A 20-GHz Bandwidth Power Amplifier for Phased Array 5G New Radio Transmitters

A 27-47-GHz differential cascode power amplifier for millimeter-wave 5G new radio applications is presented. The PA is a three-stage design using inductively coupled impedance transformers with 31-dB nominal power gain. A device periphery ratio of 1:2:6 is adopted for predriver, driver, and final stage, respectively. A gain equalization technique was used in the interstage transformers to obtain the required bandwidth with high gain flatness. To enable the use of 2.7-V supply, a cascode topology was employed in all three stages. A small signal gain of 31 dB was achieved with a 3-dB bandwidth of 20 GHz, equivalent to a 54% fractional bandwidth centered at 37 GHz. A saturated output power of 20.6 dBm was measured at 38.5 GHz. With a 100-MHz 64-QAM OFDM modulated signal at 37 GHz and at EVM =-25 dB, an output power of 11.6 dBm and an ACLR1 of-32/-30.8 dBc were obtained. An SiGe HBT BiCMOS process with f_{\mathrm{ MAX}} = 330 GHz was used for fabrication. The PA has an active area of 0.28 mm2 and is measured to a best in class FOM of 94.7 dB.