Substrate integrated waveguide (SIW) filers are good candidates to substitute for bulky and expensive metallic waveguide filters. Many methods are used to developed specific filter responses. One of them is using defected ground structures (DGS) in SIW filters to generate desired transmission zeros, which cannot be used in waveguide filters. In this paper, an elliptical third order bandpass SIW filter is designed in WLAN frequency band using the DGS technique. It is also shown that this technique reduces the filter size while providing good filtering response. The central frequency and fractional bandwidth of the filter is 2.4 GHz and 16.2%, respectively. Manuscript profile