A DC-87.8-GHz Switched-Type Attenuator With Switched Capacitor Branch in 40-nm CMOS

The brief presents a 5-bit switched-type attenuator (STA) working from DC to 87.8 GHz. In addition to T-type and II-type attenuation cells with capacitive compensation technique in shunt branch, a new II-type-based compensation method with switched capacitor branch is proposed, which effectively reduces phase errors at high frequencies without compromising the amplitude errors. The STA in this brief is fabricated in 40-nm CMOS technology and the active core area is 0.019 mm2, which demonstrates 15.5-dB attenuation range with 0.5-dB tuning step. Across the operational band, the insertion loss of reference state is 1.4-5.3 dB and the return loss is better than 9 dB for all states. From DC to 87.8 GHz, the RMS amplitude and phase errors are below 0.5 dB and 5.4(?) respectively.