A 70–160-GHz Ultrawideband Amplifier Utilizing Reverse-Side Grounded Balun With Balance Compensation in 130-nm SiGe Process

This letter presents a two-stage broadband amplifier from 70 to 160 GHz, covering the entire W band, F band, and most of the D band. To address the challenges of wideband, low loss, and balanced matching, a reverse-side grounded (RSG) balun is proposed. By incorporating a frequency expansion capacitor and a balance compensation capacitor, the balun achieves <0.1-dB amplitude and <0.3° phase imbalance, while maintaining an insertion loss below 0.8 dB. The measured results demonstrate a peak gain of 20 dB, making it a compact and cost-effective amplifier solution for millimeter-wave (mmWave) systems.