A low sidelobe broadband low cross-polarization planar dipole antenna array

Abstract

The present invention discloses a low sidelobe broadband low cross-polarization planar dipole antenna array, comprising a multilayer dielectric substrate; a first metal surface; a second metal surface; a feed network; a dipole antenna array; each dipole antenna unit comprises a top dipole arm, a middle dipole arm, and a bottom dipole arm; the first metal surface is connected to one end of the top dipole arm; the second metal surface is connected to one end of the bottom dipole arm; the feed network comprises a signal conducting strip and a metallized through hole; the signal conducting strip at the output end of the feed network is directly connected to the signal input end of each dipole antenna unit; the antenna array etches a pair of slits at appropriate positions, so that the dipole works in a half-wavelength mode and a 1.5 times wavelength mode at the same time, greatly improving the impedance bandwidth of the dipole antenna. The antenna array adopts a SICL structure for feeding, which can effectively suppress the cross polarization of the dipole antenna, and the SICL structure works in a quasi-TEM mode without a cutoff frequency.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas and relates to a low sidelobe antenna array, in particular to a low sidelobe broadband low cross-polarization planar dipole antenna array. Background Art

[0002] In recent years, with the development of millimeter wave systems, people have become more and more interested in the research of high-efficiency millimeter wave antenna arrays. Many millimeter wave band applications require the integration of planar antennas with back-end links to reduce the overall system size and improve system integration. Planar dipole antennas are considered to be a promising antenna due to their compact structure, low manufacturing cost, stable radiation performance, and easy integration with active circuits. However, the design of broadband dipole antennas in the millimeter wave band faces the challenges of how to broaden the bandwidth and how to improve cross-polarization.

[0003] For decades, many methods have been studied to broaden the working bandwidth of dipoles. The main methods include using a butterfly dipole, using a logarithmic periodic structure, adding a director array, or using a broadband balun. As another type of planar antenna, a butterfly dipole antenna fed by an integrated balun has been widely developed for wireless communications at microwave frequencies. These antennas can achieve broadband or multi-band operation, but their disadvantage is that they are large in size, and the balun structure not only increases the size of the antenna, but also increases the design difficulty.

[0004] In the millimeter wave frequency band, whether microstrip balun feeding or substrate integrated waveguide (SIW) feeding is used, the relative thickness of the dielectric substrate becomes thicker, and the strong cross-polarization component of the feeding part makes the cross-polarization of the antenna poor. In addition, since SIW needs to meet certain lateral dimensions to support the propagation of waveguide modes, the component size is relatively large in the lower microwave band. However, some people use double-sided dipoles fed by microstrip baluns to reduce cross-polarization, but this often requires a more complex structure. Some people also use differential feeding to reduce cross-polarization, but this structural feeding structure is more complicated and not convenient for array integration. Summary of the invention

[0005] The purpose of the present invention is to address the shortcomings of the existing dipole antenna feeding method and narrow bandwidth. By using the substrate integrated coaxial line (SICL) feeding method, cross polarization can be effectively suppressed. The planar array unit adopts a bent long-arm dipole with a slot, and a broadband low sidelobe antenna array with cross polarization suppression function is proposed, which can solve the defects of cross polarization and narrow bandwidth in the existing dipole feeding technology. The antenna adopts the SICL feeding method to suppress the cross polarization generated by the feeding network. By using the T-section unequal power divider feeding network, the sidelobe level of the antenna array radiation pattern is greatly improved. This method is not only simple in structure and clear in principle, but also easy to process and has a low design cost, and has great application potential.

[0006] The low sidelobe broadband low cross-polarization planar dipole antenna array of the present invention is a multi-layer vertical arrangement structure, comprising:

[0007] A multi-layer dielectric substrate, which includes, from top to bottom, a first dielectric substrate, a third dielectric substrate, and a second dielectric substrate;

[0008] A first metal surface, which is located on the upper surface of the first dielectric substrate;

[0009] A second metal surface, which is located on the lower surface of the second dielectric substrate;

[0010] Feeding network;

[0011] The dipole antenna array consists of 2 n The antenna is composed of dipole antenna units, where n is a natural number greater than or equal to 2;

[0012] Each dipole antenna unit includes a top dipole arm, a middle dipole arm, and a bottom dipole arm; one side surface of the first metal surface is connected to one end of the top dipole arm of each dipole antenna unit, and the first metal surface is used as a reflector of the dipole; the other end of the top dipole arm of each dipole antenna unit is suspended;

[0013] One side surface of the second metal surface is connected to one end of the bottom dipole arm of each dipole antenna unit, and the second metal surface is used as a reflector of the dipole; the other end of the bottom dipole arm of each dipole antenna unit is suspended;

