A Compact D-Band 360° Active Differential Phase Shifter for Sub-Terahertz Phased-Array Antennas in 40Nm CMOS

This study presents the design of a D-band $156-\text{GHz}$ active differential phase shifter intended for transceiver circuits in phased array antennas to receive terahertz signals. The proposed phase shifter utilizes a tunable active circuit composed of seriesconnected NMOS transistors, where the bias voltage is controlled to adjust the drain-source resistance. This configuration enables both continuous and fixed phase shifts. The phase shift range is extended to cover the full 360° by connecting multiple adjustable phase shifter units in series, employing a $0^{\circ} / 60^{\circ}$ phase shift switch, and incorporating a Gilbert cell as a $0^{\circ} / 180^{\circ}$ phase switch. The circuit is fabricated using TSMC's 40 nm CMOS process, ensuring a compact layout and facilitating miniaturization. Measurement results confirmed the circuit operates effectively, demonstrating its potential for further research and practical applications.