CN116995440A - Electromagnetic transparent base station antenna and array based on frequency selection surface - Google Patents
Electromagnetic transparent base station antenna and array based on frequency selection surface Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
- H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
- H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
- H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/0006—Particular feeding systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/061—Two dimensional planar arrays
- H01Q21/065—Patch antenna array
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
- H01Q5/30—Arrangements for providing operation on different wavebands
- H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
- H01Q5/314—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors
- H01Q5/335—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors at the feed, e.g. for impedance matching
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Abstract
The invention provides an electromagnetic transparent base station antenna based on a frequency selective surface, which comprises a reflection ground and a low-frequency antenna arranged above the center of the reflection ground in an overhead mode, wherein the low-frequency antenna consists of the frequency selective surface with a low-high-frequency radar scattering cross section and a good low-frequency impedance bandwidth, and the high-frequency electromagnetic transparency and the low-frequency impedance bandwidth can be controlled independently and are not interfered with each other. Measurements indicate that when the antenna is applied to an array covering 1.7-2.7GHz (45%) and 3.3-3.8GHz (14%), a stable radiation pattern is exhibited in both low and high frequency antennas. The average gains of the low and high frequency antennas were 8.69dBi and 8.15dBi, respectively. Experimental results prove that the electromagnetic transparent base station antenna based on the frequency selection surface has good application prospect in a double-frequency shared aperture array.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to an electromagnetic transparent base station antenna and an array based on a frequency selective surface.
Background
In modern communications, 5G has evolved rapidly, with which 2G/3G/4G will still coexist for a long period of time. Therefore, it is a necessary trend that the multiband base station antennas operate simultaneously in a limited space. In order to save space and cost, dual-frequency shared aperture arrays have been widely studied and several layouts have emerged.
The embedding scheme skillfully plugs the high-band (HB) antenna into the low-band (LB) antenna due to different sizes. But HB antennas are relatively close to LB antennas, resulting in mutual coupling between antennas of different frequency bands. The stacking scheme has attracted attention as a good alternative. It has been found that an additional Frequency Selective Surface (FSS) is required between the LB and HB antennas, resulting in complexity of the array. Finally, interleaving schemes have attracted a great deal of attention. The layout is not limited by the frequency ratio of HB and LB antennas, and the space utilization rate is high. Although the interleaving scheme is a common configuration in practice, the shielding effect of the LB antenna on the HB antenna is not negligible.
To date, researchers have developed several solutionsThe scheme is to mitigate the occlusion effect in the interleaving scheme. 1) First, FSS with good Electromagnetic (EM) regulatory capability is inserted into a dual frequency shared aperture array. However, the addition of FSS not only complicates the antenna structure but also increases the profile. 2) The second method is to obtain a low-scattering LB antenna by adding extra branches or slots on the basis of the existing antenna. Periodic split-ring resonators were creatively introduced into LB antennas to achieve low radar cross-section (low-RCS) at HB to perform frequency assessment of electromagnetic stealth performance of LB antennas. In documents S.J.Yang, Y.Yang and X.Y. zhang, "Low scattering element-based aperture-shared array for multiband base stations," IEEE trans.antenna s Propag, vol.69, no.12, pp.8315-8324, dec.2021. Periodic split-ring resonators were creatively introduced into LB antennas to achieve low radar cross section (low-RCS) at HB. In documents W.Niu, B.Sun, G.Zhou and z.lan, "Dual-band aperture shared antenna array with decreased radiation pattern distortion," IEEE trans.antennas production, vol.70, no.7, pp.6048-6053, jul.2022, two side chokes are skillfully loaded on the LB antenna, reducing the radiation pattern distortion of the HB antenna. However, a trade-off is necessary between reducing the good impedance performance of the RCS and LB antennas. 3) The third method starts with a low-RCS FSS, obtaining an EM transparent low-RCS FSS (FSS-based) antenna at HB, as compared to the second method. In document [23 ]]D.He, Q.Yu, Y.Chen and S.Yang, "Dual-band shared-aperture base station antenna array with electromagnetic transparent antenna elements," IEEE Trans. Antenna s production, vol.69, no.9, pp.5596-5606, sep.2021. FSS is designed as a dipole to effectively suppress the blocking effect. While the impedance of the LB antenna is matched (|S) 11 |<-10 dB) is limited by its EM transparency, both good properties cannot be achieved at the same time. In the literature s.j. Yang and x.y. Zhang, "Frequency selective surface-based dual-polarized high-gain antenna," IEEE trans.antenna products, vol.70, no.3, pp.1663-1671, mar.2022, metallic mesh strips and 4 x 4 periodic patches are neatly combined into an LB antenna of FSS-based to reduce its shielding effect on HB elements. In addition, the low-RCS and LB antenna performance can be controlled separately.However, the bandwidth of LB antennas is limited by FSS itself, only 16%.