[0014] The third dielectric substrate is located on the lower surface of the first dielectric substrate and is used to bond the first dielectric substrate and the second dielectric substrate;

[0015] The feeding network adopts SICL feeding, and the SICL includes a signal conductive strip located between the third dielectric substrate and the second dielectric substrate, and a plurality of metallized through holes periodically distributed on both sides of the signal conductive strip and on the output end side of the feeding network;

[0016] The feed network has a signal input terminal, 2 n signal output terminal; the above 2 n The signal conducting strip at each signal output end is directly connected to the signal input end of each dipole antenna unit; the signal input end of each dipole antenna unit is one end of the middle layer dipole arm; the other end of the middle layer dipole arm of each dipole antenna unit is suspended;

[0017] Preferably, the second metal surface has the same shape and size as the first metal surface.

[0018] Preferably, the dipole antenna units in the dipole antenna array are arranged at equal intervals.

[0019] Preferably, the top dipole arm and the first metal surface are located in the same plane, the middle dipole arm and the signal conducting band of the SICL are located in the same plane, and the bottom dipole arm and the second metal surface are located in the same plane.

[0020] Preferably, there is a certain distance between the top of the dipole antenna array and the boundary of the dielectric substrate.

[0021] Preferably, the top dipole arm and the bottom dipole arm have the same orientation, and the middle dipole arm and the layer dipole arm and the bottom dipole arm have opposite orientations.

[0022] More preferably, the top dipole arm, the middle dipole arm and the bottom dipole arm have the same structural size, and the connecting arm between the top dipole arm and the first metal surface, the connecting arm between the middle dipole arm and the signal conduction band of the SICL, and the connecting arm between the bottom dipole arm and the second metal surface overlap relatively.

[0023] Preferably, the top dipole arm, the middle dipole arm, and the bottom dipole arm all include a connecting arm and a transverse arm; wherein one end of the connecting arm is connected to one end of the transverse arm, the connecting arm and the transverse arm are arranged vertically, and the other end of the transverse arm is bent inward;

[0024] Preferably, a cut angle is provided at the junction of the connecting arm and the lateral arm of the top dipole arm, the middle dipole arm and the bottom dipole arm, and a gap is etched in the lateral arm;

[0025] More preferably, the slot is parallel to the connecting arms of the dipole arms.

[0026] Preferably, the gap between the middle dipole arm and the gap between the upper dipole arm in the dipole antenna unit is L d1 Meet L d1 =λ0 / 2; λ0 is the wavelength corresponding to the center operating frequency of the dipole antenna.

[0027] Preferably, the length L of the dipole antenna unit d2 Meet L d2≥2*L d1 .

[0028] Preferably, the distance L from the lateral arm of each dipole arm in the dipole antenna unit to the reflector is st Meet L st <λ0 / 4.

[0029] Preferably, the feeding network is a T-shaped power divider feeding network. After determining the excitation amplitude of each port according to Taylor distribution, a parallel feeding method is adopted to achieve equal-phase and unequal-amplitude excitation of each port of the array, and the T-shaped feeding network is realized in the form of a microstrip line.

[0030] As a preferred embodiment, the distance between two rows of metal vias in the SICL structure is W out Should meet f m is the maximum frequency in the millimeter wave band, c is the speed of light in vacuum, ε r Represents the relative dielectric constant of the dielectric substrate;

[0031] Specific working principle: When the antenna is working, due to the etching of the gap at the appropriate position on the dipole arm, the dipole antenna works in the half-wavelength mode and the 1.5 times wavelength mode at the same time, introducing a new resonance point, and the impedance matching of the low-frequency part is significantly improved, thereby significantly widening the working bandwidth. A pair of face-to-face dipoles are placed on the first metal surface and the second metal surface, and the SICL signal conduction band is placed in the middle as part of the dipole. In this case, the lateral electric field component perpendicular to the dipole arm is expected to be offset, thereby effectively suppressing cross-polarization. The T-shaped power divider feed network is used to realize the port excitation required for Taylor distribution to achieve low side lobes, thereby achieving low side lobes.

[0032] The present invention has the following advantages:

[0033] (1) The antenna array has a pair of slots etched at appropriate locations, allowing the dipole to work in both the half-wavelength mode and the 1.5-wavelength mode simultaneously, greatly improving the impedance bandwidth of the dipole antenna.

[0034] (2) The antenna array adopts SICL structure feeding, which can effectively suppress the cross-polarization of the dipole antenna. Moreover, the SICL structure works in the quasi-TEM mode and has no cutoff frequency.

