Compact bidirectional repeaters for wireless communication systems

• US 20040160376A1
• Filed: 08/12/2003
• Published: 08/19/2004
• Est. Priority Date: 02/10/2003
• Status: Active Grant

• Current Assignee: CalAmp Corporation
• Original Assignee: California Amplifier Inc.
• Inventors: Upadhey, Vishwanaph G., Kelkar, Kris, Hornsby, James J., Aleman, Shawn, Sanford, Gary G.
• Granted Patent: US 7,009,573 B2
• Time in Patent Office: Days
• US Class Current: 343/770
• CPC Class Codes: H04B 7/15571 by signal isolation, e.g. isolation by frequency or by antenna pattern, or by polarization

Abstract

Compact bidirectional repeaters are provided for wireless communication systems. Their compact size is realized with repeater structures that include different-polarization antennas, back lobe suppressing structures, circuit feedback paths, antenna-feedback detectors, and automatic gain control.

Claims

1. A bidirectional repeater, comprising:

a first antenna arranged to have a first polarization;

a second antenna arranged to have a second polarization that differs from said first polarization by a polarization difference;

a first amplifier circuit configured to receive a first signal from said first antenna and to provide an amplified first signal to said second antenna; and

a second amplifier circuit configured to receive a second signal from said second antenna and to provide an amplified second signal to said first antenna.

2. The repeater of claim 1, wherein said polarization difference is between 60 and 120 degrees.

3. The repeater of claim 1, wherein said polarization difference is substantially 90 degrees.

4. The repeater of claim 1, wherein one of said first and second antennas is a dipole antenna.

5. The repeater of claim 1, wherein one of said first and second antennas is a slot antenna.

6. The repeater of claim 1, wherein one of said first and second antennas is a cavity-backed slot antenna.

7. The repeater of claim 1, wherein said first antenna is a slot antenna having a first polarization and said second antenna is a cavity-backed slot antenna having a second polarization that is substantially orthogonal to said first polarization.

8. The repeater of claim 1, further including:

a first choke arranged to reduce feedback signals from said first antenna to said second antenna; and

a second choke arranged to reduce feedback signals from said second antenna to said first antenna.

9. The repeater of claim 8, wherein:

said first choke is arranged to form a shorted first cavity and define a slot that electromagnetically couples said first cavity to said first antenna; and

said second choke is arranged to form a shorted second cavity and define a slot that electromagnetically couples said second cavity to said second antenna.

10. The repeater of claim 8, wherein at least one of said first and second chokes comprises two chokes arranged on opposite sides of one of said first and second antennas.

11. The repeater of claim 8, wherein at least one of said first and second chokes is arranged to substantially surround one of said first and second antennas.

12. The repeater of claim 1, wherein said first antenna is a slot antenna having a first polarization and said second antenna is a cavity-backed slot antenna having a second polarization that is substantially orthogonal to said first polarization and further including:

a first choke arranged to reduce feedback signals from said first antenna to said second antenna; and

a second choke arranged to reduce feedback signals from said second antenna to said first antenna.

13. The repeater of claim 1, further including:

a first feedback circuit that extracts a first sample signal from a portion of said first amplifier circuit and provides a first feedback signal to another portion of said first amplifier circuit that reduces feedback from said second antenna to said first antenna; and

a second feedback circuit that extracts a second sample signal from a portion of said second amplifier circuit and provides a second feedback signal to another portion of said second amplifier circuit that reduces feedback from said first antenna to said second antenna.

14. The repeater of claim 13, wherein:

said first amplifier circuit includes a detector that senses the presence of antenna feedback signals from said second antenna; and

said first feedback circuit includes at least one of a variable phase shifter and a variable attenuator that, in response to said detector, alters at least one of phase and amplitude of said first feedback signal to substantially reduce said antenna feedback signal.

15. The repeater of claim 13, wherein:

said second amplifier circuit includes a detector that senses the presence of antenna feedback signals from said first antenna; and

said second feedback circuit includes at least one of a variable phase shifter and a variable attenuator that, in response to said detector, alters at least one of phase and amplitude of said second feedback signal to substantially reduce said antenna feedback signal.

16. The repeater of claim 1, wherein at least one of said first and second amplifier circuits includes:

a low noise amplifier;

a power amplifier;

a downconversion mixer and an upconversion mixer between said low noise amplifier and said power amplifier; and

at least one channel-selection filter between said downconversion and upconversion mixer.

