Waveguide filter

A waveguide filter having a passband and a stopband, for conveying passband frequency components of an electromagnetic signal, while suppressing stopband frequency components of the electromagnetic signal, the filter comprising:

• a substrate integrated waveguide (SIW) formed in a dielectric layer sandwiched between first and second opposing planar conductive layers, the SIW having a chain of sequentially coupled conterminous multimode SIW cavities defined on their perimeters by an array of conductive vias connecting the first and the second conductive layers through the dielectric layer, the chain having first and second ends;
• an input transmission line coupled to the first end of the chain, for coupling the electromagnetic signal to the first end of the chain;
• and
• an output transmission line coupled to the second end of the chain, for outputting the passband frequency components of the electromagnetic signal from the second end of the chain;
• wherein a distance between neighboring vias of the array of conductive vias is less than one half of a shortest wavelength of the electromagnetic signal in the SIW cavities.