CN108666747B - Low-profile array antenna - Google Patents

Abstract

The invention discloses a broadband low-profile tightly-coupled array antenna applied to a wireless communication system, which comprises a metal cavity, a power distribution network, an annular feed structure, a capacitive loading loop unit and an SMA coaxial adapter. The metal cavity surrounds the array antenna and is used for realizing the conformal installation of the antenna and the aircraft and the improvement of a radiation pattern. The invention effectively reduces the profile height of the antenna by introducing the annular feed structure and the capacitive loop loading unit, and reasonably designs the array spacing of the antenna array by the mutual coupling effect between the antenna units, thereby expanding the working frequency band and realizing the low profile, wide band and common type design of the array antenna. Compared with the prior art, the invention has the advantages of simple structure, common molding, easy processing, low section, wide working frequency band and the like. Therefore, it is applicable to a wireless communication system of a wide frequency band.

Description

A low profile array antenna

technical field

The invention belongs to the field of wireless communication, and in particular relates to a low-profile, wide-band, and generic array antenna design method, which can be applied to modern wireless communication equipment.

Background technique

With the development of wireless communication systems, antennas, as an important part of them, have also encountered unprecedented development and challenges. As the front-end antenna of receiving and transmitting communication systems, the requirements in missile-borne wireless communication systems are getting higher and higher. Therefore, the development of an antenna with miniaturized, broadband, low profile, stable omnidirectional radiation pattern and gain characteristics has received more and more attention.

At present, many articles on the design of vertically polarized antennas are available in open journals, such as Weihua Tan et al. For a sleeve antenna with vertical polarization and omnidirectional radiation characteristics, the antenna height is 0.25λ (λ is the wavelength corresponding to the center operating frequency), which is a standard selected for the design of traditional monopole antennas. This scheme adopts the traditional monopole antenna design method, and the antenna height satisfies a quarter wavelength. However, according to such an antenna design method, the height of the antenna will be too high, and the purpose of conformalization of the missile-borne antenna cannot be achieved; An antenna with low profile characteristics is proposed. Its antenna height is only 0.18λ (λ is the wavelength corresponding to the central operating frequency). Although the antenna has a low profile height, its bandwidth is only 27.1%. The radiator scheme reduces the antenna height. However, this solution cannot meet the requirement of simultaneous operation of multiple frequency bands, and its cross-polarization on the azimuth plane is only -10dB.

In order to solve the above problems, the present invention provides a broadband antenna design method based on the tight coupling effect, which can well overcome the above deficiencies, and provides a conformal array with low profile, wide frequency band, and better pattern performance. Antenna Design Method.

SUMMARY OF THE INVENTION

Object of the invention: Aiming at the shortcomings of high profile, narrow working bandwidth and deterioration of radiation pattern performance in the prior art, the purpose of the present invention is to provide a low profile common type array antenna design method with enhanced bandwidth. First of all, the present invention adopts a semi-circular annular feeding structure and a capacitive loading loop ring, which effectively reduces the height of the antenna section; secondly, the present invention utilizes the mutual coupling effect between adjacent units reasonably and improves the impedance matching in the working frequency band Features, expand the working frequency band of the antenna array. At the same time, the invention installs the 1×6 one-dimensional tightly coupled circular array in the metal cavity, which effectively realizes the conformal installation between the antenna and the aircraft and the improvement of the radiation pattern of the azimuth plane.

