10-Gbit/s Quadrature Phase-Shift-Keying Modulator and Demodulator for 120-GHz-Band Wireless Links

This paper presents a 120-GHz-band 10-Gbit/s quadrature phase-shift-keying (QPSK) modulator and demodulator. To reduce system complexity, the modulator employs direct modulation, and the demodulator uses differentially coherent detection. We fabricated the modulator monolithic microwave integrated circuit (MMIC) and demodulator MMIC with 0.1-μm-gate InP HEMTs. The test element of the modulator had a static error-vector magnitude of 10%. We mounted the modulator and demodulator MMICs in separate modules. The size of the modules was 20 mm × 8 mm × 25 mm. The main lobe in the spectrum of 10-Gbit/s QPSK signals ranged from 123 to 133 GHz. The bit error rate for 10-Gbit/s 2⁷ - 1 pseudorandom binary sequence data was smaller than 10^-10 at a received power of -38.5 dBm.