A Design of Wideband Microwave Delay Line With Long Delay Time

Traditional microstrip delay lines require sacrificing circuit area to achieve longer time delays, which is highly unfavorable for miniaturization of the electronic equipment, especially in the microwave low-frequency range. To increase the delay time of planar circuits, this letter proposes a combined structure of the open-circuit branch and parallel grounding strips. This combined structure enhances slow-wave transmission effects and reduces coupled eddy current effects. Thereby, the delay time is increased. Within the frequency range of 1.65 GHz to 2.15 GHz, for a single delay unit, the maximum group delay time can reach 1.3 ns, with an average transmission loss 0.5 dB. Moreover, this basic delay unit is also very easy to cascade to achieve longer delay times. The delay time of the four-unit cascaded delay line maximum reaches 7.4 ns, with an average transmission loss less than 2.6 dB.