Low frequency analysis of large dual reflector compact ranges

Large dual, doubly curved reflector compact ranges are typically designed for antenna and payload testing of spacecraft antennas and/or transponder units. The applicable frequency bands are therefore at or above the L-Band. In the recent past several customer requests were raised related to UHF frequency operations at a dual reflector compact range. In order to analyze these effects at UHF frequencies, detailed 3D simulations with a precise CAD model incl. all serrated edges and a realistic feedhorn model utilizing a state-of-the-art Multilevel Fast Multimode Method (MLFMM) were carried out. Simulations at 500 and 700 MHz demonstrate clearly the possibility to utilize a large dual, doubly curved reflector range at UHF frequencies, too. However, the optimum test zone centre is not longer fixed at one position and independent from the frequency. At UHF frequencies it moves along the down-range coordinate. The lower the frequency, the closer the aperture field in front of the main-reflector. In case the AUT turntable, which indicates the practical implementation of the test zone centre, can not be displaced to the new optimum position, the test zone (quiet zone) may be located at the quasi far-field zone. In principle the results of are achieved for the dual reflector range, too.