Abstract: A radio signal processing circuit comprises multiple audio blend channels, an audio decoder, a program selector and a blending circuit. The audio blend channels are configured to receive digital audio packets for multiple supplemental audio programs. Each audio blend channel includes an audio blend buffer and a signal quality metric circuit. The signal quality metric (SQM) circuit configured to determines an audio quality indicator for the digital audio packets of the program and indicates availability of the program according to the audio quality indicator regardless of whether the program is selected for play. The program selector configured to provides digital audio packets from a selected audio blend channel to the audio decoder to produce a digital audio signal. The blending circuit blends the digital audio signal produced for the selected audio blend channel with a signal representing silence according to the audio quality indicator for the audio blend channel.

Abstract: A radio signal processing circuit comprises multiple audio blend channels, an audio decoder, a program selector and a blending circuit. The audio blend channels are configured to receive digital audio packets for multiple supplemental audio programs. Each audio blend channel includes an audio blend buffer and a signal quality metric circuit. The signal quality metric (SQM) circuit configured to determines an audio quality indicator for the digital audio packets of the program and indicates availability of the program according to the audio quality indicator regardless of whether the program is selected for play. The program selector configured to provides digital audio packets from a selected audio blend channel to the audio decoder to produce a digital audio signal. The blending circuit blends the digital audio signal produced for the selected audio blend channel with a signal representing silence according to the audio quality indicator for the audio blend channel.

Abstract: A method of processing a digital radio broadcast signal in a digital radio receiver includes: receiving baseband signal samples at a first sample rate; adjusting the sample rate of the baseband signals based on a difference between a receiver clock and a transmitter clock to produce adjusted baseband signal samples at a second sample rate; filtering the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples, wherein the digital component and the analog component are synchronous; and separately demodulating the digital component and the analog component to produce a digital output signal and an analog output signal. A receiver that uses the method is also provided.

Abstract: A method and apparatus are provided for blending analog and digital portions of a composite digital radio broadcast signal by processing compressed audio packets to compute corresponding digital audio quality indicator values, storing the compressed audio packets in an audio blend buffer, processing audio information from each compressed audio packet stored in the audio blend buffer with an audio decoder to generate decompressed digital audio signal samples, and using the digital audio quality indicator values to guide a blending process for combining analog audio signal samples with the digital audio signal samples to produce an audio output by preventing unnecessary blending back and forth between analog and digital if the digital audio quality indicator values indicate that the compressed audio packets are degraded or impaired.

Abstract: A method of processing a digital radio broadcast signal in a digital radio receiver includes: receiving baseband signal samples at a first sample rate; adjusting the sample rate of the baseband signals based on a difference between a receiver clock and a transmitter clock to produce adjusted baseband signal samples at a second sample rate; filtering the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples, wherein the digital component and the analog component are synchronous; and separately demodulating the digital component and the analog component to produce a digital output signal and an analog output signal. A receiver that uses the method is also provided.

Abstract: A method and apparatus are provided for blending analog and digital portions of a composite digital radio broadcast signal by processing compressed audio packets to compute corresponding digital audio quality indicator values, storing the compressed audio packets in an audio blend buffer, processing audio information from each compressed audio packet stored in the audio blend buffer with an audio decoder to generate decompressed digital audio signal samples, and using the digital audio quality indicator values to guide a blending process for combining analog audio signal samples with the digital audio signal samples to produce an audio output by preventing unnecessary blending back and forth between analog and digital if the digital audio quality indicator values indicate that the compressed audio packets are degraded or impaired.

Abstract: Methods and systems for correcting a frequency error in a digital portion of a radio broadcast signal are disclosed. The methods and systems include the steps of receiving a radio broadcast signal having an analog portion and a digital portion, separating the analog portion of the radio broadcast signal and the digital portion of the radio broadcast signal, determining a coarse frequency offset of the analog portion of the radio broadcast signal, generating an error signal for adjusting a frequency of the digital portion of the radio broadcast signal, wherein the error signal is based on the coarse frequency offset of the analog portion of the radio broadcast signal, and adjusting the frequency of the digital portion of the radio broadcast signal with the error signal that is based on the coarse frequency offset of the analog portion of the radio broadcast signal, such that a frequency error in the digital portion of the radio broadcast signal is reduced below a predetermined amount.

Abstract: Methods and systems for adjusting a sampling rate of a digital radio receiver are disclosed that comprise the steps of receiving from a decoder a first frame of data having a first number of samples; determining at the digital radio receiver a phase difference between a receiver clock and a transmitter clock; generating at the digital radio receiver a second frame of data having a second number of samples, wherein the second number of samples depends on the phase difference between the receiver clock and the transmitter clock such that the second number of samples is less than the first number of samples if the transmitter clock is ahead of the receiver clock, and the second number of samples is greater than the first number of samples if the receiver clock is ahead of the transmitter clock; outputting the second frame of data having the second number of samples; and requesting a next frame of data from the decoder at a time that is earlier than a processing time for the first number of samples if the transmi

Abstract: Methods and systems for recovering a DC component in a zero-IF radio receiver are disclosed that involve receiving a frequency modulated radio frequency broadcast signal, down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component, filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed, analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component, and adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.

Abstract: Methods and systems for correcting a frequency error in a digital portion of a radio broadcast signal are disclosed. The methods and systems include the steps of receiving a radio broadcast signal having an analog portion and a digital portion, separating the analog portion of the radio broadcast signal and the digital portion of the radio broadcast signal, determining a coarse frequency offset of the analog portion of the radio broadcast signal, generating an error signal for adjusting a frequency of the digital portion of the radio broadcast signal, wherein the error signal is based on the coarse frequency offset of the analog portion of the radio broadcast signal, and adjusting the frequency of the digital portion of the radio broadcast signal with the error signal that is based on the coarse frequency offset of the analog portion of the radio broadcast signal, such that a frequency error in the digital portion of the radio broadcast signal is reduced below a predetermined amount.

Abstract: Methods and systems for recovering a DC component in a zero-IF radio receiver are disclosed that involve receiving a frequency modulated radio frequency broadcast signal, down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component, filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed, analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component, and adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.

Abstract: Methods and systems for adjusting a sampling rate of a digital radio receiver are disclosed that comprise the steps of receiving from a decoder a first frame of data having a first number of samples; determining at the digital radio receiver a phase difference between a receiver clock and a transmitter clock; generating at the digital radio receiver a second frame of data having a second number of samples, wherein the second number of samples depends on the phase difference between the receiver clock and the transmitter clock such that the second number of samples is less than the first number of samples if the transmitter clock is ahead of the receiver clock, and the second number of samples is greater than the first number of samples if the receiver clock is ahead of the transmitter clock; outputting the second frame of data having the second number of samples; and requesting a next frame of data from the decoder at a time that is earlier than a processing time for the first number of samples if the transmi

Abstract: A digital finite impulse response (FIR) filter having a shift register for receiving a digital signal, a counter for counting pulses in a sampling signal and a look-up table read-only memory (ROM) having address inputs coupled to the outputs of the stages of the FIR filter and to the outputs from the counter. The output of the ROM forms the filtered signal. This digital filter approach allows for a balance between cost and performance and is inherently flexible due to the programmable nature of its core device (ROM).