Patent ID: 6374093
Filing Date: 2002-04-16
Classification: H03D,H04B

Abstract:
A circuit arrangement for switching the frequency renga of a radio receiver, utilizing image frequency bands, to a desired frequency band selected from between a first frequency band having channels with a first bandwidth and a second frequency band having channels with a second bandwidth, whereby the frequency of a local oscillator is adapted approximately to the middle of the two selected frequency bands, characterised in that the circuit arrangement comprises:a mixer attenuating the image frequency comprising means to phase-shift a received radio frequency signal, means to mix phase-shifted received radio signal and a local oscillator signal, and means to phase-shift an intermediate frequency signal resulting from the mixing of said phase-shifted received radio signal and said local oscillator signal, said mixer having at least a first output and a second output with an intermediate frequency corresponding to the first frequency band being obtained from the first output of the mixer, and an intermediate frequency corresponding to the second frequency band being obtained from the second output; a first bandpass filters having a passsband with a width that substantially corresponds to the bandwidth of the channels of the first frequency band, coupled to said first output of said mixer; a second bandpass filter, having a passsband with a width that differs from said first bandpass filter and substantially corresponds to the bandwidth of the channels of the second frequency band, coupled to said second output of said mixer; and a switch for selecting a desired intermediate frequency corresponding to the desired frequency band either from the output of said first bandpass filter or the output of said second bandpass filter.