An RF CMOS Pulse Modulator for Wireless Communication Polar Transmitters

This letter presents a 3.5-GHz fast-transient CMOS pulse modulator tailored for the application of wireless communication polar transmitters. The techniques of loop matching and shunt LC desensitization are used to effectuate the modulator’s wideband matching and absorptive characteristics. The measured insertion loss of the modulator is 2.2 dB, and the 3-dB bandwidth is 750 MHz, ranging from 3.03 to 3.78 GHz. The rise time and fall time of the modulated pulses are 0.9 and 0.62 ns, respectively. Tested with a 20-MHz 256-QAM 5G NR signal, the RF polar transmitter using the CMOS modulators can achieve the adjacent channel leakage ratio (ACLR) better than −35 dBc.