Synthesis of RF Circuits with Negative Time Delay by Using LNA

Abstract

A demonstration of the negative time-delay by using active circuit topologies with negative group delay (NGD) is described in this paper. This negative time delay is realized with two different topologies operating in base band and modulated frequencies. The first NGD topology is composed of an RL-network in feedback with an RF/microwave amplifier. Knowing the characteristics of the amplifier, a synthesis method of this circuit in function of the desired NGD values and the expected time advance is established. The feasibility of this extraordinary physical effect is illustrated with frequency- and time-domain analyses. It is shown in this paper that by considering an arbitrary waveform signal, output in advance of about 7 ns is observed compared to the corresponding input. It is stated that such an effect is not in contradiction with the causality. The other NGD topology is comprised of a microwave amplifier associated with an RLC-series resonant. The theoretical approach illustrating the functioning of this NGD circuit is established by considering the amplifier S-parameters. Then, synthesis relations enabling to choose the NGD device parameters according to the desired NGD and gain values are also established. To demonstrate the relevance of the theoretic concept, a microwave device exhibiting NGD function of about -1.5 ns at around 1.19 GHz was designed and analyzed. The NGD device investigated in this paper presents advantages on its faculty to exhibit positive transmission gain, the implementation of the bias network and matching in the considered NGD frequency band.

Keywords

• RF Circuits
• LNA
• Negative group delay
• NGD