A six-port modulator based RF transmission system: Application in an OFDM environment

Abstract

This paper presents a cellular RF transmitter architecture based on a six-port modulator, and its application in an OFDM environment. This paper shows a possibility to apply RF transmitter based on six-port modulator to an OFDM environment, and also it shows that previous works which were limited to single-carrier transmission can be extended to multi-carrier transmission application. The proposed six-port modulator consists of three hybrid couplers, a Wilkinson power combiner, and CMOS Ron resistor banks, which can be favorably integrated into a 2.4 × 1.8 mm2 chip area. It obviates the need for DACs and mixers, which are essential components in conventional RF transmitters. A prototype chip was fabricated using the TSMC 0.13 μm CMOS process. Its performance was evaluated and verified by transmitting OFDM signals following the 3GPP standard at 1.84 GHz carrier with 1.4 MHz bandwidth. The prototype chip achieved EVM of 16.1 % and 14.6 % for QPSK and 16-QAM transmissions, respectively. This is a report implementing a new RF transmitter based on a six-port modulator for multiple subcarriers in an OFDM environment, where I/Q signals have 8.3 equivalent number of bits resolutions, respectively.