Hi, I need some help. I’m new using usrp (I have the usrp1 module and 2 wbx daughters boards installed in simulink with kit cel, http://www.cel.kit.edu/usrp.php), and I want to send a message m(t) (1khz 1v simple cosine tone) using phase modulation and receive the massage in the same usrp module (side as tx, side b as receive, connected with a sma cable); I have this model in simulink: Tx: Cosine signal source m(t)--> exp(u) block-->2^14 gain block-->usrp_sink Rx: Usrp_source-->complex to angle block-->unwrap block I’m based on Euler’s law: exp(phi)=cos(phi)+jsin(phi) where exp(phi) is baseband equivalent of carrier with variation phase. I supposed that usrp module multiplies exp(phi) by exp(2*pi*fc*t ) generating exp(2*pi*fc*t+phi) and sending it. In the receiver the usrp module multiplies by exp(-2*pi*fc*t+phi) and I got only exp(phi), after with complex to angle block and unwrap block I obtain phi(the original cosine tone). All is practically working but there is some problem: the received signal has a DC offset level with variations and some low level spurious signals, the question is how can I improve it to obtain the original signal. Images of transmitted and received signals are attached.