Investigation on Microwave Negative Group Delay Circuit

Abstract

In this article, a fundamental analytical approach and experimental verification of a radio frequency active circuit capable of exhibiting negative group delay at microwave wavelengths are presented. By using the S-parameter theory, basic properties and characteristics of the negative group delay circuit under study are established. To highlight the functionality principle of this innovative circuit, time-domain investigations based on ultra-wide-band pulse signal tests are performed. Then, the mechanism of propagating output signal envelopes in time advance compared to the input is demonstrated. To validate this concept, a prototype of a negative group delay device was designed, fabricated, and tested. Experimental results in good agreement with theory and simulation were obtained. In the frequency domain, a negative group delay of about −2.5 ns with amplification of 2 dB was measured at around 622 MHz. Due to this negative group delay effect, envelope advance of about −1.5 ns was observed by considering a pulse signal with a half-height full-width of 10 ns, which modulates a sine carrier with a frequency of 622 MHz. The negative group delay topology presented is potentially useful for the compensation of radio frequency/microwave signal delays.