A Class of Compact Substrate Integrated Waveguide Filters

Abstract

This thesis work explores the design of compact and high performance microwave filters using substrate integrated waveguide technology. A substrate integrated waveguide is aplanar version of a conventional waveguide, which is having features like planar circuit integrability, ease of fabrication, low-cost and high power handling. A class of Substrate Integrated Waveguide (SIW) and Half mode Substrate Integrated waveguide (HMSIW) bandpass filters are proposed in this context. Applications like satellite communication uses devices which can withstand high power. Therefore, SIW filters can be used for satellite applications in the microwave bands like Ku, X, C, S, and L etc.The main objective of this thesis is to design SIW bandpass filters using simple planar technology and low-cost substrates. To fulfill this, a class of compact and easily fabricable SIW bandpass filters are proposed for Ku-band (12 − 18GHz) and S-band (2 − 4GHz) applications. These filters are designed using simple electromagnetic band gap (EBG) structures and latest feeding techniques like tapered-via feeding. Filters are designed using low-cost and easily available substrate FR4 with the help of High frequency structural simulator (HFSS) V.14. The dimensions of the filters are optimized and simulation results are analyzed. The proposed Ku-band filter has proven to be compact since its footprint is 160mm2. The S-band filter has been fabricated using low-cost and easily available FR4 substrate. The measurement results are found to be good in agreement with the simulation results. Though the obtained results are similar to the other reported filters, there is a huge demand of compactness in this miniaturization era. Therefore, another well-established concept of Half-mode SIW (HMSIW) technology is used to further reduce the size of the designed filters. So a compact HMSIW bandpass filter is designed for the Ku-band applications which is almost half in size as compared to conventional SIW designs. The return loss is achieved as 45dB and insertion loss is 1.5dB in the passband of the filter, which is promising corresponding to the size. Another similar design is made for X-band (8 − 12GHz) applications using HMSIW technology. The overall footprint of the filter which shows its compactness; is 102mm 2 i.e. almost half the size of its equivalent SIW filter.