How to deal with the “damping” problem at transducer side ?

Discussion in 'General Electronics Chat' started by shengwuei, Apr 12, 2010.

  1. shengwuei

    Thread Starter Member

    Aug 22, 2008
    Dear all,

    I have a transmit/receive system which is functionally work but have “damping(?)” problem on the receive path.

    A simple system block diagram as shown below, a small but not negligible “damping” waveform can be observed both before and after receive amplifier(cycled in red as the figure below, this problem become serious after the amplification of receive amplifier).

    I am not sure this is a “damping” problem or not because the frequency of the waveform is much lower than transmitted signal(50MHz). I've added some series capacitor to filter out the waveform but found its useless. Possibly there is still some high frequency part(close to the transmitting frequency) inside the waveform so a simple low-pass filter would not work. I guess I need to find the root cause of the “damping” problem so I can make it totally disappear in the receiving path.

    Really have no idea about how to solve this problem, anyone can give me a clue on it ?

    Appreciated for your input.

  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    That looks more like DC settling as either the transmitter or receiver turn on or off.

    Depending on the transmitter design and the power / ground layout, it could also be either a power supply fluctuation or the receiver picking up signal leakage and being swamped so so something is rectifying instead of amplifying.

    How are you doing the transmit/receive switching?
    A complete circuit would help.