A C-Band High-Precision Amplitude-Phase Control Multi-Functional Chip with Symmetric Polyphase Filter and X-Type Attenuator

This paper presents an amplitude-phase control multi-function chip (APMFC) with low rms phase/amplitude error for C-band phased array applications, implemented in a $0.2-\mu \mathrm{m}$ CMOS process. It comprises a phase shifter (PS), an attenuator, and a driver amplifier. The PS uses an active vector modulation structure with a symmetric polyphase filter (PPF) layout, and this PPF achieves extremely high orthogonal signal balance (gain imbalance <0.4 dB, phase imbalance $<2^{\circ}$) and small area ($0.03 ~\text{mm}^{2}$), which are critical for the PS accuracy. The attenuator uses an X-type structure utilizing analog-controlled transistors with only an inductor and four transistors, which balances insertion loss and rms error. The measured APMFC shows minimal rms phase error of $<0.7^{\circ}$ for PS, and rms amplitude error of <0.2 dB for attenuator, respectively at the reference state, which is the best FoM value among similar works in the literature.