A 57–71-GHz Beamforming Front-End With 6.6-dB NF and 13.9-dBm OP_{1 dB} Using a Low-Loss Switchable Triple-Coil Transformer

This brief presents a 57–71-GHz transmit/receive (T/R) front-end (FE) module for large-scale phased-array transceivers. The FE consists of a T/R switch (TRSW), power amplifier (PA), low-noise amplifier (LNA), phase shifter (PS), variable gain amplifiers (VGAs), and power combiner/divider (PC/PD). To alleviate the RX signal leakage to the TX branch in the traditional asymmetric TRSW structures, a novel switchable triple-coil transformer (STCT) is proposed at the PA output, achieving a broadband high off-impedance for the RX while introducing a low loss to the TX power. In addition, to facilitate large-scale phased-array calibration, both VGA and PS feature the orthogonal amplitude and phase control, leading to low phase and gain errors. Fabricated in a 65-nm CMOS, the proposed FE achieves a peak gain of 28.4/17.3 dB with BW<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {3~dB}}$ </tex-math></inline-formula> from 54 to 70/55 to 70 GHz in TX/RX modes. Benefiting from the proposed STCT, the TX achieves an OP<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1 ~dB}}$ </tex-math></inline-formula>/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {sat}}$ </tex-math></inline-formula> of 13.9/15.4 dBm with PAE<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1~ dB}}$ </tex-math></inline-formula>/PAE<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 10.7%/13.7%, respectively. The RX achieves a minimum in-band noise figure (NF) of 6.6 dB at 66 GHz. During the gain tuning, the FE achieves an rms gain/phase error of 0.13 dB/1° and 0.1 dB/1.3° in the TX and RX modes, respectively. The 6-bit phase shifting performs an rms phase/gain error of 0.85°/1.3 dB and 0.8°/1.1 dB in the TX and RX modes, respectively.