[Discuss-gnuradio] method to improve the detection sensitivity of USRP1 with LFRX

[Yan Nie]

Dear all,

I'm using LFRX to detect a -120dBm signal. According to my measurement, the 
lowest power of signal that LFRX is able to detect is -90dBm. I tried deploy a 
preamplifier to amplify the received signal by certain dB in order to reach the 
-90dBm, but this turned out that noise is amplified as well and the signal 
still merges in noise, undetectable. I also tried to set proper bandwidth for 
the lowpass filter in order to eliminate noise and avoid the signal distortion 
to the largest extend, but this still cannot allow this weak signal be detected.


The flow-graph of my receiver is:


usrp_source_c --> Blackman lowpass filter --> file_sink(gr.sizeof_gr_complex)


The signal that I wish to detect is a 13-bit Barker code with 40 us chip rate. 
The samples frequency at receiver side is 250kHz which gives the decimation 
rate 256. Regarding with the Blackman lowpass filter, the sampling frequency 
for this filter is 35kHz, and the cutoff frequency is 17kHz, transition_width 
is 0.1kHz.


Really appreciate any of your help!


Yan