Dither Enhances PWM Transmitter Resolution for 5G UHF Bands

The inherent resolution of traditional PWM (pulse width modulation) RF (radio frequency) modulation is not high to achieve 256QAM modulation in the 5G OFDM (orthogonal frequency division multiplexing) 700MHz UHF (ultra-high frequency) bands system. This paper proposes a method that can significantly improve the resolution of PWM modulation, which is to introduce a dither scheme in the PWM hardware circuit. Under the same pulse width resolution frequency, the modulation of the 5G system can be increased from QPSK to 256QAM with our proposal. This paper completes the system design of the PWM modulation. With the logic circuit level simulation, the correctness of the dither scheme proposed in this paper is verified, and the RMS EVM (root mean square error vector magnitude) is reduced to about 1%, which satisfies 3GPP requirements. The dither scheme in this paper enables PWM digital RF modulation to be applied in the 5G UHF bands.