RU2786687C1 - Narrow-band waveguide antenna - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio engineering, in particular to the technology of ultra-high frequencies, and can be used in radar systems of circular scanning. The result is achieved by the fact that a narrow-band waveguide antenna consists of an expanding horn and a linear waveguide antenna array located in a carrier housing with a radio-transparent fairing installed on the side of the radiating opening of the horn, while the linear antenna array is implemented in the form of an N-channel waveguide distribution system of parallel type based on T-shaped waveguide bridge connections in the E-plane, directional couplers with T-slot coupling elements and waveguide E-tees, the outputs of which are connected to the inputs of N identical emitters, placed in an expanding horn in the longitudinal direction, and each of the emitters contains a 90° waveguide bend in the H-plane and a waveguide horn, and the design of the linear antenna array is made in a prefabricated milled housing located under the expanding horn parallel to its lower wall.

EFFECT: expansion of the operating frequency band, the elimination of the frequency dependence of the angular position of the main beam of the radiation pattern without increasing the dimensions of the antenna and ensuring a low level of side lobes.

1 cl, 5 dwg

Description

The invention relates to the radio engineering industry, in particular to the technique of microwave frequencies (SHF), and can be used in all-round radar systems (RLS) with high resolution in azimuth and range.

A well-known narrow-beam antenna of the 3-cm range, developed by NPF "Mikran" (see Buyanov Yu.I., Dotsenko V.V. and others. A narrow-beam antenna of the 3-cm range for a surveillance radar with high range resolution // Materials of the 10th International Conference "Microwave Engineering and Telecommunication Technologies", Sevastopol, September 13-17, 2010, pp. 538-539), which is formed from eight subarrays in the form of linear vibrator antenna arrays with serial excitation, connected to the inputs of an 8-channel common-mode adder, forming a falling amplitude distribution in the horizontal plane. The adder and sublattices are made on the basis of an asymmetric strip line. To form a radiation pattern (DN) in the vertical plane, the subarrays are placed in a longitudinal horn. The main parameters of the antenna: operating frequency band: 9280-9580 MHz; beam width at minus 3 dB: 1° in the horizontal plane, 27° in the vertical plane; maximum sidelobe level (UBL): minus 20 dB; opening length: 1.84 m. The disadvantages of this construction are the need for deterioration of the UBL to enable the constructive implementation of the device, a high level of insertion loss, as well as limiting the allowable power supplied to the antenna by a value of the order of 10-20 W, which is due to the design of the adder and sublattices antennas based on an unbalanced strip line.

The closest analogue, singled out as a prototype of the claimed device, is an antenna system manufactured by Terma (Denmark), consisting of an expanding horn and a linear waveguide antenna array placed in it in the form of a rectangular waveguide with variable-slope slots cut along a narrow wall (21 feet High Gain Antenna System [Electronic resource] Access mode: https://manualzz.com/download/35330648 Access date: 06/10/2020). The expanding horn and the waveguide-slotted grating are located in a carrier housing with a radio-transparent fairing mounted on the side of the radiating opening of the horn. This design makes it possible to form a pattern with a maximum UBL of minus 28 dB, a width of minus 3 dB in the horizontal and vertical planes of no more than 0.36° and 11°, respectively, and a gain of at least 38 dB. Operating frequency band 9140-9500 MHz. The maximum level of average power supplied to the antenna is 600 W. Antenna dimensions: 6560×410×637 mm.

However, the disadvantage of this technical solution is the deviation of the angular position of the main beam of the RP with a change in the operating frequency (about 1 ° / 100 MHz), which is caused by sequential excitation of slots of a linear waveguide-slot grating and leads to significant restrictions in terms of expanding the bandwidth of the emitted / received signal to improve resolution radar capabilities in range. In addition, phase distribution errors in the radiating aperture, associated with technological difficulties in ensuring the required dimensional accuracy of the expanding horn structure with an antenna length of the order of 200λ (where λ is the wavelength), will lead to the problematic implementation of the claimed UBL.

The task to be solved by the claimed invention is to create a broadband narrowly directed waveguide antenna without frequency dependence of the angular position of the main beam of the DN with a high gain, low UBL and external dimensions not exceeding the dimensions of the antenna selected as a prototype.

