A W-band high-gain Cassegrain antenna and design method

Abstract

The present invention discloses a W-band high-gain Cassegrain antenna, comprising a feed source, a mounting structure sleeved on the feed source, a pressure ring structure arranged on the top of the mounting structure, and an antenna main surface and an antenna sub-surface installed in the pressure ring structure. The antenna of the present invention operates in the W-band, has a high frequency and a short wavelength, can achieve a narrow beam and low side lobes, and can provide higher accuracy and resolution; the feed source adopts an integrated structural form, which is divided into a feeding rectangular waveguide, a rectangular to circular conversion waveguide and a radiating circular waveguide, avoiding the error caused by the split screw connection method, and the phase center stability and consistency of the circular radiation form are better; the antenna main surface and the sub-surface structure are constructed of resin materials with suitable shape structural parts, and then silver-plated on them, effectively reducing the surface occlusion caused by the traditional sub-surface support rod.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter wave antennas, and in particular to a W-band high-gain Cassegrain antenna and a design method thereof. Background Art

[0002] At present, millimeter wave antennas are widely used in aerospace, target detection and identification, atmospheric remote sensing, maritime satellites, radio astronomy and other fields. Antenna transmitting and receiving systems are used in millimeter wave detection systems in various fields. In order to achieve high gain and narrow beam, single transmitting antenna and double reflecting antenna are usually used. The W band belongs to the millimeter wave frequency band, which has the advantages of all-weather and high resolution, and has the inherent characteristics of short wavelength and wide bandwidth. The short wavelength makes the W band target detection equipment small in size, light in weight and good in maneuverability. These advantages are required by accurate weapons and various aircraft. At the same time, under the same caliber antenna, the short wavelength can achieve narrow beam and low side lobe, so it can provide extremely high accuracy and good resolution, and also provide detection accuracy and tracking capability at low elevation angles; the wide bandwidth can reduce the multipath effect and clutter influence, so that the system has strong anti-interference ability, and at the same time, a higher Doppler frequency shift can be obtained for low radial speed targets, thereby improving the detection and identification capabilities of slow targets; the W band Cassegrain antenna is mainly composed of a horn feed, a main reflector, a sub-reflector and a fixed bracket.

[0003] The sub-surface fixed support structure of the traditional Cassegrain antenna is generally a bracket type, which has the following main shortcomings:

[0004] First, the secondary surface support structure exerts additional pressure or stress on the secondary surface, causing deformation or damage to the secondary surface;

[0005] Second, the bracket is in the reflection area of ​​the main surface, which will increase the aperture shielding area of ​​the main surface of the antenna and reduce the overall radiation efficiency of the antenna;

[0006] The target detection system equipped with the antenna generates mechanical vibration or impact during movement, which will also cause the bracket to generate corresponding mechanical vibration and impact, resulting in deformation or displacement of the sub-surface. Summary of the invention

[0007] The present invention provides a W-band high-gain Cassegrain antenna and a design method thereof, which solve the problems raised in the above-mentioned background technology.

[0008] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a W-band high-gain Cassegrain antenna, including a feed source, a mounting structure sleeved on the feed source, a pressure ring structure arranged on the top of the mounting structure, and an antenna main surface and an antenna sub-surface installed in the pressure ring structure.

[0009] Preferably, the mounting structure consists of a left connecting member and a right connecting member, and the left connecting member and the right connecting member are fixedly connected by bolts.

[0010] Preferably, the pressure ring structure is composed of a lower washer and an upper washer, and the lower washer and the upper washer are fixedly connected by screws;

[0011] The feed source is fixed to the bottom of the lower gasket through a mounting structure.

[0012] Preferably, the main surface of the antenna includes a polycarbonate transparent member and a silver curved surface, the secondary surface of the antenna includes a polycarbonate transparent member and a silver curved surface, and both sides of the main surface of the antenna and the secondary surface of the antenna are provided with fixed limiting protrusions formed in one piece.

[0013] Preferably, the feed source comprises a standard WR rectangular waveguide structure for feeding, a conversion structure from a rectangular waveguide to a circular horn structure, and a radiating circular horn structure, and the three-section structure is integrally formed;

[0014] A through hole adapted to the feed source is provided on the main surface of the antenna.

