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Phase Shift Measurement and Equalization



Jan 1, 1970
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?

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

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.