CN111193111B

CN111193111B - PMI foam annular antenna housing

Info

Publication number: CN111193111B
Application number: CN202010010861.3A
Authority: CN
Inventors: 李响; 谢义水; 段恒毅; 郑雪晓
Original assignee: Southwest Electronic Technology Institute No 10 Institute of Cetc
Current assignee: Southwest Electronic Technology Institute No 10 Institute of Cetc
Priority date: 2020-01-06
Filing date: 2020-01-06
Publication date: 2021-06-15
Anticipated expiration: 2040-01-06
Also published as: CN111193111A

Abstract

The invention discloses a PMI foam annular antenna housing, and aims to provide an antenna which is high in transmission efficiency, small in transmission loss, light in weight, good in shock absorption and has a filtering function. The invention is realized by the following technical scheme: the appearance of the annular antenna housing is a cylinder with a chamfer, a cavity for placing an antenna unit is arranged in the cylinder, a frequency selection surface of a periodic array structure is formed by embedding a passive resonance unit in the cylinder wall to form a spatial filter, and the filter surrounds the annular cylinder wall to form a flexible microstrip filter network; when incident electromagnetic waves pass through the filter network, the electrons are oscillated by the acting force of the electric field, so that induced current is formed on the metal surface of the filter network, part of energy of the incident electromagnetic waves is converted into kinetic energy for maintaining the oscillation state of the electrons, the other part of energy passes through the frequency selection surface and is transmitted to the antenna unit, and the PMI antenna housing carries the filter network to selectively filter the electromagnetic waves in the non-antenna working frequency band.

Description

PMI foam annular antenna housing

Technical Field

The invention relates to a structural member for protecting an antenna system from an external environment, in particular to a rigid antenna housing with filtering performance.

Background

The antenna housing is a shell-shaped multifunctional wave-transmitting structure for protecting an antenna system, can prevent the antenna system from being damaged under various severe environments such as wind, rain, ice, snow, sand, dust, solar radiation, pneumatic heating and the like on the outside in terms of mechanical performance, has good electromagnetic wave penetration characteristics on the electrical performance, and particularly has a direct relation between the wave-transmitting performance and the filtering capacity of electromagnetic waves in the working frequency band of the antenna and the performance index of the antenna.

Currently, most radomes are in the form of a protective case for an antenna system, and the inner space of the radome is used for placing functional components of the antenna. Because the antenna housing is a barrier in front of the antenna, radiation waves of the antenna can be absorbed and reflected, the free space energy distribution of the antenna is changed, the electrical performance of the antenna is influenced to a certain extent, and in order to enable the loss of electromagnetic waves penetrating through the antenna housing to be as low as possible, the traditional rigid antenna housing is usually a shell-shaped structure formed by a single medium or multiple layers of media. With the development of antenna technology and the increasing anti-interference requirement, the development direction of the antenna cover is changing from a simple wave-transparent function to a frequency-selective filtering function which can allow electromagnetic wave signals to pass and shield interference signals.

The single-medium radome is generally in a uniform plane or curved surface structure, and the single-medium radome is mainly made of a composite material formed by coating reinforcing fibers (mostly one or more of carbon fibers, glass fibers and quartz fibers) and thermosetting resin (mainly unsaturated polyester, epoxy resin, phenolic resin, vinyl resin, butadiene resin, styrene-butadiene resin and the like), and also can be a medium material with a single component. The thickness of the wall of the enclosure is related to the operating wavelength in order to reduce reflection and obtain better wave-transparent performance. Although the thin-wall structure has good electromagnetic wave transmittance, the inherent frequency is low, and the thin-wall structure is easily damaged by a mechanical environment, so that the thickness of the radome cannot obtain ideal electrical performance only according to the working wavelength, and the structural performance such as the size and the shape of the radome, environmental conditions, mechanical parameters of used materials and the like must be considered.

The multilayer dielectric radome is mostly of a multilayer structure with a sandwich of honeycomb, foamed plastic and the like sealed inside a composite material, and if a frequency selection filter network interlayer is sealed inside the multilayer dielectric radome, the radome has the functions of frequency selection and filtering and can selectively enable electromagnetic waves with target frequency to penetrate through. The multilayer radome with the filtering function disclosed in patent CN105186131B can selectively allow electromagnetic waves within the working frequency range of the antenna to pass through, and the technology is a way for realizing stealth of a fighter plane, can also be used for solving the problem of interference of environmental clutter on the antenna, and is applied to the fields of aviation and guidance. Compared with a single-medium radome, the multilayer-medium radome has more complete wave-transmitting function and more excellent mechanical property, but the manufacturing process is more complex, and the manufacturing cost is relatively higher.

Although the rigid radome using the materials such as the fiber reinforced resin has the characteristics of high strength, strong weather resistance, mature technology, wide application and the like, the rigid radome is not suitable for being manufactured into a curved surface with large curvature or a three-dimensional shape with complex shape, a thin shell structure is not beneficial to resisting severe mechanical environment, and the composite radome with a multilayer structure has the advantages of complex manufacturing process, poor processability and higher cost.

