Method and apparatus for measuring the strength of a radio signal frequency

• US 4,549,311 A
• Filed: 03/20/1985
• Issued: 10/22/1985
• Est. Priority Date: 08/03/1982
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: McLaughlin, Michael J.
• Primary Examiner(s): Bookbinder, Marc E.
• Application Number:
  US06/714,063
• Time in Patent Office: 216 Days
• Field of Search: 455/52, 455/62, 455/67, 455/10, 455/133-135, 455/166, 455/277, 455/278, 375/100
• US Class Current: 455/277.1
• CPC Class Codes: H04B 7/0805 with single receiver and antenna switching H04B7/0822 takes precedence
• CPC Class Codes: H04B 7/0808 comparing all antennas before reception

Abstract

An improved method and apparatus for measuring the strength of a radio frequency (RF) signal subject to Rayleigh fading is described. The strength of the RF signal is sampled two or more times during a predetermined time interval and the sampled signal strength having the largest magnitude is selected. The selected signal strength is a reasonably accurate measure of the signal strength since the true average strength of a Rayleigh fading signal is close to its peak signal strength. The inventive method and apparatus is particularly well adapted for use in a scanning receiver located in a base station radio of a cellular radiotelephone communications system. The scanning receiver includes an antenna selector for selecting one of a plurality of sector antennas, an RF signal receiver tunable to a plurality of different RF signal frequencies, an analog-to-digital converter for converting RF signal strength samples to a binary data signal, and a microprocessor together with peripheral devices for controlling the operation of the antenna selector, RF signal receiver and analog-to-digital converter.

Claims

1. A method of determining for a plurality of radio channels which of a plurality of antennas is receiving the strongest radio frequency (RF) signal experiencing to Rayleigh fading and transmitted from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different one of the radio channels, each of said antennas receiving RF signals from a corresponding portion of the geographical area and couplable to receiving means having an output signal, said method comprising the steps of:

(a) tuning said receiving means to each of the radio channels in sequence; and

(b) for each radio channel;

(i) coupling said receiving means to each antenna in a predetermined sequence;

(ii) sampling the receiving means ouput signal N times while coupled for a predetermined time interval to each antenna, where N is an integer number greater than one; and

(iii) after sampling all antennas, selecting for communications on the radio channel the antenna for which at least one of its N samples has a magnitude greater than the magnitude of any of the N samples for all other antennas.

2. The method according to claim 1, further including the step of repeating said step (b) after a predetermined time.

4. The method according to claim 1, wherein said sampling step (ii) further includes the step of converting each sample of the receiving means output signal to a digitized sample.

5. The method according to claim 1, wherein said selecting step (iii) further includes the steps of:

selecting the largest sample for each antenna; and

selecting for communications on the radio channel the antenna whose largest sample has a magnitude greater than the magnitude of the largest samples of all other antennas.

6. Apparatus for determining for a plurality of radio channels which of a plurality of antennas is receiving the strongest radio frequency (RF) signal experiencing Rayleigh fading and transmitted from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different one of the radio channels, each of said antennas receiving RF signals from a corresponding portion of the geographical area and couplable to receiving means having an output signal, said apparatus comprising:

means for tuning said receiving means to each of the radio channels in sequence;

means for coupling for each radio channel said receiving means to each antenna in a predetermined sequence;

means for sampling for each radio channel the receiving means output signal N times while coupled for a predetermined time interval to each antenna, where N is an integer number greater than one; and

means for selecting for communications on each radio channel the antenna for which at least one of its N samples has a magnitude greater than the magnitude of any of the N samples for all other antennas.

7. The apparatus according to claim 6, wherein said sampling means takes a second set of N samples of the receiving means output signal for each antenna after a predetermined time.

8. The apparatus according to claim 6, wherein said sampling means takes additional sets of N samples of the receiving means output signal for each antenna during consecutive predetermined time intervals.

9. The apparatus according to claim 6, wherein said sampling means further includes means for converting each sample of the receiving means output signal to a digitized sample.

10. The apparatus according to claim 6, wherein said selecting means further includes means for selecting the largest sample for each antenna.

11. A method of determining for each radio channel which of a plurality of antennas is receiving the strongest radio frequency (RF) signal experiencing Rayleigh fading and transmitted from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different radio channel, each of said antennas receiving RF signals from the geographical area and couplable to receiving means having an output signal, said method comprising the steps of:

(a) tuning said receiving means to each of the radio channels in sequence; and

(b) for each radio channel;

(i) coupling said receiving means to each antenna in a predetermined sequence;

(ii) sampling the receiving means output signal N times while coupled for a predetermined time interval to each antenna, where N is an integer number greater than one; and

(iii) after sampling all antennas, selecting the antenna for which at least one of its N samples has a magnitude greater than the magnitude of any of the N samples for all other antennas.

