Abstract: A demodulator (20) extracts a digital sub-carrier signal from a modulated signal and provides the sub-carrier signal in clock and data format. Demodulation occurs with two mixing stages (32, 40, 42) and at sampling frequencies that are independent from the frequency of transmission of the modulated signal. Matched filters (44, 46) try to match the received sub-carrier signal with a predefined bi-phase pulse shape. Phase correction is applied at a low sampling frequency. After phase correction, digital interpolation is used to re-sample the sub-carrier signal.

Abstract: A noise blanker (40, 106) monitors and removes noise from a sampled signal by adaptive filtering (98, 150) the sampled signal to generate trained adaptive filter prediction coefficients. The sampled signal is provided as an output signal when the noise blanker is in a training mode. A noise monitor (34, 154) detects whether noise contained within the sampled signal exceeds a predetermined threshold and provides a control signal in response to the detecting. The noise blanker is placed in a prediction mode for a predetermined amount of time in response to asserting the control signal. A prediction output signal is generated using a plurality of prediction coefficients as an all-pole filter. The prediction output signal has minimal noise content.

Abstract: One embodiment of the present invention relates to noise control of one or more signals. In one embodiment, impulsive-type noise events, such as multipath noise events or pops, may be detected and suppressed to reduce signal distortion. For example, in one embodiment related to a radio receiver (100), a predictor (436) having an adaptive filter (402) is used in combination with a fast attack slow decay mechanism (434) to provide noise control signals (352, 358) which may then be used to suppress noise events. In one embodiment, the fast attack slow decay mechanism includes applying a wide bandwidth filter at the onset of a noise event to quickly track variations in an error signal and applying a narrow wide bandwidth filter a peak of the noise event is detected in order to smooth variations in the error signal (410). This allows for improved psycho-acoustic perception. In one embodiment, the radio receiver is a mobile radio receiver.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

Abstract: A method for stopping on a radio station includes calculating a radio signal quality (205) using a multipath echo indicator and determining if the radio signal quality is greater than a predetermined signal quality threshold (210). A zero crossings indicator of a demodulated signal may be used (225) to reduce a false alarm rate. An apparatus includes an antenna (105), a local oscillator (110) coupled to the antenna, an analog-to-digital converter circuit (115) coupled to the local oscillator, a demodulator circuit (120) coupled to the analog-to-digital converter circuit, a signal strength determining circuit (125) coupled to the analog-to-digital converter circuit, a logarithmic circuit (150) coupled to the signal strength determining circuit, a multipath echo bandpass filter (155) coupled to the logarithmic circuit, and a stop-on-station circuit (145) coupled to the demodulator circuit, the multipath echo bandpass filter, and the logarithmic circuit.

Abstract: A radio receiver (100) has an IF (intermediate frequency) filter (200) for automatically adjusting its intermediate frequency. The filter (200) includes a filter bank (304), an accumulative sub-band formation (322) and an accumulative sub-band power estimator/switch control (324). The filter bank (304) generates sub-bands, each sub-band having a predetermined frequency range. The accumulative sub-band formation (322) selectively sums the sub-bands to provide lowpass filters having incrementally increasing bandwidth. Power estimates of the lowpass filters are used to determine which lowpass filter output is appropriate for adjacent station interference. Also, if there is no adjacent station interference, the IF filter (200) selects the appropriate filter output depending on the signal strength of the desired station.

Abstract: A radio receiver (100) has an IF (intermediate frequency) filter (200) for dynamically adjusting its intermediate frequency. The filter (200) includes a filter bank (301), power/amplitude estimator circuits (308, 310, 312), and weighting circuits (314, 316, 318). The filter bank (301) generates sub-bands, each sub-band having a predetermined frequency range. The power/amplitude estimators (308, 310, 312) provide an estimated power/amplitude in each sub-band. A filter control (320) uses the power/amplitude estimates to determine a percentage of each sub-band signal that is permitted to be coupled a summation circuit (319). The summation circuit (319) sums the weighted sub-band signals to provide a filtered output signal to a demodulator (212).

Abstract: A digital FM demodulator employs a baseband phase lock loop (BBPLL), which is particularly effective for long range reception, for combining and demodulating a pair of signals represented by the mathematical expression A(t)ej&thgr;(t) to result in an approximation of d&thgr;/dt. This approximation is then subjected to an inverse of the linear approximation of the frequency response of the BBPLL that produces a very accurate &thgr;. This is conveniently achieved with a IIR filter whose transfer function happens to be the same as the inverse of the linear approximation of the frequency response of the BBPLL. The derivative is then taken of &thgr; to produce a very accurate d&thgr;/dt, the desired result for the output of an FM demodulator. To aid operation of the BBPLL, the incoming digital intermediate frequency is upsampled by a combination of sample and hold and FIR filtering prior to being processed by the BBPLL.

Abstract: A digital FM demodulator employs a baseband phase lock loop (BBPLL), which is particularly effective for long range reception, for combining and demodulating a pair of signals represented by the mathematical expression A(t)ej&thgr;(t) to result in an approximation of d&thgr;/dt. This approximation is then subjected to an inverse of the linear approximation of the frequency response of the BBPLL that produces a very accurate &thgr;. This is conveniently achieved with a IIR filter whose transfer function happens to be the same as the inverse of the linear approximation of the frequency response of the BBPLL. The derivative is then taken of &thgr; to produce a very accurate d&thgr;/dt, the desired result for the output of an FM demodulator. To aid operation of the BBPLL, the incoming digital intermediate frequency is upsampled by a combination of sample and hold and FIR filtering prior to being processed by the BBPLL.

Abstract: A cost effective digital stereo decoder (216) for Digitized Intermediate Frequency (DIF) FM radio receiver (100). After FM demodulation (212), a multiplex signal (MPX) at a high sampling rate is mixed with free-running local quadrature mixers (308, 320) to shift the (L−R) stereo signal to baseband. The MPX signal is also mixed with a free-running locally generated carrier signal to translate an embedded 19 KHz pilot tone signal to 1 KHz. The pilot tone signal is decimated to a low sampling rate to permit a phase-lock loop (PLL) to be applied to the lower rate signal to estimate the phase of the pilot signal. An FM blender controller is used to attenuate high frequency noise and improve audio quality. The receiver may be implemented in software and be customer configurable to have various operating characteristics.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

Abstract: A radio receiver (100) has an IF (intermediate frequency) filter (200) for dynamically adjusting its intermediate frequency. The filter (200) includes a filter bank (301), power/amplitude estimator circuits (308, 310, 312), and weighting circuits (314, 316, 318). The filter bank (301) generates sub-bands, each sub-band having a predetermined frequency range. The power/amplitude estimators (308, 310, 312) provide an estimated power/amplitude in each sub-band. A filter control (320) uses the power/amplitude estimates to determine a percentage of each sub-band signal that is permitted to be coupled a summation circuit (319). The summation circuit (319) sums the weighted sub-band signals to provide a filtered output signal to a demodulator (212).

Abstract: A demodulator (20) extracts a digital sub-carrier signal from a modulated signal and provides the sub-carrier signal in clock and data format. Demodulation occurs with two mixing stages (32, 40, 42) and at sampling frequencies that are independent from the frequency of transmission of the modulated signal. Matched filters (44, 46) try to match the received sub-carrier signal with a predefined bi-phase pulse shape. Phase correction is applied at a low sampling frequency. After phase correction, digital interpolation is used to re-sample the sub-carrier signal.