Chebyshev Filter Design Using Vias as Quasi-Transmission Lines in Printed Circuit Boards

This paper presents a novel concept for microwave filter design using vias (plated through-holes) in multilayered printed circuit boards. By using the concept that vias accompanied by a sufficient number of ground vias in close proximity can be approximated as transmission lines in a certain frequency range, corresponding effective impedances and phase velocities for different configurations of vias and ground vias are deduced. By controlling these transmission-line parameters, standard microwave filter methodology is applied for the design of low-pass and bandpass Chebychev filters in the frequency range of 5-20 GHz. Measurements and full-wave simulation results are presented as validation. Advantages and limitations of the proposed method are discussed.