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[linrad] Detecting phase modulation with undersampling
I has anyone any experience of demodualting phase modulated signals?
I am tryiing to measure the phase shift between two signals, when they
are derrived from the same source? I guess you could say this is a form
of phase modulation, but whereas for normal 'PM' receiver you don't have
access to crystal developing the signal in the first place, I do in this
The problem is I need to undersample this. I have an A/D that can do 65
MS/s, but the input can be upt to 200 MHz - in pracitce I will use 70
MHz. However, since the bandwidth of the signal is narrow (< 1 kHz), I
am not breaking the Nyquist criteria, which states you need to sample at
no less than twice the *bandwidth* of the signal, and not twice the
frequency as most people seem to think.
I then intend doing the processing on a dedicated DSP chip (TI 6701),
rather than a PC's CPU.
I realise this is not exactly what the Linrad project is, but i though
some here might have some ideas.
Dr. David Kirkby PhD CEng MIEE
Senior Research Fellow
Department of Medical Physics
University College London
11-20 Capper St
London WC1E 6JA
Tel: 020 7679 6406 (direct line)
Tel: 020 7679 6262 (office)