Yagi antenna is really easy to be used. It has good directivity, and has a high gain compared with the dipole antenna. It is particularly good to use it to measure the long-distance communications. If yagi wifi antenna is matched with the elevation and azimuth rotation control device, it can be arbitrary to contact with the spacecraft, including the direction of the radio, this feeling cannot be gotten from the upright antenna.
Composition of the Typical Yagi Antenna
Typical Yagi antenna should have three pairs of oscillators, and the entire structure is the shape of Chinese "wang". The connected sub or main oscillator is connected with the feeder, ranking among the three pairs of oscillators. reflector is slightly longer than the active transducer, it is at the side of the active transducer, plays the role of weakening the radio wave coming from this direction or a radio wave emitted from the antenna; wave director is shorter than oscillators which is located on the other side of the active transducer, it can enhance the wave coming from one direction, or a radio wave emitted in this direction. There may be many directors, and each length is shorter than its neighboring and close to the active oscillator. Usually the five-element Yagi wifi antenna (Three directors, a reflector and an active oscillator) is sufficient. Each director and reflector is made of a metal rod. No matter how many "units", all oscillators are at certain intervals parallel fixed in a beam. The beam is also made of a metallic material.
Operating Principles of Yagi Antenna
Director is slightly shorter than a half wavelength, the main oscillator is equal to half the wavelength, the reflector is slightly longer than the one-half wavelength, the two transducer spacing is about a quarter of wavelength. In this case, the director of the induced signal was capacitive; the electromagnetic waves of the director induction will radiate to the master oscillator, radiation signal after a quarter-wavelength away from the air, it lags behind in directly 90 degree, reach the main oscillator signal exactly offsets the front due to "advanced", both of the same phase, so the signal superposition, has been strengthened. The reflector is slightly longer than the half wavelength, is inductive, the current lags 90 °, another lag of 90 ° plus radiation to the process, the main oscillator, with just a difference of 180 ° from the direction of the reflector is directly applied to the main oscillator signal, played offset. One direction is strengthened and the other direction is weakened, there will be a strong directivity.
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