COMPARISON OF 2 INTEGRATED BICMOS 950 MHZ DIRECT I Q MODULATORS/

Two integrated direct I/Q modulators suitable for direct upconversion with an output frequency of 950 MHz and baseband frequencies of 60 to 500 kHz are fabricated in a 1.2 mu m and 0.8 mu m BiCMOS process, resp ectively, and their performance under various operating conditions is discussed. The modulators use different phase shifter topologies, one of which is based on digital CML latches and the other on differential pairs with resistive and capacitive emitter degeneration. Both circui ts are operated using a single 5 V supply and they consume 50 mA or 11 5 mA depending on the topology. The main properties of the CML modulat or are, for example, an output power of -11 +/- 0.5 dBm at 100 MHz and -15 +/- 2.25 dBm at 950 MHz over the temperature range of -10 to +85 degrees C, LO suppression of 38 dBc and image rejection of 41 dBc.