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FM/AM broadcast signal converter

  • US 5,020,147 A
  • Filed: 04/10/1989
  • Issued: 05/28/1991
  • Est. Priority Date: 04/26/1988
  • Status: Expired due to Term
First Claim
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1. Apparatus for converting an FM broadcast signal to an intermediate frequency signal from which modulating information may be recovered, comprising:

  • receiving means for receiving the FM broadcast signal;

    first and second mixing means for mixing the received FM broadcast signal with first and second local oscillating signals, respectively;

    local oscillation means for generating said first and second local oscillating signals exhibiting a predetermined phase shift relative to each other and for supplying said first and second local oscillating signals to said first and second mixing means, respectively, said local oscillating signals being of a frequency such that said mixing means produce output signals in an intermediate frequency range of approximately two orders of magnitude less than the intermediate frequency normally produced from said received FM broadcast signal;

    phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to said output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other;

    combining means coupled to said phase shift means for combining said phase shifted output signals, whereby the out-of-phase image signal components are substantially cancelled; and

    filter means coupled to said combining means and tuned to the intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency for passing said output signals produced by said mixing means having frequencies within a predetermined range of said intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency.

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