Methods and systems for rapid detection of digital radio signals

Patent metadata

Field	Value
Publication number	US-9584347-B2
Application number	US-201313906465-A
Country	US
Kind code	B2
Filing date	May 31, 2013
Priority date	May 31, 2013
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

Systems and methods are disclosed for rapid detection of digital content within received radio frequency (RF) signals. The disclosed embodiments digitize received RF signals and apply a sliding window average to subsampled complex magnitudes for the digital samples to generate subsampled magnitude values. The subsampled magnitude values are then collected over a small number of symbols for the digital content, and the results are analyzed to determine whether or not digital content is present with the received signals. For example, multi-symbol histograms and magnitude ratios determined over multiple symbols can then be utilized to make the determination of whether digital content is present in the received signals. The resulting detection determination can be utilized further to control operations of systems utilizing the disclosed embodiments. The disclosed embodiments can be used, for example, to detect the presence of HD (High Definition) Radio digital content within broadcast channels.

First claim

What is claimed is:

1. A receiver system for detecting digital content in a radio frequency (RF) channel, comprising:
front-end circuitry configured to receive radio frequency (RF) signals and to output signals associated with a channel within the RF signals;
analog-to-digital conversion (ADC) circuitry configured to receive the output signals and to output digital samples having a real component (I) and an imaginary component (Q);
complex magnitude determination circuitry configured to receive the digital samples and to generate complex magnitudes for the digital samples;
sliding window averaging filter circuitry configured to subsample the complex magnitudes for each of a plurality of symbols, to apply a sliding window average to the subsampled complex magnitudes to generate a plurality of averaged subsampled magnitude values for each symbol based upon subsampled complex magnitudes within sliding windows of subsampled complex magnitudes, and to output the averaged subsampled magnitude values for each symbol; and
shape detection circuitry configured to determine if digital content is present within the channel having a digital content shaping function, the digital content shaping function being associated with digital content to be detected, the shape detection circuitry comprising:
buffer circuitry configured to store the averaged subsampled magnitude values for each symbol, each averaged subsampled magnitude value having an associated index value; and
detection circuitry configured to detect a minimum value within the stored averaged subsampled magnitude values for each symbol, to output an index value associated with the detected minimum value for each symbol, and to form an index count histogram based upon index values output for the plurality of symbols;
wherein the index count histogram includes count values associated with the index values output for the plurality of symbols; and
wherein the shape detection circuitry is further configured to use the count values within the index count histogram to determine if digital content is present within the channel having the digital content shaping function;

wherein the digital content is included within OFDM (orthogonal frequency division multiplexed) symbols transmitted within the channel, and wherein the digital content shaping function comprises a pulse shaping function applied to each OFDM symbol.

2. The receiver system of claim 1 , wherein the sliding window averaging filter circuitry comprises a first subsampler configured to receive the complex magnitudes and to output subsampled values, averaging filter circuitry configured to average a varying plurality of the subsampled values within a sliding window of subsampled values and to output averaged values, and a second subsampler configured to subsample the averaged values and to output the averaged subsampled magnitude values.

3. The receiver system of claim 1 , wherein the shape detection circuitry is further configured to determine a peak count value within the index count histogram and to compare the peak count value to a threshold value to determine if digital content is present within the channel having the pulse shaping function for the OFDM symbols.

4. The receiver system of claim 1 , wherein the sliding window averaging filter circuitry and the shape detection circuitry are configured to independently process two sidebands within the channel to generate first and second index count histograms, and wherein the shape detection circuitry is further configured to combine the first and second index count histograms to generate a combined index count histogram, to determine a peak count value within the combined index count histogram, and to compare the peak count value to a threshold value to determine if digital content is present within the channel having the pulse shaping function for the OFDM symbols.

5. The receiver system of claim 1 , wherein the shape detection circuitry is further configured to determine an index value associated with a peak count value within the index count histogram and to compare multiple index values over time to determine if digital content is present within the channel having the pulse shaping function for the OFDM symbols.

6. The receiver system of claim 1 , wherein the sliding window averaging filter circuitry and the shape detection circuitry are configured to independently process two sidebands within the channel to generate first and second index values and to compare multiple first and second index values over time to determine if digital content is present within the channel having the pulse shaping function for the OFDM symbols.

7. The receiver system of claim 1 , further comprising control circuitry configured to output a detection signal indicating whether or not digital content is determined to be present.

8. The receiver system of claim 7 , wherein the digital content comprises HD (High Definition) Radio digital content included within OFDM signals transmitted within the channel.

9. The receiver system of claim 8 , wherein the OFDM signals for the HD Radio digital content is transmitted within the channel without associated analog content or is transmitted within the channel within one or more sidebands associated with a center frequency for analog content also transmitted within the channel.

10. The receiver system of claim 8 , further comprising HD demodulator circuitry configured to demodulate HD Radio digital content, and wherein the HD demodulator circuitry is configured to be powered or not powered depending upon whether or not the detection signal indicates that digital content is present within the channel.

11. The receiver system of claim 1 , wherein a detection time to determine if digital content is present within the channel is 50 or less milliseconds.

12. The receiver system of claim 1 , wherein the plurality of symbols is 20 or fewer symbols.

13. A receiver system for detecting digital content in a radio frequency (RF) channel, comprising:
front-end circuitry configured to receive radio frequency (RF) signals and to output signals associated with a channel within the RF signals;
analog-to-digital conversion (ADC) circuitry configured to receive the output signals and to output digital samples having a real component (I) and an imaginary component (Q);
complex magnitude determination circuitry configured to receive the digital samples and to generate complex magnitudes for the digital samples;
sliding window averaging filter circuitry configured to subsample the complex magnitudes for each of a plurality of symbols, to apply a sliding window average to the subsampled complex magnitudes to generate averaged subsampled magnitude values for subsampled complex magnitudes within a sliding window of subsampled complex magnitudes for each symbol, and to output the averaged subsampled magnitude values for each symbol; and
shape detection circuitry configured to determine if digital content is present within the channel having a digital content shaping function, the digital content shaping function being associated with digital content to be detected, the shape detection circuitry comprising:
demultiplexer circuitry configured to demultiplex the averaged subsampled magnitude values into a plurality of demuxed subsamples for each symbol;
a plurality of accumulators configured to accumulate the demuxed subsamples for the plurality of symbols and to generate a plurality of accumulated values; and
ratio detection circuitry configured to determine a ratio associated with the plurality of accumulated values; and
wherein shape detection circuitry is further configured to compare the ratio to a threshol

Assignees

• Silicon Lab Inc

Inventors

• Elenes Javier
• Taipale Dana

Classifications

• H04L25/03834 Primary

  using pulse shaping · CPC title

• H04L27/2605

  Symbol extensions, e.g. Zero Tail, Unique Word [UW] · CPC title

• H04L27/2649

  Demodulators · CPC title

• H04L27/2647

  Arrangements specific to the receiver only (equalisation H04L27/01) · CPC title