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Channel selection for a television receiver having low-gain high frequency RF-IF section

  • US 4,162,452 A
  • Filed: 07/05/1977
  • Issued: 07/24/1979
  • Est. Priority Date: 07/05/1977
  • Status: Expired due to Term
First Claim
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1. In a channel selector for a television receiver including a radio frequency section and an intermediate frequency section, the combination comprising:

  • spectrum filter means disposed in the radio frequency section for receiving radio frequency signals representative of a plurality of television channels and for filtering at least one frequency spectrum of television channels from the received signals;

    at least one mixing means connected to the output of said spectrum filter means, said mixing means including a metal semiconductor field effect transistor and having first and second inputs coupled to simultaneously receive said frequency spectrum of television channels from said spectrum filter means and mixing signals of a selected intermediate frequency for frequency shifting the selected frequency channel of said frequency spectrum of television channels to a high intermediate frequency substantially greater than 45 MHZ;

    channel selecting filter means having an input coupled to the output of said mixing means for filtering said selected frequency channel at said high intermediate frequency so as to pass said selected frequency channel;

    second mixing means disposed in the intermediate frequency section and having first and second inputs coupled to simultaneously receive the filtered selected frequency channel at said high intermediate frequency from the output of said channel selecting filter means and mixing signals of a predetermined fixed frequency for frequency shifting said filtered selected frequency channel at said high intermediate frequency to a substantially lower second intermediate frequency; and

    amplifier means having a relatively high gain disposed in said intermediate frequency section and connected to the output of said second mixing means for providing gain to said filtered selected frequency channel at the lower second intermediate frequency, the added gain provided by said amplifier means in said intermediate frequency section being substantially in excess of the total gain provided to the signal in the radio frequency section through said channel selecting filter means.

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