Ultra-wideband directional antenna applied to 5G communication indoor distribution system

Abstract

The invention discloses an ultra-wideband directional antenna applied to a 5G communication indoor distribution system, which comprises a Vivaldi antenna and a metal back cavity, and is characterized in that the Vivaldi antenna comprises two antenna metal surfaces, a feed metal strip line and a metal director oscillator; the antenna metal surface comprises a first metal panel, a second metal side wall panel and a third metal side wall panel; the first metal panel is provided with a trumpet-shaped notch; the two second metal side wall panels are arranged along the side edges of the trumpet-shaped notch respectively to form a two-dimensional trumpet surface; the two third metal side wall panels are respectively connected with the outer ends of the second metal side wall panels; and the feed metal strip line is located between the antenna metal surfaces and excites the double-layer metal surfaces, and current distribution is symmetrical, so that a balanced balun feed structure is formed. According to the invention, the characteristics of ultra wide band and low profile are realized, the gain in the working frequency band is stable, the radiation pattern also has good directivity and symmetry, and the whole antenna is of a metal structure, so that the cost is low and the processing is easy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antennas, and particularly relates to an ultra-wideband directional antenna applied to a 5G communication indoor distribution system. BACKGROUND

[0002] In order to meet the needs of increasingly complex wireless communication scenarios, a new generation of wireless communication technology has realized a leapfrog development in transmission rate, time delay, connection scale and the like. In the middle and high layers and underground layers of high-rise buildings, the shielding effect of building materials will cause loss of wireless signals, affecting signal reception and communication quality. Only the distribution of outdoor base station antennas cannot meet the needs of indoor communication, and it is necessary to transmit mobile signals to every corner of the building through a building indoor distribution antenna system to solve the problems of indoor signal strength and quality, so the research on indoor distribution terminal antennas has great significance. Since different communication systems occupy different frequency bands, different operators have different demands for frequency bands. Taking China Unicom as an example, the frequency bands are divided into Band8 (904-960MHz), Band3 (1735-1860MHz), Band1 (1940-2155MHz), Band40 (2300-2320MHz), n77 (3300-3400Mhz), n78 (3500-3600MHz) and the like. In order to provide 2G / 3G / 4G / 5G communication services at the same time, the indoor antenna needs to cover multiple frequency bands. Some traditional indoor terminal antennas integrate low-frequency dipoles, medium-frequency dipoles and high-frequency dipoles by using a combiner to meet the multi-band coverage, but this scheme is complex in design and high in cost. If a single antenna is used to realize the coverage of the working frequency band, the design scheme will be greatly simplified and the cost will be reduced. Since the selection and design of the terminal antenna are largely limited by the shape of the terminal device, the reserved space and the like, the design scheme also needs to meet the needs of miniaturization, low profile, wide frequency band compatibility, stable radiation performance and the like.

[0003] Vivaldi antenna is often used in the design of wideband directional antenna due to its outstanding directional radiation characteristics and simple structure, which can better meet the demand of wideband coverage and is suitable for indoor distribution ultra-wideband directional antenna. But according to the working mechanism of traveling wave antenna, the traditional coplanar Vivaldi antenna needs to radiate through a long tapered slot, which occupies a large area and has a high profile. Although various methods have been proposed to miniaturize the Vivaldi antenna, such as slotting at the edge of the structure and using half Vivaldi, the improvement of the antenna size, especially the profile height, is limited, which does not meet the application demand of low profile. In addition, since the feed balun usually works on one side of the antenna, it leads to unbalanced feeding, which causes the deterioration of high frequency pattern and high cross polarization, and the radiation performance is unstable. Therefore, it is of great significance to design an ultra-wideband Vivaldi antenna with low profile and stable radiation performance for the application of directional terminal antenna of indoor distribution system. SUMMARY

[0004] The purpose of the present application is to propose an ultra-wideband directional antenna applied to 5G communication indoor distribution system based on the design deficiency of existing Vivaldi antenna and combined with the actual application demand, which can realize wideband coverage and has stable radiation performance in the frequency band. The present application realizes the ultra-wideband characteristics of voltage standing wave ratio less than 2 in the range of 0.79-3.85GHz, and the antenna profile height is only 0.23λ m (λ m The wavelength corresponding to the lowest working frequency of Vivaldi antenna), the radiation pattern also has good directivity and symmetry, the gain in the working frequency band is greater than 6dBi, the cross polarization is below-42dB, and the whole antenna is a metal structure, which is low in cost and easy to process.

