The antenna design is a test of the design and physical characteristics of the antenna. The antenna can be quantitatively produced in a standard manner or tailored to a specific fit. There are many types of antennas. Different types of antennas have different demands. The most general ones are three types: Rod, Dipole, and Dish.
Antenna typeRod antenna
The rod antenna is the orientation of the transceiver. It must be used when transmitting and receiving signals from all directions. The most common antennas such as portable radios, radio antennas for taxis, etc., people and cars move at any time, so the orientation is uncertain and requires omnidirectional Sending and receiving, in addition, some rod antennas will be designed in a retractable type. The extension can enhance the transmission and reception, and the shortening is convenient for storage, such as when the car enters the low parking lot and the radio is placed in the drawer.
The receiving antenna of the model radio, the radio antenna for the vehicle, and the like are all OmnidirecTIonal rod antennas.
2. Dipole antenna and Yagi antenna
The dipole antenna begins to have partial directionality. The dipole antenna is made up of two L-shaped metals (mostly aluminum or copper) and placed in a T shape. The most common application is on the amateur radio ham. The orientation must be matched for better transceiver performance. In addition, the current model is more than the Yagi-Uda Antenna (Yagi-NdaAntenna, commonly known as: fishbone antenna) used in wireless TV (ä¸è§†, 民视, etc.) is also an advanced change of the dipole antenna, mainly adding a signal at the front end of the antenna. The waveguide is provided with a signal reflector at the rear end to enhance the azimuth sensing force. More broadly, dipole antennas and Yagi antennas are linear antennas, and other linear antennas include feeder antennas (FeedingWireAntenna) and travel wave antennas (TravelWaveAntenna).
The dipole antenna is T-shaped as shown in the figure. The length of the horizontal portion of the T-shape is 1/2 of the wavelength. If the wavelength is 12.5 cm, the length of the T-shaped horizontal portion should be 6.25 cm.
Dipole antenna (left) and folded antenna (right) in linear antenna.
Professor of Tohoku Imperial University of Japan: Yagi Hideo, and lecturer of Yagi Research Office: Yuda Shintaro jointly invented Yagi and Uda Antenna, generally referred to as Yagi Antenna.
3. Disc antenna
In terms of dish antennas, the most common one is the small ear of the past (model satellite TV). Since the signal comes from the artificial satellite outside the atmosphere, after the signal energy is returned to the earth, due to the long distance and the loss of signal energy, the ground has already been Quite weak, in order to clearly receive the already weak signal, the antenna must use a cluster-like agglomerated pattern, theoretically similar to a magnifying glass, and similar to a solar thermal power generation.
The dish type is more directional than the dipole type. In order to have the best reception, the satellite TV must be aligned with the satellite orbital position outside the atmosphere. In addition, the weak signal is still weak even if the signal is concentrated, and the satellite signal is extremely high. Frequency, at which point a mediation down-conversion procedure must be performed to convert the high-frequency signal to a lower frequency, and the weak energy signal is power amplified and enhanced before being available to the more back-end application. Because the bowl-shaped and dish-shaped antennas have extremely high transmission and reception orientation, military tracking radars and illumination radars also adopt this design, which means that the derivative deformation design also has orange peel antennas (shaped like oranges that are partially peeled off). Leather) and so on.
The ground station that communicates with the satellite on the ground also uses the dish antenna to transmit and receive signals with the satellite.
Parabolic antennas are of the same type as dish and bowl antennas, and have strong radio wave transmission and reception directionality. The so-called paraboloid means that the curved portion is curved like a parabola.
Trends in solid and mobile antennasIt is not enough to understand the basics. In recent years, the application of wireless technology has become more and more extensive. In the past, various practical wirings were expected to be de-wired through wireless, making the antenna more suitable according to the needs of various occasions. The change has improved. For example, for faster transmission rates, WiFi has begun to use MIMO (MulTIpleInputMulTIpleOutput, multiple sets of transceiver antennas) technology, MIMO is the foundation necessary to implement smart antennas, not only WiFi, including WiMAX/WiBro, 3G W - CDMA and CDMA2000 also include MIMO in subsequent predetermined standards.
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