The development of antenna is closely linked with the development of radio technology. All kinds of antennas were designed to meet the practical requirements put forward at that time.
The first antenna is H R. Hertz in 1887 to verify the British J C. Maxwell put forward the theory that electromagnetic waves exist and designed the ">transmitting antenna, which is two spheres close together, and uses the spark discharge between the two spheres to generate electromagnetic waves. The receiving antenna uses a ring antenna. In 1901, G. Marconi of Italy was the first to use a large antenna to achieve ocean communication. The first practical T-shaped transmission antenna uses 50 sagging copper wires, with the top connected to the horizontal horizontal line, and hung on two support towers.
In the early days, the main application of radio was long wave trans ocean communication, and the development of antenna focused on the long wave band. Long wave antenna is characterized by large carrying power, huge structure and low efficiency.
After 1925, radio broadcasting became popular, and omnidirectional medium wave antenna gradually developed. The earliest medium wave antennas were T-shaped, inverted L-shaped and umbrella shaped antennas. In order to overcome the over amplitude modulation distortion caused by the sky wave interference fading, the guyed and self-supporting tower antennas are designed. The height of this vertical antenna can not only be very high, which can concentrate the energy of the vertical polarization wave more to radiate around along the direction of the ground, but also reduce the radiation of the horizontal polarization wave at high elevation, weaken the influence of sky wave fading, and expand the effective coverage of ground waves.
Around 1925, it was found that the ionospheric reflection could be used for short wave long-distance communication, and the required power could be greatly reduced, so the directional short wave antenna was developed rapidly. Various types of horizontal antennas and antenna arrays are designed, including in-phase horizontal antenna, double wave antenna and broadband traveling wave diamond antenna.
Although the wave channel antenna (commonly known as Yagi antenna) was proposed by Yagi and Yuda in Japan around 1927, it was not until 40 years later that Yagi antenna was developed and applied with the solution of oscillation sources and the development of ultra short wave communication. As early as 1888, H R. Hertz once proposed the idea of parabolic reflector antenna, which was not really put into practice until 1937. The horn antenna came into being in the 1930s with the development of waveguide technology. During the Second World War, microwave antennas developed rapidly due to the development of radar technology. Parabolic antenna, lens antenna, dielectric rod antenna, slotted antenna and so on all made progress to varying degrees in this period. Among them, the development of paraboloid antenna is particularly outstanding, including the design of comparator, beam scanning and generation of shaped pattern.
After the end of the Second World War, with the development of microwave relay communication, ultrashort wave mobile radio, television broadcasting and radio astronomy, and the rise of scattering communication, monopulse radar and synthetic aperture technologies, broadband bat wing television transmitting antenna, microwave relay periscope antenna, quasi non frequency varying logarithmic periodic antenna and equiangular spiral antenna appeared one after another. In the late 1950s, after the emergence of artificial satellites and intercontinental missiles, because of the urgency of arms competition and the need of electronic countermeasures, in addition to the high parameter performance of antennas such as high gain, high resolution, fast scanning and accurate tracking, it also requires antennas to have circular polarization, broadband, multi-function and conformal mounting to meet the needs of aircraft. From the 1960s to the early 1970s, the main achievements of antenna development include: ① the construction and improvement of large earth station antenna: including Cassegrain antenna, feed source, correction of main and secondary reflector, application of beam waveguide and other technologies; ② Phased array: due to the improvement of phase shifter, the application of electronic computer, the requirements of remote alert rapid response and simultaneous search and tracking of multiple targets, it has been greatly developed; ③ Many typical large radio telescopes. In addition, small aperture antennas, such as loading antennas, retro reflector antennas, active antennas and antennas on aircraft (including aircraft, rockets, missiles, satellites) also made important development in this period.
In the 1970s, with the development of radio technology in the direction of millimeter wave, submillimeter wave and light wave, the frequency multiplexing, orthogonal polarization, near-field measurement, multi beam and defocus bias of microstrip antenna, surface wave antenna, conformal array and reflector antenna, as well as the signal processing, synthetic aperture and adaptive antenna of array antenna, were also valued and developed accordingly.
In the 1980s, in addition to continuing to explore and improve the type and performance of antennas in the pioneering wave bands, a lot of research work gradually turned to the research on the transmission and reception of transient electromagnetic waves, the scattering and inverse scattering of targets, the solution of electromagnetic field boundary value problems, and the radiation and scattering of antennas in special media.
The transmission mode converter converts the radio frequency current or electromagnetic wave of the guided wave mode into the space electromagnetic wave of the diffuse wave mode, and the transmission mode converter of the inverse transformation. The so-called transmitting antenna used for the mode conversion of guided wave to diffused wave, and the so-called receiving antenna I used for the mode conversion of diffused wave to guided wave, except that the power bearing capacity and voltage bearing capacity of the transmitting antenna are far greater than those of the receiving antenna, both can be used interchangeably, and the basic characteristic parameters of the antenna remain unchanged. This is called the reciprocity theorem. Another important role of the antenna is to concentrate the energy of electromagnetic wave, that is, to concentrate the energy in the transmitting direction when acting as a transmitting antenna, while reducing the energy in other directions; When used as a receiving antenna, more energy can be intercepted from the incoming waves in the receiving direction, while the input energy can be reduced by phase cancellation for the incoming waves in other directions. This is the directivity of the antenna. Compared with non directional antenna, the increase of energy concentration is called antenna gain. The extended meaning of antenna directivity is the negative gain (attenuation) in the non communication direction, which can be used to describe another related performance index of the antenna, namely the side lobe (interference) radiation suppression of the transmitting antenna or the wave interference suppression in the non communication direction of the receiving antenna.
It can be divided into transmitting antenna and receiving antenna according to the working nature. It can be divided into communication antenna, broadcast antenna, radar antenna and so on. It can also be divided into long wave antenna, medium wave antenna, short wave antenna. The above classification methods all have the disadvantage of one species and two genera. A more perfect scientific classification method is to divide the antenna into two categories: wire antenna and plane antenna according to the principle and structural characteristics of the antenna. The wire antenna is composed of wires whose wire diameter is much smaller than the wavelength. The length of the wire is much larger than the cross section and can be compared with the wavelength. This kind of structure is difficult to realize in the microwave band, and its gain is far lower than that of the plane antenna. It is generally used for long, medium, short wave and ultra short wave. The reflector of the antenna is composed of a whole metal plate or wire grid. Its area is much larger than the square of wavelength, and its gain is much higher than that of wire antenna. This structure is difficult to achieve in the long, medium and short wave bands. The support of wire antenna is generally pole type or tower type, and the support of surface antenna is tower type or table type.
