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Re: [Discuss-gnuradio] Phase change for Transmitted Signal Bursts - The

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Phase change for Transmitted Signal Bursts - The relation to clock?
Date: Thu, 08 Aug 2013 17:53:07 -0400
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On 08/08/2013 05:25 PM, Alex Zhang wrote:

I am transmitting a series of BPSK burst signal and try to observe the phase distortion for the BPSK signal on air. But it is found that the Phases of different BPSK bursts are different. I think this change is caused by the fact that the ADC clock phases are different for the starts of every signal burst. But I don't know more details on this mechanism.


Indeed, the carrier phase for discontinous transmission will be at some random spot every time you start a burst. The hardware doesn't have any notion of "start the burst only when the clock phase is the same as it was last-time I sent a burst". Unless you have utter blind luck, your burst timing isn't ever going to be an exact multiple of the clock frequency, so there's no way the carrier phase will be in exactly the same place at the start of
  every burst.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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