The problem is solved due to the fact that a narrowly directed waveguide antenna consists of an expanding horn and a linear antenna array with parallel excitation, implemented as an N-channel waveguide distribution system based on T-shaped waveguide bridge connections in the Ε-plane, directional couplers with T - slotted coupling elements and waveguide E-tees, the outputs of which are connected to the inputs of N identical radiators placed in an expanding horn in the longitudinal direction, each of the radiators contains a waveguide bend of 90 ° in the Η-plane and a waveguide horn, and the design of a linear antenna array made in a prefabricated milled housing, located under the expanding horn parallel to its bottom wall. The N-channel waveguide distribution system is made in the form of an M-channel divider, which forms a falling amplitude distribution, each of the outputs of which is connected to the input of an N:M in-phase equal-amplitude power divider, which together with the emitters forms an (N:M)-element sublattice. (N, Μ, N:M are integers). In this case, the prefabricated milled body is formed from separate sections interconnected by means of phasing waveguides.

The essence of the invention is explained with the help of graphic material, where:

- in Fig. 1 shows a general view of a narrowly directed waveguide antenna, including an N-channel waveguide distribution system (1) of a linear antenna array, an expanding horn (2), radiators (3) of a linear antenna array placed in the horn (2) in the longitudinal direction and a radio-transparent fairing (4 ), which is installed on the side of the radiating opening of the horn (2), the antenna input (5) is shown conventionally.

- in Fig. Figure 2 shows an exploded view of the design of a linear antenna array made in a prefabricated milled housing, where the following reference designations are introduced: 1 - N-channel waveguide distribution system, 3 - emitter, 5 - input, 6 - waveguide horn, 7 - waveguide bend by 90° in the H-plane, 8 - T-shaped waveguide bridge connection in the E-plane, 9 - waveguide E-tee, 10 - waveguide directional coupler with a T-slot coupler, 11 - ballast load, 12 - 90° waveguide bend in E-planes, 13 - section transformer, 14 - drainage holes.

- in Fig. 3 shows the design of a narrowly directed waveguide antenna, consisting of a distribution system (1) and emitters (3) of a linear antenna array, an expanding horn (2), a radio-transparent fairing (4), a polarization filter (15), the antenna input is indicated by position (5) in view A To ensure the required rigidity and minimize the mass, the supporting structure is made on the principle of an aircraft spar wing using such power elements as a frame (16), a stringer (17) and a spar (18), adapted to the shape of the antenna. This approach, combined with the modern possibilities of strength calculations in CAD, makes it possible to implement a strong and lightweight design that ensures the antenna's performance during rotation at a speed of 1 rev/s and wind speeds up to 30 m/s. To level the antenna, an adjustment platform (19) is provided in the upper part of the structure. The connecting flange (20) of the antenna is shown in view A.

- in Fig. 4 shows the general and exploded views of the construction of a 256-element linear antenna array made in a prefabricated milled housing, which is formed from four sections (21) interconnected by means of phasing waveguides (22). Also in FIG. 4, the following reference designations are introduced: 23 - 64-channel power divider, 24 - 1:4 power divider, 25 - 4-element subarray. Ballast loads and fasteners are not shown in the exploded view.

- in Fig. Figure 5 shows the characteristics of a narrowly directed waveguide antenna based on a 256-element linear antenna array. The calculated and measured normalized antenna patterns in the E- and Η-planes are shown on the upper graph, the calculated frequency responses of VSWR and efficiency (curves 1 and 2, respectively) are shown on the lower graph.

To explain the principle of operation of a narrowly directed waveguide antenna, consider the purpose of its main elements.

An N-channel waveguide distribution system of a parallel type (1), which excites N identical radiators (3), is designed to form a falling amplitude distribution that provides low UBL with the required beam width and antenna opening size in the horizontal plane. The distribution system (1) and radiators (3) form a linear antenna array with parallel excitation, which makes it possible to eliminate the dependence of the angular position of the main beam of the AP on the operating frequency. The construction of a distribution system based on waveguide elements provides in-phase broadband excitation of emitters (3) with minimal insertion loss.

