The Modified Short Backfire Antenna.
Abstract
Measurements have shown it possible to increase the gain of the short backfire antenna significantly in different ways: (1) By increasing the size of the reflectors. (2) By placing extra reflectors in multiples of a half wavelength from the surface wave reflector. (3) By placing a quarter-wave ring in front of the surface of the wave reflector. The surface of the ring is perpendicular to the reflector and the ring has the same diameter as the reflector. The distance between the ring and the reflector giving maximum gain depends on the size and the number of the reflectors. The choice of parameters (size of reflectors) was based on numerical calculations using a theory developed by Drago Neilsen and Pontoppidan at the contracting laboratory. Measurements have shown a decrease in impedance bandwidth product. The levels of the backward lobe and the side lobes are increased, too, but the levels are kept at an acceptable height due to the influence of the quarter-wave ring. The beamwidths in E- and H-plane tend to be equal with increasing gain. This is an advantage if circular polarization is wanted. The modified short backfire antenna has a higher gain than any other backfire antenna of the same size (same length and diameter of the surface wave reflector). The antenna is easy to construct. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 17, 1971
- Accession Number
- AD0732506
Entities
People
- Finn A. Hass
Organizations
- Technical University of Denmark