A versatile vector modulator design for MMIC

A single-chip, monolithic microwave integrated circuit (MMIC) vector modulator designed for use in an X-band, phased array radar system is described. The design principle is capable of addressing octave bandwidths and frequencies up into the millimeter-wave region. The circuit is novel in that it is purely passive, using unpowered FETs as the control elements. Therefore, it is low noise and should be able to handle relatively large RF signal levels of up to 1 W. Analog control of the vector extends over a range of more than 30 dB for amplitude and over 0-360 degrees for phase. Swept frequency, measured phase errors are lower than +or-10 degrees for a 10% instantaneous bandwidth anywhere in X-band (8-12 GHz).<>