38-GHz Phased Array Transmitter and Receiver Based on Scalable Phased Array Modules With Endfire Antenna Arrays for 5G MMW Data Links

This article presents the 38-GHz phased array 32-element Tx and 16-element Rx with 2-GHz IF and 5-GHz LO for fifth-generation (5G) millimeter-wave (MMW) communications. The Tx and Rx beamformers and upconverters/downconverters are fabricated in 65-nm CMOS. The PAs and LNAs near antenna ends are fabricated in 0.15- $\mu \text{m}$ GaAs pHEMT. The eight-element Tx and four-element Rx phased array printed circuit board (PCB) modules integrated with multiple integrated circuits (ICs) and endfire antennas are implemented as unit cells. Four pieces of Tx modules are vertically stacked to construct an $8\times {4}$ brick array (planar array), while four Rx modules are to construct a $4\times {4}$ array. According to 38-GHz over-the-air (OTA) measurements, the 32-element Tx shows 47.5-dBm equivalent isotropic radiated power (EIRP) at OP $_{\mathrm {1 ~dB}}$ with −35.2-dB image rejection ratio (IMRR) and −37.4-dB $\times 8$ LORR. The 16-element Rx at 38 GHz shows −4-dBm OP $_{\mathrm {1~dB}}$ with −28-dB IMRR and −36.6-dB LORR. The Tx and Rx support the beam scanning around ±60° azimuth and ±30° elevation planes. The Tx-to-Rx wireless data link demonstrates 64 quadrature amplitude modulation (QAM)/400 M-BR, 256 QAM/200 M-BR, and 512 QAM/100 M-BR in 20 m. To the best of our knowledge, this work is the first 5G 37-/39-GHz phased array Tx/Rx using the scalable brick array configuration and demonstrating competitive performances compared with previous works.

I. Introduction

Phased array transmitters (Txs) and receivers (Rxs) consisting of the multiple RF front ends and antenna arrays are adopted for the fifth-generation (5G) millimeter-wave (MMW) communications due to the high equivalent isotropic radiated power (EIRP), signal-to-noise ratio (SNR), and dynamic beamsteering with high directivity for wireless high-speed data links [1], [11]. Besides, since the completed 5G communications are the coexistence of the 5G sub-6-GHz and MMW, and the 5G MMW will launch following the earlier commercialized sub-6 GHz [12]–[15], the IF and LO frequencies of the 5G MMW front ends should be lower than 6 GHz, which could be compatible with the established sub-6-GHz system to alleviate the complexity of the coexisted system with a lower building cost [1]–[5]. Moreover, the EIRP of the -element phased array Tx increases with dB, while the SNR of the -element phased array Tx/Rx increases with dB, and the increased EIRP and SNR improve the quality of digitally modulated signals, such as the quadrature amplitude modulation (QAM) signals, for high-speed data links in a long distance [6], [16]. Therefore, for 5G MMW base station (BS) to achieve a broad area coverage, the large-scale phased array is necessary. Furthermore, because the -element phased array is composed of replicate RF front ends and antennas with regular arrangements, the scalable circuit designs and configurations of RF integrated circuit (IC) and packaged module are definitely critical and feasible to implement large-scale phased arrays with simple integration/assembly. Nevertheless, the scalable RF ICs and modules also have lower costs, which are more attractive to commercial mobile communications.