Multi-Layer Microwave Filter for WLAN

Due to the development of wireless communications and the appearance of new systems there is high demand in small size, low cost filters with high performance. Hence, miniaturization of band pass filters with improvement of their characteristics is a big challenge in modern filters design. This is achieved by improvement of conventional concepts and approaches, as well as by introduction of new topologies and designs. Multi-layer concept in conventional filter designing prove to be the best approach to meet the challenges in modern filter design. In this research work, a new method to design a Multi-layer band pass filter (BPF) is presented for WLAN applications. This method is based on a simple principle: different substrates (dielectric constants) will result different resonant frequencies for a resonator. The basic structure of this method is studied and then a planar band pass filter is designed to utilize in this structure. To reduce the filter size, dual layer filter is proposed but increase in insertion loss due to multi-layer coupling. To overcome this issue, the Substrate Integrated Waveguide (SIW) filter is established based on multilayer technique. To prove the concept of microwave WLAN filter, the operating central frequency of 2.44 GHz is demonstrated and validated through simulation and measurement. Finally, the multilayer configuration with dielectric substrates showed that the bandwidth is broaden up, insertion loss, return loss and size are reduced than single layer configuration.