A Wideband True-Time-Delay Phase Shifter with 100% Fractional Bandwidth Using 28 nm CMOS

A fully integrated passive true-time-delay (TTD) phase shifter is presented for a wideband phased array antenna using 28-nm CMOS technology. By using a delay-compensation technique, a linear phase characteristic is achieved within a wide frequency range over 8-24 GHz. A combined bridged-tee network (BTN) delay cell is proposed to accomplish the delay compensation with the most significant bit (MSB) at 29.6 ps and the least significant bit (LSB) at 7.4 ps, which are 45° and 180° at 16 GHz, respectively. The measured insertion loss is in the range of 7.8-12 dB with an RMS gain error less than 1.4 dB from 8 GHz to 24 GHz. In addition, the measured RMS TTD phase and delay errors are less than 1.6 ps and 1.5°, respectively, within 8-24 GHz. The chip size of the proposed TTD phase shifter is 0.48 mm2.