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Fish bone antenna

Fishbone antenna, also called edge antenna, is a special short wave receiving antenna. At regular intervals by the two collections online connection of a symmetric oscillator, the symmetric oscillator are received after a small capacitor collection online. At the end of the collection line, that is, the end facing the communication direction, a resistance equal to the characteristic impedance of the collection line is connected, and the other end is connected to the receiver through a feeder. Compared with the rhombus antenna, the fishbone antenna has the advantages of small sidelobe (that is, strong receiving capacity in the main lobe direction, weak receiving capacity in other directions), small interaction between the antennas and small area; Disadvantages are low efficiency, installation and use are more complex.

Yagi antenna

Also called the antenna. It is composed of several metal rods, one of which is a radiator, a long reflector behind the radiator, and a few short ones in front of the radiator. A folded half - wave oscillator is usually used in the radiator. The maximum radiation direction of the antenna is the same as the pointing direction of the guide. Yagi antenna has the advantages of simple structure, light and strong, convenient feeding; Disadvantages: narrow frequency band and poor anti-interference. Applications in ultrashort wave communication and radar.

Fan antenna

It has metal plate and metal wire type two forms. Among them, is the fan metal plate, is the fan metal wire type. This kind of antenna widens the frequency band because it increases the sectional area of the antenna. Wire sector antennas can use three, four or five metal wires. Sector antennas are used for ultrashort wave reception.

Double cone antenna

The double cone antenna consists of two cones with opposite cone tops, and feeds at the cone tops. The cone may be made of a metal surface, wire or mesh. Just like the cage antenna, the frequency band of the antenna is widened as the sectional area of the antenna increases. The double cone antenna is mainly used for ultrashort wave reception.

Parabolic antenna

A paraboloid antenna is a directional microwave antenna consisting of a paraboloid reflector and an radiator mounted on the focal point or focal axis of the paraboloid reflector. The electromagnetic wave emitted by the radiator is reflected by the paraboloid, forming a very directional beam.

Parabolic reflector made of metal with good conductivity, there are mainly the following four ways: rotating paraboloid, cylindrical paraboloid, cutting rotating paraboloid and elliptic edge paraboloid, the most commonly used is rotating paraboloid and cylindrical paraboloid. Half wave oscillator, open waveguide, slotted waveguide and so on are generally used in radiators.

The parabolic antenna has the advantages of simple structure, strong directivity and wide operating frequency band. The disadvantages are: because the radiator is located in the electric field of the parabolic reflector, the reflector has a large reaction to the radiator, and it is difficult to get a good match between the antenna and the feeder. The back radiation is larger; Poor degree of protection; High production precision. The antenna is widely used in microwave relay communication, tropospheric scatter communication, radar and television.

Horn paraboloid antenna

The horn paraboloid antenna consists of two parts: a horn and a paraboloid. The paraboloid covers the horn, and the vertex of the horn is at the focal point of the paraboloid. The horn is the radiator, it radiates electromagnetic waves to the paraboloid, the electromagnetic waves after the paraboloid reflection, focused into a narrow beam emitted. The advantages of the horn paraboloid antenna are: the reflector has no reaction to the radiator, the radiator has no shielding effect on the reflected waves, and the antenna matches well with the feeding device; The back radiation is small; High degree of protection; The operating frequency band is very wide; Simple structure. Horn paraboloid antennas are widely used in trunk relay communications.

Horn antenna

Also called Angle antenna. It is composed of a uniform waveguide and a horn waveguide with a gradually increasing cross section. Horn antenna has three forms: fan horn antenna, horn horn antenna and conical horn antenna. Horn antenna is one of the most commonly used microwave antennas, generally used as a radiator. Its advantage is wide working frequency band; The disadvantage is larger size, and for the same caliber, its directionality is not as sharp as the parabolic antenna.

Horn lens antenna

It is composed of a horn and a lens mounted on the horn aperture, so it is called a horn lens antenna. See Lens antenna for the principle of lens. This kind of antenna has a rather wide operating frequency band, and has higher protection than parabolic antenna. It is widely used in microwave trunk communication with a large number of channels.

Lens antenna

In the centimeter band, many optical principles can be applied to antennas. In optics, a spherical wave radiated by a point source at the focal point of a lens can be transformed into a plane wave by refraction through the lens. The lens antenna is made using this principle. It consists of a lens and an radiator placed at the focal point of the lens. There are two kinds of lens antenna: dielectric decelerating lens antenna and metal accelerating lens antenna. The lens is made of low - loss high - frequency medium, thick in the middle and thin around. A spherical wave emanating from a radiation source is slowed down as it passes through a dielectric lens. So the spherical wave has a long path of deceleration in the middle part of the lens, and a short path of deceleration in the periphery. As a result, a spherical wave passes through the lens and becomes a plane wave, that is, the radiation becomes oriented. A lens consists of a number of metal plates of different lengths placed in parallel. The metal plate is perpendicular to the ground, and the closer it is to the middle, the shorter it is. The waves are parallel to the metal plate

Medium propagation is accelerated. When a spherical wave from a radiation source passes through a metal lens, it is accelerated along a longer path closer to the edge of the lens and a shorter path in the middle. As a result, a spherical wave passing through a metal lens becomes a plane wave.

