Antenna selection control circuit

• US 4,977,616 A
• Filed: 10/26/1989
• Issued: 12/11/1990
• Est. Priority Date: 11/30/1987
• Status: Expired due to Term

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Goode, Steve H., Baker, James C., Kazecki, Henry L., Linder, Donald L., Dennis, Donald W.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Smith, Ralph
• Application Number:
  US07/428,429
• Time in Patent Office: 411 Days
• Field of Search: 455/132-134, 455/135, 455/33, 455/52, 455/277, 370/29
• US Class Current: 455/277.2
• CPC Class Codes: H04B 7/0808 comparing all antennas before reception
• CPC Class Codes: H04B 7/0811 during preamble or gap period
• CPC Class Codes: H04B 7/0814 based on current reception conditions, e.g. switching to different antenna when signal level is below threshold

Abstract

An antenna switch control circuit for use in achieving antenna selection diversity in TDM RF receivers. RSSI for at least one antenna is monitored during time slots containing information not of interest. This information can then be compared with other antenna performance information to allow a selection to be made such that the receiver generally operates with the antenna receiving the strongest signal. In one embodiment, all possible antennas are monitored during a time slot containing information not of interest. In another embodiment, RSSI for the selected antenna can be monitored during the time slot of interest, such that antenna selection can again be varied should the selected antenna diminish in performance.

Claims

1. An antenna selection control circuit for use with a TDM RF receiver having at least two antennas for receiving an information signal, which information signal is comprised of time slots of interest that contain information of interest to the receiver and other time slots that contain information not of interest to the receiver, comprising:

(A) first means for developing signals related to received signal quality for at least two of said antennas, wherein said signal is developed for at least one of said antennas during a time slot that contains information not of interest to the receiver;

(B) second means responsive to said first means for comparing said developed signals to identify which of said at least two antennas received a signal of higher quality;

(C) third means responsive to said second means for causing said receiver to use said identified antenna during a subsequent time slot that contains information of interest to the receiver.

2. The antenna selection control circuit of claim 1 wherein said first means develops said signals for at least two of said antennas during a time slot that contain information not of interest.

3. The antenna selection control circuit of claim 1 wherein said signal quality comprises signal strength.

4. An antenna selection control circuit for use with a TDM RF receiver having at least two antennas for receiving an information signal, which information signal is comprised of time slots that contain information of interest to the receiver and other time slots that contain information not of interest to the receiver, comprising:

(A) first means for developing signals related to received signal quality for at least two of said antennas during a time slot that contains information not of interest to the receiver;

(B) second means responsive to said first means for comparing said developed signals to identify which of said at least two antennas received a signal of higher quality;

(C) third means responsive to said second means for causing said receiver to use said identified antenna during a subsequent time slot that contains information of interest to the receiver.

5. The antenna selection control circuit of claim 4 wherein said signal quality comprises signal strength.

6. The antenna selection control circuit of claim 4 wherein said first means includes sample and hold means for sampling, during a first TDM time slot prior to a TDM time slot that contains information of interest, a first signal related to received signal quality from a selected one of said antennas and for providing an output signal related to said sampled signal.

7. The antenna selection control circuit of claim 4 and further including:

(A) fourth means for comparing, during said next subsequent time slot that contains information of interest to the receiver, a reference signal with a signal related to received signal quality for said selected antenna, and for providing a comparison output signal related to said comparison; and

(B) antenna switch control means for responding to said fourth means output signal by causing said receiver to select a different one of said antennas for receiving said signal when said signal related to received signal quality for said selected antenna is less than said reference signal during said time slot that contains information of interest to the receiver.

8. The antenna selection control circuit of claim 7 wherein said reference signal is related to a mean value of received signal quality for said selected antenna during said time slot that contains information of interest.

9. An antenna selection control circuit for use with a TDM RF receiver having at least two antennas for receiving an information signal, comprising:

(A) sample and hold means for sampling, during a first TDM time slot prior to a TDM time slot that contains information of interest to the receiver, a first signal related to received signal strength from a selected one of said antennas and for providing an output signal related to said sampled signal;

(B) comparator means responsive to said sample and hold means for comparing, during said first TDM time slot, said output signal from said sample and hold means with a second signal related to received signal strength from a different selected one of said antennas, and for providing a comparator output signal related to which of said antennas has received a stronger signal; and

(C) antenna switch control means for responding to said comparator output signal by selecting which of said antennas is used by said receiver to receive the information signal in said TDM time slot that contains information of interest to the receiver.

10. The antenna selection control circuit of claim 9 and further including:

(D) reference signal means for providing a reference signal related to a mean value of received signal strength for said selected antenna during said TDM time slot that contains information of interest to the receiver;

(E) second comparator means responsive to said reference signal means for comparing, during said TDM time slot that contains information of interest to the receiver, said reference signal with a signal related to received signal strength for said selected antenna, and for providing a second comparator means output signal related to said comparison;

(F) second antenna switch control means for responding to said second comparator means output signal by causing said receiver to select a different one of said antennas for receiving said signal when said signal related to received signal strength for said selected antenna is less than said reference signal during said TDM time slot that contains information of interest to the receiver.

11. A method of selecting an antenna for a TDM RF receiver having at least two antennas for receiving a signal of interest, which signal is comprised of time slots that contain information of interest to the receiver and other time slots that contain information not of interest to the receiver, said method comprising the steps of:

during a time slot that contains information not of interest to the receiver and preceding a time slot that contains information of interest to the receiver;

(A) sampling and holding a signal related to received signal quality for one of said antennas;

(B) comparing said sampled and held signal with a second signal related to received signal quality for a second one of said antennas;

(C) selecting, based upon said comparison, one of said antennas to be used to receive said signal of interest in a next occurring time slot that contains information of interest to the receiver.

12. The method of claim 11 and including the additional steps of:

during a time slot that contains information of interest to the receiver that occurs subsequent to said time slot that contains information not of interest to the receiver;

(D) monitoring a signal related to received signal quality for said selected antenna;

(E) comparing said monitored signal with a reference signal;

(F) in response to said comparison between said monitored signal and said reference signal, deciding whether to select a different antenna.

13. The method of claim 12 wherein said reference signal is related to a mean value of received signal quality for said selected antenna during said time slot that contains information of interest.

14. The method of claim 13 wherein in step F, a decision is made to select a different antenna when said monitored signal is less than 10 dB below said reference signal.