The distribution system (1) includes Μ binary power dividers Ν:Μ (24), the input of each of which is connected to the corresponding output of the M-channel divider (23), which forms a falling amplitude distribution in the horizontal plane. The M-channel divider (23) is made on the basis of T-shaped waveguide bridge connections in the E-plane (8) and directional couplers with T-slot couplers (10). The power divider N:M (24) contains (N:M)-1 non-decoupled waveguide E-tees (9) and together with emitters (3) forms an (N:M)-element sublattice (25). The use of sublattices (25) makes it possible to simplify the design and improve the weight and size characteristics of the N-channel waveguide distribution system (1). In this case, the periodic amplitude modulation of the field distribution leads to some deterioration in the LDL of the RP due to the appearance of quantization lobes. In a particular case, a 256-element linear antenna array of 64 subarrays (see Fig. 4), when forming a falling amplitude distribution that provides a theoretical UBL of no more than minus 33 dB with a DN width of no more than 0.35 °, has quantization side lobes at levels minus 32 dB and minus 49 dB.

Emitters (3) are made in the form of waveguide horns (6) of linear polarization consistent with the surrounding space, connected to the outputs of the distribution system (1) through a 90° waveguide bend in the H-plane (7), and are designed to excite an expanding horn (2) , which forms a pattern in the vertical plane. The polarization filter (15), optionally used as part of the antenna, makes it possible to operate in the circular polarization mode. To protect against external influencing factors, a linear antenna array, an expanding horn (2) and a polarizing filter (15) are placed in a carrier housing with a radio-transparent fairing (4) made on the basis of composite materials and installed on the side of the radiating opening of the horn (2). The antenna input is made in the form of a rectangular waveguide of standard section.

A distinctive feature of the design of a narrowly directed waveguide antenna is that the linear antenna array is made in a prefabricated milled housing, which consists of two halves - aluminum plates, mated along the line of zero currents of the waveguide topology. At the same time, the body of the linear array is located under the expanding horn parallel to its lower wall, which makes it possible to provide the required characteristics of the antenna without increasing its dimensions. In addition, the prefabricated milled body is structurally divided into separate sections (21), interconnected by means of phasing waveguides (22). These technical solutions make it possible to provide low UBL by increasing the accuracy of milling the waveguide topology of the sections and the possibility of adjusting the electrical lengths of the channels of the distribution system (1) in order to minimize phase distribution errors associated with technological difficulties in manufacturing the expanding horn structure (2) with the necessary tolerances with a significant opening length antennas (100…200λ).

At the applicant enterprise, within the framework of R & D for the creation of an airfield surveillance radar, design documentation for a narrowly directed waveguide antenna based on a 256-element linear array was developed, prototype and first serial samples were manufactured, a prototype radar successfully passed acceptance and certification tests, which confirms the possibility of practical implementation of the proposed inventions. The antenna has the following characteristics: operating frequency band: 9000-9450 MHz; beam width at minus 3 dB, not more than: 0.35° in the horizontal plane, 11° in the vertical plane; maximum sidelobe level: minus 25 dB; realized gain factor not less than 38 dB; antenna dimensions: no more than the dimensions of the prototype.

Thus, the technical result achieved by the implementation of the proposed invention is the expansion of the operating frequency band, ensuring a low level of side lobes and eliminating the frequency dependence of the angular position of the main beam of the AP without increasing the dimensions of the antenna, which improves the resolution of the radar in range due to the possibility of expanding bands of the emitted/received signal.

Claims (1)

A narrowly directed waveguide antenna consisting of an expanding horn and a linear waveguide antenna array located in a carrier housing with a radio-transparent fairing installed on the side of the radiating opening of the horn, while the linear antenna array is implemented in the form of an N-channel waveguide distribution system of a parallel type based on T-shaped waveguide bridge connections in the E-plane, directional couplers with T-slot coupling elements and waveguide E-tees, the outputs of which are connected to the inputs of N identical radiators placed in an expanding horn in the longitudinal direction, each of the radiators containing a waveguide bend of 90 ° in H-planes and a waveguide horn, and the design of the linear antenna array is made in a prefabricated milled housing located under the expanding horn parallel to its lower wall, characterized in that the N-channel waveguide distribution system is made in the form of an M-channel divider, forming its decreasing amplitude distribution, each of the outputs of which is connected to the input of an in-phase equal-amplitude power divider N:M, which together with the emitters forms an (N:M)-element sublattice, and the prefabricated milled body is formed from separate sections interconnected by means of phasing waveguides.

Images