5GHz CMOS All-Pass Filter-Based True Time Delay Cell

Analog CMOS time-delay cells realized by passive components, e.g., lumped LC delay lines, are inefficient in terms of area for multi-GHz frequencies. All-pass filters considered as active circuits can, therefore, be the best candidates to approximate time delays. This paper proposes a broadband first-order voltage-mode all-pass filter as a true-time-delay cell. The proposed true-time-delay cell is capable of tuning delay, demonstrating its potential capability to be used in different systems, e.g., RF beam-formers. The proposed filter achieves a flat group delay of over 60 ps with a pole/zero pair located at 5 GHz. This proposed circuit consumes only 10 mW power from a 1.8-V supply. To demonstrate the performance of the proposed all-pass filter, simulation results are conducted by using Virtuoso Cadence in a standard TSMC 180-nm CMOS process.