Disclosure of Invention
The invention aims at: the defects of the prior art are overcome, and an electromagnetic transparent base station antenna and an array based on a frequency selective surface are provided. Unlike the conventional approach to retrofitting an original antenna, an LB antenna consisting of low-RCS2X2FSS units is introduced into a 2X 2HB array. Therefore, the radiation performance of the HB antenna is well recovered, and the blocking effect of the LB antenna on the HB antenna is restrained. More importantly, the electromagnetic transparency characteristics and impedance matching of the LB antenna can be controlled independently, which is highly desirable to avoid time consuming optimizations.
In order to achieve the purpose of the invention, the electromagnetic transparent base station antenna based on the frequency selection surface comprises a rectangular reflection ground and a low-frequency antenna arranged above the center of the reflection ground in an overhead mode, wherein the low-frequency antenna comprises the frequency selection surface which is overlapped from bottom to top, a low-frequency antenna medium substrate and two Y-shaped feed structures which are arranged in an orthogonal mode and used for exciting two polarized energies of the low-frequency antenna; the frequency selective surface is composed of frequency selective surface units arranged in a 2 x 2 array structure, the frequency selective surface units have square loops, and the frequency selective surface unit is characterized in that: the low-frequency antenna dielectric substrate is characterized in that a metal sheet which is positioned inside the square loop and used for improving high-frequency electromagnetic transparency and is insulated from the square loop is arranged on the lower surface of the low-frequency antenna dielectric substrate, and a transverse gap or a vertical gap or a cross gap is formed in the metal sheet.
Further, the lower surface of the low-frequency antenna dielectric substrate is also provided with a step width arm arranged at the outer corner of the square loop and a crossed vertical strip line arranged between adjacent square loops for improving the bandwidth of low-frequency impedance.
It should be noted that the added metal sheet does not affect the adjustment of the impedance bandwidth of the low-frequency antenna, so that the adjustment of the low-frequency impedance bandwidth and the adjustment of the high-frequency electromagnetic transparency are independent of each other and do not interfere with each other, thereby simplifying the design process of the antenna and improving the design efficiency of the antenna.
Further, the metal sheet is a rectangular metal sheet, the slit is a through length, and the rectangular metal sheet is divided into two or four small metal sheets by the through length slit.
In addition, the invention also claims a dual-frequency base station antenna array, which comprises a high-frequency antenna array and is characterized in that: the electromagnetic transparent base station antenna based on the frequency selection surface is arranged above the reflection ground in an overhead mode, and is located below the low-frequency antenna.
The core part of the base station antenna is to provide an electromagnetic transparent low-frequency antenna based on a frequency selection surface, wherein a metal sheet with a gap is additionally arranged on the frequency selection surface of the low-frequency antenna in a square loop, so that the electromagnetic transparent performance of high frequency is improved, and the energy of the high-frequency antenna below the low-frequency antenna is radiated outwards almost without shielding. The base station antenna array with a compact structure covers double frequencies of 1.7-2.7GHz (45%) and 3.3-3.8GHz (14%), and shows stable radiation modes in both LB and HB antennas. The average gains for the LB and HB antennas were 8.69dBi and 8.15dBi, respectively. Experimental results verify that the proposed low-RCS FSS-based antenna is attractive in a dual frequency shared aperture array.
Drawings
Fig. 1 is a schematic view of an electromagnetic transparent base station antenna array based on a frequency selective surface according to the present invention, (a) a perspective view, (b) a top view, (c) a top view of a low frequency antenna, and (d) a top view of a high frequency antenna.
Figure 2 is a diagram of the design evolution process of the frequency selective surface according to the present invention.
Fig. 3 shows simulation results of four FSS schemes, (a) normalized RCS, (b) LB antenna S parameters.
