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 TX featuring a wide-angle-scanning load-compensation technique is demonstrated. This technique is based on a modified Doherty structure incorporating a digital-controlled phase shifter and adaptive bias circuit and aim to compensate for antenna-load impedance variation of large-scale phased-array systems during beam scanning. Based on calculated beam-angle-dependent antenna-load impedances, the technique can autonomously adjust the phase difference between the main and auxiliary paths of the Doherty PAs, thereby enabling the main-path PA always operate with a consistent antenna load. The measurement results show that a single path attains 0.2-2.5 dB gain enhancement and 0.2-3.2 dB OP1dB improvement within 4:1 VSWR circle. And a prototype 4-element phased-array 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 of -20° and 1.2dB at -30°, compared with that without enabling the method.