Abstract: A waveguide bandpass filter for use in microwave and millimeter-wave satellite communications equipment is presented. The filter is based on a substrate integrated waveguide (SIW) having several cascaded oversized SIW cavities. The filter is implemented in a printed circuit board (PCB) or a ceramic substrate using arrays of standard metalized via holes to define the perimeters of the SIW cavities. Transmission lines of a microstrip line, a stripline or coplanar waveguide are used as input and output feeds. The transmission lines have coupling slots for improved stopband performance. The filter can be easily integrated with planar circuits for microwave and millimeter wave applications.