| 摘要 |
PURPOSE:To obtain a low-cost antenna reduced at its performance deterioration by setting up a circular polarized wave generator enabled to save the parts of a wave guide, constitute a blocking only by the center part of a parabola and improve its voltage standing wave ratio. CONSTITUTION:Since the output end of a down converter 6 has a normal square waveguide, a pyramid horn 9 can be directly connected to the output end and a converter can be made unnecessary. Straight polarized waves from the pyramid horn 9 are converted into circular polarized waves by the circular polarized wave generator 10, reflected to the parabolic antenna 1 and radiated to the space. The circular polarized wave generator 10 is constituted by a glid 14, a dielectric plate 12 and a metallic plate 13. The direction of the glid 14 is inclined from the polarized wave direction of incident wave E from the pyramid horn 9 by 45 deg.. The thickness of the dielectric plate 12 is 2t near the center axis of the horn and (t) at the periphery. The neighborhood of the horn center axis contributes to the standing wave ratio of the pyramid horn 9, and if it is defined that 5=lambda/ 8.gammaxsi<1/2> (xsigamma: specific inductive capacity), radio waves returned from the glid 14 and the metallic plate 13 to the pyramid horn 9 are phase-reversed at the neighborhood, so that the voltage standing wave ratio is improved. |
