Waveguide filter employing common phase plane coupling

Abstract

Bandstop (FIGS. 1-3) and bandpass (FIGS. 4, 5) filters are presented utilizing broad and narrow wall resonator coupling in a rectangular waveguide (11 and 37) at a common cross sectional reference plane. For the bandstop filter, the resonators (12, 13) are resonant at a common frequency f.sub.0 to provide a two-pole bandstop response in a filter of minimal longitudinal dimensions. For the compact bandpass filter, each tone rejection is provided by a pair of resonators (31, 35) coupling to the electromagnetic field signal at two points one from a broad wall and the other from a narrow wall of the waveguide (37) but displaced by some multiple of a half wavelength. Another pair of resonators (33, 34) are in common cross sectional plane relationship to the first pair but located on a wall of different width to provide rejection of a tone at the other end of the passband. The use of resonators with different resonant frequencies at a common cross sectional plane avoids possible interresonator coupling. Additional pairs of resonators (e.g., 32, 36) may be interleaved with these resonator locations. Each resonator (e.g., 13) is associated with an aperture (e.g., 19) and has its major portion extending into a housing (e.g., 18) located exterior to the waveguide (e.g., 11).