17. A bidirectional repeater, comprising:

first and second antennas;

a first amplifier circuit configured to receive a first signal from said first antenna and to provide an amplified first signal to said second antenna;

a second amplifier circuit configured to receive a second signal from said second antenna and to provide an amplified second signal to said first antenna;

a first feedback circuit that extracts a first sample signal from a portion of said first amplifier circuit and provides a first feedback signal to another portion of said first amplifier circuit that reduces feedback from said second antenna to said first antenna; and

a second feedback circuit that extracts a second sample signal from a portion of said second amplifier circuit and provides a second feedback signal to another portion of said second amplifier circuit that reduces feedback from said first antenna to said second antenna.

18. The repeater of claim 17, wherein:

at least one of said first and second amplifier circuits includes a detector that senses the presence of antenna feedback signals between said first and second antennas; and

at least one of said first and second feedback circuits includes at least one of a variable phase shifter and a variable attenuator that, in response to said detector, alters at least one of phase and amplitude of at least one of said first and second feedback signals to substantially reduce said antenna feedback signals.

19. The repeater of claim 18, wherein said detector is a signal detector.

20. The repeater of claim 18, wherein said detector is a current sensor.

21. The repeater of claim 17, wherein at least one of said first and second amplifier circuits includes:

a low noise amplifier;

a power amplifier;

a downconversion mixer and an upconversion mixer between said low noise amplifier and said power amplifier;

a local oscillator that provides conversion signals to said downconversion and upconversion mixers; and

at least one channel-selection filter between said downconversion and upconversion mixers.

22. The repeater of claim 21, wherein at least one of said first and second amplifier circuits further includes a variable attenuator that establishes a power level of a corresponding one of said amplified first signal and said amplified second signal.

23. The repeater of claim 17, wherein:

said first antenna is arranged to have a first polarization; and

said second antenna is arranged to have a second polarization that differs from said first polarization by a polarization difference between 60 and 120 degrees.

24. The repeater of claim 17, wherein said first antenna is a slot antenna having a first polarization and said second antenna is a cavity-backed slot antenna having a second polarization that is substantially orthogonal to said first polarization.

25. The repeater of claim 17, further including:

a first choke arranged to reduce feedback signals from said first antenna; and

a second choke arranged to reduce feedback signals from said second antenna.

26. The repeater of claim 17, wherein at least one of said first and second antennas is an antenna array.

27. The repeater of claim 17, further including a cable that couples at least one of said first and second antennas to said first and second amplifier circuits to facilitate positioning therebetween.

28. The repeater of claim 17, wherein said first antenna and at least an adjoining portion of said first amplifier circuit are duplicated to provide first and second reception circuits to thereby facilitate operational selection of one of said first and second reception circuits.

29. The repeater of claim 20, wherein said first antenna and at least an adjoining portion of said second amplifier circuit are duplicated to provide first and second transmission circuits that provide a plurality of transmitted signals.

30. A bidirectional repeater, comprising:

a first antenna arranged to have a first polarization;

a second antenna arranged to have a second polarization that differs from said first polarization by a polarization difference;

a first amplifier circuit that, with a first gain, amplifies a first signal from said first antenna to thereby provide an amplified first signal to said second antenna;

a second amplifier circuit that, with a second gain, amplifies a second signal from said second antenna to thereby provide an amplified second signal to said first antenna;

a detector that senses the presence of feedback between said first and second antennas; and

a variable attenuator in at least one of said first and second amplifier circuits that responds to said detector and adjusts at least one of said first and second gains to eliminate said feedback.

31. The repeater of claim 30, wherein said detector is a current sensor that senses currents in said repeater.

32. The repeater of claim 30, wherein said detector is a signal detector that senses signals in at least one of said first and second amplifier circuits.

33. The repeater of claim 30, further including a controller that adjusts said variable attenuator in response to said detector.

34. The repeater of claim 30, wherein at least one of said first and second amplifier circuits includes:

a low noise amplifier;

a power amplifier;

a downconversion mixer and an upconversion mixer between said low noise amplifier and said power amplifier; and

at least one channel-selection filter between said downconversion and upconversion mixer.

35. The repeater of claim 30, wherein said polarization difference is between 60 and 120 degrees.

36. The repeater of claim 35, wherein said first antenna is a dipole antenna and said second antenna is a slot antenna.

37. The repeater of claim 30, further including:

a first choke arranged to reduce feedback signals from said first antenna to said second antenna; and

a second choke arranged to reduce feedback signals from said second antenna to said first antenna.

38. The repeater of claim 37 wherein at least one of said first and second chokes is arranged to form a shorted cavity and define a slot that electromagnetically couples said cavity to at least one of said first and second antennas.