[0015] A W-band high-gain Cassegrain antenna design method comprises the following steps:

[0016] Step S1, determining the diameter of the main surface of the Cassegrain antenna according to the requirements of the target detection system for the antenna gain and the detection system aperture;

[0017] Step S2, determining the focal diameter ratio and curve function of the main reflector of the Cassegrain antenna according to the requirements of the target detection system on the overall volume of the antenna and the system noise;

[0018] Step S3, determining the diameter and curve function of the Cassegrain antenna side surface according to the requirements of the target detection system for the antenna side lobe and half-power beam width;

[0019] Step S4, determining the elongation of the front end horn of the feed source and the horn opening angle according to the detection system and the sub-reflector of the Cassegrain antenna;

[0020] Step S5, determining the waveguide at the rear end of the Cassegrain antenna feed source according to the requirements of the target detection system for the rear end structure design;

[0021] Step S6, determining the main surface and the secondary surface structure shape, material and processing technology according to the target detection system's requirements for antenna lightweight and strength design;

[0022] Step S7, assembling the horn feed, the main reflector, the sub-reflector, and the pressure ring in the above steps, fixing the main surface and the sub-surface of the antenna with the pressure ring, fixing the feed and the main surface and the sub-surface with a fixing bracket, and fastening them with screws;

[0023] Step S8, by measuring the far-field radiation pattern, gain performance parameters and voltage standing wave ratio of the assembled Cassegrain antenna in a microwave darkroom environment, confirming that various indicators meet the requirements of the target detection system, the design of the W-band Cassegrain antenna is completed.

[0024] The beneficial effects of adopting the above technical solution are:

[0025] 1. The antenna operates in the W band with high frequency and short wavelength, which can achieve narrow beam and low sidelobe, and can provide higher accuracy and resolution.

[0026] 2. The feed source adopts an integrated structure, which is divided into a feeding rectangular waveguide, a rectangular to circular conversion waveguide and a radiating circular waveguide, avoiding the error caused by the split screw connection method, and the phase center stability and consistency of the circular radiation form are better.

[0027] 3. The main and sub-surface structures of the antenna are constructed with resin materials to form suitable structural parts, which are then silver-plated, effectively reducing the surface obstruction caused by traditional sub-surface support rods.

[0028] Fourth, use a pressure ring to assemble the main surface and the auxiliary surface, and add two limit fixing points at specific positions of the resin structural parts of the main and auxiliary surfaces to facilitate the distinction of the phase positions of the main and auxiliary surfaces to avoid installation errors, and to facilitate the installation and limit of the overall structure of the antenna and the target detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of a W-band Cassegrain antenna;

[0030] Figure 2 It is a schematic diagram of the structure of a W-band Cassegrain antenna from another perspective;

[0031] Figure 3 This is a schematic diagram of the structure after the gasket is removed;

[0032] Figure 4 This is a schematic diagram of the structure after the antenna sub-surface is reduced;

[0033] Figure 5 This is a schematic diagram of the structure after the main surface of the antenna is reduced;

[0034] Figure 6 It is the assembly drawing of the feed source and mounting structure;

[0035] Figure 7 It is a logic control diagram of a W-band high-gain Cassegrain antenna design method;

[0036] Figure 8 It is the S-parameter diagram of the W-band Cassegrain antenna;

[0037] Fig. 9 is the radiation gain diagram of the W-band Cassegrain antenna;

[0038] Fig.10 is the main radiation pattern of the W-band Cassegrain antenna;

[0039] in:

[0040] 1. Feed source; 2. Installation structure; 21. Left connecting piece; 22. Right connecting piece; 3. Pressing ring structure; 31. Lower gasket; 32. Upper gasket; 4. Antenna main surface; 5. Antenna secondary surface; 6. Fixed limit bump. DETAILED DESCRIPTION

[0041] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0042] Embodiment 1:

[0043] Specifically, Figures 1 to 6 As shown, a W-band high-gain Cassegrain antenna includes a feed source 1, a mounting structure 2 sleeved on the feed source 1, a pressure ring structure 3 arranged on the top of the mounting structure 2, and an antenna main surface 4 and an antenna sub-surface 5 installed in the pressure ring structure 3.

[0044] It should be noted that the main surface includes the polycarbonate transparent part and the silver curved surface, and the curved surface function is z=x 2 / 4 / 50.5; the secondary surface includes a polycarbonate transparent part and a silver surface, and the surface function is z 2 =8.78 2 +8.78 2 ·x 2 / 24.05 2 .

[0045] The mounting structure 2 is composed of a left connecting member 21 and a right connecting member 22, and the left connecting member 21 and the right connecting member 22 are fixedly connected by bolts.

[0046] It should be noted that holes are also provided on the tops of the left connecting member 21 and the right connecting member 22 , which are connected by screws and lower washers 31 .