3. The method according to claim 15, further including the step of repeating said step (b) at consecutive predetermined time intervals.

12. The method according to claim 11, further including the step of repeating said step (b) after a predetermined time.

13. The method according to claim 11, further including the step of repeating step (b) at consecutive predetermined time intervals.

14. The method according to claim 11, wherein said sampling step (ii) further includes the step of converting each sample of the receiving means output signal to a digitized sample.

15. The method according to claim 11, wherein said selecting step (iii) further includes the steps of:

selecting the largest sample for each antenna; and

selecting for communications on the radio channel the antenna whose largest sample has a magnitude greater than the magnitude of the largest samples of all other antennas.

16. Apparatus for determining for each radio channel which of a plurality of antennas is receiving the strongest radio frequency (RF) signal experiencing Rayleigh fading and transmitted from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different radio channel, each of said antennas receiving RF signals from the geographical area and couplable to receiving means having an output signal, said apparatus comprising:

means for tuning said receiving means to each of the radio channels in sequence;

means for coupling for each radio channel said receiving means to each antenna in a predetermined sequence;

means for sampling for each radio channel the receiving means output signal N times while coupled for a predetermined time interval to each antenna, where N is an integer number greater than one; and

means for selecting for each radio channel the antenna for which at least one of its N samples has a magnitude greater than the magnitude of any of the N samples for all other antennas.

17. The apparatus according to claim 16, wherein said sampling means takes a second set of N samples of the receiving means output signal for each antenna after a predetermined time.

18. The apparatus according to claim 16, wherein said sampling means takes additional sets of N samples of the receiving means output signal for each antenna during consecutive predetermined time intervals.

19. The apparatus according to claim 16, wherein said sampling means further includes means for converting each sample of the receiving means output signal to a digitized sample.

20. The apparatus according to claim 16, wherein said selecting means further includes means for selecting the largest sample for each antenna.

21. A method of determining for each radio channel the strength of the radio frequency (RF) signal experiencing Rayleigh fading and received by a plurality of antennas from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different radio channel, each of said antennas receiving RF signals from the geographical area and couplable to receiving means having an output signal, said method comprising the steps of:

(a) tuning said receiving means to each of the radio channels in sequence; and

(b) for each radio channel;

(i) coupling said receiving means to each antenna in a predetermined sequence;

(ii) sampling the receiving means output signal N times while coupled for a predetermined time interval to each antenna, where N is an integer number greater than one; and

(iii) after sampling all antennas, selecting the sample which has a magnitude greater than the magnitude of any of the other samples.

22. The method according to claim 21, further including the step of repeating said step (b) after a predetermined time.

23. The method according to claim 21, further including the step of repeating step (b) at consecutive predetermined time intervals.

24. The method according to claim 21, wherein said sampling step (ii) further includes the step of converting each sample of the receiving means output signal to a digitized sample.

25. The method according to claim 21, wherein said selecting step (iii) further includes the steps of:

selecting the largest sample for each antenna; and

selecting the largest sample which has a magnitude greater than the magnitude of the largest samples of all other antennas.

26. Apparatus for determining for each radio channel the stength of the radio frequency (RF) signal experiencing Rayleigh fading and receiving by a plurality of antennas from a plurality of remote stations each having an unknown location in a geographical area and transmitting on a different radio channel, each of said antennas receiving RF signals from the geographical area and couplable to receiving means having an output signal, said apparatus comprising:

means for tuning said receiving means to each of the radio channels in sequence;

means for coupling for each radio channel said receiving means to each antenna in a predetermined sequence;

means for sampling for each radio channel the receiving means output signal N times while coupled for a predetermined time interval to each antenna;

where N is an integer number greater than one; and

means for selecting the sample which has a magnitude greater than the magnitude of any of the other samples.

27. The apparatus according to claim 26, wherein said sampling means takes a second set of N samples of the receiving means output signal for each antenna after a predetermined time.

28. The apparatus according to claim 26, wherein said sampling means takes additional sets of N samples of the receiving means output signal for each antenna during consecutive predetermined time intervals.

29. The apparatus according to claim 26, wherein said sampling means further includes means for converting each sample of the receiving means output signal to a digitized sample.

30. The apparatus according to claim 26, wherein said selecting means further includes means for selecting the largest sample for each antenna.