To provide a compact and low-cost filter for short waves (microwave signals in 1-25 GHz bands and milliwave signals over 25 GHz).

The filter comprises a dielectric material, at least two micro strip antennas and a frequency selective surface including a metal pattern in a metal frame. The frequency selective surface is used for filtering electromagnetic signals propagating in the frame. Not only the resonance frequency of the frequency selective surface but the geometrical shapes of the antennas and the frequency selective surface determine that the filter is a band pass filter, a band rejection filter, a notch filter, or a composite filter thereof. Upon removal of the frequency selective surface, its composite structure acts as a delay circuit for delaying the electromagnetic signals by a time delay defined as the function of the dielectric constant of the dielectric material.