RU2742380C1 - Laser plasma antenna - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to the field of antenna equipment and can be used for transmission and reception of electromagnetic signals in a wide range of wavelengths. Technical result is achieved due to the fact that in the laser plasma antenna instead of the gas-discharge plasma a semiconductor plasma is used, which is formed in the special waveguide semiconductor structure using a laser or light-emitting diode source, due to the power control of which the initially high resistance of the semiconductor structure can be reduced by several orders and vice versa, when the light source is switched off, it will pass into the weakly conducting state (kOhm and higher), and by connecting the light source to the waveguide structures through the optical distribution device, switching between waveguide semiconductor antennas with different configurations can be performed.

EFFECT: technical result is improvement of parameters of electromagnetic compatibility, simplification of design and addition of new functional capabilities.

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Description

Technology area

The invention relates to the field of antenna technology and can be used to emit and receive electromagnetic radiation in the radio and microwave range.

State of the art

Known laser antenna (analog), in which the emitting element is an ionized column of air created by a laser beam and similar to the emitting metal rod. The laser antenna consists of a laser, which is designed to create a laser beam, a focusing device and a circuit for connecting the signal source to the base of the ionized air column (US Patent No. 3404403, 343-700, 1968).

The disadvantage of the analogue is a high level of energy consumption for the formation and maintenance of a plasma channel of high conductivity in air, low functionality of the device, due to the well-known difficulties in obtaining plasma channels with high conductivity in atmospheric air, as well as the impossibility of prompt adjustment of the resistance of this plasma formation.

Known plasma transmitting and receiving antenna (analog), in which the emitting element is a gas-discharge plasma generated by a plasma generator. Plasma transmitting and receiving antenna consists of a plasma generator with an electrode system, which is designed to create plasma formations, a control system, decoupling and switching information signals, a power system (RF Patent, No. 2255394, H01Q 1/00, 2005).

The disadvantage of the analogue is a high level of energy consumption for the creation of a plasma formation, low functionality of the device due to the well-known difficulties in obtaining plasma formations with stable properties, as well as the need to use high-voltage power systems, which impairs the electromagnetic compatibility of such a device.

The closest in technical essence and the achieved technical result (prototype) is a known plasma antenna, which is a radiating element in the form of a plasma formation, which is placed inside a dielectric tube containing a plasma-forming gas at reduced pressure. (RF Patent No. 2014106756, H01Q 13/00, 2015).

The disadvantage of the prototype is the high level of energy consumption for the creation and maintenance of the gas-discharge plasma, the impossibility of a significant increase in the plasma concentration under conditions of low gas pressure, the low overall functionality of the device, which contains a gas-discharge tube and a high-voltage power supply unit for producing a gas-discharge plasma.

The essence of the invention

The technical objective of this invention is to reduce the weight and size parameters and power consumption of the antenna device, as well as to increase its functional characteristics by increasing the reliability, structural strength of the device and the ability to quickly control the characteristics of the antenna.

The technical result is achieved due to the fact that in the plasma antenna, instead of the gas-discharge plasma, a semiconductor plasma is used, formed in a special waveguide structure using a laser or LED radiation source. The antenna resistance and the concentration of the semiconductor plasma formed in this waveguide are regulated by increasing the power of the light source and can be reduced by several orders of magnitude, and when the light source is turned off, it will again turn into a weakly conducting state (1 kΩ and higher). To estimate the plasma concentration, n _n , created by a light source in a semiconductor structure, you can use the following formula:

n _n = N / V = P * k _g * t ₁ / (V * E _g );

here N is the number of nonequilibrium carriers in a semiconductor created due to the internal photoelectric effect upon irradiation of a semiconductor with a band gap E _g ; V is the volume of the semiconductor in the waveguide structure; P is the power of the laser (LED) light source (we assume that all the energy is absorbed in the semiconductor structure); k _g is the efficiency of electron-hole pair generation upon irradiation with a laser or LED light source; t ₁ is the characteristic lifetime of nonequilibrium carriers in a semiconductor. Due to the choice of the light source, the type of semiconductor and the geometry of the semiconductor structure, the concentration of electrons in the plasma can be varied in the range n = 10 ¹⁰ -10 ¹⁸ cm ^-3 . Since the characteristic energy of the band gap for most semiconductors is E _g ~ l eV, then for the most widespread and cheap diode lasers with λ = 975 nm, the efficiency of formation of an electron-hole pair is more than an order of magnitude higher (k _g ~ 0.8) than the efficiency of the formation of electron-ion pairs in a gas-discharge plasma; there, a significant portion of the energy is spent on the excitation of the vibrational and electronic states of gas molecules (in the case of inert gases and metal vapors, on the excitation of the electronic levels of atoms). Modern diode and fiber lasers in the 800-1000 nm range are reliable, compact, have high power and efficiency (50% and higher). For these wavelengths, light guides are available, including hollow ones with low loss and low cost.

