| 摘要 |
A phase control mechanism for broadcast RF transmission using pairs of transmission lines feeding a dual port antenna continuously monitors phase error between either the signals carried by the two lines or the physical heights of the bottom elbows where the two lines turn upward to ascend a tower. The mechanism minimizes phase error by altering the propagation time in one or both lines. Causes for such phase errors include climatic conditions such as unmatched heating by sunlight and cooling by wind. Effects of such phase errors include beam tilt and reduction in effective broadcasting range. Systems for which such phase control is applicable include broadband transmission systems carrying one or more channels of television and radiating them using a single antenna on a tower.
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