A CMOS dual channel, 100 MHz-1.1 GHz transmitter for cable applications

A dual channel wideband transmitter for cable applications with more than a decade frequency coverage consists of two parallel transmitters that are both fully operational from 100 MHz up to 1.1 GHz, Using a single-ended current-mode output topology, the RF output signals are losslessly combined. The on-chip integrated oscillators have measured 55 MHz-1200 MHz tuning range. The 3/sup rd/-order harmonic of the oscillator signal is filtered by a wideband active buffered polyphase filter. Using this filter, a linear mixer topology and a linear output driver, all distortion components are below -40 dBc. Intermodulation products of the two channels are all below -48 dBc. This guarantees that the parallel channels do not disturb the other channels in the frequency band even without any channel-specific filtering. Each channel delivers the required -16 dBm RF output signal in a 75 /spl Omega/ double terminated load. The measured noise floor is situated at -139.8 dBc/Hz. The chip is in standard 0.5 /spl mu/m CMOS.