A 2.17-pJ/Bit 110-to-170-GHz OOK Transmitter With 40-Gb/s Data Rate and 40-dB On-Off Ratio in 28-nm CMOS

This article presents a D-band on-off keying (OOK) transmitter fabricated in a 28-nm CMOS process. A current-controlled OOK modulator is proposed to generate high-speed modulated signal, in which a local oscillator (LO) cancellation structure is employed to simultaneously enhance the on-state forward gain and the off-state isolation. Moreover, a four-stage neutralized power amplifier (PA) is designed to provide sufficient output power over a broadband range, where a transistor-based capacitor is used for neutralization to enhance robustness against process variation and temperature fluctuation. The transistor configuration and neutralization capacitance for the last amplifier stage are precisely designed to maximize the gain while ensuring output power and stability. With effective gain arrangement across stages and a practical output matching strategy, the PA exhibits a wideband performance in both small-signal and large-signal states. Through measurement, the proposed transmitter exhibits an output power exceeding 10 dBm and an on-off ratio of over 40 dB. Its 3-dB output power bandwidth is from 110 to 170 GHz, covering the entire D band to support a high-speed OOK communication. Without the assistance of digital signal processing (DSP) for equalization (EQ), the measurements demonstrate an error-free on-wafer data rate of up to 40 Gb/s with a 2.17-pJ/bit efficiency and over-the-air (OTA) data rates of 21 and 15 Gb/s at distances of 3 and 8 cm, respectively, with a bit error rate (BER) of less than $10^{-12}$ .