[0005] The present application is an ultra-wideband directional antenna applied to 5G communication indoor distribution system, which comprises a Vivaldi antenna and a metal back cavity, wherein the Vivaldi antenna is located above the metal back cavity. The Vivaldi antenna comprises two mirror-symmetrically arranged antenna metal surfaces, a feed metal strip and a metal monopole; there is a spacing between the two antenna metal surfaces. The antenna metal surface comprises a first metal panel, a second metal side wall panel and a third metal side wall panel; the first metal panel is perpendicular to the metal back cavity, and a horn-shaped notch is opened at the top of the first metal panel; two second metal side wall panels are arranged along the side edges of the horn-shaped notch respectively to form a two-dimensional horn surface; two third metal side wall panels are connected with the outer ends of the two second metal side wall panels respectively and connected with the upper end of the first metal panel. The feeding metal strip line is located between the two antenna metal surfaces and keeps the same distance with the two antenna metal surfaces, which can stimulate the double-layer metal surface and the current distribution is symmetrical, forming a balanced bar feed structure. The metal director dipole is suspended above the feeding metal strip line.

[0006] Preferably, the two sides of the trumpet-shaped notch adopt arc shape.

[0007] Preferably, the third metal side wall panel is used as a bending radiation arm, which is rectangular in structure and is arranged perpendicularly to the antenna metal surface.

[0008] Preferably, the second metal side wall panel is triangular in structure, one of the top angles of which is close to the smaller opening position of the trumpet-shaped notch, and the opposite side length of the top angle is the same as the length of the adjacent side of the third metal side wall panel.

[0009] Preferably, the distance between the metal director dipole and the feeding metal strip line is 0.25λ0, and λ0 is the wavelength corresponding to the center working frequency of the antenna unit.

[0010] Preferably, the first metal panel is further provided with a first circular slot, which is located below the smaller opening of the trumpet-shaped notch and is communicated with the trumpet-shaped notch.

[0011] Preferably, the two sides of the first metal panel are further provided with a plurality of slot lines and a plurality of second circular slots arranged along the side of the trumpet-shaped notch.

[0012] Preferably, the feeding metal strip line 1-2 adopts L-shaped strip line, which includes longitudinal line and horizontal line; the center of the horizontal line is located at the smaller opening position of the trumpet-shaped notch, and the bottom of the longitudinal line is not in contact with the metal back cavity.

[0013] Preferably, the metal back cavity adopts a box structure with open upper end, and the top end of the side wall is lower than the top end of the antenna metal surface.

[0014] Preferably, rectangular slots with the same width and the same length are etched on the four side walls of the metal back cavity.

[0015] The present application has the following advantages: The antenna adopts balanced feed structure, the feeding metal strip line is located between the two antenna metal surfaces and keeps the same distance with the two antenna metal surfaces, which can stimulate the double-layer metal surface and the current distribution is symmetrical, forming a balanced bar feed structure.

[0016] The antenna can improve the antenna radiation performance, reduce the antenna transverse size and reduce the antenna profile height by etching slots at the edge of the vertical antenna metal surface, bending part of the radiation arm and adding metal side wall at the trumpet-shaped notch.

[0017] The antenna operating frequency range is 0.79-3.85GHz, the voltage standing wave ratio is less than 2, multiple communication frequency ranges can be covered simultaneously, and the antenna can be used as a feasible scheme of a 5G communication indoor distribution system terminal antenna.

