The Coaxial Cavity Antenna Implementation in the N-Port (Four and Eight) Feed Configuration

摘要

A coaxial cavity antenna, developed and patented by Raytheon, exhibits low dispersion over wide field-of-view (FOV) and multiple octaves or Ultra Wideband. This antenna is typically fabricated as a four point feed design, but an N-port, and specifically an eight-port, design is described. Both Finite Element modeled data and test data is presented on 1 to 2 GHz and 2 to 4 GHz versions of the four- and eight-port coaxial cavity antenna, as shown in figure 1. This antenna has essentially a flat phase and amplitude response over a +/- 60 degree FOV. The antenna design is scaleable over multiple frequency ranges, and antennas have been built covering frequency ranges from 20 MHz to as high as 44 GHz, with bandwidths on the order of four and one-half octaves. Multiple polarizations are still possible, but different mode responses are exhibited for each four-port versus eight-port feed design. The eight-port design is compared to the four-port with respect to the natural polarizations radiated in each case. Natural base polarizations are still dual linear, but coincident modal polarizations can be made the same or different depending on the application. The case of a monopulse tracking feed is illustrated with the presented data. Performance differences are noted for the four- versus eight-port feed designs.