Synthesis and design of narrowband bandpass filters in waveguide technique
The design and realisation of a high order bandpass filter for millimetre wave signals is presented. It is purely based on split-block hollow-metal waveguide technology. The synthesis process starting at the equivalent lowpass filter is demonstrated, involving the use of K-inverters and equivalent circuits for waveguide discontinuous. This results in a compact iris filter with less than 1.2GHz bandwidth at 94GHz and more than 40 dB suppression at 0.5 GHz offset while the insertion loss is kept as low as 3 dB. The design is verified by EM simulation and experimental characterisation of a manufactured prototype to underline the potential of the filter for innovative system design in the millimetre wave range.