A frequency agile monolithic QPSK modulator with spectral filtering and 75 /spl Omega/ differential line driver

This monolithic modulator combines both digital signal processing and analog techniques to realize a high bit-rate quadrature phase-shift keyed (QPSK) modulator. It includes a digital baseband pulse shaping network, analog quadrature modulator, agile carrier generator, spectral shaping, and transmit power control for interfacing to wireline transmission media. Nominal data rates are 256 kbit/s with a carrier range of 8.096-20.128 MHz in 32 kHz steps. Maximum output level is 62 dBmV into a 75 /spl Omega/ load. The features of 1.2 /spl mu/m mixed signal BiCMOS technology permit both signal processing and power line drivers to be collocated while achieving better than 85 dB cross-talk isolation.