Rapid autonomous scan in FM or other receivers with parallel search strategy, and circuits, processes and systems

A wireless signal band searching process having a tuning direction and comprising:

• automatically tuning a receiver to a specified channel frequency to deliver a signal channel and an image channel separate from each other;
• electronically measuring at least one primary metric for the signal channel and electronically evaluating whether the signal channel has any signal that satisfies a criterion based on the at least one primary metric;
• when the signal channel fails such criterion, then branching to an inside loop to analogously evaluate the image channel relative to a similar criterion;
• when the image channel fails the similar criterion, then record-keeping by electronically entering an indication of the image frequency into an invalid-channel record;
• adjusting a channel frequency specifying value to re-specify a channel frequency in the tuning direction;
• accessing the invalid channel record based on the adjusted channel frequency specifying value to determine whether the re-specified channel frequency is indicated as an invalid channel, and if so, then electronically repeating the adjusting and accessing until such invalid channel indication is absent for a currently adjusted value;
• and
• then repeating two or more of the tuning, electronic measuring, electronic evaluating, record-keeping, adjusting, and accessing steps until a signal channel reached that satisfies the criterion.

A power managed circuit comprising:

• a de-rotation circuit having a signal channel output and a separate image channel output;
• a first low pass filter and a second low pass filter connected to said signal channel output and said image channel output respectively;
• a signal strength module coupled for measuring respective signal strengths from said first low pass filter and from said second low pass filter;
• and
• a power management circuit operable for frequency scanning based at least in part on said signal strength module and further operable to selectively enable and disable the first low pass filter and said second low pass filter alternately during the frequency scanning and to disable said second low pass filter after such frequency scanning is completed.

An integrated circuit system comprising:

• a receiver tunably operable to receive signal channels;
• at least one coexisting radio;
• and
• a processor operable to control the at least one coexisting radio, and further to control the receiver in a channel scanning mode that concurrently receives multiple channels and that retunes the receiver based on invalid-channel information derived from the receiver in the multiple channels to at least sometimes jump by plural channels in the frequency scanning mode;
• wherein said processor is operable to execute a low intermediate frequency de-rotator with signal band and image band outputs, and to parallelize a frequency scan for the channel scanning mode according to instances of absence of transmission in both the signal band and the image band outputs;
• and
• wherein the frequency scan is over a frequency raster that has a spacing, and said processor includes a cyclic buffer supporting such channel scanning mode and having a capacity for invalid-channel indications at least equal in number to a ratio of twice the low intermediate frequency divided by the spacing of the frequency raster.

A frequency scanning process having a tuning direction and for scanning a band of channels having a nominal channel width, the process comprising:

• tuning a wireless receiver based on specified channel frequency to receive plural signal channels and plural image channels;
• de-rotating the plural signal channels and plural image channels to a signal output and to a separate image output;
• filtering the signal output with a passband at least twice the nominal channel width and filtering the image output with a passband at least twice the nominal channel width thereby to provide a signal filter output substantially free of image channels and an image output substantially free of signal channels;
• electronically measuring the signal filter output as a whole to determine whether it is the case that both A) the plural signal channels are substantially empty of valid signals and B) the plural image channels are substantially empty of valid signals;
• when that case is present, electronically entering into a storage one or more identifiers representing the plural image channels;
• and
• adjusting a channel frequency specification value to represent a re-specified channel frequency in the tuning direction;
• accessing the storage to determine whether the re-specified channel frequency is indicated as an invalid channel, and if so, then repeating the adjusting and accessing until such indication is absent;
• and
• then repeating to retune in the tuning direction based on the respecified channel frequency, and perform the electronic measuring and evaluating, adjusting and accessing steps until a set of signal channels is reached that has that least one valid signal.