The lens antenna has the following advantages:

1. Side lobe and back lobe are small, so the direction diagram is better;

2. The precision of manufacturing lens is not high, so it is convenient to manufacture. Its disadvantages are low efficiency, complex structure and high price. Lens antennas are used in microwave relay communication.

Slot antenna

One or several narrow slots are opened on a large metal plate and fed with a coaxial line or waveguide. The antenna formed in this way is called a slotted antenna, also known as a slit antenna. To obtain unidirectional radiation, a cavity is made at the back of the metal plate, and the groove is fed directly by the waveguide. The slotted antenna has a simple structure and no protrusion, so it is especially suitable for high-speed aircraft. The disadvantage is that it is difficult to tune.

Dielectric antenna

Dielectric antenna is a low loss high frequency dielectric material (generally with polystyrene) made of round rod, one end of which is fed with a coaxial line or waveguide. 2 is an extension of the inner conductor of the coaxial line, forming a oscillator to excite electromagnetic waves; 3 is the coaxial line; 4 is the metal sleeve. The function of the sleeve is not only to clamp the dielectric rod, but also to reflect the electromagnetic wave, so as to ensure that the electromagnetic wave is excited by the inner conductor of the coaxial line and propagates to the free end of the dielectric rod. The advantages of dielectric antenna are small size and sharp directionality. The disadvantage is that the medium is lossy and therefore inefficient.

Periscope antenna

In microwave relay communications, antennas are often mounted on very high supports, so long feeders are needed to feed the antennas. Too long feeder will cause many difficulties, such as complex structure, high energy loss, distortion caused by energy reflection at the feeder junction, etc. To overcome these difficulties, a periscope antenna can be used, which consists of a lower mirror radiator mounted on the ground and a upper mirror reflector mounted on a bracket. The lower mirror radiator is generally a parabolic antenna, and the upper mirror reflector is a metal plate. The lower mirror radiator emits electromagnetic waves upward and reflects them off the metal plate. The advantages of periscope antenna are low energy loss, low distortion and high efficiency. It is mainly used in microwave relay communication with small capacity.

The spiral antenna

It's an antenna with a helical shape. It is composed of conductive good metal helix, usually with coaxial line feed, coaxial line of the center line and one end of the helix is connected, the outer conductor of the coaxial line and the ground metal network (or plate) is connected. The radiation direction of the helical antenna is related to the circumference of the helix. When the circumference of the helix is much smaller than a wavelength, the direction of the strongest radiation is perpendicular to the axis of the helix. When the circumference of the helix is on the order of one wavelength, the strongest radiation occurs along the axis of the helix.

Antenna tuner

An impedance matching network that connects a transmitter to an antenna, called an antenna tuner. The input impedance of the antenna varies greatly with the frequency, while the output impedance of the transmitter is certain. If the transmitter and the antenna are directly connected, when the frequency of the transmitter changes, the impedance mismatch between the transmitter and the antenna will reduce the radiation power. Using an antenna tuner, it is possible to match the impedance between the transmitter and the antenna so that the antenna has the maximum radiated power at any frequency. Antenna tuners are widely used in ground, vehicle, ship and aviation shortwave radio stations.

Log periodic antenna

It's a wide-band antenna, or a frequency independent antenna. Is a simple log-periodic antenna whose dipole lengths and intervals comply with the following relation: the τ dipole is fed by a uniform two-wire transmission line, which is switched between adjacent dipoles. This antenna has the characteristic that every characteristic at frequency F will be repeated at every frequency given by τ or f, where n is an integer. These frequencies are all equally spaced on a log bar, and the period is equal to the log of τ. Hence the name logarithmic periodic antenna. Log-periodic antennas simply periodically repeat the radiation pattern and impedance characteristics. But for such a structure, if τ is not much less than 1, its characteristic changes in a period are very small, so it is basically independent of frequency. There are many kinds of log-periodic antennas, such as log-periodic dipole antenna and monopole antenna, log-periodic resonant V-shaped antenna, log-periodic spiral antenna, etc. The most common one is log-periodic dipole antenna. These antennas are widely used in bands above short and short waves.