Electronics

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

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

Henry Kolesnik · Guest

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

--

73
Hank WD5JFR
<stephen_cochrane@hotmail.com> wrote in message
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