[0035] (3) Compared with ordinary dipole antenna arrays, this antenna array has a lower sidelobe level and has a simple structure, making it easy to design and process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0037] Figure 2 is a side view of the present invention;

[0038] Figure 3 is a top view of the present invention;

[0039] Figure 4 is a schematic diagram of the intermediate feeder network layer of the present invention;

[0040] Figure 5 It is a schematic diagram of the feeding network of the T-shaped power divider of the present invention;

[0041] Figure 6 It is a reflection coefficient simulation diagram of the present invention;

[0042] Figure 7 is a gain simulation diagram of the present invention;

[0043] Figure 8 It is a comparison of the simulation results of the main polarization and cross polarization of the normalized E-plane and H-plane at 24GHz of the present invention;

[0044] Fig. 9 It is a comparison of the simulation results of the main polarization and cross polarization of the normalized E-plane and H-plane at 35GHz of the present invention;

[0045] Fig.10 It is a comparison of the simulation results of the main polarization and cross polarization of the normalized E-plane and H-plane at 46GHz of the present invention;

[0046] Markings in the figure: first metal surface M1, first dielectric substrate S1, third dielectric substrate S3, second dielectric substrate S2, second metal surface M2, upper dipole arm D1, middle dipole arm D2, bottom dipole arm D3, feeding network 1, metallized through holes on both sides of SICL 2, dipole etched gap 3, metallized through holes between SICL 4, T-section equal-dividing power divider 5, T-section unequal-dividing power divider 6, power division ratio of the power division node of the T-section power divider feeding network 7. DETAILED DESCRIPTION

[0047] The present invention is further analyzed below in conjunction with specific embodiments.

[0048] like Figure 1 As shown, the low sidelobe broadband low cross-polarization planar dipole array antenna is a multi-layer vertical arrangement structure, including a first metal surface M1, a first dielectric substrate S1, a third dielectric substrate S3, a feeding network 1, a second dielectric substrate S2, and a second metal surface M2; wherein the first dielectric substrate S1 and the second dielectric substrate S2 adopt Taconic TLY-5, with a dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.254 mm; the third dielectric substrate S3 adopts Rogers4450F, with a dielectric constant of 3.52, a loss tangent of 0.004, and a thickness of 0.1 mm;

[0049] like Figure 2 , 3 As shown, each dipole antenna unit includes a top dipole arm D1, a middle dipole arm D2, and a bottom dipole arm D3; wherein the top dipole arm D1 and the bottom dipole arm D3 are right metal arms, and the middle dipole arm D2 is a left metal arm; the top dipole arm D1, the middle dipole arm D2, and the bottom dipole arm D3 are all bent long arms, and each arm has an etched slit 3; wherein the slit width is 0.3 mm, and the dipole arm length L d1 2.6mm, L d2 is 5.2mm, and the distance between the dipole arm and the reflector is L st 1.85mm;

[0050] One side surface of the first metal surface M1 is connected to one end of the top dipole arm D1 of each dipole antenna unit, and the first metal surface is used as a reflector of the dipole; the other end of the top dipole arm D1 of each dipole antenna unit is suspended;

[0051] One side surface of the second metal surface is connected to one end of the bottom dipole arm of each dipole antenna unit, and the second metal surface is used as a reflector of the dipole; the other end of the bottom dipole arm D3 of each dipole antenna unit is suspended;

[0052] The third dielectric substrate S3 is located on the lower surface of the first dielectric substrate S1 and is used to bond the first dielectric substrate S1 and the second dielectric substrate S2;

[0053] like Figure 4 As shown, the signal conducting band at each signal output end of the feeding network is directly connected to one end of the dipole arm of the middle layer;

[0054] The feeding network is located on the lower surface of the third dielectric substrate S3 and the upper surface of the second dielectric substrate S2. The feeding network 1 is directly connected to the left metal arm of the dipole array, and forms a complete dipole array with the metal arms of the first metal surface M1 and the second metal surface M2. The two sides of the feeding network 1 are provided with metallized through holes 2 that form a periodic distribution of the SICL structure. The metallized through holes 2 on both sides of the SICL are spaced W apart. out 2.1mm;

[0055] like Figure 5As shown, the antenna array feeding network 1 adopts a 1-to-8 parallel-fed T-section power divider feeding network, wherein the labels P1, P2, P3...P7, P8 are ports connecting the array antenna to the feeding network. This 1-to-8-way T-section power divider feeding network is designed using microstrip lines, and the feeding network is directly connected to the middle layer dipole arm D2 to provide the corresponding excitation amplitude to achieve the shaping effect required for the array. In this embodiment, a set of amplitude excitations of the required sidelobe levels are first obtained using Taylor synthesis analysis through MATLAB. The required amplitude ratio of the array is 0.306:0.462:0.747:1:1:0.747:0.462:0.306, and then the amplitude ratio is converted into a dB value, and the corresponding unequal power divider is designed according to the converted dB value;

[0056] The second metal surface M2 is located on the lower surface of the second dielectric substrate S2 and has the same shape and size as the first metal surface M1.

