The Design of Branch-Guide Couplers, with Applications to the Suppression of Spurious Frequencies

This investigation was the result of a program to suppress the harmonic frequency output from high-power transmitters without causing undue reflection of the attenuated frequencies. The attenuation is produced by a rejection filter (which took the form of a waveguide, lowpass, "waffle-iron" filter). To protect the transmitter, a "harmonic pad" is placed between it and the rejection filter to absorb most of the power in the reflected harmonics (in this case, up to the tenth harmonic), while introducing negligible insertion loss in the transmitter fundamental band.