A novel double folded quarter mode substrate integrated waveguide (DFQMSIW) resonator is proposed. The dominant resonant mode of the proposed resonator is TE101 mode. The size of the DFQMSIW cavity is reduced nearly by 94% compared with the conventional SIW cavity. A three order cascaded DFQMSIW filter with a center frequency of 2.84GHz and a fractional bandwidth of 11.5% is implemented. The measured results show that the filter insertion losses are below -1.8 dB and return losses are better than -15dB. Good agreement between simulated and measured results demonstrates the validity of the proposed method.