[0047] The pressure ring structure 3 is composed of a lower washer 31 and an upper washer 32, and the lower washer 31 and the upper washer 32 are fixedly connected by screws;

[0048] The feed source 1 is fixed to the bottom of the lower gasket 31 through the mounting structure 2 .

[0049] It should be noted that half of the lower gasket 31 is sunken for storing the antenna main surface 4, and a plurality of holes are provided on the lower gasket 31 and the upper gasket 32 ​​for fixing together by screws, and a through groove adapted to the fixed limiting protrusion 6 is provided on the lower gasket 31;

[0050] It should be noted that during installation, the antenna main surface 4 and the antenna secondary surface 5 are placed together on the lower gasket 31, and then the upper gasket 32 ​​is closed and fixed by screws, thus completing the assembly of the antenna.

[0051] The antenna main surface 4 includes a polycarbonate transparent member and a silver curved surface, the antenna sub-surface 5 includes a polycarbonate transparent member and a silver curved surface, and both sides of the antenna main surface 4 and the antenna sub-surface 5 are provided with integrally formed fixed limiting protrusions 6.

[0052] It should be noted that the fixed limiting protrusion 6 cooperates with the through groove to ensure that the antenna main surface 4 and the antenna sub-surface 5 are installed in the target detection system and can be limited and fixed, ensuring the stability of the antenna and not being affected by mechanical vibration and impact of the target detection system, avoiding changes in antenna performance, and achieving antenna performance stability, reliability and consistency.

[0053] The feed source 1 includes a standard WR10 rectangular waveguide structure for feeding, a conversion structure from a rectangular waveguide to a circular horn structure, and a radiating circular horn structure, and the three-section structure is integrally formed.

[0054] The antenna main surface 4 is provided with a through hole adapted to the feed source 1 .

[0055] It should be noted that the phase center of the circular speaker radiation is stable and consistent, and the one-piece structure avoids the electrical performance error introduced by the split screw hard connection method.

[0056] Embodiment 2:

[0057] Specifically, Figures 7 to 10 As shown, a W-band high-gain Cassegrain antenna design method includes the following steps:

[0058] Step S1, determining the diameter of the main surface of the Cassegrain antenna according to the requirements of the target detection system for the antenna gain and the detection system aperture;

[0059] It should be noted that the maximum gain of the Cassegrain antenna in this embodiment needs to be at least 34 dB, and the radiation efficiency of the comprehensive Cassegrain antenna is generally 50%-70%. By calculating that the Cassegrain antenna with a diameter of 110 mm can meet the gain requirement of target detection, that is, the diameter of the main reflective surface of the antenna is determined to be 110 mm;

[0060] Step S2, determining the focal diameter ratio and curve function of the main reflector of the Cassegrain antenna according to the requirements of the target detection system on the overall volume of the antenna and the system noise;

[0061] It should be noted that a small focal ratio means a small depth of the reflecting surface, minimal obstruction, a small forward extension of the feed source, and low overall system noise; a large focal ratio means better off-focus performance, but the overall volume of the antenna increases. In this embodiment, the target detection system requires the overall volume of the antenna and the system noise to be as small as possible, and requires the antenna radiation beam to be deflected by -3.2° to -2.8°. The antenna is off-focus. Considering comprehensively, a focal ratio of 0.45 is selected, and the focal length of the main reflecting surface is 50 mm. Combined with the equation and diameter of the main reflecting surface determined in step 1, the main reflecting surface of the Cassegrain antenna can be determined;

[0062] Step S3, determining the diameter and curve function of the Cassegrain antenna side surface according to the requirements of the target detection system for the antenna side lobe and half-power beam width;

[0063] It should be noted that the target detection system in this embodiment requires the antenna side lobe to be less than -8dB and the beam width to be 1.8° to 2.2°. According to the Cassegrain antenna magnification M=10, the equation and diameter of the sub-reflector are obtained to determine the sub-reflector of the antenna;

[0064] Step S4, determining the elongation of the front end horn of the feed source and the horn opening angle according to the detection system and the sub-reflector of the Cassegrain antenna;

[0065] It should be noted that after the sub-reflector of the Cassegrain antenna is determined, the two foci of the sub-reflector are determined accordingly. One focus coincides with the focus of the main reflector, and the other focus coincides with the phase center of the feed source. The elongation of the front end of the feed source and the size of the horn mouth can be determined by the position of the phase center and the diameter of the sub-reflector.

