Radio receiver having a dynamic bandwidth filter and method therefor

• US 6,658,245 B2
• Filed: 03/28/2001
• Issued: 12/02/2003
• Est. Priority Date: 03/28/2001
• Status: Expired due to Term

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Li, Junsong, Seaberg, Charles E., Su, Jie
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Nguyen, Simon
• Application Number:
  US09/818,337
• Publication Number:
  US 20020142746A1
• Time in Patent Office: 979 Days
• Field of Search: 455/307, 455/154.1, 455/168.1, 455/176.1, 455/178.1, 455/180.1, 455/187.1, 455/266, 455/276.1, 455/280, 455/281, 455/339, 455/306, 455/200.1, 375/232, 375/225, 375/227, 375/260, 375/267, 375/340, 375/347, 375/349, 375/350
• US Class Current: 455/307
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H

Abstract

A radio receiver (100) has an IF (intermediate frequency) filter (200) for dynamically adjusting its intermediate frequency. The filter (200) includes a filter bank (301), power/amplitude estimator circuits (308, 310, 312), and weighting circuits (314, 316, 318). The filter bank (301) generates sub-bands, each sub-band having a predetermined frequency range. The power/amplitude estimators (308, 310, 312) provide an estimated power/amplitude in each sub-band. A filter control (320) uses the power/amplitude estimates to determine a percentage of each sub-band signal that is permitted to be coupled a summation circuit (319). The summation circuit (319) sums the weighted sub-band signals to provide a filtered output signal to a demodulator (212).

Claims

1. A radio receiver comprising:

an input portion having a tuner for selectively receiving an input modulated signal and mixing the input modulated signal with a local signal to generate an intermediate frequency signal;

a filter bank for receiving the intermediate frequency signal and generating a plurality of sub-band signals, each of the plurality of sub-band signals having a predetermined frequency range;

a monitoring circuit coupled to the filter bank, the monitoring circuit measuring a predetermined parameter of each of the sub-band signals and providing a plurality of parameter signals in response thereto;

a control circuit coupled to the monitoring circuit for receiving the plurality of parameter signals, the control circuit provides one or more control signals which determine a percentage of each of the sub-band signals which is permitted to be coupled to an output terminal;

a summing circuit coupled to the output terminal for receiving the percentage of each of the sub-band signals from the monitoring circuit and adding the percentage of each of the sub-band signals to provide a filtered output signal; and

a demodulator coupled to the summing circuit for demodulating the filtered output signal to provide an audio output signal with optional data.

2. The receiver of claim 1 wherein the parameters comprise measuring either power of the sub-band signals or measuring amplitude of the sub-band signals.

3. The receiver of claim 1 further comprising:

a plurality of weighting circuits coupled to the filter bank and the control circuit, each of the plurality of weighting circuits receiving a predetermined one of the one or more control signals and applying a weighting factor to a predetermined one of the sub-band signals, the weighting factor determining the percentage of each of the sub-band signals.

4. The receiver of claim 1 wherein the control circuit further comprises:

a first timeframe power/amplitude averaging circuit for receiving the plurality of parameter signals, the first timeframe power/amplitude averaging circuit performing a time averaging function on each of the parameters and providing a first plurality of averaged parameter signals, each of which corresponding to a predetermined frequency sub-band, and a first of which corresponding to a lowest frequency sub-band and being used as a reference signal;

a second timeframe power/amplitude averaging circuit for receiving the plurality of parameter signals, the second timeframe power/amplitude averaging circuit performing a time averaging function on each of the parameters which is shorter in time than the time averaging function performed by the first timeframe to provide a second plurality of averaged parameter signals;

a first plurality of comparators coupled to the first timeframe power/amplitude averaging circuit, the first plurality of comparators comparing whether the first of the plurality of averaged parameter signals from the first timeframe power/amplitude averaging circuit is greater than a first product of a predetermined threshold value and a predetermined one of the plurality of averaged parameter signals, the first plurality of comparators providing a first portion of the control signals;

a second summing circuit coupled to the second timeframe power/amplitude averaging circuit, the second summing circuit adding each of the second plurality of averaged parameter signals to provide a first sum signal;

a second plurality of comparators coupled to the second timeframe power/amplitude averaging circuit, the second plurality of comparators comparing whether a predetermined one of the second plurality of averaged parameter signals is greater than a second product of a second threshold value and the first sum signal to provide a second portion of the control signals;

a third summing circuit coupled to the first timeframe power/amplitude averaging circuit, the third summing circuit adding each of the first plurality of averaged parameter signals to provide a second sum signal; and

a third plurality of comparators coupled to the first timeframe power/amplitude averaging circuit, the first plurality of comparators comparing whether a predetermined one of the first plurality of averaged parameter signals is greater than a third product of a third threshold value and the second sum signal to provide a third portion of the control signals.

5. The receiver of claim 4 wherein the predetermined threshold value comprises a plurality of differing values.

6. The receiver of claim 4 wherein the receiver is an FM receiver and the first portion of control signals limits passage of the intermediate frequency signal in response to detection by the first timeframe power/amplitude averaging circuit of either adjacent interference or the adjacent interference being frequency overdeviated.

7. The receiver of claim 6 wherein the second portion of control signals limits passage of the intermediate frequency signal in response to a lack of detection by the first timeframe power/amplitude averaging circuit of adjacent interference and when long term average power/amplitude is below a threshold.

8. The receiver of claim 4 wherein the receiver is an FM receiver and the third portion of control signals limits passage of the intermediate frequency signal in response to a detection by the first timeframe power/amplitude averaging circuit of when a long term average power/amplitude of the receiver is either above or below respective predetermined ratios or when there is over-deviation of the input modulated signal.

