stevieboy01
Guest
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 Posted:
Sun Feb 27, 2005 7:04 pm Post subject:
Phase Shift Measurements and Equalizer |
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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
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
Steve
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Henry Kolesnik
Guest
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| Posted:
Sun Feb 27, 2005 8:19 pm Post subject:
Re: Phase Shift Measurements and Equalizer |
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A coil of coax of appropriate length in one channel might be a solution.
You can easily view the phase difference of the signals on a two channel
scope.
--
73
Hank WD5JFR
"stevieboy01" <stephen_cochrane@hotmail.com> wrote in message
news:8a656a08.0502270504.70836b63@posting.google.com...
| Quote: | 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
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
Steve |
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