[0066] In this embodiment, the target detection system uses a beam deflection of 3° for target detection. In order to form a stable phase center, the feed horn uses a circular shape for radiation. Steps S1 to S3 have determined the main reflector and sub-reflector of the antenna. One focus of the sub-reflector must coincide with the focus of the main reflector, and the other focus coincides with the phase center of the horn. Therefore, the position of the horn phase center is also determined by the focal position. Then, the elongation and the size of the horn mouth of the feed horn can be determined by the edge illumination level of the sub-reflector -8dB.

[0067] Step S5, determining the waveguide at the rear end of the Cassegrain antenna feed source according to the requirements of the target detection system for the rear end structure design;

[0068] It should be noted that, in this embodiment, the target detection system requires a rectangular feed port with low feeding loss and convenient system integration, so the feed waveguide of the antenna adopts a standard rectangular waveguide for feeding, and the radiation waveguide surface of the feed in the above step S4 is a circular waveguide, and the structure connecting the feeding waveguide and the radiation waveguide adopts a rectangular-circular transformation structure, and the three parts are integrally connected;

[0069] Step S6, determining the main surface and the secondary surface structure shape, material and processing technology according to the target detection system's requirements for antenna lightweight and strength design;

[0070] It should be noted that, in this embodiment, a resin material is used for mold opening, and then a silver plating process is performed on the resin structure to form a reflective surface, and a 20 mm pressing edge is reserved at the edge of the resin structure;

[0071] Step S7, assembling the horn feed, the main reflector, the sub-reflector, and the pressure ring in the above steps, fixing the main surface and the sub-surface of the antenna with the pressure ring, fixing the feed and the main surface and the sub-surface with a fixing bracket, and fastening them with screws;

[0072] It should be noted that, in this embodiment, in order to facilitate the installation of the antenna, a pressure ring is used to assemble the main surface and the secondary surface, and two limit fixing points are added at specific positions of the supporting structure of the main and secondary surfaces to facilitate the installation of the overall antenna structure and the target detection system.

[0073] Then assemble the horn feed, main reflector, sub-reflector, pressure ring, main surface and sub-surface of the antenna with a pressure ring designed in steps 1 to 7, and fasten the feed with screws to form a Cassegrain antenna, in which the position of the sub-surface relative to the main surface is fixed by two limit stops at specific positions of the supporting structure of the main and sub-surfaces.

[0074] Step S8, by measuring the far-field radiation pattern, gain performance parameters and voltage standing wave ratio of the assembled Cassegrain antenna in a microwave darkroom environment, confirming that various indicators meet the requirements of the target detection system, the design of the W-band Cassegrain antenna is completed.

[0075] The beneficial effects of the present invention are mainly reflected in the following aspects, which will be described in detail one by one below:

[0076] (1) Realization of high precision and high resolution

[0077] The antenna of the present invention operates in the W band, which is characterized by high frequency and short wavelength. Specifically, the frequency range of the W band is roughly between 75 and 110 GHz, and its wavelength is much shorter than that of the common microwave frequency band. Such characteristics enable the antenna to form a narrow beam and low side lobe, thereby greatly improving the directivity and anti-interference ability of the antenna system. In practical applications, this means that the antenna can provide higher measurement accuracy and resolution, which has significant advantages for application scenarios such as target detection and imaging.

[0078] For example, in radar systems, the use of W-band antennas can achieve more accurate tracking and positioning of targets, reducing false alarms and missed alarms; in the field of remote sensing imaging, high-resolution antennas can capture more detailed ground information, providing more reliable data support for geological exploration, environmental monitoring, etc.

[0079] (2) Integrated design of feed structure

[0080] The feed source of the present invention adopts an integrally formed structure, which is specifically divided into three parts: a feeding rectangular waveguide, a rectangular to circular conversion waveguide, and a radiating circular waveguide; this design effectively avoids the error problem that may be caused by the traditional split screw connection method; after long-term use, the split screw connection may cause the connection accuracy to decrease due to loosening, deformation, etc., thereby affecting the overall performance of the antenna; the one-piece design fundamentally solves this problem and ensures the stability and consistency of the feed source structure.

[0081] In addition, the circular radiation form has better phase center stability and consistency; the phase center is an important parameter in the antenna radiation field, which determines the distribution characteristics of the antenna radiation field; the circular radiation form can better ensure the stability and consistency of the phase center, thereby improving the radiation efficiency and pointing accuracy of the antenna.

[0082] (3) Application of resin materials and silver plating

[0083] The main surface and sub-surface structure of the antenna of the present invention use resin materials to construct suitable shape structural parts; the resin material has excellent properties such as light weight, high strength, and corrosion resistance, and is very suitable for the manufacture of antenna structures; at the same time, by performing silver plating on the resin structural parts, the conductivity and reflection efficiency of the antenna can be further improved.

