Monolithic HEMT LNAS for radar, EW, and COMM

Three monolithic high electron-mobility transistor (HEMT) low-noise amplifiers (LNAs) were developed that were designed for 7-11-GHz airborne radar, 2-18-GHz electronic warfare, and 20-GHz military satellite communications applications. The first LNA is a two-stage feedback amplifier at X-band, using a 0.5- mu m combined optical stepper and E-beam (electron-beam) lithographic process with a 1.2-dB noise figure at 10 GHz with 15-dB gain, and a typically less than 1.8-dB noise figure from 7-11 GHz. The second is a 2-18-GHz distributed amplifier demonstrating a 3.0-5.2-dB noise figure with approximately 11 GHz. The second is a 2-18-GHz distributed amplifier demonstrating a 3.0-5.2-dB noise figure with approximately 11 dB gain from 2-18 GHz. Finally, a three-stage 20-GHz amplifier using 0.25- mu m direct-write E-beam lithography with a less than 2.0-dB noise figure from 18-23 GHz with 29-dB associated gain is described. All the MMICs were fabricated with selectively doped AlGaAs/GaAs heterostructures grown on undoped GaAs substrates.<>