Compact L-band Filter in a k-band Radiometer for Atmospheric Attenuation over Line-of-Sight Links

In this paper, the design, realization and characterization of a square loop, dual mode resonator ring (SL-DMRR) band-pass filter operating in the L-band is described. This filter is designed and constructed to be used at the output of the intermediate frequency (IF) of a k-band radiometer for measuring atmospheric attenuation of wireless links between 22-23 GHz. The proposed filter, operating at a center frequency of 1.1 GHz with bandwidth of 200 MHz has been designed and constructed on Duroid 6010 substrate (k_r = 10.2). To achieve low insertion and return losses on the filter response, the gap between the input/output stubs and the SL-DMRR has been optimized. The simulated and measured S-parameters show an excellent agreement. The filter has been tested in the radiometer scheme and 200 MHz band-pass is successfully achieved.