RU2571582C2 - Deflection system for controlling plane electromagnetic wave - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: deflection system for controlling a plane electromagnetic wave based on a microwave periodic structure consists of n layers of ferrielectric material divided by n-1 layers of a linear dielectric material. In order to generate an electric field gradient in the ferrielectric plate in a direction perpendicular to the direction of propagation of the plane wave, the ferrielectric layers are coated on both sides by microwave radiation-transparent electrodes.

EFFECT: low control voltage value and induced electromagnetic losses.

6 cl, 3 dwg

Description

The invention relates to the field of telecommunication technologies, and more particularly to devices for controlling electromagnetic waves, and can find application in radar and similar devices.

Devices for controlling directed electromagnetic waves, that is, beams, are usually constructed on the basis of the principle of a phased array antenna. In the theory of antennas, a phased array is usually called a set of antennas in which the relative phase shift in each antenna is set so that the radiation pattern of the entire set of antennas has a maximum in the desired direction, and the reception or emission of signals from undesirable directions is suppressed. A typical phased array consists of a series of emitters and phase shifters, usually semiconductor, ferrite or ferroelectric. In US patent No. 4333901 [1] describes the device and the principle of operation of such a device with a radically simplified design. This device basically has several ferroelectric ceramic plates coated with conductive films through which a control voltage is applied. Individual sections of the ferroelectric layers can be considered as phase shifters, in which the magnitude of the phase shift can change with a change in the dielectric constant of the ferroelectric layer due to the control voltage applied to the conductive films. Subsequently, on the basis of such a technical solution, a number of devices were patented that operate on a similar principle and have a similar design (see, for example, US patent No. 5309166 [2]).

The prototype diagram [1] is presented in figure 1. The device is a phased array for controlling electromagnetic waves, which includes a first layer 16 of active (ferroelectric) material with parallel inner surface 18 and outer surface 20, as well as a second layer 22 of active (ferroelectric) material with parallel inner layer 24 and outer surface 26 and the second layer is adjacent to the first. An electrically conductive grounded surface 28 made of tin and indium oxide is located between the first layer 16 and the second layer 22 and is in electrical contact with the first inner surface 18 and the second inner surface 24. The first row of parallel electrodes 30, 32, 34, each of which made in the form of a thin strip of tin and indium oxide, placed on the first outer surface 20, the second row of parallel electrodes 36, 38, 40, each of which is also made in the form of a thin strip of tin and indium oxide false similarly to the second outer surface 26, but perpendicularly to the first row electrodes. The first antireflection (matching) coating 42 is placed on the first outer surface 20, the second antireflection (matching) coating 44 is placed on the outer surface 26.

The prototype [1] and analogues based on the same principle have the following disadvantages:

- high level of control voltage;

- large insertion loss.

The problem to which the claimed invention is directed is to develop an improved design of a deflecting system that provides a reduction in the magnitude of the control voltage and the introduced electromagnetic losses.

The technical result is achieved by developing a deflecting system for controlling an electromagnetic plane wave based on a microwave periodic structure, while the deflecting system consists of n layers of ferroelectric material with electrodes placed on both sides of each layer, separated by n + 1 layers of linear dielectric material, where n> 1 is a positive integer, and the deflecting system is configured to supply a control voltage to the electrodes with the formation of a gradient and the electric field in the ferroelectric plate in a direction perpendicular to the direction of propagation of the plane wave.

In other words, the claimed invention, as well as the prototype [1], is based on the use of ferroelectric materials, however, the principle of its operation is based on the effect of the propagation of slow waves in a periodic structure.

For a better understanding of the essence of the claimed invention, the following is a detailed description with the use of graphic materials.

Figure 1 Prototype (US patent No. 4333901).

Figure 2 A deflecting system based on a periodic ferroelectric structure with matching layers.

Figure 3 A deflecting system based on a periodic ferroelectric structure with air gaps.

