Fully Integrated D-Band Direct Carrier Quadrature (I/Q) Modulator and Demodulator Circuits in InP DHBT Technology

This paper presents design and characterization of D-band (110-170 GHz) monolithic microwave integrated quadrature up- and down-converting mixer circuits with on-chip RF and local oscillator (LO) baluns. The circuits are fabricated in 250-nm indium-phosphide double heterojunction bipolar transistor technology. The mixers require an external LO signal and can be used as direct carrier quadrature modulator and demodulator to implement higher order quadrature amplitude modulation formats. The up-converter has a single-sideband (SSB) conversion gain of 6 dB with image and LO suppression of 32 and 27 dBc, respectively. The chip can provide maximum output RF power of 2.5 dBm, a third-order output intercept point of 4 dBm, and consumes 78-mW dc power. The down-converter exhibits 14-dB SSB conversion gain with 25-dB image rejection ratio, and 11.5-dB SSB noise figure. The chip consumes 74-mW dc power and can deliver maximum output IF power of 4 dBm. Both chips have the same size with active area of 560 μm × 440 μm including the RF and LO baluns.