US 6,389,270 B1Granted

Station scan method and apparatus for radio receivers

AssigneeCirrus Logic, Inc.

InventorsJames M. Nohrden, Brian P. Lum Shue Chan

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Abstract

Station scan circuitry for a radio-frequency receiver and corresponding methods are disclosed that efficiently determine the presence of a station on available channels. The station scan circuitry includes circuitry that determines if the signal power on a given channel exceeds a threshold value. Additional circuitry compares the channel signal strength and the adjacent channel signal to determine if a ratio of the two exceeds a threshold level. If both the signal power and the signal strength ratio are sufficient, the station scan circuitry indicates that a station has been found. To make the signal strength comparison, the station scan circuitry includes circuitry for determining a post-filter signal strength and a pre-filter signal strength for the received signal.

Claims28

Dependent claims

A digital audio receiver for processing audio information, comprising:

analog to digital converter circuitry having an in-phase (I) digital output signal and a quadrature (Q) digital output signal;
filter circuitry coupled to receive digital signals from the analog to digital converter circuitry and having pre-filter output signals and post-filter output signals wherein the pre-filter output signals comprise pre-filter digital I and Q signals and the post-filter output signals comprise post-filter digital I and Q signals and wherein the filter circuitry comprises:
first filter circuitry coupled to receive the I and Q digital output signals from the analog to digital converter circuitry, the pre-filter digital I and Q signals being the output signals from the first filter circuitry;
and
second filter circuitry coupled to receive the pre-filter digital I and Q signals, the post-filter I and Q signals being the output of the second filter circuitry;
and
wherein the first filter circuitry comprises finite impulse response filters or infinite impulse response filters and the second filter circuitry comprises finite impulse response filters or infinite impulse response filters;
and
station scan circuitry coupled to the pre-filter output signals and the post-filter output signals and having a station found signal as an output, the station found signal being asserted depending upon a comparison between magnitudes of the pre-filter output signals and the post-filter output signals.

6 more elements

A radio receiver system for processing audio information transmitted by a radio station, comprising:

an antenna;
a frequency converter coupled to receive a signal from the antenna, the frequency converter being tunable to select a desired radio station frequency;
and
a digital receiver coupled to receive a signal from the frequency converter and having
a digital audio signal as an output, the digital receiver comprising:
analog to digital converter circuitry;
filter circuitry coupled to receive a digital signal from the analog to digital converter circuitry and having a pre-filter output signal and a post-filter output signal wherein the post-filter output signal is a desired channel signal corresponding to a desired channel at the desired radio station frequency and the pre-filter output signal is at least reflective of an adjacent channel signal corresponding to an adjacent channel that is adjacent to the desired channel at an adjacent frequency;
and
a station scan circuitry coupled to the pre-filter output and the post-filter output signal and having a station found signal as an output, the station found signal being asserted when a magnitude of the desired channel signal and a magnitude of the adjacent channel signal are compared and determined to be substantially equal in value;
and
control circuitry coupled to receive the station found signal and to control the tuning of the frequency converter.

8 more elements

A digital audio receiver for processing audio information, comprising

analog to digital converter circuitry;
filter circuitry coupled to receive a digital signal from the analog to digital converter circuitry and having a pre-filter output signal and a post-filter output signal wherein the post-filter output signal is a desired channel signal corresponding to a desired channel at a desired radio station frequency and the pre-filter output signal is at least reflective of an adjacent channel signal corresponding to an adjacent channel that is adjacent to the desired channel at an adjacent frequency;
and
a station scan circuitry coupled to the pre-filter output signal and the post-filter output signal and having a station found signal as an output, the station found signal being asserted when a magnitude of the desired channel signal and a magnitude of the adjacent channel signal are compared and determined to be substantially equal in value.

1 more element

A station scan method for digital receivers, comprising:

selecting a radio station frequency;
tuning a frequency converter to the radio station frequency;
converting analog audio information at the selected radio station frequency to a digital signal;
filtering the digital signal from the analog to digital converter circuitry to produce a pre-filter output signal and a post-filter output signal wherein the post-filter output signal is a desired channel signal corresponding to a desired channel at the selected radio station frequency and the pre-filter output signal is at least reflective of an adjacent channel signal corresponding to an adjacent channel that is adjacent to the desired channel at an adjacent frequency;
determining a magnitude of the desired channel signal and a magnitude of the adjacent channel signal;
asserting a station found signal when the magnitude of the desired channel signal and the magnitude of the adjacent channel signal are compared and determined to be substantially equal in value;
and
selecting a different station and repeating the above steps until the station found signal is asserted.

5 more elements

Dependencies are inferred from the claim text.