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Re: [Discuss-gnuradio] Find and look to center frequency and phase of ba

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Find and look to center frequency and phase of bandwidth with help of stored original version of that
Date: Sun, 20 Aug 2017 20:12:36 +0200
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Dear Mohammad,

Is the 1 MHz carrier modulated? If yes, what is its bandwidth? Are the two signals correlated?

I'm pretty sure that *if* you go the LMS / adaptive route, then there will be no way around synchronization. I'm *not* sure that it's the optimal route to take!

Best regards,


On 20.08.2017 18:11, mohammad nejati wrote:
Hi ,
It is difficult to explain what i need but i want to try it .

I have a single modulated carrier with 5 Mhz bandwidth i send it throw
cable and receive delayed version of that with a good SNR like 45dB .

I store i/q sample in last stage of transmitter ,
In cable i add one 1 Mhz carrier with lower power into exactly 5 mhz
equipped bandwidth of carrier (1Mhz carrier is hidden in 5 Mhz carrier
due to lower signal power) .
what i want to do is in receiver subtract transited signal from
received signal in a proper delay and phase and recover 1 Mhz carrier

I use LMS algorithm for adaption and subtraction and that work only
when received i/q sample have exactly same center frequency with
stored transmitted i/q sample which in reality with SDR board and zero
if architecture it is almost impossible . i don't want find center
frequency of received carrier with method like costas loop , because
modulated signal may have difference modulation like 64 QAM , 16 QAM ,
32APSK , BPSK ... i want find and lock received center frequency and
phase with help of that i stored a correct version of that before
transmit .

i attached an image of subtracted signal and recovered smaller carrier
(which is in an ideal condition without frequency drift).

Thank you ,

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