Technical solutions:

A low-profile array antenna based on strong coupling bandwidth enhancement, comprising: a metal cavity, a dielectric substrate, a metal foil layer, an inner metal sheet, an outer metal sheet, and a metal body; wherein,

The metal cavity is a single-layer thin-walled concave disk-shaped structure with a small hole in the center; the dielectric substrate is located in the inner layer of the concave surface of the metal cavity and is fixed on the bottom plate of the metal cavity near the center; the other side of the dielectric substrate A metal foil layer is printed, and the pattern shape of the metal foil layer is a symmetrical shape of radiation, specifically N branch terminals radiating continuously from the center to the outside;

The number of the outer metal sheets is N, which are fixed on the dielectric substrate. The shape of each outer metal sheet includes three folding planes. The upper planes of each outer metal sheet are separated from each other and arranged in a circle with a gap. Ring pattern, the plane where the ring pattern is located is parallel to the adjoining plane of the dielectric substrate; the other two planes are adjacent to the upper plane of the dielectric substrate, forming a structure in the shape of a through hole;

The number of the inner-layer metal sheets is N, each inner-layer metal sheet is located inside the outer-layer metal sheet, and is fixed in the through-hole structure between the outer-layer metal sheet and the dielectric substrate, and the inner-layer metal sheet is composed of three folding planes. Composition, the three corresponding folding planes of the inner metal sheet and the outer metal sheet are parallel, and the size is smaller than that of the outer metal sheet, each inner metal sheet and each outer metal sheet are separated from each other, and each inner metal sheet is separated from each other. The sheets are evenly distributed along the circumferential direction, and their distribution centers coincide with the outer metal sheets;

The metal body penetrates the dielectric substrate, connects the inner layer metal sheet and the metal cavity, so that the two are in a conductive state, and the number of N is greater than 3 and less than 20.

For the array antenna, the coupling strength between the antenna elements is controlled by controlling the distance D between the antenna elements, and the capacitive reactance component formed by the electromagnetic coupling effect cancels the inductive reactance component between the antenna element and the reflector, thereby realizing the frequency band of the array antenna. widen. At the same time, due to the tight coupling effect, the working frequency band of the array antenna will be extended to the low frequency, so as to realize the broadband and miniaturization design of the array antenna.

Fundamental:

The most common form of a tightly coupled array antenna is an array composed of antenna elements with strong coupling, that is, with strong coupling between adjacent antenna elements. The tight coupling between the antenna elements allows the electromagnetic field to propagate between adjacent elements. This antenna array can achieve a current distribution similar to that of the current sheet antenna array, thereby extending the resonant current length and enhancing the operating bandwidth. The tight coupling technique actually widens the operating bandwidth of the antenna by extending its lowest cutoff frequency. However, for a linearly arranged finite array, due to the different positions of each array unit in the array, the electromagnetic environment of each array unit is also different, and the coupling degree between the units is also different. Especially for the unit at the edge of the array, due to the truncation of the array unit, the coupling effect of the edge antenna unit is deteriorated, the matching is misaligned, and the standing wave is deteriorated. In order to improve this situation, resistive truncation is usually used, but this method will reduce the efficiency of the antenna and increase the size. Therefore, the present invention adopts the method of annular tightly coupled array to make each unit end connected, thereby ensuring the same coupling condition of each unit, avoiding the truncation effect of the finite array, and realizing the broadband design of the antenna.

The present invention has the following beneficial effects:

1. The present invention introduces a loop feed unit and a capacitive loading loop loop, so that the antenna section height is less than 0.19λ (λ is the wavelength corresponding to the center operating frequency), the impedance bandwidth is greater than 38.7% and the cross-polarization is less than -20dB.

2. The difference of the present invention is that the coupling strength between adjacent antenna units is controlled by the tight coupling design between the adjacent antenna units, and the capacitive reactance component formed by the electromagnetic coupling effect is used to cancel the inductive reactance component between the antenna unit and the reflector, so as to achieve the desired effect. The frequency band of the array antenna is broadened, and the truncation effect of the one-dimensional tightly coupled array antenna is avoided. Through the mutual coupling effect between adjacent antennas, not only the distance between the antenna elements can be reduced, but also the electromagnetic coupling between the antenna elements can be enhanced, so that the operating frequency is shifted to the low frequency, thereby reducing the size of the array antenna, and effectively improving the impedance matching and working bandwidth.

3. The present invention further introduces a metal cavity, realizes the common installation between the antenna and the aircraft, and effectively improves the radiation pattern of the antenna on the azimuth plane.

