A Broad-Band Interdigital Circuit for Use in Traveling-Wave-Type Amplifiers

Because of its high-power handling capacity, the interdigital circuit has been considered for use in traveling-wave-type amplifiers. An analysis is presented here which indicates that this type of circuit can be arranged to give constant phase velocity over a wide bandwidth (30 per cent), as required to give constant gain. The analysis is qualitatively checked experimentally. The impedance parameter (proportional to the cube of the gain in db) is approximately the same as the flattened helix (such as has been used for the magnetron amplifier) and about one-third that of the conventional circular helix.