An All-Digital Outphasing Transmitter IC for Ka-Band Bit-to-RF Concurrent Multi-Beam DBF Array

Abstract

The first Ka-band DTX-based bit-to-RF multi-beam transmitter array is demonstrated in this work. The DTX IC features a prototype digital outphasing architecture with a 4x frequency multiplication scheme and a piecewise varactor array (PVA) linearization technique. Further, a compact wideband ADPLL with 24-bit phase shifting is integrated, eliminating the high-frequency LO distribution and improving the phase/gain alignment in the array. Leveraging these techniques, a low-cost 24.5-30GHz DTX is fabricated in 40nm CMOS. It achieves an EVM of-24.2dB for 16QAM without calibration and only occupies a core area of 1.2 x1.35mm2. Bit-to-RF concurrent multi-beam forming is demonstrated with a lx8 uniform linear array (ULA) and the best normalized energy/area efficiency are achieved.