![]() ![]() As a result, such a collinear antenna radiates at a low angle to the horizon and has a gain greater than that of a half-wave dipole. In addition, a quarter-wave transmission line segment transforms a short circuit at one of its ends into an infinite impedance at the other, and all linear segments, as it were, “see themselves as” isolated from each other. However, only linear segments take part in the radiation of such an antenna, since a two-wire line does not radiate, and these segments are all in-phase and their radiation is summed up. In other words, the total electrical length of the collinear antenna spike has not changed. Trust me, the high frequency current will not notice anything. Then we, leaving the segments with the same phase of the current, fold the segments with the opposite phase in half, obtaining from them quarter-wave segments of a two-wire transmission line. The radiation pattern of such a spike consist of many lobes at different angles to the horizon. The high-frequency current is distributed along it in such a way that in adjacent segments of length λ/2 it flows in an opposite phase. Let's say we have a vertical wire spike with a length that is a multiple of half the wavelength. In fairness, it should be noted that in the classical version a horizontal symmetrical antenna is viewed, but we will simplify the model to the “lamer” level. On this example, you can understand on the fingers how it turns out. One of them - using quarter-wave transmission line segments - is a classic version of the Franklin antenna. There are several ways to form such an antenna array. A collinear antenna is an antenna array of in-phase half-wave dipoles with serial excitation, elongated in a single line, hence the name - collinear. It has been known for a long time and is often called the Marconi-Franklin antenna. The vertical collinear antenna is an omnidirectional high gain antenna.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2023
Categories |