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IQ demodulation help - RF Cafe Forums
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antennaant
Post subject: IQ demodulation help Posted: Sat Sep 12,
2009 4:16 am
Lieutenant
Joined: Mon Dec 11, 2006 3:17
pm
Posts: 2
This suddenly came up in a MRI class. I kinda understand
IQ modulation (both amplitude and phase are modulated). But how does
IQ demodulating a signal help, specially MRI signal.
In case you
don't know a MRI signal, its just a exponentially decaying sine.
Also, what is instantaneous phase ?
Top
Jose Arrina
Post subject: Re: IQ demodulation helpPosted: Wed Sep 16, 2009 12:25
pm
Lieutenant
Joined: Thu Mar 30, 2006 9:01 am
Posts: 4
Hi antennaant:
I'm fairly new at quadrature systems,
but basically breaking down a signal into I and Q components allows
you to discern angle of arrival, or phase. If you have two detectors
orthogonal to each other (90 deg), then mathematically they are independent.
So, assuming both antennas are subject to the same signal, the amplitudes
of each relative to the other indicates phase. It's a sin vs. cos calculation.
This scheme is used in threat detector systems for determining angle
of arrival.
_________________
... Jose' Arrina
Posted 11/12/2012
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