A compact monopole planar end-fire array antenna with parasitic decoupling

Abstract

The invention discloses a parasitic decoupled compact monopole planar end-fire array antenna, which relates to the field of array antennas. The antenna mainly comprises: a parasitic loaded metal cut-angle disc (1); a parasitic short-circuit column (2); a parasitic monopole (3); a radiation loaded metal cut-angle disc (4); a radiation short-circuit column (5); a radiation monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9). By loading the cut-angle metal disc, the profile height of the planar end-fire array is further reduced. A copper plating with a special structure is designed to eliminate the edge effect produced by the finite-size irregular dielectric floor and improve the unit-active radiation pattern. A parasitic decoupling structure is introduced to eliminate the strong coupling effect of adjacent ports, improve port isolation, and increase the actual gain of the end-fire array antenna after optimization.

Description

Technical Field

[0001] The invention relates to an array antenna, in particular to a parasitic decoupled compact monopole planar end-fire enhanced array antenna. Background Art

[0002] With the development of electronic science and technology, radio has gradually become the mainstream mode of mobile communication. Antennas, as signal transmitting / receiving terminals of wireless communication systems, play an important and irreplaceable role. A single antenna is subject to the radiation principle, and its gain and scanning angle width are small, and it is gradually unable to meet the high index requirements of specific high gain, high directivity, strong anti-interference ability, etc. in practical applications. If multiple unit antennas of the same or different structures are arranged in a certain pattern on the radiation aperture surface or radiation space, the collection of these antennas can work together to meet higher parameter requirements. Such a collection of antennas is called an array antenna.

[0003] In array antennas, end-fire arrays are usually used in various high-speed scanning carriers because of their higher directivity coefficient and stronger end-fire scanning performance. It is well known that once the unit structure in the array antenna is determined, the directivity coefficient of the array antenna can be further improved by reducing the unit spacing. However, this improvement is not endless, because the unit structure size cannot be infinitely small, and too small unit spacing will lead to strong unit mutual coupling, making the optimization process counterproductive. Therefore, in the actual end-fire enhancement, it is necessary to consider the specific unit structure and coupling conditions to design a compact end-fire array that meets the requirements.

[0004] In some studies, researchers often confuse actual gain with directivity coefficient and over-optimize excitation, resulting in some excitations with optimized directivity coefficient having poor actual gain. Compact array antenna architectures often appear in these problems. This is because compact array antennas usually have strong adjacent port isolation, which causes most of the power to be directly reflected after input, and only a small part of the power is used for antenna radiation. In order to improve the radiation effect of compact planar end-fire array antennas, it is necessary to study the relationship between the decoupling structure and the port scattering parameters from the perspective of decoupling.

[0005] A. Ramachandran et al. introduced a defective ground decoupling structure for a dual-unit dual-band MIMO antenna system in A four-port MIMO antenna using concentric square-ring patches loaded with csrr for high isolation. It can be seen that the disadvantage of defective ground treatment is that some structures loaded into the defective ground have specific resonance characteristics, which may have opposite radiation characteristics at the same operating frequency, or the resonance point of the radiation characteristic is different from the original array resonance point, thus affecting the radiation characteristics of the antenna unit. Therefore, when introducing a defective ground structure, it is necessary to weigh its advantages and disadvantages and introduce a decoupling structure under the condition that the requirements are met.

[0006] Wu Keli et al. proposed a four-element symmetric parasitic resonant decoupling structure based on dummy element loading in A decoupling technique for four-element symmetric arrays with reactively loaded dummy element. The disadvantages of parasitic structure decoupling are also obvious. First, the introduced parasitic structure is similar to the original radiation structure and occupies a large array space. Second, the introduced parasitic structure requires multiple simulations to select the optimal parameter index, so as to achieve the decoupling purpose without affecting the original bandwidth matching.

[0007] Although the concept of end-fire arrays has been proposed a long time ago, there is still a certain gap in the research on compact end-fire arrays. The design difficulties of end-fire arrays mainly include the following points: 1. Compact end-fire arrays require unit antennas to have small physical dimensions and low profile heights, which brings difficulty to the design; 2. Compact end-fire arrays usually have extremely strong coupling effects, which brings difficulties to subsequent end-fire matching; 3. A finite size compact end-fire array will have a strong edge effect at the edge units, causing its radiation pattern to be distorted. Summary of the invention

[0008] In view of the above technical background, the present invention proposes a parasitic decoupled compact monopole planar end-fire array antenna, which improves the port scattering parameters and radiation characteristics of the compact planar end-fire array by introducing a parasitic decoupling structure, thereby achieving the effect of planar end-fire enhancement. The antenna array overcomes the disadvantages of extremely low isolation and radiation efficiency of adjacent ports in the traditional compact monopole planar end-fire array, and achieves end-fire radiation enhancement while ensuring a low profile of the antenna array.

