A Broadband Dual-Band Negative Group Delay Circuit With Flat Group Delay

A broadband dual-band negative group delay circuit (NGDC) with flat group delay is proposed. Without the cascade structure, the proposed NGDC consists of an open-circuited coupled lines connected with a resistor through transmission lines and a matching network. The flatness of the negative group delay (NGD) and center frequencies of the lower and upper bands can be designed through changing the characteristic impedance of the transmission lines. And the NGD time is adjusted by modifying the parameters of the coupled line. Low GD ripple could be achieved by the proposed dual-band NGDC with a small circuit size. To verify the design concept, a dual-band NGDC is simulated, fabricated, and measured. The measured NGD times are −0.51 ns at the center frequencies of 0.32 and 1.39 GHz with insertion loss of 20.8 and 21.2 dB, respectively. The flat-NGD bandwidth reaches 32.8% from 0.275 to 0.380 GHz and 6.8% from 1.350 to 1.445 GHz with 10% group delay fluctuation.