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circuit design for multiband auto tunning radio

Discussion in 'Electronic Design' started by litu, Aug 13, 2007.

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  1. litu

    litu Guest

    friends,
    i want to make an project in my academics.
    i.e. MULTIBAND (AM/FM) radio with AUTO TUNNING.
    i know the design procedure for the radio circuit but i have no idea
    about the design of the auto tunning circuit that will scan both AM
    and FM bands.
    so please any body having any idea share with me.

    thanking you

    with regards
    Pradipta
     
  2. use varactor diodes to take care of the capacitance tuning for the RF, VCO.

    have station detector circuit that detects when tuned to the station....
    (without false triggering).

    Simple.

    Joe
     
  3. JosephKK

    JosephKK Guest

    litu posted to sci.electronics.design:
    Simple, factor for the common parts versus the band unique parts and
    build it. Dithering will provide the autotuning information.
     
  4. (Assuming analog transmission): It's not that simple. Use a PLL to
    tune the Local Oscillator to each frequency in the band. When the RSSI
    (received signal strength indicator) reaches a pre-determined
    threshold, stop at that frequency. Use a counter to count the I.F.
    This makes sure the received signal is on frequency. False stops are
    still possible but less likely.

    If you don't have access to the RSSI signal, you will need to convert
    your I.F. signal amplitude to a log scale for the thresholding
    measurement.

    This is how we did it in the late 80's.

    Frank
     
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