[0018] The antenna has a whole structure mainly made of metal, is simple in structure and low in cost, and is easy to mass process. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a three-dimensional structure schematic diagram of the ultra-wideband directional antenna.

[0020] Figure 2 It is a main body diagram of the ultra-wideband directional antenna.

[0021] Figure 3 It is an x-direction side view of the ultra-wideband directional antenna (without a metal back cavity).

[0022] Figure 4 It is a y-direction side view of the ultra-wideband directional antenna (without a metal back cavity).

[0023] Figure 5 It is a front view of the ultra-wideband directional antenna.

[0024] Figure 6 It is a working frequency range reflection coefficient simulation diagram of the ultra-wideband directional antenna.

[0025] Figure 7 It is a working frequency range gain simulation diagram of the ultra-wideband directional antenna.

[0026] Figure 8 Fig. (a) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 0.8GHz. Figure 8 Fig. (b) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 1.7GHz.

[0027] Figure 9 Fig. (a) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 2.5GHz. Figure 9 Fig. (b) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 3.7GHz.

[0028] Figure 10 Fig. (a) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 2.5GHz. Figure 10 Fig. (b) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 3.7GHz.

[0029] Figure 11 Fig. (a) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 2.5GHz. Figure 11 Fig. (b) is a normalized E-plane and H-plane main polarization and cross polarization simulation result comparison of the ultra-wideband directional antenna at 3.7GHz.

[0030] Marked in the figure: 1, Vivaldi antenna; 11, antenna metal surface; 111, first metal surface panel; 1111, horn-shaped notch; 1112, first circular slot; 1113, slot line; 1114, second circular slot; 112, second metal side wall panel; 113, third metal side wall panel; 12, feeding metal strip line; 13, metal director; 2, metal back cavity; 21, rectangular slot. DETAILED DESCRIPTION

[0031] The application will be further analyzed in combination with specific embodiments.

[0032] The embodiment provides an ultra-wideband directional antenna applied to a 5G communication indoor distribution system, the working frequency band is 0.79-3.85GHz, the related working frequency bands of 2G / 3G / 4G / 5G can be covered at the same time, through balanced feeding, the feeding bar is arranged in the middle of two pieces of vertically arranged and mirror-symmetric antenna metal surfaces 11, the current on the two-side antenna metal surfaces is symmetrically distributed and the common-mode current is inhibited, the stability of the radiation pattern can be ensured and the cross polarization is inhibited. In view of the problem of high profile of the Vivaldi antenna, some slot lines are etched on the edge of the antenna metal surface 11, the current path is prolonged, so as to reduce the transverse size of the antenna and reduce the certain profile height, and according to the current distribution on the gradual change slot line at high frequency, part of the radiation arm is bent, so that the profile height of the antenna can be greatly reduced. Since the current of the Vivaldi antenna is mainly concentrated on the edge of the horn-shaped notch 1111 during operation, the impedance matching at low frequency is unstable, and the current is uniformly distributed on the two-dimensional antenna metal surface 11 to improve the impedance matching at low frequency. The whole antenna is a metal structure, easy to process and low in cost, can solve the problems of insufficient bandwidth, large size and high cost existing in the design of the existing indoor terminal antenna, has very great application potential. As shown in Figure 1 、 Figure 2 , specifically, the antenna structure comprises a Vivaldi antenna 1 and a metal back cavity 2, wherein the Vivaldi antenna 1 is located above the metal back cavity 2. The Vivaldi antenna 1 comprises two antenna metal surfaces 11 arranged in mirror symmetry, a feeding metal strip line 12 and a metal director 13. There is a spacing between the two antenna metal surfaces 11. As an example, the feeding metal strip line 12 can be fixed in the middle of the two antenna metal surfaces 11 through a first plastic fixing piece, the length of the first plastic fixing piece and the spacing W gap1 between the feeding metal strip line 12 and the antenna metal surface 11 are the same. The two antenna metal surfaces 11 can also be fixed vertically in the metal back cavity 2 through a second plastic fixing piece. The metal director 13 can also be suspended above the feeding metal strip line 12 through a third plastic fixing piece and does not contact the two antenna metal surfaces 11.

