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LF: Phase Modulator

To: [email protected]
Subject: LF: Phase Modulator
From: "James Moritz" <[email protected]>
Date: Fri, 15 Dec 2000 15:17:11 +0000
Organization: University of Hertfordshire
Reply-to: [email protected]
Sender: <[email protected]>
Dear Andy, LF Group,

To generate linear phase shift, how about a PWM:

Generate a sawtooth at carrier frequency, feed into one input of a comparator. Other comparator input is analogue "phase" signal. The higher the "phase" voltage, the later in the cycle the comparator changes state, ie more phase lag. You could get a square wave back again by dividing by 2; this would also limit the phase shift to 180 degrees, which is probably what you want.

Main problem might be that you would have to design the circuit so that a transition would definitely occur somewhere on the cycle, whatever the analogue input voltage was - otherwise you would lose the carrier altogether.

Cheers, Jim Moritz
73 de M0BMU


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