The foam housing structure allows for electrically thicker cover walls to meet structural load requirements due to the lower dielectric constant and loss tangent of the material compared to other common radome materials. The connection between the foam blocks can be glued to form a uniform integral shell, and the foam block has good electrical performance and is suitable for working at high frequency and wide frequency band. The foam plastic is often used for the inner core of a composite material multilayer antenna housing or filled in the antenna housing due to the ultralow density, low dielectric constant, high wave transmittance and excellent processing performance of the foam plastic. The conventional foam plastic is generally low in density and poor in strength, and is only applied to a small-sized radome with high electromagnetic performance requirements and low mechanical strength requirements under a general condition.

Polymethacrylimide (PMI) foam is the hardest radome core material foam plastic under the condition of equal density at present, and the mechanical parameters of the PMI foam can be directly used as the radome of an antenna circuit in some occasions with low requirements on mechanical property and weather resistance. Compared with other material radomes, the PMI radome has the advantages of low dielectric constant, low density, good processability, high temperature resistance, low price, rapid molding and the like. However, for antennas with frequency selective filtering requirements, the PMI foam antenna housing cannot be directly compounded with a filter network like fiber reinforced resin, so that at present, no PMI foam antenna housing with a filtering function for providing surface support for forming of the filter network is provided.

The frequency selective surface itself is not energy absorbing but may have a frequency selective and polarization selective effect on the passing electromagnetic waves. FSS can be generally divided into two categories: patch type and slot type. The former is the periodic expansion of the metal patch, and the latter is the periodic expansion of the slotting unit on the metal patch. When electromagnetic waves of one resonant frequency are incident on the above two unit structures, the patch type exhibits total reflection, while the slot type exhibits exactly the opposite behavior.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the PMI foam annular array radome which has the advantages of good electrical property, high transmission efficiency, small transmission loss, light weight, good shock absorption and low cost, is suitable for complex modeling and is well processed and has the frequency selection filtering function.

The above object of the present invention can be achieved by the following technical solutions: a PMI foam ring radome, comprising: the antenna housing is characterized in that the annular antenna housing is a cylinder with a chamfer in appearance, a cavity for accommodating an antenna unit is formed in the cylinder, a frequency selection surface of a periodic array structure is formed by embedding passive resonance units in the inner wall of the cylinder, the frequency selection surface forms a spatial filter, and the filter surrounds the inner wall of the annular cylinder to form a flexible microstrip filter network 2; when incident electromagnetic waves pass through the filter network, the electrons are oscillated by the acting force of an electric field, so that induced current is formed on the metal surface of the filter network, part of energy of the incident electromagnetic waves is converted into kinetic energy required for maintaining the oscillation state of the electrons, the other part of energy passes through the frequency selection surface and is transmitted to the antenna unit, and the PMI antenna housing 1 carries the filter network to selectively filter out electromagnetic waves in a non-antenna working frequency band.

Compared with the prior art, the invention has the following beneficial effects.

The electric performance is good, the transmission efficiency is high, and the transmission loss is small. The invention adopts PMI foam with uniform texture and isotropy as a main material, has lower dielectric constant and dielectric loss compared with fiber reinforced resin material, has more excellent wave-transmitting performance than a thin-wall structure, and has good electromagnetic radiation transmission performance in electricity.

The frequency selection filter function is provided. The PMI foam clamping ring 3 is embedded in the flexible filter network in the PMI foam cover 1, and the PMI foam clamping ring 3 is tightly attached to the flexible filter network, so that the flexible filter network is sealed in the PMI foam material in an accurate three-dimensional form required by design. The filtering network designed by utilizing the frequency selection mechanism enables the antenna housing to penetrate through the electromagnetic wave of a specific frequency band according to requirements, and the working performance of the antenna is greatly improved.

Light weight and good shock absorption. The PMI foam cover 1 adopts a complex three-dimensional modeling instead of a thin-wall structure, has structural strength of a PMI foam material with enough thickness, has environmental stress resistance, can resist the environmental high temperature of 200 ℃, has the density of only dozens of kilograms per cubic meter, is far lower than that of other common metal and nonmetal radome materials, takes the PMI foam as a foam plastic variety with the highest strength, has lower density, higher tensile strength and elastic modulus, does not absorb water, resists high temperature, has the structural strength capable of meeting the use requirements of various types of antennas, and has a foaming structure determining that the material has excellent shock resistance, vibration isolation and shock absorption capacity, can protect an antenna system from the influence of the external environment, prolong the service life of each part of the antenna system, and protect the surface and the position accuracy of the antenna.

