Development of low loss waveguide filters for radio-astronomy applications

In this paper the modeling, fabrication and experimental characterization of a wideband band-pass filter operating in W-band (75-110 GHz) is presented. This new high-performance waveguide filter can have several potential applications and will particularly be relevant in radio-astronomy receivers. The classical direct coupled cavity-based synthesis is first used. Then, an efficient full-wave analysis based on the mode matching technique is carried out, leading to a tenth order all-pole filter design. Two different prototypes were fabricated using an accurate electroforming machining technique. A good agreement between simulation and measurements is obtained with negligible frequency shift and 15 dB return loss level. One should note the low level of insertion loss reported of about 0.4 dB within the band-pass, which is a critical parameter for low-noise receivers.