DRGH Antenna With Improved Gain and Beamwidth Performance

Double-ridge guide horn (DRGH) antennas are widely used in antenna and EMC testing facilities as feed antennas and gain transfer standards. Increasing the low-frequency gain to obtain a more constant 3 and 10 dB beamwidth, over the operating frequency band of 1-18 GHz, will result in a more uniform illumination of the devices under test. In this communication, the ridge profiles of a conventional DRGH antenna with dimensions complying with the requirements of MIL-STD-461F are modified to produce a more constant beamwidth, especially from 3 GHz upward. The width of the ridges is tapered along the axial length of the DRGH to increase effective radiating aperture and reduce the beamwidth, at lower frequencies. An accurate numerical model was developed of the conventional 1-18 GHz DRGH antenna and modified ridges were implemented. The radiation properties of a prototype antenna were measured in a compact antenna range. Simulated and measured results are presented for the modified DRGH antenna.