A new kind of broadband output circuit of rectangular π-TM310 mode double-gap cavity loaded by coaxial line filter is propounded and its feasibility is demonstrated. Some attention-getting cruxes

such as the influence of adjacent modes on the gap impedances and the power capacity of the coaxial line output circuit

are discussed. Smaller length-width ratio and a concave structure of rectangular cavity are adopted to magnify the frequency interval between the π-TM310 mode and adjacent modes. Then the disturbance from non-working modes can be effectively suppressed. The beam holes are disposed on novel but suitable positions so that the characteristic impedances along different beam holes are more uniform

and remain uniform after the rectangular π-TM310 mode double-gap cavity is loaded by a coaxial line filter. Our research results show that the optimum designed output circuit of rectangular π-TM310 mode double-gap cavity loaded by coaxial line filter has a very wide band. The relative bandwidth in X band reaches 14% or so. But the output power capacity is relatively low

about a few hundreds of kW

because the cavity’s coupling hole with the coaxial line is relatively small

furthermore

in which there is a metal pin. So the output circuit is fit for medium power broadband multi-beam klystrons of X band or higher frequency.