FM SIGNAL QUALITY MEASUREMENT

• US 20100151807A1
• Filed: 11/29/2007
• Published: 06/17/2010
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: Popescu, Andrei Barbu
• Granted Patent: US 8,498,596 B2
• Time in Patent Office: Days
• US Class Current: 455/226.200
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1646 adapted for the reception of stereophonic signals
• CPC Class Codes: H04B 17/318 Received signal strength

Abstract

A signal quality estimator for estimating the quality of signal reception in a signal receiver, the signal quality estimator comprising: a first filter for filtering a signal received by the receiver to isolate a frequency band therein; and a signal analyzer for forming an indication of the degree to which the amplitude of the signal in that frequency band varies over time, to serve as an estimate of the quality of signal reception in the receiver.

Claims

1. A signal quality estimator for estimating the quality of signal reception in a signal receiver, the signal quality estimator comprising:

a first filter arranged to filter a signal received by the receiver to isolate a frequency band that includes a pilot signal; and

a signal analyzer configured to form an indication of the degree to which the amplitude of the signal in that frequency band varies over time, said indication serving as an estimate of the quality of signal reception in the receiver.

2. A signal quality estimator as claimed in claim 1, wherein the signal analyzer comprises:

an amplitude estimator for forming an estimate of the time-variance of the amplitude of the signal in the frequency band; and

a signal estimator for forming the said indication in dependence on the magnitude of the estimate formed by the amplitude estimator.

3. A signal quality estimator as claimed in claim 2, wherein the amplitude estimator comprises:

an amplitude detector for detecting the time-variant amplitude of the signal in the frequency band; and

a second filter for filtering time-constant components from the output of the amplitude detector so as to form the estimate of the time-variance of the amplitude of the signal in the frequency band.

4. A signal quality estimator as claimed in claim 3, wherein the amplitude detector operates periodically to set the value of its output to be representative of the maximum amplitude of the signal in the frequency band during a preceding period.

5. A signal quality estimator as claimed in claim 3, wherein the amplitude detector is a peak detector.

6. A signal quality estimator as claimed in claim 3, wherein the second filter is a high-pass filter.

7. A signal quality estimator as claimed in claim 2, wherein the signal estimator is arranged to form the said indication in dependence on the average magnitude of the estimate formed by the amplitude estimator.

8. A signal quality estimator as claimed in claim 2, wherein the signal estimator comprises a rectifier followed by a low-pass filter.

9. A signal quality estimator as claimed in claim 1, wherein the frequency band includes 19 kHz.

10. A signal quality estimator as claimed in claim 1, wherein the first filter has a 3 dB bandwidth of less than 100 Hz.

11. A signal receiver comprising a signal quality estimator as claimed in claim 1.

12. A signal receiver as claimed in claim 11, wherein the receiver comprises:

a frequency demodulator for frequency demodulating a received signal to form a demodulated signal,

and wherein the first filter takes the demodulated signal as its input.

13. A signal receiver as claimed in claim 12, comprising a signal recovery unit for recovering a traffic signal from the demodulated signal, the signal recovery unit being arranged to recover the traffic signal by means of a pilot signal passed in the said frequency band.

14. A signal receiver as claimed in claim 11, wherein the signal receiver is an FM broadcast radio receiver.

15. A method for estimating the quality of signal reception in a signal receiver, the method comprising:

filtering a signal received by the receiver to isolate a frequency band that includes a pilot signal;

forming an indication of the degree to which the amplitude of the signal in that frequency band varies over time; and

using said indication as an estimate of the quality of signal reception in the receiver.

16. A method as claimed in claim 15, wherein the step of forming an indication of the degree to which the amplitude of the signal in that frequency band varies over time comprises:

forming an estimate of the time-variance of the amplitude of the signal in the frequency band; and

forming the said indication in dependence on the magnitude of the estimate formed by the amplitude estimator.

17. A method as claimed in claim 16, wherein the step of forming an estimate of the time-variance of the amplitude of the signal in the frequency band comprises:

detecting the time-variant amplitude of the signal in the frequency band; and

filtering time-constant components from the output of the amplitude detection step so as to form the estimate of the time-variance of the amplitude of the signal in the frequency band.

18. A method as claimed in claim 17, wherein the step of detecting the time-variant amplitude of the signal in the frequency band comprises periodically setting the value the output of the amplitude detection step to be representative of the maximum amplitude of the signal in the frequency band during a preceding period.

19. A method as claimed in claim 16, comprising forming the said indication in dependence on the average magnitude of the estimate formed by the amplitude estimator.

20. (canceled)