Compact Odd-Order Band-Pass Filters Using Capacitively Coupled Spiral Resonators

In this article, a new topology for designing compact, band-pass filters of odd-order (N = 3, 5, 7, . . .) is presented. The technique is based on using resonators with parallel RLC type resonance with high loaded quality factor (QL) in conjunction with the capacitively loaded, slow-wave transmission lines. Using the approach presented in this article compact band-pass filters with bandwidths as small as 5% to as wide as 50% can easily be designed. The principles of operation of the proposed filter along with experimental results of several different fabricated prototypes are presented and discussed in this article. © 2008 Wiley Periodicals, Inc