Phase is a relative measurement. Against what are you measuring the
incoming phase?
You can measure a PSK signal instantaneous phase-shift by computing the
arctran2 between adjacent critically-sampled samples. But there's no way
to look at a signal and say "what is its absolute phase" without having
something against which to measure said phase.
On 2017-03-23 12:53, Trejo Treviño wrote:
> I am aware that a random phase shift will be introduced by the channel, but I
> need a method to measure the received phase (even if it does not exactly
> match the one from the transmitter) and store it, so I can then run some
> statistics on them This is why I think that the TX and RX do not need to be
> phase-synchronized.
>
> Best,
>
> FERNANDO TREJO
>
> -------------------------
>
> FROM: Discuss-gnuradio
> <discuss-gnuradio-bounces+f.trejotrevino=jacobs-university...@gnu.org> on
> behalf of Marcus Müller <marcus.muel...@ettus.com>
> SENT: Wednesday, March 22, 2017 7:02:35 PM
> TO: discuss-gnuradio@gnu.org
> SUBJECT: Re: [Discuss-gnuradio] Measure and record the phase at the receiver
>
> Hi Fernando!
> On 03/22/2017 06:51 PM, Trejo Treviño, Fernando Alberto wrote:
>
>> Hi Marcus!
>>
>> I am implementing a transmitter and a receiver model using two USRP N210s.
>> Both are using GFSK modulation, and the data is transmitted at 2.4 GHz.
> Cool :)
>
>> I would like to add a phase shift at the transmitter side via the use of a
>> multiplier block with an exponential.
> Ah, so a multiply_const with a constant of
> $e^{j\frac{2\pi}{f_\text{sample}\varphi}$, yeah.
>
>> Then, at the receiver I would like to receive this transmitted signal and
>> check if the phase matches the one that was transmitted. This is why I need
>> a measuring method.
> Well, you can't see absolute phase without further ado - that would need your
> TX and RX to be phase-synchronized (you don't know the electrical length
> between your transmitter and receiver, it's absolutely random by itself).
>
> Best regards,
> Marcus
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