A Combined Aliasing-Free Outphasing Transmitter

This paper presents a mobile communication transmitter architecture that exploits band-limited pulse-width modulation (BL-PWM) combined with outphasing to eliminate aliasing and image distortions. The proposed combined outphasing-aliasing free PWM transmitter (COAF-PWMT) shows very high linearity and high power efficiency as it can use switch-mode power amplifiers (SMPAs) or linear power amplifiers operating at peak power. The transmitter is implemented using two 130 nm CMOS class-D power amplifiers and experimentally validated with both 1.5 MHz LTE signals and 10 MHz 5G NR signals at a carrier frequency of 700 MHz. Experimental results for the 1.5 MHz LTE signal show that the COAF-PWMT achieves an ACLR of 54.3 dBc and an average efficiency of 15.7%. The architecture improves ACLR by 22.6 dB and power efficiency by 4.4% compared to the aliasing-free PWM transmitter (AF-PWMT). It also provides a 14.3 dB ACLR and 2.2% efficiency boost over the Gibbs-phenomenon-reduced aliasing-free PWM transmitter (GR-AFPWMT), and a 15.0 dB ACLR improvement over the modified aliasing-free PWM transmitter (MAF-PWMT). Compared to the aliasing-compensated PWM transmitter (AC-PWMT), the COAF-PWMT increases ACLR by 19.5 dB with similar efficiency. For the 10 MHz 5G NR signal, the COAF-PWMT reaches an ACLR of 42 dB, which is 6 dB better than the GR-AFPWMT, and improves efficiency by 1.6%. These results show the COAF-PWMT's promise for highly linear and efficient RF transmitter design in future wireless systems.