Multi-layer bandpass filter

An innovative approach to reducing the longitudinal dimensions of a filter made using SIW (Substrate Integrated Waveguide) technology is presented. To reduce the size of the filter, a method of bending a fourth-order filter with inductive diaphragms is proposed. The frequency response of the filter has a shape close to rectangular, which significantly improves its selectivity. The developed filter has the following parameters: a bandwidth of 250 MHz, a reflection coefficient of no more than -20 dB, and a transmission coefficient in the range from -0.2 to -0.5 dB. The filter is made on a standard FR-4 substrate with a dielectric constant of 2.2 and on a paper substrate with a dielectric constant of 6. A comparison of the frequency characteristics of the computer model and the created prototypes demonstrated a good agreement between the theoretical and experimental results.