Adaptive identifying signal detector

• US 5,020,141 A
• Filed: 11/03/1989
• Issued: 05/28/1991
• Est. Priority Date: 10/02/1987
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Meszko, William R.
• Primary Examiner(s): KUNTZ, CURTIS A
• Application Number:
  US07/432,334
• Time in Patent Office: 571 Days
• Field of Search: 455/161, 455/168, 455/194, 455/200, 455/212, 455/218, 455/219, 455/222, 455/165, 455/166, 455/35-38, 455/58, 455/213, 455/221
• US Class Current: 455/166.1
• CPC Class Codes: H03G 3/342 Muting when some special characteristic of the signal is sensed which distinguishes it from noise, e.g. using speech detector H03G3/344, H03G3/345 take precedence
• CPC Class Codes: H03G 3/348 Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits
• CPC Class Codes: H03G 5/24 in frequency-selective amplifiers
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal

Abstract

A radio receiver capable of receiving more than one channel, one of which channels may be a priority channel, wherein some communications may be accompanied by a sub-audible continuous identifying signal, which signal can be detected by the radio in an adaptive way. In particular, a wideband, rapid detect approach can be utilized in the absence of a determination that adjacent identifying signals are present. To the extent such adjacent signals are present, the radio selects a narrowband, slower detection approach, or, in the alternative, shifts the bandpass characteristics of the wideband approach in an attempt to avoid the adjacent interfering signal.

Claims

1. In a radio receiver having:

receiver means for receiving, on any of a plurality of channels, radio frequency signals including an information signal, wherein some of said radio frequency signals also include squelch control signal;

channel selection means for selecting which of said plurality of channels will be received;

first detector means for detecting presence of a particular one of said squelch control signals within a first period of time;

squelch means for selectively rendering said information signal audible and inaudible; and

channel scanning means for causing;

said channel selector means to select a particular channel;

said channel selection means to retain said particular channel when said

first detector means detects said particular one of said

squelch control signals; and

said squelch means to render said information signal audible, an improvement comprising;

second detector means for detecting presence of said particular one of said squelch control signals within a second period of time, wherein said second period of time is less than said first period of time; and

control means for controlling which of said detector means is used to detect said particular one of said squelch control signals, such that said channel scanning means will cause said channel selection means to retain said particular channel and will cause said squelch means to render said information signal audible when either of said first and second detector means, as controlled by said control means, detects said particular one of said squelch control signals.

2. The improvement of claim 1 wherein said first detector means includes a first filter having a first bandpass and said second detector means includes a second filter having a second bandpass, wherein said first bandpass is wider than said second bandpass.

3. A method of scanning a radio communications channel that may include an information signal, wherein said information signal may be accompanied by a squelch control signal, the method comprising the steps of:

A) monitoring said radio communications channel from time to time;

B) estimating whether a particular one of said squelch control signals is present on said radio communications channel, such that said estimating is concluded within a first period of time;

C) discontinuing monitoring of said radio communications channel when said estimating does not indicate presence of said particular one of said squelch control signals;

D) continuing monitoring of said radio communications channel when said estimating does indicate presence of said particular one of said squelch control signals, and confirming that said particular one of said squelch control signals is present on said radio communications channel, wherein said confirming is concluded within a second period of time, which second period of time is longer than said first period of time;

E) discontinuing monitoring of said radio communications channel when said confirming step fails to confirm presence of said particular one of said squelch control signals.

4. The method of claim 3 wherein said estimating step includes the step of passing said squelch control signal, if present, through a first filter having a first bandpass that will pass said squelch control signal therethrough.

5. The method of claim 4 wherein said confirming step includes the step of passing said squelch control signal, if present, through a second filter having a second bandpass that will pass said squelch control signal therethrough and that is narrower than said first bandpass.

6. The method of claim 5 and further including, in step e, the steps of shifting said first bandpass of said first filter.