Good processability and low cost. The PMI foam structural member adopted by the invention can be formed by machining a plate or a bar, can also be formed by quick foaming by utilizing a die, and is suitable for manufacturing the radome with a complex shape. The built-in flexible filter network is manufactured in a relatively simple tiled mode through a relatively simple process, and can be embedded into the radome for accurate fixation without a coating process, so that the built-in flexible filter network has the characteristics of good processability and low cost compared with most of filter radomes with the same specification.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by the following specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 1 is a schematic view of an annular radome according to an embodiment of the PMI foam radome of the present invention, and a partial cross-section is implemented on a 3PMI foam snap ring 3 to show a spatial form of a 2 flexible microstrip filter network 2 enclosed inside the radome.

Fig. 2 is a longitudinal cross-sectional cut-away view of the annular radome embodiment of fig. 1.

Fig. 3 is a schematic diagram of the inner flexible microstrip filter network 2 of the annular radome embodiment of fig. 1 in an unfolded state prior to assembly.

In the figure: PMI foam hood; 2. a flexible microstrip filter network; PMI foam cards.

The invention will now be described by way of example and with reference to the accompanying drawings.

Detailed Description

Fig. 1 and 2 are shown. In a preferred embodiment described below, a PMI foam annular radome, comprises: the hollow-pedestal cone annular radome shell is characterized in that the annular radome is a cylinder with a chamfer in appearance, a cavity for accommodating an antenna unit is arranged in the cylinder, a passive resonance unit is embedded in the inner wall of the cylinder to form a frequency selection surface of a periodic array structure, the frequency selection surface forms a spatial filter, and the filter surrounds the inner wall of the annular cylinder to form a flexible microstrip filter network 2; when incident electromagnetic waves pass through the filter network, the electrons are oscillated by the acting force of an electric field, so that induced current is formed on the metal surface of the filter network, part of energy of the incident electromagnetic waves is converted into kinetic energy required for maintaining the oscillation state of the electrons, the other part of energy passes through the frequency selection surface and is transmitted to the antenna unit, and the PMI antenna housing 1 carries the filter network to selectively filter out electromagnetic waves in a non-antenna working frequency band.

The PMI foam cover 1 can be machined and molded by a PMI foam plate, and further, can be foamed and molded rapidly by a mold. The flexible filter network 2 is closely fitted and embedded in the PMI foam cover 1 through the PMI foam snap ring 3, and the flexible filter network 2 is sealed in the PMI foam material in a precise three-dimensional form required by design. The PMI foam retainer ring 3 may be attached to the PMI foam cover 1 as necessary, or may be directly integrally formed with the PMI foam cover 1. The PMI foam cover 1 is a hollow cavity, and a circular array mounting hole is formed in an annular cylindrical barrel body of the outer outline of the PMI foam cover. The PMI foam cover 1 is formed by machining a PMI foam plate or by rapid foaming using a mold.

See fig. 3. The flexible microstrip filter network 2 is functionally a spatial filter. The flexible microstrip filter network 2 may be a metal pattern engraved on a flexible dielectric material, or may be a separately presented wire mesh. Further, the flexible microstrip filter network 2 includes, but is not limited to, a metal pattern inscribed on a flexible dielectric material, including, but not limited to, a polyimide film.

What has been described above is merely one embodiment of the present invention. It should be noted that variations and modifications can be made by those skilled in the art without departing from the principles of the present invention. Such modifications and variations are considered to be within the scope of the invention.

Claims

1. A PMI foam ring radome, comprising: a hollow column cap cone annular radome shell which takes uniform and isotropic PMI foam as main material, it is characterized in that the PMI foam cover (1) is a hollow cavity, circular array mounting holes are formed on an annular cylinder of the external outline of the PMI foam cover, the annular radome is a cylinder with a chamfer, a cavity for arranging an antenna unit is arranged in the cylinder, a frequency selection surface of a periodic array structure is formed by embedding a passive resonance unit in the cylinder wall, the frequency selection surface forms a spatial filter, the filter surrounds the inner wall of the annular cylinder to form a flexible microstrip filter network (2), the flexible microstrip filter network (2) is functionally a spatial filter, the flexible filter network (2) is tightly attached and embedded in the PMI foam cover (1) through the PMI foam snap ring (3) and is sealed in the PMI foam material in an accurate three-dimensional form; when incident electromagnetic waves pass through the filter network, the electrons are oscillated by the acting force of an electric field, so that induced current is formed on the metal surface of the filter network, part of energy of the incident electromagnetic waves is converted into kinetic energy required for maintaining the oscillation state of the electrons, the other part of energy passes through the frequency selection surface and is transmitted to the antenna unit, and the PMI antenna housing (1) carries the filter network to selectively filter out the electromagnetic waves in a non-antenna working frequency band.

2. The PMI foam annular radome of claim 1 wherein: the PMI foam cover (1) is formed by machining a PMI foam plate or by rapid foaming by using a mold.

3. The PMI foam annular radome of claim 1 wherein: the flexible microstrip filter network (2) is a metal pattern or a separately presented metal wire mesh which is carved on a flexible medium material.