[0033] As shown in Figure 3 ,Figure 4 、 Figure 5 The antenna metal surface 11 comprises a first metal panel 111, a second metal side wall panel 112, and a third metal side wall panel 113. The first metal panel 111 is perpendicular to the metal back cavity 2, and a horn-shaped notch 1111 is formed on the top of the first metal panel 111. Two second metal side wall panels 112 are respectively arranged along the side edges of the horn-shaped notch 1111 to form a two-dimensional horn surface. Two third metal side wall panels 113 are respectively connected to the outer ends of the two second metal side wall panels 112 and to the upper end of the first metal panel 111. The feeding metal strip line 12 is located between the two antenna metal surfaces 11 and maintains the same distance with the two antenna metal surfaces 11, which can simultaneously excite the double-layer metal surface and the current distribution is symmetrical, forming a balanced-barrel feeding structure. The feeding barrel is connected with a 50Ω coaxial line to excite the Vivaldi antenna to work.

[0034] The metal director monopole 13 is suspended above the feeding metal strip line 12.

[0035] In one embodiment, the metal back cavity 2 adopts a box structure with an open upper end, and the top end of the side wall is lower than the top end of the antenna metal surface 11. The bottom surface of the box serves as a metal floor.

[0036] In one embodiment, the two side edges of the horn-shaped notch 1111 adopt an arc shape. The second metal side wall panel 112 also adopts an arc panel.

[0037] In one embodiment, the width of the smaller opening end of the horn-shaped notch 1111 satisfies L slot1 ≤0.02λ g , and λ g is the wavelength corresponding to the highest working frequency of the Vivaldi antenna.

[0038] In one embodiment, the third metal side wall panel 113 serves as a bent radiation arm, which has a rectangular structure and is arranged perpendicularly to the antenna metal surface 11. The bent radiation arm is parallel to the metal floor of the metal back cavity 2, and the width W ant is 71mm. The bending degree of the radiation arm is 90°, and the bending directions of the two sides of the antenna metal surface 11 are opposite. The distance h ant from the bent radiation arm to the metal floor satisfies h ant <λ0 / 4, and λ0 is the wavelength corresponding to the central working frequency of the Vivaldi antenna.

[0039] In one embodiment, the second metal side wall panel 112 has a triangular structure, one of the top angles of which is close to the smaller opening position of the horn-shaped notch 1111, and the length of the opposite side of the top angle is the same as the length of the connected side of the third metal side wall panel 113.

[0040] In one embodiment, the distance between the metal director 13 and the feeding metal strip line 12 is 0.25λ0, where λ0is the wavelength corresponding to the center operating frequency of the antenna unit.

[0041] In one embodiment, the first metal panel 111 further has a first circular slot 1112, which is located below the smaller opening of the horn-shaped notch 1111 and communicates with the horn-shaped notch 1111.

[0042] In one embodiment, the first metal panel 111 further has a plurality of slot lines 1113 and a plurality of second circular slots 1114 arranged along the side edges of the horn-shaped notch 1111. The second circular slots 1114 can communicate with the slot lines 1113.

[0043] In one embodiment, the feeding metal strip line 12 is composed of an impedance transformer and a fan-shaped stub. The impedance transformer comprises two metal strip lines with different widths, and a fan-shaped structure is introduced at the stub part of the end of the metal strip line. Specifically, an L-shaped strip line is used, which includes a longitudinal line and a horizontal line. The center of the horizontal line is located at the position of the smaller opening of the horn-shaped notch 1111, and the bottom of the longitudinal line is not in contact with the metal back cavity 2.

[0044] In one embodiment, the metal back cavity 2 has a rectangular slot 21 with the same width and the same length etched on the four side walls.