List of figures

The essence of the invention is illustrated by the figures: FIG. 1 and FIG. 2, which shows a general diagram of a plasma antenna and schematically shows an example of a cross-section of a waveguide semiconductor structure, in which plasma is formed when irradiated from a light source, the radiation of which is delivered to the semiconductor structure through a quartz fiber.

FIG. 1 indicates: 1 - waveguide semiconductor structure, 2 - metal conductor (bus) through which ohmic contact with the semiconductor is provided, 3 - dielectric plate (board), on which semiconductor structures are attached, 4 - light source with optical distribution device; 5 - fiber-optic channels through which radiation is introduced into semiconductor waveguide structures.

FIG. 2 indicates: 6 - schematically shows laser (light-emitting diode) radiation propagating along the light guide; 7 - quartz fiber (or a cavity when a quartz capillary is used) through which radiation propagates; 8 - dielectric protective shell of quartz fiber; 2 - metal conductor through which ohmic contact with the semiconductor is made; 9 - semiconductor coating outside the quartz fiber (or the inner surface of the quartz capillary), in which semiconductor plasma appears when light radiation hits; 10 schematically shows that the surface of the fiber on which the semiconductor coating is located is specially modified to allow diffuse scattering of light radiation.

Implementation of the invention

The device consists of a system of waveguide semiconductor structures 1, fixed on a radio-transparent surface 3. Each semiconductor structure 9 has an electrical contact with a metal bus 2, to which the receiving-transmitting equipment is connected, and, in addition, is connected by a fiber-optic channel 5 to a radiation source 4, which is a laser diode or LED.

The device works as follows: when light radiation 6 hits a part of the fiber 7 (hollow waveguide structure) covered with semiconductor 9, and absorption of radiation in it, region 9 becomes conductive and can serve as a transceiver antenna. Board 3 (see Fig. 1) can accommodate a large number of semiconductor-coated light guides (as shown in Fig. 2) with characteristic diameters of 200-300 μm and different lengths (from 1 cm to several meters) of silica fiber, depending depending on the frequency of the transmitter, it is always possible to choose the structure of the optimal length to which the radiation from the laser or LED source will be transported, in order to optimize the working space, the light guides and hollow structures can be located not on a plane, but on a radio-transparent cylindrical surface, while the radiation source and other equipment will be housed inside the dielectric cylinder. The conductivity of the plasma cladding arising in the semiconductor coating of the waveguide structure will be uniquely set by the power of the light source absorbed in the semiconductor 9. Let the length of the part of the silica fiber covered with a semiconductor (for example, Si) be 10 cm, the diameter of the silica fiber 200 μm, and the thickness of the semiconductor coating 20 microns. Then, taking into account the characteristic lifetime of nonequilibrium carriers t ₁ = 100 μs, for the power of a laser diode with λ = 980 nm P = 1 W, we obtain: N _e = (P⋅k _g ⋅t ₁ / (V⋅E _g )) ≈ 4.5⋅10 ¹⁷ cm ^-3 .

Thus, for radio and microwave waves, the plasma is supercritical and a fiber in a semiconductor sheath is analogous to a metal wire. A similar result will be obtained for a hollow waveguide structure covered with a semiconductor from the inside. The high conductivity of the corresponding waveguide semiconductor structure will be maintained only while it is being irradiated, which makes it possible to connect the specified antennas only for the time of receiving or transmitting a radio signal. To reduce ohmic losses, several waveguide structures of the same length can be irradiated simultaneously. Let us consider a structure in the form of a cylindrical cavity with an inner diameter of 240 μm; then, with a semiconductor coating thickness of 20 μm, it will be identical to the fiber with a semiconductor cladding discussed above. Switching from one emitting structure to another is carried out electronically without the use of mechanical movement of the antenna nodes and high-voltage power supply systems are not used, which significantly increases the overall reliability and service life of the declared antenna device. The cost of materials (quartz fiber or capillary, semiconductor coating made of germanium) for the manufacture of the fiber and the waveguide structure is commensurate with the cost of materials required for the manufacture of fiber-optic communication lines of the same length and cross-section, the cost of LED sources with a power of 1 W for the near-infrared range is steadily decreasing with increasing reliability and resource of work. Currently, near-IR lasers and IR LEDs are widely available on the market and are available to the general consumer. Powerful IR LEDs are used to illuminate plants in greenhouses, in security and safety systems, and are used to illuminate objects when observed through night vision devices.

Claims (1)

Laser plasma antenna, including an emitting element in the form of a plasma formation, formed in a set of solid-state waveguide semiconductor structures that have electrical contact with a transceiver of electromagnetic signals, and also additionally connected via fiber-optic channels through an optical distribution device with a light source, quantum energy which is sufficient to create a photoplasma due to the internal photoelectric effect in a semiconductor structure.

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