Description of drawings

The present invention has 6 drawings in total

Fig. 1 is the overall structure diagram of the array antenna of the present invention;

Fig. 2 is the structure diagram of the antenna unit of the present invention;

Fig. 3 is the top view of the power division network of the present invention;

Fig. 4 is the return loss of the present invention;

Fig. 5 is the E-plane pattern of the present invention at center frequency 2.4GHz;

Fig. 6 is the H-plane pattern of the present invention at center frequency 2.4GHz;

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and in detail below with reference to the accompanying drawings in the embodiments of the present invention.

Referring to Fig. 1, the formed tightly coupled array antenna has a metal cavity height Hg, adjacent antenna elements are separated by D, the height is H, the antenna elements are surrounded by the origin as the center, and the radius is R _in to form a tightly coupled common type array antenna.

A low-profile array antenna includes a metal cavity 101, a dielectric substrate 301, a metal foil layer 302, an inner metal sheet 201, an outer metal sheet 202, and a metal body 204; wherein,

The metal cavity 101 is a single-layer thin-walled concave disk-shaped structure with a small hole in the center; the dielectric substrate 301 is located in the inner layer of the concave surface of the metal cavity 101 and is fixed on the bottom plate of the metal cavity 101 near the center; A metal foil layer 302 is printed on the other side of the substrate 301, and the pattern shape of the metal foil layer 302 is a radially optional symmetrical shape, specifically N branch terminals continuously radiating outward from the center;

The number of the outer metal sheets 202 is N, which are fixed on the dielectric substrate 301. The outer shape of each outer metal sheet 202 includes three folding planes, and the upper planes of each outer metal sheet 202 are separated from each other and arranged into one A ring pattern with a gap, the plane where the ring pattern is located is parallel to the adjoining plane of the dielectric substrate 301; the other two planes are adjacent to the upper plane of the dielectric substrate 301, forming a structure in the shape of a through hole;

The number of the inner-layer metal sheets 201 is N, and each inner-layer metal sheet 201 is located inside the outer-layer metal sheet 202 and fixed in the through-hole structure between the outer-layer metal sheet 202 and the dielectric substrate 301 . 201 is composed of three folding planes, the inner metal sheet 201 is parallel to the three corresponding folding planes of the outer metal sheet 202, and the size is smaller than the outer metal sheet 202, and each inner metal sheet 201 and each outer metal sheet are parallel. 202 are separated from each other, and each inner layer metal sheet 201 is evenly distributed along the circumferential direction, and its distribution center coincides with each outer layer metal sheet 202;

The metal body 204 penetrates the dielectric substrate 301 and connects the inner layer metal sheet 201 and the metal cavity 101, so that the two are in a conductive state,

The number of N is greater than 3 and less than 20.

There are metal pads 203 on the connection part between the inner-layer metal sheet 201 and the dielectric substrate 301, the metal pads 203 are plated on the dielectric substrate 301, and each inner-layer metal sheet 201 is welded to the metal by welding. The disk 203 is welded as a whole, and the metal body 204 and the metal pad 203 are connected to each other.

When N is an even number, the shape of the metal foil layer 302 is a combination of multiple "herringbone" patterns;

The distance H between the outer metal sheet 202 and the dielectric substrate 301 is between 0.1 and 0.3 times the working wavelength, and the edge height Hg of the metal cavity 101 is greater than H and less than three times H.

The geometric center spacing of the adjacent outer metal sheets 202 is D is 0.3λ-0.55λ, where λ is the center frequency of the working frequency band. The dielectric substrate 301 is an F4B plate with a dielectric constant of 2.2. The above-mentioned low-profile antenna also includes an SMA connector 303 . The SMA connector 303 is located in the center of the metal cavity 101 . The inner core of the SMA connector 303 penetrates the central hole of the metal cavity 101 and is connected to the metal foil layer 302 . The conductors are connected to the lower surface metal coating surface of the dielectric substrate 301 .

