Abstract: A microwave distributed-constant filter of a band-pass characteristic having at least one attenuation pole comprises resonator rods, each of which has an open and a shorted end and of which two first are inductively coupled in series through at least one second resonator rod. The first resonator rods are capacitively coupled direct to each other with a projection attached adjacent on at least one of the first resonator rods to the open end thereof. The first resonator rods may be coupled directly to input and output terminals of the filter. Alternatively, two third resonator rods may be interposed between the respective ones of the first resonator rods and the input and the output terminals. The third resonator rods may be inductively coupled direct to each other.

Abstract: In a circulator comprising at least three ports, a pair of opposing conductors providing the ports, and a ferrimagnetic piece between the conductors, a gap appearing between the ferrimagnetic piece and the conductor or conductors is taken up by a spring member located in the gap. The conductors serve as an opposing pair of conductors of a waveguide of the circulator. Alternatively, the conductors serve as ground plates of a stripline with a center conductor disposed between the ground plates and with a pair of ferrimagnetic pieces disposed on both sides of the center conductor between the ground plates. In the latter case, a pair of spring members is preferably located between the ferrimagnetic pieces and the respective ground plates. Preferably, the spring member is made of phosphor bronze and comprises a plate in contact with the ferrimagnetic piece and legs extended from the plate towards the respective ports and brought into contact with the adjacent one of the opposing conductors.

Abstract: A band-rejection filter which rejects harmonic components of the fundamental frequency of the output of a helix type travelling-wave tube is built into the connection of the output connection from the tube to its external circuit. A wide variety of specific filter structures are disclosed.