Abstract: An adaptive filter for an FM receiver comprises a digital filter, an error detection section for detecting an error between the amplitude of the output signal of the digital filter and a reference value, and a coefficient updating section for updating tap coefficients so as to minimize the error detected. The reference value for determining the error is variably set according to the amplitude of an input signal. This eliminates the effect of Doppler fading included in the reception wave and stabilize the adaptive processing. Thus, the adaptive filter can remove multipath distortion with reliability.

Abstract: A multipath elimination filter comprises a digital filter for receiving a digitalized FM modulation signal or phase modulation signal as its input signal, and eliminating multipath distortion from the input signal by adjusting tap factors for the input signal, an envelope detecting section for detecting an envelope of the input signal to generate a reference signal, an error detecting section for generating an error signal by performing a differential operation on a desired signal generated by the digital filter and the reference signal, an error component limiting section for monitoring the error signal for a direct-current component and controlling an amplitude of the error signal to generate a corrected error signal, and a tap factor updating section for adjusting the tap factors based on the corrected error signal so that the amplitude of the error signal approaches zero. This makes the entire system converge toward stabilization to eliminate multipath distortion.

Abstract: A receiver capable of stabilizing its multipass removal filter and thus ensuring an acceptable reception performance, without being affected by a change in the reception sensitivity or the like. The receiver comprises a front end unit for outputting an intermediate frequency signal by mixing/detecting, in accordance with a local oscillation signal, a high frequency received signal received by a reception antenna, an A/D converter for converting an intermediate frequency signal into a digital intermediate frequency signal and outputting the same, an amplitude adjuster for adjusting the amplitude of the digital intermediate frequency signal to a predetermined value and outputting the same, and a multipass removal filter for removing a multipass distortion of a signal outputted from the amplitude adjuster and then outputting a desired signal.

Abstract: A receiver capable of removing multipass distortion and improving an S/N. The receiver of the invention comprises a multipass removal filter for removing the multipass distortion from an intermediate frequency signal digitized by an A/D converter, an FM detector for detecting a desired signal outputted from the multipass removal filter, a mute processor and a high frequency removal filter as well as a stereo demodulator which are provided for processing a composite signal outputted from the FM detector and demodulating the same into left-right channel signals. The receiver further comprises a first field strength detector for detecting a first field strength from the intermediate frequency signal, a second field strength detector for detecting a second field strength from the desired signal, and a noise amount detector for detecting a noise component of the second field strength.

Abstract: An adaptive filter for an FM receiver comprises a digital filter, an error detection section for detecting an error between the amplitude of the output signal of the digital filter and a reference value, and a coefficient updating section for updating tap coefficients so as to minimize the error detected. The reference value for determining the error is variably set according to the amplitude of an input signal. This eliminates the effect of Doppler fading included in the reception wave and stabilize the adaptive processing. Thus, the adaptive filter can remove multipath distortion with reliability.

Abstract: An adaptive filter for an FM receiver comprises a digital filter, an error detection section for detecting an error between the output amplitude of the digital filter and a reference value, and a coefficient updating section for updating tap coefficients so as to minimize the error detected. The coefficient updating section determines the amounts of update of the tap coefficients based on a value determined by applying square root compression conversion processing to the amounts of correlation between delayed values of the input signal and an output signal. Thus, the adaptive filter can perform proper adaptive processing at high speed, thereby eliminating multipath distortion with reliability.

Abstract: An adaptive filter for an FM receiver comprises a digital filter, an error detection section for detecting an error between the output amplitude of the digital filter and a reference value, and a coefficient updating section for updating tap coefficients so as to minimize the detected error. Further, a delay circuit is provided in an output stage of the digital filter so as to reduce an operation load. Thus, the adaptive filter can improve an operation accuracy of the digital filter, thereby eliminating multipath distortion with reliability.