The filter's reduction in size becomes a significant difficulty because it frequently has a considerable impact on the wireless system's overall dimensions. This chapter's goal is to introduce fresh ideas that have been made to shrink filters that yet perform admirably. Then, a variety of filters that have been created are revealed. Some microstrip filters are miniaturized using coupled lines, quasilumped elements, and stub topology, and other structures are based on resonators. The structures presented are optimized and validated for different frequency bands (GPS, DCS, ISM, mobile phone, WIMAX). The filter is introduced in its overall context. Using ADS, HFSS, and CST-MWS, a full-wave electromagnetic analysis has been successful in assessing the electrical performances of the suggested structures.