Compact Substrate Integrated Waveguide Wideband Bandpass Filter With Post-Manufacturing Tuning Capabilities

In this paper, a miniaturized wideband bandpass filter in coaxial substrate integrated waveguide (SIW) technology is presented. To improve the response selectivity and coupling control, a multi-layer structure has been implemented, introducing both strong magnetic and electric couplings. To reduce the physical size of the device, surfaced-mounted device (SMD) capacitors have been integrated on the top layer. These allow both resonant frequency and capacitive coupling level control. Thus, a 4-th order Chebyshev filter with an absolute bandwidth (BW) of 2.9 GHz centered at 5.35 GHz has been designed, fabricated and measured. An extremely small filter size of $7 \times 7$ ,mm2 has been obtained. A study of manufacturing tolerances are also presented in this paper, together with a post-manufacturing response correction allowed by the SMD elements. As it is shown in the paper, the filter’s out-of-band rejection can be easily enhanced by introducing additional transmission zeros (TZs).