Compact Multi-State All-Pass Network Delay Cell for True-Time Delay

초록

A novel compact multi-state all-pass network (APN) is proposed for true-time delay (TTD) applications. A second-order APN, which is commonly used, implements only a single state within a unit delay cell. As a result, additional external blocks, such as single-pole-double-throw (SPDT) switches and reference cells, are required for delay state control. In contrast, the proposed multi-state APN can implement three states within a unit delay cell without any additional external blocks, facilitating a more compact realization of the TTD. This multi-state APN delay cell features perfect matching properties and ensures a constant delay difference between its states. In this paper, a TTD is implemented using the proposed multi-state APNs designed with a 0.13 μm PD-SOI process, achieving a 4 ps delay resolution over a frequency band of 6 - 18 GHz. Compared to a conventional 3-bit switched-line TTD with the same frequency range and resolution, the proposed design includes one additional state, resulting in a controllable delay range that is 4 ps larger while achieving a 51.3% reduction in size, as well as similar RMS delay error and normalized delay variation performance. © 2025 IEEE.