[0009] The radiating monopole antenna unit that constitutes the array resonates at 3GHz, with a resonant bandwidth of 210MHz, and is a narrowband end-fire antenna. The monopole antenna unit uses metal loading of the top cut-angle disc to further reduce the unit profile height. The antenna unit profile height is about 0.085 (the wavelength corresponding to the center frequency). In order to eliminate the current gathered by the top-loaded disc during the main mode radiation, a metal column is used to short-circuit the cut-angle metal disc and the finite common floor. The antenna unit adopts a bottom-fed feeding method, with a coaxial interface reserved, and the feeding end can also be processed by microstrip printing. In a compact planar array environment, due to the limited common floor area, the edge units of the array will have edge radiation effects, and the corresponding radiation characteristics and reflection characteristics will be affected, and the radiation pattern and standing wave ratio of the active unit will be deteriorated to a certain extent. The common floor is specially copper-plated, and a layer of copper plating of a special shape is loaded on the top of a dielectric plate of a certain thickness. The reflection of the top disc and the copper-plated structure is used to improve the edge effect of the finite compact planar end-fire array. In order to meet the radiation characteristics such as low profile and end-fire, please refer to Figure 1 The basic structure of the antenna unit includes: a radiating loaded metal cut-angle disc (4); a radiating short-circuit column (5); a radiating monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9).

[0010] In order to improve the coupling effect of this compact array, a special parasitic decoupling structure is designed and loaded at the intersection of the diagonal lines of the corresponding radiating monopole units. In order to meet the low-profile characteristics, a similar metal cut-angle disk is loaded on the top of the parasitic monopole. In order to eliminate the original coupling path of the adjacent units, a new coupling path needs to be introduced, so the metal disk on the top of the parasitic monopole adopts a different cutting method. In order to eliminate the current accumulated by the top-loaded disk when radiating the main mode, the parasitic monopole uses a metal column to short-circuit the cut-angle metal disk and the finite common ground plane. To eliminate the coupling effect of this compact array, please refer to Figure 3 The basic structure of the parasitic decoupled compact planar end-fire array includes: a parasitic loaded metal cut-angle disk (1); a parasitic short-circuit column (2); a parasitic monopole (3); a radiating loaded metal cut-angle disk (4); a radiating short-circuit column (5); a radiating monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9).

[0011] The innovations of the present invention include the following points:

[0012] (1) In order to reduce the cross-sectional height of the antenna unit, a metal loading method of a top cut-angle disc is used. At the same time, in order to eliminate the current accumulated by the top-loaded disc during the main mode radiation, a metal column is used to short-circuit the cut-angle disc and the finite common ground plane.

[0013] (2) The common floor is treated with special copper plating. A layer of copper plating with a special shape is loaded on the top of a dielectric plate of a certain thickness. The reflection of the top disk and the copper plating structure is used to improve the edge effect produced by the finite common floor.

[0014] (3) Design a special parasitic decoupling structure and load it at the intersection of the diagonals of the corresponding radiating monopole units, so as to improve the coupling effect of the compact array and enhance the end-fire characteristics and radiation efficiency of the array.

[0015] The present invention is characterized in that the cross-sectional height of the antenna unit is reduced by utilizing the special copper plating treatment of the top cut-angle metal disk and the common floor, the edge effect brought by the finite floor is improved, and a special parasitic decoupling structure is designed to improve the coupling effect of the compact array and improve the array end-fire characteristics and radiation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the structure of the compact monopole radiating antenna unit introduced in the present invention.

[0018] Figure 2 It is a schematic diagram of the structure of the compact monopole planar end-fire array antenna introduced in the present invention.

[0019] Figure 3 It is a schematic diagram of the corresponding port scattering parameters of the compact planar end-fire array introduced in the present invention.

[0020] Figure 4 It is a schematic diagram of the power pattern corresponding to the compact planar array excitation optimization introduced in the present invention.

[0021] Figure 5 It is a schematic diagram of the structure of the parasitic decoupled compact monopole planar end-fire array antenna introduced in the present invention.

[0022] Figure 6 It is a schematic diagram of the corresponding port scattering parameters of the parasitic decoupled compact planar end-fire array introduced in the present invention.

[0023] Figure 7 It is a schematic diagram of the corresponding power pattern of the parasitic decoupled compact planar array excitation optimization introduced in the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiment is only one embodiment of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should belong to the protection scope of the present invention.

[0025] Please refer to Figure 1 and Figure 2 . Figure 1 The present invention is a schematic diagram of a compact monopole radiating antenna unit structure provided by an embodiment of the present invention. The unit mainly comprises: a radiating loaded metal corner-cut disk (4); a radiating short-circuit column (5); a radiating monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9). The unit is a monopole radiator with a corner-cut metal disk loaded on the top and a coaxial feeding structure at the bottom. Figure 2 This is a schematic diagram of the structure of a compact monopole planar end-fire array provided by an embodiment of the present invention. The antenna array shown in the figure is a 37-element monopole planar end-fire array, and the array outline is an octagon. The array is cut around the corners on the basis of a 7×7 evenly spaced planar array. The unit antenna operates in the S band, the center frequency is 3GHz, and the array unit spacing is 30mm, which is 0.3 times the working wavelength. It is a compact planar end-fire array; the array uses a finite-size irregular floor, and the floor outline is the same as the array outline, that is, an octagon after cutting. By changing the feeding phase and amplitude of different units, end-fire scanning of the compact planar array can be achieved.

