Howell George Henry

94 GHz subharmonically pumped MMIC mixer

A 94-GHz subharmonically pumped antiparallel diode pair MMIC (monolithic microwave integrated circuit) mixer with a short-circuit sum frequency termination is described. Advantages of the mixer configuration include (1) reduced conversion loss, (2) elimination of the need for an area-consuming hybrid junction while retaining the separation of local oscillator (LO), RF, and intermediate frequency ports, (3) inherent LO noise sideband suppression, and (4) very small size and cost.<<ETX>>

A compact 3W X-band GaAs MMIC amplifier based on a novel multi-push-pull circuit concept

A description is given of the design, fabrication and testing of a two-stage X-band GaAs MMIC (monolithic microwave integrated circuit) based on a novel multi-push-pull circuit design. The MMIC output stage employs an 8 mm MESFET arranged as four 2 mm MESFET unit cells alternately driven anti-phase. The first stage employs two 1.3 mm MESFETs, one for each signal phase. This circuit design and layout results in virtual grounds between adjacent FET cells making possible the elimination of several space-consuming components required for conventional MMIC designs, thereby shrinking the amount of expensive GaAs real estate required and improving yield and bandwidth.<<ETX>>

A GaAs monolithic array of impedance matched antenna/detector pixels for a 94 GHz imaging system

The design, fabrication, and performance of a 4*4 pixel array of monolithic GaAs 94-GHz detector circuits is described. This large chip is developed to be a tile for much larger arrays consisting of thousands of pixels for 94-GHz imaging. Each pixel is a slot antenna on one face coupled through the GaAs to a microstrip circuit containing a Schottky-barrier diode on the opposite face. The microstrip circuit provides an optimum impedance match between the diode and the slot antenna so that no additional tuning to free space is required. The diode is fabricated using a selective ion implantation process optimized for uniformity, repeatability, and yield, and has zero-bias capacitance and series resistance, respectively, of 14 fF and 15 Omega . Process control is essential, because variations in diode parameters can mismatch and detune the circuit. With the diode optimally forward-biased for square-law operation and a video bandwidth of 1 MHz, the tangential signal sensitivity (TSS) peaked in the 92-96-GHz range and was always better than -50 dBm at 94 GHz.<<ETX>>