Re: [Discuss-gnuradio] DBPSK and USRPs

[mleech]

How much attenuation do you have in the path between the TX and RX?  What daughtercards?  Two separate USRPs, or a single, looped back?

If you turn the RX gain up, does the RX FFT change?  Are you on the RX2 port on the RX side?

 

 

 

On 2015-10-26 15:33, Washbourne, Logan wrote:

I looked at the spectrums of both sides and the RX side looks to be inundated with a lot of noise. I'm not sure if its my environment or my USRPs, but I really expected to see some resemblance of a signal. I am posting links to screencaps of the TX and RX sides.

http://imgur.com/GBTHw8T- TX
http://imgur.com/DBy8gqs - RX

Logan Washbourne

Electrical Engineering Graduate Student

(Electromagnetics)

On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller <address@hidden> wrote:

Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether, due to frequency offset, some of the wanted signal simply gets cut off; admittedly, with 2S/sym that's not too likely...

Best regards,
Marcus

On 26.10.2015 19:16, Washbourne, Logan wrote:

I am using 250k!

 

 

Logan Washbourne

Electrical Engineering Graduate Student

(Electromagnetics)

On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller <address@hidden> wrote:

Hello!
what's the sampling rate you're using?

Best regards,
Marcus

On 26.10.2015 18:38, Washbourne, Logan wrote:

Hello all,

I'm trying to take a step back from my previous postings and try a simple approach to try and understand working with over the air communications with the USRPs. Let me know if it would be better to post this in the USRPs-Users list.

I'm trying to have a simple TX and simple RX side so I can eliminate and unnecessary complications.

The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)

RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink

I'm checking the progress of the communication by looking at a constellation plot that is connected directly to the USRP SOURCE block on the receiver side. I'm getting a very elliptical shape, more spread out in the horizontal direction but not by much. I'm also looking at the bits from the receiver side in matlab and my preamble is not showing up.

These were the same problems I had when trying to use a correlated system for OTA communications. I feel like I'm missing something really simple.

Does anyone know of a simple TX, RX grc setup that I can use to test my USRPs?

Again, I really appreciate the help you guys give.

Logan Washbourne

Electrical Engineering Graduate Student

(Electromagnetics)

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