Limiting audible noise introduction through FM antenna tuning

• US 7,817,969 B2
• Filed: 09/21/2007
• Issued: 10/19/2010
• Est. Priority Date: 02/12/2007
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Anand, Seema B., Rofougaran, Maryam, Rofougaran, Ahmadreza (Reza), Castaneda, Jesus Alfonso
• Primary Examiner(s): LE, NHAN T
• Application Number:
  US11/858,957
• Publication Number:
  US 20080192807A1
• Time in Patent Office: 1,124 Days
• Field of Search: 455/63.1, 455/114.2, 455/296, 375/346
• US Class Current: 455/114.2
• CPC Class Codes: H03D 3/002 Modifications of demodulators to reduce interference by undesired signals H03D3/248 takes precedence
• CPC Class Codes: H03J 2200/06 Tuning of antenna
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank

Abstract

An FM receiver including an FM antenna that receives continuous wavelength signals, where the FM receiver is coupled to the FM antenna and operable to alter a center frequency of a gain profile of the FM antenna. The FM receiver includes a low noise amplifier module that is coupled to amplify the continuous wavelength signal to produce an amplified RF signal therefrom. A down conversion module is coupled to mix the amplified RF signal with a local oscillation to produce an information signal. A filter module is coupled to filter the information signal to produce a filtered information signal. A demodulation module is coupled to capture audio information from the filtered information signal. A signal monitoring module is coupled to monitor the FM signal quality of a received continuous wavelength signal. The signal monitoring module produces a signal quality indication therefrom. An antenna control module produces a signal value based upon the signal quality indication, wherein the signal value operates to alter the center frequency of a gain profile of the FM antenna.

Claims

1. A method to limit audible noise introduction through FM antenna tuning, in which an FM antenna is coupled with lumped tuning circuitry to alter a center frequency of a gain profile of the FM antenna, the method comprises:

receiving an incoming continuous wavelength signal that corresponds to an FM frequency band;

determining signal quality information of the received incoming continuous wavelength signal; and

when the signal quality information drops below a predetermined performance threshold,

frequency hopping across the FM frequency band at a scanning frequency interval by altering the center frequency of the gain profile of the FM antenna with the lumped tuning circuitry;

determining a scanned frequency having a greatest signal quality information from a plurality of scanned frequencies within the FM frequency band; and

setting the center frequency of the gain profile of the FM antenna to the frequency of the scanned frequency with the greatest signal quality information.

2. The method of claim 1, wherein the setting the center frequency of the gain profile of the FM antenna to the scanned frequency having the greatest signal quality information comprises:

determining the frequency associated with the scanned frequency having the greatest signal quality information; and

altering the center frequency of the gain profile of the FM antenna based upon the difference of the scanned frequency with a desired channel frequency.

3. The method of claim 2 wherein the altering the center frequency of the gain profile of the FM antenna comprises:

changing an impedance of the lumped tuning circuitry.

4. The method of claim 1 further comprises:

when the signal quality information drops below a second predetermined performance threshold,

frequency hopping across a subset of the FM frequency band at a dithering frequency interval, the frequency subset includes a present center frequency of the gain profile of the FM antenna, wherein the dithering frequency interval is less than the scanning frequency interval;

determining a dithered frequency having a greatest signal quality information from a plurality of dithered frequencies within the frequency subset of the FM frequency band; and

setting the center frequency of the gain profile of the FM antenna to the frequency of the dithered frequency having the greatest signal quality information.

5. The method of claim 4, wherein the frequency hopping at the scanning frequency interval occurs periodically to ensure that the frequency subset includes appropriate portions of the FM frequency band.

6. The method of claim 1 wherein the frequency hopping occurs at a rate sufficient to avoid audible detection.

7. The method of claim 6 wherein the rate is at least 1.0 MHz.

8. The method of claim 1 wherein the signal quality information comprises at least one of a measured received signal strength and a measured signal-to-noise ratio (SNR).