Antenna and feeder matching analysis

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What is meant by matching? Simply put, the feed line terminal connected load impedance ZL is equal to the feed line characteristic impedance Z0, called the feed line terminal is matched connection. Matching, there is only the incident wave on the feed line to the terminal load, and no reflected wave generated by the terminal load, so when the antenna as the terminal load, matching can ensure that the antenna to obtain all the signal power. As shown in the figure below, when the antenna impedance is 50 ohm, and 50 ohm cable is matched, and when the antenna impedance is 80 ohm, and 50 ohm cable is not matched.

If the antenna oscillator diameter is thicker, the antenna input impedance with the frequency change is smaller, easy and feed line to keep matching, then the antenna working frequency range is wider. Conversely, it is narrower.

In practice, the input impedance of the antenna will be affected by the surrounding objects. In order to make the feed line and antenna good match, in the erection of the antenna also need to measure, appropriate to adjust the local structure of the antenna, or add matching device.

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