A Dual-Band Vector-Sum Phase Shifter using I-Q Phase Compensation Technique for 5G Applications

This paper investigates a dual-band vector-sum phase shifter operating at 5G millimeter-wave $(\mathrm{mmW})$ bands. It is implemented in a $22\mathrm{~nm}$ FD-SOI technology to prove the concept. The phase shifter core is composed of a poly-phase-filter (PPF) for differential quadrature signal generation and an amplitude control block for vector amplitude tuning. An advanced phase compensation technique has been studied and applied to eliminate the degradation of the PPF phase accuracy due to circuit parasitics. Continuous 360° phase control is demonstrated at 28GHz and 38GHz. The proposed design achieves an average gain of about $5\mathrm{~dB}$ at 28GHz and $8\mathrm{~dB}$ at 38GHz at a total DC power of $19.5\mathrm{~mW}$. The measured root-mean-square (RMS) amplitude-and phase-errors are $0.1\mathrm{~dB}$ and 1.3° at 28GHz and $0.1\mathrm{~dB}$ and 0.7° at 38GHz. To the best knowledge of the authors, this is the first dual-band vector-sum phase shifter operating at 5G mmW-bands in $22\mathrm{~nm}$ FD-SOI.

I. Introduction

One of the main challenges in wireless communications at millimeter-wave frequencies is the large Free-Space Path-Loss (FSPL) of the transmitted signals. Without increasing the power of transmission, it strongly limits the maximum distance of communication and the channel capacity because of the limited Signal-to-Noise-Ratio (SNR) at the receiver side. Phased-array systems can be employed to overcome this point by shaping the radio waveform (beamforming) and steering the wave beam towards the target direction, where the wave forming greatly enhances the transmitted power density at the receiver side and improves the SNR [1]. Phase shifters are the key component of those phased-array systems. Upon the working principle, phase shifters can be divided into three different types: switching-type phase shifters (STPS), vector-sum phase shifter (VSPS) and reflection-type phase shifter (RTPS). Motivated by the zero power consumption, passive phase shifters operating at bands have been researched intensively. A passive STPS was demonstrated in [2], in work [3] a passive VSPS was presented and [4] has shown a passive RTPS. However, the passive phase shifters suffer from high insertion loss, which is a critical drawback. Different from passive phase shifters, active phase shifters can provide low insertion loss with 360° phase control at moderate DC power [1], [5]–[11]. The mmW-bands allocated for -applications are distributed in two band-sets -28GHz band from 24.25GHz to 29.5GHz and 38GHz band from 37GHz to 40GHz [12]. It is superior to design a phase shifter supporting operation in both two band-sets from the cost point of view. Active phase shifters capable of covering both band-sets were rarely reported. Among the active phase shifters mentioned above, only the work in [10] has shown a broadband design supporting both 5G bands. However, the broadband property generally lowers the gain (higher insertion loss) and causes high power consumption.