Abstract:
The invention provides an audio signal processing system in which a magnitude spectrum of a frequency domain audio signal is processed based on a measure of multipath interference. The processing keeps the magnitude spectrum approximately fixed during periods of multipath interference, for example by replacing it with a temporally smoothed version of the magnitude spectrum. The magnitude spectrum (processed if required) and the phase spectrum are combined to derive a frequency domain output, which is transformed to the time domain.
Abstract:
An AM/FM radio system for a vehicle that is selectively impedance matched to the particular tuned frequency of interest so that noise received by other frequencies does not affect the received signal. The radio system includes an HMI allowing a user to select an AM or FM radio station and a radio tuner responsive to a signal from the HMI identifying the selected radio station. The tuner tunes the radio system to the radio station, and provides a signal to the HMI identifying the radio station. The HMI places a message on a vehicle bus identifying the radio station that the radio tuner is tuned to. An antenna controller receives the message from the vehicle bus to selectively control an impedance matrix to provide impedance matching for the selected radio station frequency. The antenna controller also selectively tunes antenna radiating elements to the particular tuned frequency.
Abstract:
An electronic circuit (100) for use in a wireless receiver (1720). The circuit (100) includes an audio demodulator (15), an audio envelope portion (35) operable to deliver an audio envelope signal, a high pass filter (38) coupled between the audio demodulator (15) and the audio envelope portion (35), a volume control (25) fed by the audio demodulator (15) and operable to provide a controllable audio signal output, and a controller (45) responsive to the audio envelope portion (35) to provide an attenuation control to the volume control (25). Other circuits, receivers, processes of operation, processes of manufacture, and processes of testing are disclosed.
Abstract:
The circuit arrangement includes a first low-pass filter (2) for filtering an input signal (H3) proportional to the strength of a received radio signal; a second low-pass filter (3) for filtering the input signal (H3); a first weighting circuit (7) for weighting the first low-pass filter output signal with first coefficients to form a first weighted output signal; a circuit device for forming a masking signal for reducing stereo channel isolation from the first weighted output signal; a second weighting circuit (5) for forming a second weighted output signal weighted with second coefficients from the first low-pass filter output signal or the second low-pass filter output signal according to a switching signal (DD2) indicative of interference in the audio signals; a switch device (4) for selecting the first low-pass filter output signal for weighting in the second weighting circuit means (5) when no interference is indicated by the switching signal (DD2) and the second low-pass filter output signal for weighting in the second weighting circuit means (5) when interference is indicated by the switching signal (DD2); and a circuit device for forming a masking signal for damping the audio signal from the second weighted output signal.
Abstract:
A high-cut and high-blend control voltage generating circuit for activating a noise reduction circuit of an FM stereo receiver is configured to be simply responsive to multipath noises and never to plug noises. A changing and discharging circuit in the control voltage circuit may have a relatively long charging time constant, and the voltage control circuit may be configured to be simply responsive to multipath noises above a predetermined level. Thus the circuit is much less liable to operate erroneously.
Abstract:
A pulse position modulated (PPM) signal is derived from an input FM signal, and first and second switching signals are derived which are opposite in phase and correspond to alternating half cycles of the PPM signal. First and second opposite phase subcarrier signals are derived synchronized to the pilot signal in the input FM signal, and various combinations of the switching and subcarrier signals are multiplied together and the multiplication products combined to obtain left and right channel outputs.
Abstract:
In an FM stereo-receiver, a noise reduction circuit includes a by-pass circuit connected between the output of an FM detector and an earth potential point, the time constant of which is controlled to continuously vary the frequency characteristic at a path from the FM detector to an MPX circuit, thereby greatly reducing a high frequency noise inherent therein.
Abstract:
A pilot signal cancelling circuit for an FM multiplex demodulator wherein the amplitude of the cancelling signal tracks that of the pilot signal contained in or mixed into the composite signal. The amplified composite signal is synchronously detected with the fixed amplitude 19 KHz pilot signal extracted by a phase lock loop 2, and the detector output is filtered to remove high frequency components and then converted to a current variation in a d.c. amplifier 13. The output of the latter is fed to a current controlled attenuator 14 together with the fixed amplitude pilot signal, and the level adjusted attenuator output is then inverted, divided into left and right channel components by the 38 KHz sub-carrier signals, and fed to adders in the multiplex demodulator outputs to cancel the pilot signal components therein.
Abstract:
Unwanted pilot signal components in the "L" and "R" outputs of a stereophonic FM multiplex demodulator are cancelled by inverting the 19KHz pilot signal, separately multiplying or gating it with the opposite phase 38KHz subcarrier signals, and adding the multiplier or gate outputs to the "L" and "R" demodulator outputs. The multiplication produces signals equal in amplitude but opposite in phase to the contaminating pilot signal components, whereby the latter are effectively cancelled by the addition function.
Abstract:
A wireless receiver (10) includes a down converter module (210) operable to deliver a signal having a signal bandwidth that changes over time, a dynamically controllable filter module (200) having a filter bandwidth and fed by said down converter module (210), and a measurement module (295) operable to at least approximately measure the signal bandwidth, said dynamically controllable filter module (200) responsive to said measurement module (295) to dynamically adjust the filter bandwidth to more nearly match the signal bandwidth as it changes over time, whereby output from said filter module (200) is noise-reduced. Other wireless receivers, electronic circuits, and processes for their operation are disclosed.