One of the implemented variants of the inventive system is presented in Figure 2. The main function of the system is the deviation of the incident plane electromagnetic wave generated outside the proposed system. The proposed design consists of matching layers (201 and 202) and a series of ferroelectric layers (203, 204, 205), separated by layers of linear dielectric material (206, 207). For certain parameters of linear and ferroelectric layers (permittivity and electric length), this design has the properties of a microwave periodic structure: the presence of so-called “slow waves” (phase velocity in a periodic structure is slower than in a regular line), band-pass and band-block frequency characteristics. Moreover, the phase velocity of the signals (for frequencies corresponding to the bandwidth frequency response of the structure) propagating in the proposed system depends on the difference in the characteristic impedances of neighboring layers (ferroelectric and linear dielectric). The wave resistance of the ferroelectric layer, determined by the dielectric constant, can change under the action of an applied electric field between the layers of electrodes 208, 209, 210 and the grounded layers 211, 212, 213 located on the surface of the ferroelectric layers. To reduce insertion loss in the system, layers 208-213 must be made of a material with high resistance and transparent to microwaves; the execution of these surfaces in the form of a set of strips is allowed. Thus, a gradient of the electric field is formed in the ferroelectric plate in the direction perpendicular to the direction of wave propagation, which leads to a change in the phase velocity of the wave in various parts of the system and, as a result, leads to a deviation of the phase front of the wave. It should be noted that a decrease in the dielectric constant of ferroelectric ceramics leads to a shift in the passband of the proposed structure to higher frequencies. To achieve maximum efficiency of the deviation of the wave from the deflector, the operating frequency should be chosen near the right cut-off frequency of the passband. The maximum tuning frequency is determined from the condition that the right and left cut-off frequencies of the pass-band for the structure coincide, both without control voltage and under control voltage.

A preferred embodiment of the proposed deflector structure is shown schematically in FIG. 3. The main difference from the previously mentioned option is the absence of matching layers and the use of air gaps instead of linear dielectric layers. Such a design should have the following parameters: the electric length of the ferroelectric layers 203, 204, 205 and air gaps 301, 302 corresponds to ¼ and ½ λt, respectively, where λt is the wavelength in the corresponding medium at the operating frequency. In order to supply a control voltage, electrodes transparent to microwaves 208, 209, 210, 211, 212, 213 are applied to both sides of the ferroelectric layers 203, 204, 205. Compared with the first option, the proposed structure of the deflector is more attractive from the point of view of simplifying manufacturing (lack of matching and linear dielectric layers), reduce losses and control voltage.

In the practical implementation of the inventive deflecting system, the elements 201, 202, 203, 204, 205, 206, 207 are manufactured using traditional ceramic technology. A linear dielectric is used to make matching layers 201, 202 and layers 206, 207 separating ferroelectric layers. Active layers 203, 204, 205 are made from ferroelectric materials. The layers 208, 209, 210, 211, 212, 213 of the electrodes must have a thickness t << δ (where t is the thickness, δ is the depth of the skin layer) to reduce signal loss, therefore, thin film deposition technology (magnetron sputtering) is used for their manufacture , salt-gel technology or laser ablation). The layers 208, 209, 210, 211, 212, 213 of the electrodes should be placed on both sides of the active layers 203, 204, 205. After applying the layer of electrodes, the strip structure of the electrodes is formed, for example, using photolithography. As the material of the electrodes 208, 209, 210, 211, 212, 213, in particular, ZnO, TiO ₂ , TaN and solid solutions of Si, Ti and Ce are used.

The invention can be used in the field of telecommunications and radar scanning systems.

Claims (6)

1. A deflecting system for controlling a plane electromagnetic wave based on a microwave periodic structure, consisting of n layers of a ferroelectric material, separated by n-1 layers of a linear dielectric, where n> 1 is a positive number, and the ferroelectric layers are coated on both sides transparent for microwave radiation by electrodes to form an electric field gradient in a ferroelectric plate in a direction perpendicular to the plane wave propagation direction. 2. The system according to claim 1, characterized in that the electrode layers on both sides of the ferroelectric layers are made in the form of strips. 3. The system according to claim 1, characterized in that the layers of the linear dielectric are made in the form of air gaps. 4. The system according to claim 3, characterized in that the electric length of the air gap is equal to λ / 4 and the electric length of the ferroelectric layer is equal to λ / 2. 5. The system according to claim 1, characterized in that the linear dielectric layers are made of ceramic. 6. The system according to claim 5, characterized in that at least two layers of a linear dielectric are configured to match the wave resistance of the deflecting system with the wave resistance of the surrounding space.

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