Abstract: Based on requirements of large scale scanning steer, instantaneous bandwidth, and improvement of signal distortion causing by aperture crossing for phased array antenna, the technique of S-band diplex and high accuracy design for true time delay (TTD) module is proposed. Utilizing receiving/ transmitting switcher, sext-bit delay line, delay module, and logical-driving circuits, total 64 delay states and maximum delay time 19. 4 ns is realized. Focused on receiving/ transmitting switching, small-scale delay, large-scale delay, simulation validation incorporates with micro-assemble technology, the delay module is guaranteed. For example, a 6-bit 63λ delay module is designed, whose measurement shows amplitude fluctuation is better than 1 dB, delay phase/ amplitude accuracy are within ±10° and ±0. 5 dB.