Negative Group-Delay Phenomenon Analysis With Distributed Parallel Interconnect Line

This paper describes an original theory on negative group-delay (NGD) topology of parallel interconnect line (PIL). The proposed topology consists of a fully distributed circuit without lossy lumped components. The PIL voltage transfer function (VTF) is derived from the equivalent transfer matrix. Then, the frequency-dependent expressions of the PIL VTF gain and group delay are extracted. It is shown that the NGD phenomenon can be generated when the PIL is lossy and presenting different electrical lengths. The fundamental NGD properties versus the PIL parameters are established. This NGD concept was validated with implemented two microstrip PIL circuits. The theoretical and measured group-delay behaviors are well correlated. As expected theoretically, the demonstrator with identical 50-Ω characteristic impedance enables to generate NGD of about -4 ns at 1.75 GHz under -5-dB attenuation. Similarly, an -2.1-ns NGD level at 1.99 GHz was occurred with the other 50 Ω/117 Ω characteristic impedances NGD circuit under only -2.5-dB attenuation loss. The NGD function can be potentially used for the microwave signal integrity improvement.