A novel circuit theory of all-pass Negative group delay (NGD) function is investigated. The NGD function is implemented with unity direct chain feedback (UDCF) system. The active circuit is built with an operational amplifier in feedback with a lossy transmission line (TL). The UDCF topology S-parameter model is established versus TL parameters. The NGD analysis is elaborated from the frequency dependent transmission coefficient. The NGD behavior characterization is developed. The synthesis method allowing to determine the UDCF topology parameters in function of the targeted NGD values, gain and reflection coefficient is formulated. The all-pass NGD function is validated with a proof-of-concept (POC) design. Frequency and time domain simulations confirm the feasibility of the innovative all-pass NGD function. With S-parameter analysis, it was shown that the UDCF circuit exhibits NGD up to −۷-ns with gain more than 0-dB and reflection coefficient −۲۰-dB. More importantly, time-domain analysis illustrates how the transient tested voltage outputs can be in advance compared to the input.

Introduction

Despite the spectacular development of the modern technology, the delay effect remains an open problem in several areas of engineering [1]–[۴]. The performances of electrical, electronic, automatic and many more systems depend undesirably to the delay effects. The analytical link between the delay and system operation can be quantified from the system transfer functions. The system unit-step and harmonic responses illustrate how the delay degrade the performances. For example, the detrimental influence of time delays can be found in different aspects of automatic system analyses [5]–[۷]. Among the concerning system, we can cite that very recently a prediction scheme for input delay was investigated [8], and a linear system stability condition was established as a function of the dwell-time parameters [9]. Nowadays, time delays constitute one of key parameters to be taken into account during the design and fabrication of automatic and electronic engineering systems. Improved studies on the time-delay effect are necessary during the engineering system design phase. Time-delay modules can be found at all levels of several engineering systems. For example, time-delay systems were applied to control the time lags used in vibrational feedback control [10]. An improved stabilization technique dedicated to linear systems with time delay has been proposed in [11].