A monolithic GaAs IC for heterodyne generation of RF signals

An integrated heterodyne signal-generating GaAs chip is reported. This circuit contains: an on-chip local oscillator with external inductors tunable by means of on-chip variable capacitors from 2.1 to 2.5 GHz; a doubly balanced mixer with associated drive circuitry; and an IF preamplifier. The circuit delivers +6 dBm (equivalent 50 Ω) into the designed load impedance of 200 Ω with -30-dBc harmonic distortion over a 1.4-GHz 3-dB bandwidth. Circuit elements presented include: a unique variable-threshold limiter, a self-biasing push-pull oscillator, doubly balanced mixer, and a self-biasing unity-gain phase splitting amplifier.