What Is a Slot Antenna?

An antenna formed with a slot on the conductor surface is also called a slot antenna. The typical slot shape is long and approximately half a wavelength in length. The slot can be fed by a transmission line across its narrow side, or by a waveguide or a resonant cavity. At this time, a radio frequency electromagnetic field is excited on the gap, and electromagnetic waves are radiated to the space.

In recent years, flat slot antennas have received widespread attention and research due to their low profile, integration, and easy array. Slot antennas are antennas that have slots in waveguides, metal plates, coaxial lines, or resonant cavities, and electromagnetic waves radiate through the slots to external space. Its characteristics are light weight, good planar structure, easy to conform to the installation object. The aperture array amplitude distribution of the slot array antenna is easy to control, and the aperture surface utilization rate is high, and low sidelobe or very low sidelobe can be realized. At the same time, the slot antenna also has the advantages of firm structure, simple and compact, easy to process, convenient feeding, and simple installation.

Planar antennas are more and more popular due to their low profile, integration, and easy array. Slot flat antenna is a typical planar antenna, which just meets the development trend and requirements of modern wireless communication systems, and has received widespread attention and research. A slot antenna is a type of aperture antenna formed by opening a slot in a metal plate, a waveguide, a coaxial line, or a resonant cavity, and electromagnetic waves are radiated to the outer space through the slot. Its biggest feature is its low profile, with a good paperback structure, which is easy to conform to the installation object, so it is called a "thin paper" antenna. The slot array antenna is easy to control the amplitude distribution in the antenna aperture plane. The aperture plane has high utilization rate, small size and light weight, and can achieve low or very low side lobes. At the same time, the slot antenna also has the advantages of solid structure, simple and compact, easy to process, economical cost, convenient feeding, simple installation, concealability, and decoration.

There are two types of slot antennas commonly used, one is a slot on a metal flat plate-a flat slot antenna, and the other is a slot-waveguide slot antenna on a waveguide wall. In recent years, waveguide slot array antennas have been widely used due to a series of outstanding advantages such as low loss, high radiation efficiency and stable performance, while flat slot antennas have developed slowly due to large losses, low power capacity, low efficiency, and low efficiency. ^[1]

The gap on the infinitely thin and infinitely thin plane is called the ideal gap. Ideal gap

A slot array can be formed using multiple slots. There are two types of slot arrays: resonant arrays and non-resonant arrays. Each slot in the resonant array is excited in phase; each slot in a non-resonant array has a certain phase difference, so its maximum radiation direction is not in the normal direction of the array, but at an angle to the normal. The advantage of the non-resonant array is the wider frequency band. ^[1]

Slot antennas are generally used in microwave-band radar, navigation, electronic countermeasures, and communications equipment, and because they can be made into conformal structures, they are particularly suitable for high-speed aircraft. Slot antennas were used in China's first satellite. Since the 1960s, waveguide slot array antennas (including area arrays that form phase scans or frequency scans) have been rapidly developed and applied because they are easy to control the excitation of each slot to obtain a specific aperture field distribution and have a simple structure. Ultra-low sidelobe antennas (with sidelobe levels below -40 dB) were first implemented with waveguide slot arrays in the late 1960s.

Slot antennas are widely used in ground, shipborne, airborne, navigation, meteorological, port management, beacon and missile-borne radars, and mobile communications, satellite broadcasting and other fields due to their characteristics. With the development of the theory and practice of conformal antennas, the use of slot antennas will occupy a more important position. For antennas used in moving objects, the slot antenna can be said to be an ideal choice, because it can be made flush with the surface of the object, there are no raised parts, and it will not bring additional air resistance when used on the surface of a fast aircraft. Does not affect the movement of the object. Therefore, the slot antenna can be used for flying objects in outer space and fast-moving objects on the ground, water, and air.

At present, wireless communication technologies such as communication technology, wireless local area network, and point-to-point microwave communication services are developing at a rapid pace, and the demand for corresponding antennas is increasing. Such antennas generally require low cost, easy manufacturing, and easy installation and adjustment. These communication services are often carried out in cities, between groups of buildings, and in buildings. Due to the diversity and spatial separation of building structures, there are more requirements for the structure and performance of antennas, and there are more antennas. For the needs of a large modern building, dozens or even hundreds of various antennas are often installed. Antennas used for indoor installation are generally installed on the top of an indoor wall or wall. The use of small flat antennas is not only easy to install, but also easy to achieve concealment or decoration. At the same time, the use of a planar slot antenna can also easily achieve beam tunability to achieve coverage of a specific area in the room, thereby reducing electromagnetic radiation, improving radiation efficiency, and avoiding unnecessary electromagnetic damage. It can be seen that the planar slot antenna should be able to play its due role in these new communication technology fields due to its unique advantages. ^[1]