The Measured Performance of a Millimetre-Wave Frequency Multiplexing Unit for Trunk Waveguide Communication

A rectangular waveguide commutating-hybrid array channelling filter and a centre-excited band branching unit have been combined to form a frequency division multiplexing (f.d.m.) network in the 32-50GHz frequency region. These units terminate the circular waveguide in a millimetric trunk communication system. The 32-90GHz frequency range is divided into transmit-receive sub-bands by the band branching unit which also transduces the TE
₀₁
° mode in circular waveguide into the TE
₁₀
□ mode of rectangular waveguide. A commutating-hybrid array, constructed from rectangular waveguide, further divides each 32-40GHz and 41-49GHz sub-bands into sixteen individual channels spaced 0.5GHz apart. For these sub-bands the average insertion losses measured for the complete f.d.m. network, i.e. between the circular waveguide input to the channel output, are 2.0 and 2.88dB. This paper summarizes the operating principles and measured electrical characteristics. A statistical analysis of results is presented together with an outline of the mechanical construction employed.