[0026] For end-fire arrays, smaller spacing will lead to strong radiation shielding and coupling effects. Please refer to Figure 3 , describes the scattering parameters of the corresponding ports of the compact planar end-fire array involved in the present invention. It can be seen that the isolation between adjacent ports of the compact planar end-fire array is poor. Please refer to Figure 4 , the optimal directivity coefficient excitation and the optimal actual gain excitation corresponding power pattern of the array before decoupling are given. It can be seen that the optimal directivity coefficient solution leads to a very low corresponding actual gain when the coupling is poor, and has no practical application value.

[0027] Please refer to Figure 5This embodiment provides a parasitic decoupling compact planar end-fire array structure. It mainly includes: a parasitic loaded metal cut-angle disc (1); a parasitic short-circuit column (2); a parasitic monopole (3); a radiation loaded metal cut-angle disc (4); a radiation short-circuit column (5); a radiation monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9). By introducing a parasitic monopole at the center intersection of four adjacent units, a new coupling path is constructed to eliminate the influence of the original coupling. The parasitic monopole does not perform feeding radiation, so its terminal is short-circuited; the terminal of the radiation monopole is connected to the coaxial structure for active feeding.

[0028] Please refer to Figure 6 , the distribution diagram of scattering parameters of each port after decoupling. The isolation between port 1 and port 2 is improved from 7.9967dB to 17.6684dB, the isolation between port 1 and port 4 is improved from 8.2702dB to 18.3227dB, the isolation between port 1 and port 5 is improved from 9.2122dB to 24.3572dB, and the isolation between port 1 and port 6 is improved from 9.2822dB to 19.4922dB. The adjacent ports with poor isolation have all been improved. Although the reflection coefficient of port 1 increases from -28.3504dB to -20.9699dB, and the corresponding bandwidth decreases from 335Hz to 262MHz, it still meets the narrowband radiation requirements, so the negative impact of the parasitic structure can be ignored. It can be seen that the isolation between the central array element and its adjacent array elements of the compact planar end-fire array with the introduction of the parasitic decoupling structure is improved, and the coupling effect is eliminated. Please refer to Figure 7 , power patterns corresponding to different excitations after decoupling.

[0029] It can be seen that the optimal main polarization directivity coefficient excitation of the decoupled array can obtain directivity coefficients and actual gains that are better than those of ordinary end-fire matching. At the same time, the optimal main polarization directivity coefficient excitation corresponds to the largest directivity coefficient among all excitation configurations, which is 3.862dB higher than ordinary end-fire matching and 0.737dB higher than the optimal main polarization gain excitation. The optimal main polarization gain excitation can obtain the largest actual gain among all excitation configurations, which is 3.366dB higher than ordinary end-fire matching and 0.794dB higher than the optimal main polarization directivity coefficient excitation. It is concluded that the analytical solution of the optimal main polarization directivity coefficient and the optimal main polarization gain of the decoupled array have practical application value. Although the matching bandwidth is reduced, it can bring higher gain improvement and directivity coefficient improvement.

[0030] The above is a description of the present invention and its implementation scheme provided to engineers and technicians familiar with the field of the present invention. These descriptions should be regarded as illustrative rather than restrictive. Engineers and technicians can make specific operations based on the ideas in the claims of the invention, and naturally can make a series of changes to the implementation scheme based on the above. All of the above should be regarded as the scope of the present invention.

Claims

1. A parasitic decoupled compact monopole planar end-fire array antenna, the unit structure of which comprises: Parasitic loading of a metal chamfered disc (1); Parasitic shorting column (2); Parasitic monopole (3); A radiation-loaded metal cut-angle disc (4); a radiation short-circuit column (5); a radiation monopole (6); a copper-plated structure (7); an irregular dielectric floor (8); and a coaxial feeding interface (9); wherein the parasitic decoupling structure is loaded at the intersection of the diagonal lines of the corresponding radiation monopole, the radiation-loaded metal cut-angle disc is arranged on the top of the radiation monopole, the parasitic cut-angle disc is arranged on the top of the parasitic monopole, the radiation short-circuit column connects the radiation-loaded metal cut-angle disc and the finite common floor, the parasitic short-circuit column connects the parasitic metal cut-angle disc and the finite common floor, and the copper-plated structure is located on the top of the irregular dielectric floor; The array adopts a finite-sized irregular floor whose contour is the same as the array contour. The reflection of the top disk and the copper-plated structure is used to improve the edge effect of the finite-sized compact planar end-fire array.

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