Johnathan Corgan wrote: > On Thu, Feb 12, 2009 at 5:43 AM, Bruhtesfa Ebrahim > <li...@ruby-forum.com> wrote:
> It sounds like, since you have perfect synchronization between > transmitter and receiver, that what you have after downconversion in > the daughterboard is DC + noise. That is, the transmitted carrier > (plus noise and multipath from the channel) is being mixed with a > synchronized local oscillator, resulting in only the noise components > being left in the complex baseband signal GNU Radio is receiving. > There will also be a DC component based on the path delay and > wavelength causing a phase shift between the transmitted carrier phase > and and the receiver LO phase. > > Johnathan Thank you Johnathan! What makes it strange is the dependence on gain.when the linear gain in the spectrum panel(usrp_fft.py)is set to 0,the signal at the center(the DC)is 5dB higher than the noise level.When I increase the gain, the difference between the DC and noise level keeps decreasing and finally the DC level is equal to the noise level. Specifically, for a linear gain >=20, the signal around DC is not visible(it is equal to the noise level). is this gain dependence normal? Bruhtesfa -- Posted via http://www.ruby-forum.com/. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
