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Basic Knowledge Of Antennas
Apr 07, 2017

1. Antenna: (antenna) is a device that transforms the energy of high frequency current or waveguide form into electromagnetic waves and launches out the prescribed direction or restores the electromagnetic waves from a certain direction to a high-frequency current.

2. Antenna classification: 1 classification by use: can be divided into communication antenna, TV antenna, radar antenna and so on; 2. Classified according to the working frequency band: can be divided into shortwave antenna, ultra short wave antenna, microwave antenna, etc. 3) According to the directional classification: can be divided into the antenna, directional antenna and so on; 4, according to the contour classification;

Three, the omni-directional antenna, that is, in the horizontal direction of the graph of the uniform radiation, that is generally said no directivity, in the vertical direction of the graph has a certain width of the beam, in general, the smaller the width of the wave flap, the greater the gain.

Four, directional antenna, in the horizontal direction of the display of a certain angle range of radiation, which is commonly referred to as directional, in the vertical direction of the graph has a certain width of the beam, the same as the full antenna, the smaller the width of the disc, the greater the gain.

5. Gain gain is the ratio of the power density of the signal produced by the actual antenna and the ideal radiant unit in the same space at the same point as the input power is equal. It quantitatively describes the extent to which an antenna is concentrated on the input power of radiation. The gain obviously has close relation with the antenna direction graph, the direction graph main flap is narrower, the sidelobe smaller, the gain is higher. This can be used to understand the physical meaning of gain------to produce a certain size signal at a certain distance. If the ideal non-directional point source is used as the transmitting antenna, the input power is required for 100W, while the gain is G = 13 db = 20 of a directional antenna as the emitter, the input power needs only 100/20 = 5W. In other words, the gain of an antenna, on its maximum radiation direction of the effect, and the non-directional ideal point source compared to the input power magnification.

6, the antenna operating frequency range (bandwidth) Whether it is transmitting antenna or receiving antenna, they always work in a certain frequency range (bandwidth), the antenna band width has two different definitions------One is: in standing wave than the SWR ≤ 1.5 pieces, the antenna's working band width; one means that the bandwidth of the antenna gain falls within 3 decibels range. In the mobile communication system, usually according to the former definition, specifically, the antenna band width is the antenna's standing wave than the SWR 1.5 when the antenna's operating frequency range. Generally speaking, the antenna performance is different at each frequency point in the width of the working band, but the performance degradation caused by this difference is acceptable.

7. Introduction of 3G related knowledge

• What is 3G licence: A new generation of mobile communication systems with multimedia communication, such as wireless communication and Internet. Like the business license of each industry, it is necessary to have the permission of the relevant State Department to operate this business.

• Why to send 3G licences: According to the Chinese market space, to promote the competition in China telecom market; effective utilization frequency; specification segment, number segment will be from 15 to 18; Controlling the operation cost, and so on, relate to the development of China's mobile communication industry. To get a 3G licence, any operator should have five strengths: the first is the network strength. The second is the strength of capital. Third, technical strength. Fourth, the business strength. Fifth, user strength. China Telecom, Netcom's PHS system, China Mobile, Chinese unicom. So you said the wrong, not the package does not include the question, is you say the manufacturer certainly does not have this strength.