Custom Design

“Guided Wave Technology has been supplier of phase matched filters for our airborne synthetic aperture and polarimetric radiometers for more than a decade.

These filters have spanned frequency bands from 1.4 GHz to 40 GHz and have been characterized by their accuracy and ability to perform under extreme environmental conditions”

Sten Schmidl Søbjærg

Associate Professor
Electromagnetic Systems
Technical University of Denmark  

Band pass Filters for L-Band (1.4 GHz) Polarimetric Radiometer

Technology: Six pole quasi elliptic folded combline filter. Four transmission zeroes are added to increase rejection

The picture below shows a part of DCRS's polarimetric Ka band radiometer (34 GHz), aimed at determining the wind speed and direction over the sea surface. The instrument is combined with a scanning antenna to provide an imaging polarimetric radiometer system. The system is flown on a C-130 transport aircraft.
The radiometer consists of two isolated identical receivers (part of one is shown). It is very important that the phases of the two waveguide filters are identical. This has been achieved by using photolithographic manufacturing processes of the filtering inserts. The design does furthermore not contain tuning screws which assures the highest mechanical and electrical stability.
  

Measured response of 34 GHz waveguide filter used in DCRS's airborne radiometer.
This filter has been designed taking 23 modes into account. The filtering insert is a copper ladder etched from 0.1 mm thick copper foil - similar to the X-band filter shown above. The shown result is "first shot" with no screw tuning applied.