Microwave Cavity Filters are widely used in RF systems for high Q signal filtering. But their bulky sizes at lower operating frequencies make them quite inconvenient to be used especially in the frequency range 1-4 GHz, which is the range of most of the commercial wireless applications. This thesis work aims to enhance the usability of cavity filters in these lower frequency ranges, by exploring a unique re-entrant structure for the cavity filter design. The study further explores the use of superconductors in the design to for improve the performance of the filters by reducing the associated losses. After verifying the basic workability of the concept, a coupled re-entrant cavity filter design is proposed with an equivalent high Q.