Slow-wave structures for millimetre-wavelength backward-wave oscillators

The design of slow-wave circuits in discussed with particular reference to the problems encountered at millimetre wavelengths. The mathematical analysis is not included but appropriate references are given where possible. The importance of the correct choice of group velocity and its effect upon other parameters of the circuit in stressed and an outline of an analysis aimed at the determination of the actual losses is given. The possibilities are examined of three-dimensional slow-wave structures. Finally, narrow-band and broad-band ladder circuits are described and, in more detail, the stub-supported meander line which has a wide pass-band. A method of achieving a satisfactory match between the stub-supported meander line and an external waveguide is indicated.