A 5-10 GHz octave-band AlGaAs/GaAs HBT-Schottky diodedown-converter MMIC

The authors describe an AlGaAs/GaAs heterojunction bipolar transistor (HBT) X-band down-converter monolithic microwave integrated circuit (MMIC) which integrates a double double-balanced Schottky mixer and five stages of HBT amplification to achieve greater than 30 dB conversion gain over an RF bandwidth from 5 to 10 GHz. In addition, an output IP3 as high as +15 dBm has been achieved. The Schottky diodes are constructed from the existing N^$collector and N⁺ subcollector layers of the HBT molecular beam epitaxy (MBE) device structure. A novel HBT amplifier topology employing active feedback which provides wide bandwidth in a compact area is used for the RF, LO, and IF amplifier stages. The complete down-converter MMIC is realized in a 3.6×3.4 mm² area, is self-biased through a 6 V supply, and consumes 530 mW. This MMIC represents the highest complexity X-band down-converter MMIC demonstrated using GaAs HBT-Schottky diode technology