System for dual diversity receiver using switched LNAS

1. A dual diversity receiver that includes first and second antennas to receive first and second radio signals provided in a wireless channel, wherein the first and second antennas produce first and second antenna signals that are representative of the received radio signals, the receiver comprising:

a first LNA that receives the first antenna signal and produces a first amplified signal;

a second LNA that receives the second antenna signal and produces a second amplified signal; and

selection logic to monitor a signal characteristic of said first and said second amplified signals and a channel characteristic of the wireless channel, and select one of the first LNA and the second LNA so that its output is processed by the receiver; wherein

said selection is based at least in part upon said signal characteristics and said channel characteristic, and wherein said signal characteristic is a signal strength measurement and said channel characteristic is a coherence time.

2. The receiver of claim 1 , wherein the first and second LNAs further comprise first and second bias generator circuits that control the operation of their respective LNA based on a selection signal.

3. The receiver of claim 1 , wherein said selection logic is configured to switch between said first and said second LNA when the signal strength of the provided signal is less than a threshold value or when the elapsed time receiving the current signal exceeds the coherence time of the wireless channel; wherein the threshold value is based the signal strength of the previously selected amplified signal.

4. The receiver of claim 1 wherein said selection logic comprises a switching apparatus integrated within said first and said second LNAs; wherein said switching apparatus is operative to switch said output from said first and said second LNAs.

5. A method for operating a dual diversity receiver that includes two antennas to receive a radio signal, wherein each antenna produces an antenna signal that is representative of the radio signal, the method comprising the steps of: inputting the antenna signal from each antenna to a corresponding LNA that produces an amplified signal;

providing one of the amplified signals to the receiver;

determining the coherence time of the wireless channel;

determining the signal strength of the provided signal;

selecting one of the amplified signals to be provided to the receiver, said selecting based at least in part on the signal strength and the coherence time; and

repeating the steps of determining and selecting.

6. The method of claim 5 wherein said selecting comprises switching the provided amplified signal when the signal strength of the provided signal is less than a threshold value or when the elapsed time receiving the signal is greater than the coherence time of the wireless channel; wherein the threshold value is based on the signal strength of the previously provided amplified signal.

7. The method of claim 6 , further comprising using a digital filter to measure said coherence time.

8. The method of claim 7 wherein said digital filter is an IIR filter.

9. A dual diversity receiver system for receiving signals in a wireless channel, comprising:

a receiver circuit;

a first antenna to receive a radio signal and produce a first antenna signal;

a second antenna spatially separated from said first antenna to receive said radio signal and produce a second antenna signal;

a first LNA to receive said first antenna signal and produce a first amplified signal;

a second LNA to receive said second antenna signal and produce a second amplified signal; and

selection logic to selectively provide one of the first amplified signal or the second amplified signal to the receiver circuit, said selection based at least in part upon a signal characteristic of the first amplified signal and the second amplified signal, and a channel characteristic of the wireless channel, wherein said signal characteristic is a signal strength measurement and said channel characteristic is a coherence time.

10. The receiver of claim 9 wherein said selection logic is configured to switch between said first and said second LNA when the signal strength of the Currently selected signal falls below a threshold value or the elapsed time receiving the current signal exceeds the coherence time of the wireless channel; wherein the threshold value is based on the signal strength of the previously selected amplified signal.

11. The receiver system of claim 9 wherein said selection logic comprises a switching apparatus integrated within said first and said second LNAs.

12. The receiver system of claim 10 , further comprising using a digital filter to measure said coherence time.

13. The receiver of claim 12 wherein said digital filter is an IIR filter.