40-GS/s Delta-Sigma Modulator in 250-nm InP DHBT for Radio-over-Fiber

This paper presents a delta-sigma modulator (DSM) for use with a radio-over-fiber (RoF) transmitter. Its maximum sampling rate is 40 GS/s, which is higher than any other to the best of the author's knowledge. To achieve high-speed operation, an analog-based architecture utilizing 250-nm indium phosphide (InP) double-heterojunction bipolar transistor (DHBT) technology is proposed. Measurement results of a fabricated chip showed signal-to-noise ratios (SNR) of 44.7 dB and 38.1 dB for 7-dBm single-tone input with the frequencies of100 MHz and 400 MHz, respectively.