[0045] For example, the length L gnd of the metal back cavity 2 is 175 mm, and the width W gnd is 160 mm. The Vivaldi antenna 1 is made of metal copper / aluminum with a thickness of 1 mm, and the metal back cavity 2 is also made of metal copper / aluminum with a thickness of 1 mm. The distance W yin between the two antenna metal surfaces 11 is 7.5 mm, the width L ant of the antenna metal surface 11 is 143 mm, and the height H ant is 87 mm. The width L slot1 of the smaller opening of the horn-shaped notch 1111 is 1.2 mm, which satisfies L slot2 ≤ 0.02λ g , and the width L slot2 of the larger opening is 87 mm. The distance W gap1 and W gap2 between the feeding metal strip line 12 and the two antenna metal surfaces 11 are both 3 mm. The feeding metal strip line 12 uses two impedance transformers for impedance matching. The lower end part of the longitudinal line has a width W feed1 of 7.6 mm, and the upper end part has a width W feed2 of 3.2 mm. The length Lfeed 45mm. The first circular slot 1112 has a radius R1 of 12.1mm. The height H of the metal director 13 suspended between the horizontal lines of the feed metal strip line 12 yin 29mm, and the length L of the metal director 13 yin 27mm, and the width W yin 7.5mm. The thickness of the feed metal strip line 12 is 1.5mm.

[0046] When the antenna provided by the above embodiment is in operation, signals are transmitted to the Vivaldi antenna 1 by a 50Ω coaxial line connected to the feed balun. Electromagnetic energy is coupled to the horn-shaped notch 1111 at the narrow end of the first circular slot 1112 through the feed metal strip line 12, and the current has a traveling wave characteristic along the horn-shaped notch 1111, and the current density gradually decreases from the narrow slot to the wide slot. At the narrow end of the horn-shaped notch 1111, the width is much smaller than λ0 / 2, and the electromagnetic field is confined between the slot lines, and the energy propagates in a quasi-TEM mode. When the current propagates along the horn-shaped notch 1111, as the slot lines widen, the current path gradually lengthens, the equivalent propagation constant decreases, and the phase velocity decreases to produce a gradual phase delay. When the slot line width approaches λ0 / 2, the phase delay causes the sector wave front of the electromagnetic wave to mismatch the slot line geometry, and the antenna begins to radiate energy into free space, producing directional radiation. In order to reduce the asymmetric current distribution introduced by unbalanced feeding and suppress the generation of unnecessary cross-polarization components, the antenna metal surfaces 11 on both sides are in balanced distribution with the feed metal strip line 12, which can effectively suppress cross-polarization and improve the symmetry of the radiation pattern. A plurality of slots are etched at the edges of the antenna, so that the current at the edges of the antenna is distributed along the slots, the current path is lengthened, the working frequency band of the antenna is extended to lower frequencies, and the size of the antenna is reduced. The antenna radiation arm is bent by 90° at the current zero point in the vertical direction according to the current distribution, so that only the current in the same direction exists on the horizontal metal surface after bending, thereby reducing the profile while improving the high-frequency pattern and reducing the pattern lobes. By connecting the second metal side wall panel 112 with the same curvature at the horn-shaped notch 1111, the current distribution changes from along the slot line to along the metal surface, and the impedance matching of the low-frequency part is obviously improved, so that the working bandwidth of the antenna can be significantly widened.

[0047] Figure 6 FIG. 6 is a simulation result of the voltage standing wave ratio of the ultra-wideband directional antenna applied to the 5G communication indoor distribution system of the present application. In the range of 0.79-3.85GHz, the voltage standing wave ratio is less than 2, which indicates that the antenna achieves good impedance matching, and the working frequency band can cover multiple communication frequency bands at the same time, having an ultra-wideband characteristic.

[0048] Figure 7For the gain simulation result figure of the application of the ultra-wideband directional antenna applied to the 5G communication indoor distribution system of the application, the gain in the working frequency band is greater than 6dBi, the highest gain reaches 11.6dBi, and the gain requirement of the indoor terminal antenna is met.