9. The receiver of claim 4 wherein the control circuit asserts the first portion of the control signals to limit passage of the intermediate frequency signal before asserting either the second portion of control signals or the third portion of control signals, and the control circuit asserts the first portion of the control signals and the third portion of the control signals before asserting the second portion of control signals.

10. The receiver of claim 1 wherein the percentage of each sub-band signal that is permitted to be coupled to the output terminal varies dynamically in a predetermined range.

11. The receiver of claim 1 wherein the receiver receives signals in one of the following products:

an FM receiver, an AM receiver, a land mobile phone, a television receiver, a personal digital assistant product, a computer, a wireless communication device, a satellite receiver or an OFDM (orthogonal frequency division multiplexer) receiver.

12. The receiver of claim 1 wherein a user may selectively configure the monitoring circuit to control and vary a number of sub-bands which may be modified in response to predetermined values of the one or more control signals.

13. The receiver of claim 1 further comprising status circuitry coupled to the control circuit for utilizing the one or more control signals and providing at least an indication as to how many sub-band signals are permitted to be passed to the summing circuit and what reception quality exists.

14. The receiver of claim 1, wherein the filter bank comprises a plurality of sub-band filters, each of the plurality of sub-filters having a linear phase response and for generating a corresponding one of the plurality of sub-band signals, wherein when the percentage of each of the sub-band signals is added by the summing circuit to provide a filtered output signal having desired-passband and linear-phase bandpass filter characteristics.

15. A method of dynamic filtering in a receiver, comprising:

selectively receiving an input modulated signal with a tuner and mixing the input modulated signal with a local signal to generate an intermediate frequency signal;

generating a plurality of sub-band signals, each of the plurality of sub-band signals having a predetermined frequency range;

measuring a predetermined parameter of each of the sub-band signals and providing a plurality of parameter signals in response thereto;

providing one or more control signals which determine a percentage of each of the sub-band signals which is permitted to be coupled to an output terminal;

generating the percentage of each sub-band signal and adding the percentage of each of the sub-band signals to provide a filtered output signal; and

demodulating the filtered output signal to provide an audio output signal.

16. The method of claim 15 further comprising:

applying a weighting factor to a predetermined one of the sub-band signals, the weighting factor determining the percentage of each of the sub-band signals.

17. A dynamic receiver with varying reception parameters comprising:

a filter bank for receiving an input signal and generating a plurality of sub-band signals, each of the plurality of sub-band signals having a predetermined frequency range;

a monitoring circuit coupled to the filter bank, the monitoring circuit measuring a predetermined parameter of each of the sub-band signals and providing a plurality of parameter signals in response thereto;

a control circuit coupled to the monitoring circuit for receiving the plurality of parameter signals, the control circuit provides one or more control signals which determine a percentage of each of

the sub-band signals which is permitted to be coupled to an output terminal; and

a summing circuit coupled to the output terminal for receiving the percentage of each of the sub-band signals from the monitoring circuit and adding the percentage of each of the sub-band signals to provide a filtered output signal.

18. The receiver of claim 17 further comprising:

a plurality of weighting circuits coupled to the filter bank and the control circuit, each of the plurality of weighting circuits receiving a predetermined one of the one or more control signals and applying a weighting factor to a predetermined one of the sub-band signals, the weighting factor determining the percentage of each of the sub-band signals.

19. The receiver of claim 18 wherein the control circuit:

a first timeframe power/amplitude averaging circuit for receiving the plurality of parameter signals, the first timeframe power/amplitude averaging circuit performing a time averaging function on each of the parameters and providing a first plurality of averaged parameter signals, each of which corresponding to a predetermined frequency sub-band, and a first of which corresponding to a lowest frequency sub-band and being used as a reference signal;

a second timeframe power/amplitude averaging circuit for receiving the plurality of parameter signals, the second timeframe power/amplitude averaging circuit performing a time averaging function on each of the parameters which is shorter in time than the time averaging function performed by the first timeframe to provide a second plurality of averaged parameter signals;

a first plurality of comparators coupled to the first timeframe power/amplitude averaging circuit, the first plurality of comparators comparing whether the first of the plurality of averaged parameter signals from the first timeframe power/amplitude averaging circuit is greater than a first product of a predetermined threshold value and a predetermined one of the plurality of averaged parameter signals, the first plurality of comparators providing a first portion of the control signals;

a second summing circuit coupled to the second timeframe power/amplitude averaging circuit, the second summing circuit adding each of the second plurality of averaged parameter signals to provide a first sum signal;

a second plurality of comparators coupled to the second timeframe power/amplitude averaging circuit, the second plurality of comparators comparing whether a predetermined one of the second plurality of averaged parameter signals is greater than a second product of a second threshold value and the first sum signal to provide a second portion of the control signals;

a third summing circuit coupled to the first timeframe power/amplitude averaging circuit, the third summing circuit adding each of the first plurality of averaged parameter signals to provide a second sum signal; and

a third plurality of comparators coupled to the first timeframe power/amplitude averaging circuit, the first plurality of comparators comparing whether a predetermined one of the first plurality of averaged parameter signals is greater than a third product of a third threshold value and the second sum signal to provide a third portion of the control signals.

20. The receiver of claim 17 further comprising:

status circuitry coupled to the control circuit for utilizing the one or more control signals and providing at least an indication as to how many sub-band signals are permitted to be passed to the summing circuit and what reception quality exists.

21. The receiver of claim 17 further comprising:

a fixed frequency prefilter coupled to the filter bank, the fixed frequency prefilter receiving the input signal and prefiltering the input signal to provide a reduced sampling frequency signal to the filter bank, thereby simplifying design complexity of the filter bank.