Example 1: (A certain aircraft is used as an inquiry and response antenna)

The first step: the metal cavity is made of metal aluminum with relatively low density, the array antenna unit is made of metal copper, and the power division network is made of F4B dielectric substrate.

The second step: According to the mechanical performance requirements, electrical performance requirements and space size constraints of the antenna, the tight coupling design of the annular distributed antenna element and the conformal design of the metal cavity are carried out.

The height of the antenna is about 0.19 times of the working wavelength of the inquiry and response antenna, and the working bandwidth of the optimized array antenna is about 38.7%.

The third step is to prepare a 1×6 one-dimensional tightly coupled circular area array by annular distributed arrangement.

The array antenna unit is selected by bending a metal copper plate with a thickness of 0.4mm, and 6 sets of antenna units can be prepared at one time, and the antenna units are installed on the dielectric substrate in a circular distribution manner to form a 1×6 one-dimensional tightly coupled circular shape face array. And the power division network printed on the dielectric substrate is used to complete the feeding of the array antenna.

Step 4: Prepare the metal cavity by means of CNC machining.

According to the structural characteristics of the array antenna and the installation size requirements of the aircraft, the metal cavity is machine-milled and cut to complete the preparation of the metal cavity.

The fifth step: according to the structural requirements of the common type antenna, install the array antenna in the metal cavity to form a common type array antenna.

Example 2: (A certain aircraft is used as a navigation antenna)

The first step: the metal cavity is made of metal aluminum with relatively low density, the array antenna is made of metal copper, and the power division network is made of F4B dielectric substrate.

The second step: According to the mechanical performance requirements, electrical performance requirements and space size constraints of the antenna, the tight coupling design of the annular distributed antenna element and the conformal design of the metal cavity are carried out.

Adopting the ring-shaped distributed tightly coupled design, the operating bandwidth of the optimized array antenna reaches 38.7%, which is 29.1% higher than that of a single antenna unit.

The third step is to prepare a 1×6 one-dimensional tightly coupled circular area array by annular distributed arrangement.

The array antenna unit is selected by bending a metal copper plate with a thickness of 0.4mm, and 6 sets of antenna units can be prepared at one time, and the antenna units are installed on the dielectric substrate in a circular distribution manner to form a 1×6 one-dimensional tightly coupled circular shape face array. And the power division network printed on the dielectric substrate is used to complete the feeding of the array antenna.

Step 4: Prepare the metal cavity by means of CNC machine tool processing.

According to the structural characteristics of the array antenna and the installation size requirements of the aircraft, the metal cavity is machine-milled and cut to complete the preparation of the metal cavity.

The fifth step: according to the structural requirements of the common type antenna, install the array antenna in the metal cavity to form a common type array antenna.

The effect of the present invention can be further described in combination with the simulation results:

1. Simulation content

1.1 Use the commercial simulation software HFSS_15.0 to simulate and calculate the port return loss of the array antenna used in the above embodiment, and the result is shown in FIG. 4 .

1.2 utilize the commercial simulation software HFSS_15.0 to carry out simulation calculation to the far-field pattern of the array antenna adopted in the above-mentioned embodiment, the result is as shown in Figure 5, wherein: Figure 5 is the dual polarized antenna unit adopted in the example at 2.4GHz vertical plane normalized radiation pattern.

1.3 utilize the commercial simulation software HFSS_15.0 to carry out simulation calculation to the far-field pattern of the array antenna adopted in the above-mentioned embodiment, the result is as shown in Figure 6, wherein: Figure 6 is the dual polarized antenna unit adopted in the example at 2.4GHz horizontal plane normalized radiation pattern.

2. Simulation results

Referring to FIG. 4 , with the return loss less than -10dB as the standard, the operating frequency band of the array antenna selected in the embodiment is 1.79GHz-2.65GHz, and the common relative bandwidth is 39%.

