Multimode harmonic power meter for circular overmoded waveguide at second and third harmonics

A device for measuring the power of higher order harmonics in circular waveguides is presented. The device is constructed of several single-mode TEM waveguides (typically coaxial cables) which are coupled to the circular waveguide. Coupling is implemented by means of small inclined slots. Based on a technique of statistical analysis for the power coupling coefficient averaged over all coaxial lines, the total power of the higher order harmonics can be estimated. A uniform statistical distribution of the amplitudes of high order modes is assumed, from which the mean value, standard deviation and probability density function for the averaged power coupling coefficient can be found.