A Compact Dual-Band Negative Group Delay Circuit with Independently Adjustable Characteristics

A compact dual-band negative group delay (NGD) circuit with independently adjustable characteristics is proposed. The proposed NGD circuit is extremely simple, which only consists of a microstrip line coupled with two different-length open-circuited microstrip lines. The center frequencies of both NGD bands are respectively determined by the lengths of the open-circuited microstrip lines. The independent adjustment of NGD times for both bands is achieved by tuning the coupling gaps. To verify the proposed method, an NGD circuit prototype with a size of 0.59λg x 0.20λg is designed, fabricated, and measured. From the measured results, NGD times are -4.8 ns and -5.3 ns at the center frequencies of 1.228 GHz and 1.575 GHz, respectively. The insertion loss is lower than 2.7 dB and the return loss larger than 12.6 dB in both NGD bands. The simulated and measured results are in good agreement