Referring to FIG. 5 , it is the far-field radiation pattern of the horizontal plane of the array antenna selected in the embodiment at 2.4 GHz. The pattern seen from the figure is a conical omnidirectional radiation pattern, and the cross-polarization is lower than the main pole. at least 20dB.

Referring to FIG. 6 , the far-field radiation pattern of the horizontal plane of the array antenna selected in the embodiment at 2.4 GHz is an omnidirectional pattern, and the cross polarization is at least 19 dB lower than the main polarization.

Claims (7)

1. A low-profile array antenna, characterized in that it comprises a metal cavity (101), a dielectric substrate (301), a metal foil layer (302), an inner metal sheet (201), and an outer metal sheet (202) , the metal body (204); wherein, The metal cavity (101) is a single-layer thin-walled concave disk-shaped structure with a small hole in the center; the dielectric substrate (301) is located in the inner layer of the concave surface of the metal cavity (101), and is fixed on the metal cavity (101). 101) The bottom plate is close to the center position; the other side of the dielectric substrate (301) is printed with a metal foil layer (302), and the pattern shape of the metal foil layer (302) is a radial and rotationally symmetrical shape, specifically N continuous radiation from the center branch terminal; The number of the outer metal sheets (202) is N, which are fixed on the dielectric substrate (301). The outer shape of each outer metal sheet (202) includes three folding planes. The planes are separated from each other and are arranged in a ring pattern with a gap, the plane where the ring pattern is located is parallel to the adjoining plane of the dielectric substrate (301); the remaining two planes are adjacent to the upper plane of the dielectric substrate (301), forming a through hole shape structure; The number of the inner-layer metal sheets (201) is N, and each inner-layer metal sheet (201) is located inside the outer-layer metal sheet (202) and fixed between the outer-layer metal sheet (202) and the dielectric substrate (301) In the through hole structure, the inner metal sheet (201) consists of three folding planes, the inner metal sheet (201) is parallel to the three corresponding folding planes of the outer metal sheet (202), and the size is smaller than that of the outer metal sheet (202), each inner-layer metal sheet (201) and each outer-layer metal sheet (202) are separated from each other, and the inner-layer metal sheets (201) are uniformly distributed along the circumferential direction, and the distribution center thereof is connected to each outer-layer metal sheet The sheets (202) overlap; The metal body (204) penetrates the dielectric substrate (301), connects the inner layer metal sheet (201) and the metal cavity (101), so that the two are in a conductive state, The number of N is greater than 3 and less than 20. 2. A low-profile array antenna as claimed in claim 1, characterized in that: There are metal pads (203) on the connection portion between the inner layer metal sheet (201) and the dielectric substrate (301), the metal pads (203) are plated on the dielectric substrate (301), and each inner layer The metal sheet (201) is integrally welded with the metal pad (203) in a welding manner, and the metal body (204) and the metal pad (203) are connected to each other. 3. A low-profile array antenna according to claim 1 or 2, characterized in that, when N is an even number, the shape of the metal foil layer (302) is a combination of a plurality of "herringbone"-shaped patterns. 4. A low-profile array antenna according to claim 3, characterized in that the distance H between the outer metal sheet (202) and the dielectric substrate (301) is between 0.1 and 0.3 times the working wavelength, and the metal cavity The edge height Hg of the body (101) is greater than H and less than three times H. 5. A low-profile array antenna as claimed in claim 4, wherein the geometric center spacing D of adjacent outer metal sheets (202) is 0.3λ-0.55λ, and λ is the wavelength corresponding to the center operating frequency . 6. The low-profile array antenna according to claim 5, wherein the dielectric substrate (301) is an F4B plate with a dielectric constant of 2.2. 7. A low-profile array antenna according to claim 6, characterized in that, further comprising an SMA connector (303), wherein the SMA connector (303) is located in the center of the metal cavity (101), and the SMA connector ( 303) The inner core penetrates the central hole of the metal cavity (101) and is connected to the metal foil layer (302), and the outer conductor of the SMA connector (303) is connected to the lower surface metal cladding surface of the dielectric substrate (301).

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