[0049] Figure 8 In (a)- Figure 8 In (b), Figure 9 In (a)- Figure 9 In (b), Figure 10 In (a)- Figure 10 In (b), Figure 11 In (a)- Figure 11 In (b) are the normalized E-plane and H-plane main polarization and cross polarization simulation results of the application at 0.8GHz, 1.7GHz, 2.5GHz and 3.7GHz, respectively, it can be seen that the antenna designed by the application has good directivity and symmetry in the main polarization radiation pattern of the E-plane and the H-plane, especially the high frequency pattern can remain stable, the cross polarization in the pattern designed by the application can obviously see that the cross polarization has a relatively obvious inhibitory effect, the cross polarization of the E-plane and the H-plane is below-42dB.

[0050] The above only describes the preferred embodiments of the application, and does not limit the embodiments of the application. It should be noted that for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should be included in the protection scope of the claims of the application.

Claims

1. An ultra-wideband directional antenna for use in 5G communication indoor distribution systems, characterized in that... It includes a Vivaldi antenna (1) and a metal back cavity (2), wherein the Vivaldi antenna (1) is located above the metal back cavity (2); The Vivaldi antenna (1) includes two antenna metal surfaces (11) arranged in a mirror symmetry, a feed metal stripline (12), and a metal guide element (13); there is a gap between the two antenna metal surfaces (11); The antenna metal surface (11) includes a first metal panel (111), a second metal sidewall panel (112), and a third metal sidewall panel (113); the first metal panel (111) is perpendicular to the metal back cavity (2) and has a horn-shaped notch (1111) at its top; the two second metal sidewall panels (112) are respectively arranged along the side of the horn-shaped notch (1111) to form a two-dimensional horn surface; the two third metal sidewall panels (113) are respectively connected to the outer ends of the two second metal sidewall panels (112) and connected to the upper end of the first metal panel (111); The feed metal strip (12) is located between the two antenna metal surfaces (11) and maintains the same distance from the two antenna metal surfaces (11), which can simultaneously excite the double-layer metal surfaces and the current distribution is symmetrical, forming a balanced balun feed structure. The metal directional oscillator (13) is suspended above the feeding metal strip (12).

2. The antenna according to claim 1, characterized in that, The two sides of the trumpet-shaped notch (1111) are curved.

3. The antenna according to claim 1, characterized in that, The third metal sidewall panel (113) serves as a bent radiating arm, has a rectangular structure, and is perpendicular to the antenna metal surface (11).

4. The antenna according to claim 1, characterized in that, The second metal sidewall panel (112) has a triangular structure, with one of its apex corners close to the smaller opening of the flared notch (1111), and the length of the opposite side of the apex corner is the same as the length of the adjacent side of the third metal sidewall panel (113).

5. The antenna according to claim 1, characterized in that, The distance between the metal directional oscillator (13) and the feed metal strip (12) is 0.25λ0, where λ0 is the wavelength corresponding to the center operating frequency of the antenna element.

6. The antenna according to claim 1, characterized in that, The first metal panel (111) also has a first circular groove (1112), the circular groove line (1113) is located below the smaller opening of the horn-shaped notch (1111) and is connected to the horn-shaped notch (1111).

7. The antenna according to claim 6, characterized in that, The first metal panel (111) also has multiple groove lines (1113) and multiple second circular grooves (1114) arranged along the sides of the flared notch (1111).

8. The antenna according to claim 1, characterized in that, The power supply metal strip (12) 1-2 adopts an L-shaped strip, which includes a longitudinal line and a horizontal line; the center of the horizontal line is located at the smaller opening of the trumpet-shaped notch (1111), and the bottom of the longitudinal line does not contact the metal back cavity (2).

9. The antenna according to claim 1, characterized in that, The metal back cavity (2) adopts a box structure with an open top, and the top of its side wall is lower than the top of the antenna metal surface (11).

10. The antenna according to claim 9, characterized in that, Rectangular grooves (21) of the same width and length are etched on the four sides of the metal back cavity (2).

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