A Compact Dual-Band Negative Group Delay Microwave Circuit

A compact dual-band negative group delay circuit (NGDC) is proposed. The proposed NGDC is composed of an open-circuited transmission line and two resistors connected by two transmission lines. The frequency ratio is controlled by the characteristic impedance of the transmission lines. To verify the design concept, a dual-band NGDC with the frequency ratio of n = 2 (Circuit A) and a broadband NGDC with n = 1.16 (Circuit B) are designed and fabricated. The measured group delay value of the Circuit A is -1.19 ns at the center frequencies of lower and upper bands. And the measured NGD bandwidth is 34.6% for the lower band and 16.5% for the upper band, in which the return loss and insertion loss are better than 16.9 dB and 18.2 dB, respectively. From the measurement results of Circuit B, a flat fractional NGD bandwidth of 19.8% with GD of (-1.58 +/- 0.13) ns is obtained, in which the return loss and insertion loss are better than 23 dB and 32.5 dB, respectively.