Coupled line networks for microwave realization of the discrete fractional Fourier transform*

The discrete Fourier transform is one of the critical operations in information processing, which is conveniently implemented in free-space optics using bulky optical Fourier lens configurations. In this talk, an on-chip realization of the discrete fractional Fourier transform (DFrFT) is proposed and experimentally implemented in the microwave domain utilizing a passive metamaterial coupled lines network (MCLN). This renders a lensless device capable of performing the DFrFT in real time. In its core, the MCLN comprises N  microstrip transmission lines coupled to their nearest neighbors through an array of interdigital capacitors composed of interlaced microstrip fingers. In the latter, the dimension and number of fingers allow for controlled and enhanced coupling terms that render the required DFrFT couplings highly accurate. The architecture is particularly illustrated by modelling and experimentally realizing a 16×16 MCLN so that its performance can be tested.

 

The proposed innovative approach is versatile and is capable of being used in various applications where DFrFT is an essential tool. The proposed design scheme based on MCLN is scalable across the frequency spectrum and can be applied to the millimeter and submillimeter wave systems.