Design and Analysis of a Voice Band QPSK Modem

The objective of this paper is to design and construct a modem using the Quadrature Phase Shift Key digital modulation technique. The modem is designed to transmit information over a telephone line at the rate of 1200 bits per second subject to noise and imperfect channel response in the form of magnitude and delay distortion. The device is constructed using CMOS logic to minimize power consumption. To analyze the design with respect to the above constraints, it was necessary to build a pseudorandom bit sequence generator and correlator, a variable magnitude white noise generator and a digital error detector/indicator