Folded substrate integrated waveguide cross-coupled filters with negative coupling structure for wireless systems

Abstract

In this article, a compact multilayer substrate integrated filter with pseudoelliptic power transfer function is presented. The fourth-order bandpass filter designed by optimization has a central frequency of 10 GHz with a bandwidth of 800 MHz. It possesses two transmission zeros and exhibits return loss of −30 dB. Miniaturization is achieved using folded waveguide technology. Novel negative coupling structure based on upside–down-folded iris-coupled resonators is introduced and investigated. Design procedure is briefly explained, coupling matrix is derived, and investigation of coupling elements is carried out to match calculated coupling coefficients. Results of full-wave simulation of the filter are in good agreement with the prototype.