Equivalent circuit of three-gap coupled cavity type output section

The equivalent circuit of the three-gap coupled cavity type output section is given, with which resonant frequency of resonant modes and gap impedance matrix are calculated. Based on gap impedance, mode-overlapping theory of double-gap coupled cavity is discussed, and is used to expand the bandwidth of a Ka-band three-gap coupled cavity type output section. Resonator interaction impedance of three-gap coupled cavity is obtained from energy conservation law. The circuit’s 3 dB-bandwith has reached 4.48% by adjusting circuit parameters.