A Systematic Solution for the Problem of Spectral Degradation in Multiphase TX Architectures

Abstract

With ever more stringent requirements of cellular standards it is an ongoing challenge to find the optimal RF transmitter architecture. In recent years, the multiphase transmitter (MP TX) architecture has been introduced as a promising candidate. It features high power efficiency and avoids phase modulation which is critical for upconversion of ultra-wideband signals. In this paper, the problem of unwanted spectral emission, inherent in MP TX architectures, is compensated by a proper data delay. Such an approach is considered for the first time in the multiphase architecture and achieves a spectral improvement of up to 38 dB in adjacent channels and 24 dB at the receiver (RX) duplex distance for a new radio (NR) signal with 20 MHz bandwidth. With the proposed solution the MP TX architecture becomes a highly competitive candidate for wideband signals such as LTE, LTE-CA or NR signals. In addition, a detailed and efficient implementation of the digital front-end (DFE) for the MP TX architecture including the proposed data delay is presented.