Thank you for the instant reply. Here are the responses to your
The transceiver set-up is really basic:
Random src --> DQPSK MOD --> Pulse Shape --> UHD SINK
UHD SOURCE --> FFT block
Signal amplitude? 1
Gain setting? 0dB at TX and RX sides
Antenna port? TX: TX/RX RX: RX2
I believe it is a mis-sampling mismatch. I am using 4 samples per
symbol. I should add that this problem appears to be ONLY at the TX
side. I am able to see a clean signal when the TX is at 900MHz and RX is
900.050MHz. But not the other way around.
Also, as far as the parameters go: if I want to access 900.05MHz I pass
to tune_request_t :
target frequency = 900M
LO freq = 50K
However, the result is: bad signal (i can see the peak at the center
frequency expected (900.05MHz) but the bandwidth is wide in the same
manner as if I set the center frequency manually at 900.05 rather than
I am pretty sure that the upsampling in FPGA is messed up or the
upconversion setting in the transmitter has to be done in different way.
Any advice please?
From: Jason A. [[email protected]]
Sent: Friday, April 08, 2011 12:45 PM
To: Tachwali, Yahia
Cc: [email protected]
Subject: Re: [Discuss-gnuradio] Synthesizable Frequencies for WBX?
On Fri, Apr 8, 2011 at 10:22 AM, Tachwali, Yahia [email protected]
I am experiencing some problems in transmitting/receiving at frequencies
around 900MHz for WBX board. While, I am able to do so cleanly at
900MHz, other center frequencies are not.
The signal bandwidth : 50 KHz
The sampling frequency: 200 KHz
What signal amplitude?
What gain setting?
Which antenna port?
I have tried 901MHz , 900.1MHz, 910MHz and many others but the received
signal appears to be wider than it should be. The signal level is higher than
-40dbm over the total 200 KHz range when these frequencies are used.
This usually indicates a sample rate mismatch in your flowgraph, if
you post an example to replicate your problem, it will be easier to
The only frequencies I was able to use with no problems are 900MHz,
1.8 GHz , 890MHz, 880MHz.
What could be the problem? I have tried to use “tune_request_t” in the target
frequency paramter but it gave similar bad results . Any pointers?
What parameters did you give to the tune_request_t?
Have you looked at the tune_result_t returned by set_center_freq?