals from said first antenna to an output, for coupling said RF signals to a radio receiver input;

b) a second variable, RF signal level attenuator having an input for coupling RF signals from said second antenna to an output, for coupling said RF signals to a radio receiver input;

c) at least one variable RF signal level attenuator controller, coupled to at least said first variable attenuator so as to control attenuation levels of said RF signal level attenuators;

whereby RF signals received by at least one of said first and second antennas can be selectively coupled to said radio receiver input by controlling at least said first variable RF signal level attenuator.

31. The diversity receiving apparatus of

claim 30

wherein said first and second variable RF signal level attenuators are PIN diodes.

32. The diversity receiving apparatus of

claim 30

wherein said first and second variable RF signal level attenuators are gallium arsenide field-effect transistors.

33. The diversity receiving apparatus of

claim 30

wherein said first and second variable RF signal level attenuators are bipolar junction transistors.

34. The diversity receiving apparatus of

claim 30

wherein said at least one variable RF signal level attenuator controller is comprised of a reactive network.

35. The diversity receiving apparatus of

claim 30

wherein said at least one variable RF signal level attenuator controller is an R-C circuit.

36. The diversity receiving apparatus of

claim 30

wherein said at least one variable RF signal level attenuator controller includes a microprocessor.

37. The diversity receiving apparatus of

claim 30

further including an RF signal level attenuator controller coupled to said second attenuator.

38. The diversity receiving apparatus of

claim 30

wherein said control voltage source is a microprocessor providing an analog output voltage.

39. The diversity receiving apparatus of

claim 30

wherein said control voltage source includes a microprocessor that monitors historical signal levels from said first antenna, and, when said the average of said historical signal level from said first antenna drops below a predetermined threshold signal level, said microprocessor supplies a control voltage to said first and second reactive networks in order to substantially continuously increase attenuation of the currently received signal delivered to said summing node from said first antenna and to substantially continuously decrease attenuation of the currently received signal delivered to said summing node from said second antenna.

40. The diversity receiving apparatus of

claim 30

wherein said microprocessor includes a microprocessor that de-attenuates signals from said second antenna prior to attenuating signals from said first antenna.

41. The diversity receiving apparatus of

claim 30

wherein said predetermined signal level of said signal from said first antenna is a relative signal strength indicator of radio signal strength generated by said radio receiver.

42. The diversity receiving apparatus of

claim 30

wherein said predetermined signal level of said signal from said first antenna is a signal indicating noise levels of audio signals demodulated from RF signals detected by said radio receiver.

44. The method of

claim 41

wherein said step of obtaining a first sample of the relative radio frequency signal strength includes the step of:

reading a received signal strength indicator.

45. The method of

claim 41

wherein said step of calculating an average signal strength level includes the step of:

filtering said first sample of the relative radio frequency signal strength.

46. The method of

claim 41

wherein said step of calculating an average signal strength level includes the steps:

a) converting said first sample to a numerical value;

b) arithmetically calculating a running average of said numerical value.

47. The method of

claim 41

wherein said step of calculating a radio frequency signal strength threshold signal level includes the step of dynamically adjusting said threshold using a current value of said relative radio frequency signal.

43. A method of selectively coupling at least one of at least two antennas to a radio receiver comprising the steps of:

a) obtaining a first sample of the relative radio frequency signal strength received by said radio receiver from a first antenna;

b) calculating a running average signal strength level received by said radio receiver from said first antenna;

c) calculating a radio frequency signal strength threshold signal level, below which signals from said first antenna are to be gradually attenuated prior to being coupled into said radio receiver while signals from said second antenna are to be gradually de-attenuated prior to being coupled into said receiver;

d) when the radio frequency signal strength received from said first antenna drops below said threshold signal level, increasing the signal level input to said radio receiver from said second antenna and decreasing the signal level input to said radio receiver from said first antenna.