Method and apparatus for implementing signal quality metrics and antenna diversity switching control
View Patent ↗A method for detecting the digital quality of a radio signal includes: receiving a radio signal including a digital portion modulated by a series of symbols each including a plurality of samples; computing correlation points between endpoint samples in cyclic prefix regions of adjacent symbols; and using the correlation points to produce a digital signal quality metric. Receivers that implement the method are also provided.
1. A method comprising:
(a) receiving a radio signal on a plurality of antenna elements;
(b) computing a signal quality metric for the signal received on each of the antenna elements;
(c) determining a difference value between the signal quality metric for a currently selected antenna element and the signal quality metric for each of the other antenna elements;
(d) finding the minimum difference value;
(e) determining (1) if a dwell value is greater than a multiple of the minimum difference value and (2) if the signal quality metric computed for the currently selected antenna element is less than a threshold value; and
(f) if either or both of (1) or (2) in step (e) is true, then switching from the currently selected element to one of the other antenna elements for supplying the radio signal to a receiver and repeating steps (b) through (e).
2. The method of claim 1 , further comprising:
producing a switch control signal computed in software in the receiver baseband processor, generating a hardware signal output to an external hardware switch; and
connecting one or more of the antenna elements to an input of a receiver in response to the switch control signal.
3. The method of claim 1 , wherein the threshold value is about 0.5.
4. The method of claim 1 , wherein the dwell value is adjusted based on the signal quality metric for the currently selected antenna element.
5. The method of claim 1 , wherein the dwell value is adaptively increased as a function of the signal quality metric.
6. An apparatus comprising:
a plurality of antenna elements configured to receive a radio signal;
a switch configured to connect one or more of the antenna elements to an input of a receiver; and
a processor configured to (a) compute a signal quality metric for the signal received on each of the antenna elements, (b) determine a difference value between the signal quality metric for a currently selected antenna element and the signal quality metric for each of the other antenna elements, (c) find the minimum difference value, (d) determine (1) if a dwell value is greater than a multiple of the minimum difference value and (2) if the signal quality metric computed for the currently selected antenna element is less than a threshold value, and (e) if either or both of (1) or (2) in step (e) is true, then control the switch to switch from the currently selected element to one of the other antenna elements to supply the radio signal to the receiver and repeat (a) through (d).
7. The apparatus of claim 6 , wherein the processor computes a switch control signal in software and generates a hardware signal output to control the switch.
8. The apparatus of claim 6 , wherein the threshold value is about 0.5.
9. The apparatus of claim 6 , wherein the dwell value is adjusted based on the signal quality metric for the currently selected antenna element.
10. The apparatus of claim 6 , wherein the dwell value is adaptively increased as a function of the signal quality metric.
11. A method comprising:
receiving a radio signal on a plurality of antenna elements, wherein the radio signal includes a digitally modulated component;
computing a digital signal quality metric for the signal received on each of the antenna elements;
using the digital signal quality metric for an antenna element currently supplying the radio signal to a receiver to determine if diversity switching is desired; and
producing a synthesized FM intermediate frequency proxy control signal that causes a diversity switch control to implement a desired switching of the antenna elements.
12. The method of claim 11 , wherein the synthesized FM intermediate frequency proxy control signal comprises:
an unmodulated FM intermediate frequency carrier signal when no switching is desired; or
a noise-like FM intermediate frequency signal when switching is desired.
13. The method of claim 11 , wherein the synthesized FM intermediate frequency proxy control signal is produced in software in a baseband processor of a receiver.
14. The method of claim 11 , wherein the radio signal comprises:
a hybrid signal including an analog FM component and the digitally modulated component, and the digital signal quality metric is based on the signal quality of the digitally modulated component of the hybrid signal.