[0057] Figure 6 The reflection coefficient diagram of the array designed for the present invention is simulated, and the -10dB frequency band is around 22.5-46.2GHz. Figure 7 The gain diagram of the array of the present invention is simulated, and the gain within the frequency band is above 10.3dBi, and the highest gain reaches 13.2dBi. Figure 8 , Fig. 9 , Fig.10 The simulation results of the normalized main polarization and cross-polarization of the E-plane and H-plane of the array designed by the present invention at the center frequency (35GHz), low frequency (24GHz), and high frequency (46GHz) are compared. It can be seen that the side lobes of the E-plane and H-plane radiation patterns of the antenna designed by the present invention are both around -18dB, and the cross-polarization of the array radiation pattern designed by the present invention can be obviously seen to have a large suppression function, especially the E-plane cross-polarization, which is below -28dB.

[0058] The above is only a preferred embodiment of the present invention, and does not limit the embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A low sidelobe broadband low cross-polarization planar dipole antenna array, a multi-layer vertical arrangement structure, characterized by include: A multi-layer dielectric substrate, which includes, from top to bottom, a first dielectric substrate, a third dielectric substrate, and a second dielectric substrate; A first metal surface, which is located on the upper surface of the first dielectric substrate; A second metal surface, which is located on the lower surface of the second dielectric substrate; Feeding network; The dipole antenna array consists of 2 n The antenna is composed of dipole antenna units, where n is a natural number greater than or equal to 2; Each dipole antenna unit includes a top dipole arm, a middle dipole arm, and a bottom dipole arm; one side surface of the first metal surface is connected to one end of the top dipole arm of each dipole antenna unit, and the first metal surface is used as a reflector of the dipole; the other end of the top dipole arm of each dipole antenna unit is suspended; One side surface of the second metal surface is connected to one end of the bottom dipole arm of each dipole antenna unit, and the second metal surface is used as a reflector of the dipole; the other end of the bottom dipole arm of each dipole antenna unit is suspended; The third dielectric substrate is located on the lower surface of the first dielectric substrate; The feeding network is fed by substrate integrated coaxial line SICL, wherein the SICL comprises a signal conducting strip located between the third dielectric substrate and the second dielectric substrate, and a plurality of metallized through holes periodically distributed on both sides of the signal conducting strip and on the output end side of the feeding network; The feed network has a signal input terminal, 2 n Signal output terminal; the above 2 n The signal conducting strip at each signal output end is directly connected to the signal input end of each dipole antenna unit; the signal input end of each dipole antenna unit is one end of the middle layer dipole arm; the other end of the middle layer dipole arm of each dipole antenna unit is suspended.

2. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The top dipole arm and the first metal surface are located in the same plane, the middle dipole arm and the signal conducting band of the SICL are located in the same plane, and the bottom dipole arm and the second metal surface are located in the same plane.

3. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that There is a certain distance between the top of the dipole antenna array and the boundary of the dielectric substrate.

4. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The top dipole arm and the bottom dipole arm have the same orientation, and the middle dipole arm has the opposite orientation to the layer dipole arm and the bottom dipole arm.

5. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The top dipole arm, the middle dipole arm and the bottom dipole arm all include a connecting arm and a transverse arm; One end of the connecting arm is connected to one end of the transverse arm, the connecting arm and the transverse arm are vertically arranged, and the other end of the transverse arm is bent inward; a cut angle is provided at the junction of the connecting arm and the transverse arm of the top dipole arm, the middle dipole arm and the bottom dipole arm, and a gap is etched on the transverse arm.

6. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The distance L between the gap of the middle dipole arm and the gap of the upper dipole arm in the dipole antenna unit d1 Meet L d1 =λ0 / 2; λ0 is the wavelength corresponding to the center operating frequency of the dipole antenna.

7. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The length of the dipole antenna element is L d2 Meet L d2 ≥2*L d1 , the distance L from the lateral arm of each dipole arm to the reflector st Meet L st <λ0 / 4.

8. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The feeding network is a T-shaped power divider feeding network.

9. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that The distance between two rows of metal vias in SICL structure is W out Should meet f m is the maximum frequency in the millimeter wave band, c is the speed of light in vacuum, ε r Represents the relative dielectric constant of the dielectric substrate.

10. A low sidelobe broadband low cross-polarization planar dipole antenna array as claimed in claim 1, characterized in that All dipole antenna units in the dipole antenna array operate in a half-wavelength mode and a 1.5-times-wavelength mode simultaneously.

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