A millimeter and sub-millimeter wave frequency selective surface beamsplitter for geostationary orbit microwave radiometers

We report the design of three frequency selective surface (FSS) filters used on the FengYun-4 (FY-4) microwave satellite, which separate five-frequency bands in the frequency range of 50-429 GHz with the insertion loss less than 0.4 dB, and separation between adjacent channels more than 20 dB for either TE or TM incidence. Firstly, we briefly introduce the disadvantages of two types of FSS filter: waveguide-array FSS and printed FSS, which are commonly employed in the millimeter and sub-millimeter wave band. In order to meet the insertion loss requirement and specified spectral transmission response, we adopt a filter composed of two closely spaced freestanding metal plates, which contains an array of resonant ring slot elements. Computer simulation technology (CST) is used to optimize the structural dimensions of the resonant unit and interlayer separation. Numerical results show that these FSS filters exhibit transmission loss of less than 0.4 dB and separation between adjacent channels of more than 20 dB. Simulated transmission coefficients are in close agreement with the required specification, and even exceed the performance specifications.