QPSK modulation system with recover loops-This is a model of a QPSK modulation system for transmission over a bandpass channel with fc = 100 Hz and B = 30 Hz and AWGN at the receiver. SRRC fi lters with excess bandwidth α = 0.18 are employed. The receiver includes an NDA timing recovery loop followed by a DD phase recovery loop. The transmitter?s symbol period is T and set to a value of 100 ms. The symbol period at the receiver is Tr. The model will produce six windows: Two constellation plots and two eye diagrams (for the real part only), at the output of the matched fi lters and after the recovery loops　a plot of the phase error (output of the NCO) and a plot of the fractional timing error (used in the interpolator). The frequency off set at the receiver is denoted by deltaf. The model simulates the transmission of 8000 QPSK symbols.