[0084] The traditional sub-surface support rod design often causes a certain degree of obstruction to the antenna's aperture, thereby affecting the overall performance of the antenna; the present invention uses resin materials to construct the antenna main surface and sub-surface structure, and improves the conductivity through silver plating, effectively reducing the aperture obstruction problem caused by the traditional sub-surface support rod; this not only improves the gain and efficiency of the antenna, but also makes the overall structure of the antenna more compact and beautiful.

[0085] (4) Design of the pressure ring assembly and limit fixing points

[0086] The present invention adopts a pressing ring method when assembling the main surface and the secondary surface of the antenna; the pressing ring assembly can ensure the close fit and accurate alignment between the main surface and the secondary surface, thereby improving the overall rigidity and stability of the antenna; at the same time, two limiting fixing points are added at specific positions of the resin structural parts of the main and secondary surfaces.

[0087] The functions of these two limit fixing points are mainly reflected in two aspects: one is to facilitate the distinction of the phase position of the main surface and the secondary surface so as to avoid installation errors; in actual operation, the staff can use these two limit fixing points to quickly and accurately identify the positional relationship between the main surface and the secondary surface, thereby avoiding errors in the installation process; the second is to facilitate the installation and limiting of the antenna overall structure and the target detection system; through these two limit fixing points, the antenna overall structure can be firmly installed on the target detection system and ensure that its position is stable and unchanged; this design not only improves the installation efficiency and accuracy of the antenna, but also ensures the stability and reliability of the antenna during long-term use.

[0088] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A W-band high-gain Cassegrain antenna, characterized in that: The invention comprises a feed source (1), a mounting structure (2) sleeved on the feed source (1), a pressure ring structure (3) arranged on the top of the mounting structure (2), and an antenna main surface (4) and an antenna secondary surface (5) mounted in the pressure ring structure (3).

2. A W-band high-gain Cassegrain antenna according to claim 1, characterized in that: The mounting structure (2) is composed of a left connecting member (21) and a right connecting member (22), and the left connecting member (21) and the right connecting member (22) are fixedly connected by bolts.

3. A W-band high-gain Cassegrain antenna according to claim 2, characterized in that: The pressure ring structure (3) is composed of a lower washer (31) and an upper washer (32), and the lower washer (31) and the upper washer (32) are fixedly connected by screws; The feed source (1) is fixed to the bottom of the lower gasket (31) via a mounting structure (2).

4. A W-band high-gain Cassegrain antenna according to claim 2, characterized in that: The antenna main surface (4) comprises a polycarbonate transparent part and a silver curved surface, the antenna secondary surface (5) comprises a polycarbonate transparent part and a silver curved surface, and both sides of the antenna main surface (4) and the antenna secondary surface (5) are provided with integrally formed fixed limiting protrusions (6).

5. The W-band high-gain Cassegrain antenna according to claim 1, characterized in that: The feed source (1) comprises a standard WR10 rectangular waveguide structure for feeding, a conversion structure from a rectangular waveguide to a circular horn structure, and a radiating circular horn structure, and the three-section structure is integrally formed; A through hole matching the feed source (1) is provided on the main surface (4) of the antenna.

6. A W-band high-gain Cassegrain antenna design method according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step S1, determining the diameter of the main surface of the Cassegrain antenna according to the requirements of the target detection system for the antenna gain and the detection system aperture; Step S2, determining the focal diameter ratio and curve function of the main reflector of the Cassegrain antenna according to the requirements of the target detection system on the overall volume of the antenna and the system noise; Step S3, determining the diameter and curve function of the Cassegrain antenna side surface according to the requirements of the target detection system for the antenna side lobe and half-power beam width; Step S4, determining the elongation of the front end horn of the feed source and the horn opening angle according to the detection system and the sub-reflector of the Cassegrain antenna; Step S5, determining the waveguide at the rear end of the Cassegrain antenna feed source according to the requirements of the target detection system for the rear end structure design; Step S6, determining the main surface and the secondary surface structure shape, material and processing technology according to the target detection system's requirements for antenna lightweight and strength design; Step S7, assembling the horn feed, the main reflector, the sub-reflector, and the pressure ring in the above steps, fixing the main surface and the sub-surface of the antenna with the pressure ring, fixing the feed and the main surface and the sub-surface with a fixing bracket, and fastening them with screws; Step S8, by measuring the far-field radiation pattern, gain performance parameters and voltage standing wave ratio of the assembled Cassegrain antenna in a microwave darkroom environment, confirming that various indicators meet the requirements of the target detection system, the design of the W-band Cassegrain antenna is completed.

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