A 23.6-30.0GHz Phased-Array Transmitter With Wide-Angle-Scanning Load-Compensation Technique Achieving OTA-Tested 2.9dB Array-Gain Enhancement and 1.2dB EVM Improvement

In this paper, a wideband phased-array transmitter (TX) featuring a wide-angle-scanning load-compensation technique is demonstrated. This technique aims to compensate for antenna-load impedance variation of large-scale phased-array systems during beam scanning. It is implemented by a Doherty PA integrated with two digitally controlled phase-shifting cells positioned in both the main and auxiliary paths of the PA. Based on calculated beam-angle-dependent antenna-load impedances, the technique can adjust the phase and amplitude difference between the main and auxiliary paths of the PAs, thereby enabling the main-path PA to always operate with a consistent antenna load. The proposed phased-array TX is fabricated in a 65nm CMOS process. The measurement results show that the TX achieves a 3-dB gain bandwidth of 6.4 GHz, ranging from 23.6 to 30 GHz. It has an output 1-dB compression point $\left(O P_{1 \mathrm{~dB}}\right)$ of 15.7 dBm and a saturated output power of 19.9 dBm. Thanks to the load compensation scheme, the PA attains 2.8 dB gain enhancement and $4.1 \mathrm{~dB} O P_{1 \mathrm{~dB}}$ improvement within a full-span 4:1 VSWR circle. A prototype 4-element phased-array TX is designed based on the chip. With the proposed technique, the over-the-air (OTA)-tested array gain and EVM are respectively improved by 2.9 dB at a beam angle ($\theta_{0}$) of -20° and 1.2dB at $-30^{\circ} \theta_{0}$, compared with that without enabling the method.