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Phase Shift Measurements and Phase Equalizer

Discussion in 'Electronic Basics' started by [email protected], Feb 27, 2005.

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  1. Guest

    I am attempting to characterise a phase shift in a channel so that I
    can compensate it at the receiver end using a phase equalizer. I need a
    method which produces a phase shift curve with more measurements than a
    Lissajous method produces. I was thinking possibly a phase shift
    oscillator may be the way to go with each stage producing a 45 degree
    shift, but I am unsure how to use this. I want to define the frequency
    and calculate the resulting shift. Also, I am not sure how to use an
    equalizing filter. I would probably use an all pass filter but how can
    I define where the curve goes?

    Please help. I am mightily perplexed!!!

    Steve
     
  2. stevieboy01

    stevieboy01 Guest

    Since I am working on a project already in place, I'm afraid the
    recievers have been defined already. They are Radiometrix BIM 418-40
    transceivers.

    http://www.radiometrix.co.uk/products/bimsheet.htm

    I will elaborate more........

    At present we are using a 4 level ASK digital transmission being fed
    into a DAC for RF transmission. At the receiver end, it is being
    converted back, naturally using an ADC.

    I am firstly looking to shape the pulse going in using a bandpass of
    approx 100Hz - 20kHZ. This should eliminate high frequency components
    since there is a high level of ringing as too much energy is trying to
    get through the channel. However, because of the associated phase
    shift in a non linear filter, I will have to compensate at the
    receiver. The transceivers already introduce a slight phase shift,
    which I am hoping to eliminate with an equalizer. The eye diagram at
    the receiver is poor so, especially with 4 level signalling, I hope to
    improve it.

    Cheers
     
  3. A length of coax coiled up can delay one channel. You can easily see the
    phase differnece with a 2 channel scope.
     
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