Millimeter-Wave Tunable Impedance Matching Network in an Advanced CMOS Process

The impedance matching between power amplifier and antenna remains a challenge in millimeter-band front ends, particularly when the antenna impedance varies due to the use of beamforming. This article presents a tunable impedance matching filter fabricated in a 16-nm CMOS process. The frequency of operation is 77GHz, making it suitable for millimeter-wave systems such as radar, Wi-Fi, and mobile communications. The filter is implemented using tunable quarter wavelength transmission lines. A reliability assessment supports that input powers up to 21dBm can be used without risk. The on-wafer measurements demonstrate the functionality of the filter, which can adapt load impedances with a reflection coefficient \Gamma of up to 0.37 and convert them down to less than 0.20, while keeping the source match also below 0.20 and the loss under 5.5dB. Measurements across the wafer also show low process variability.