FIG. 4 is normalized RCS and |S for LB antenna 11 Simulation results of (a) - (b) Lw 2 ,(c)-(d)Lslotw,(e)-(f)Lp 1 。
Fig. 5 is a reference antenna array.
Fig. 6 is a radiation pattern of three antenna arrays, (a) a 2.2GHz LB antenna and (b) a 3.55GHz HB antenna.
Fig. 7 is the HPBW of HB antennas in three antenna arrays.
Fig. 8 is a prototype of the proposed array, (a) top view, (b) side view.
Fig. 9 shows simulated and measured S parameters, (a) LB, (b) HB antenna.
FIG. 10 is a simulated and measured radiation pattern of (a) LB on the H plane, (b) LB on the V plane, (c) HB on the H plane, and (d) HB on the V plane.
Fig. 11 is the gain and HPBW of the simulated and measured LB and HB antennas.
Detailed Description
The invention is further explained in the following detailed description with reference to the drawings so that those skilled in the art can more fully understand the invention and can practice it, but the invention is explained below by way of example only and not by way of limitation.
The Frequency Selective Surface (FSS) has good electromagnetic control capabilities. In order to study the electromagnetic transparency characteristics of FSS-based low-band (LB) antennas, the inventors derived and analyzed the radar scatter cross section (RCS) of the FSS unit. The strength of the scattering capability of the target on the incident electromagnetic wave determines the quality of the shadow performance of the target, and the strength of the scattering capability is generally quantitatively described by using RCS, so that the shadow purpose of the target can be realized by reducing the RCS of the target, and the research of the RCS of the target is necessary. First, the expression of the target RCS is as follows:
wherein L is a loss factor, P rmin For the output power of the receiver, G is the antenna gain, lambda is the radar operating wavelength, P s For the transmitter output power, R max For radar detection distance. RCS is a measurement of the incident plane wave illumination target. From the above, R is max Exponentially decreasing with decreasing RCS. Therefore, the probability of the antenna being detected by the radar is reduced, and the electromagnetic stealth effect is correspondingly enhanced.
As shown in fig. 2, is a diagram of the design evolution process of the frequency selective surface according to the present invention. Fig. 3 (a) plots the normalized RCS for FSS units from scheme F1 to scheme F4. LB antenna composed of FSS unitsThe S parameter is shown in fig. 3 (b). As a classical square loop in scheme F1, its RCS is-2 to 5dB over the entire HB (3.3-3.8 GHz) range, as shown in FIG. 3 (a). This means that it has little electromagnetic transparency, and most of the energy of the HB antenna cannot be transmitted through the LB antenna. It follows that conventional square loop LB antennas have a blocking effect on HB antennas and are not suitable for use in shared aperture arrays. Therefore, an LB antenna having EM transparent characteristics is required to solve this problem. Subsequently, square metal sheets were added in scheme F2, yielding a minimum RCS of-28 dB at 2.98 GHz. Due to the drop, the RCS (from-14 to-6 dB) within HB is significantly reduced. To further reduce the intra-HB RCS, one square sheet metal is replaced with four small square sheets metal in scheme F3. Notably, the nadir moved to 3.7GHz and a significant drop in the RCS value within HB occurred (from-26 to-10 dB). The results show that compared with scheme F1, the maximum RCS value in HB of scheme F3 is reduced by 15dB, and the EM stealth level of HB is significantly improved. Meanwhile, the |S of LB antenna using F1-F3 units 11 There is no significant shift of i as shown in fig. 4 (b). The bandwidth of the lb antenna needs to be further extended in order to cover 1.7-2.7 ghz. The step width arms and the intersecting vertical strip line are added sequentially in scheme F4. Therefore, the return loss of the LB antenna reaches-15 dB, and the impedance bandwidth is enlarged to 45% (1.7-2.7 GHz). At the same time, isolation between two polarizations of four cells (|S) 21 I) is almost unchanged and is always greater than 25dB, as shown in fig. 3 (b). As can be seen from fig. 3 (a), the RCS in schemes F3 and F4 have little variation, which means that adjusting the impedance matching of the LB antenna does not affect its low RCS characteristics, indicating that a separate design between the RCS and the impedance bandwidth/matching of the LB antenna is ideal.
An electromagnetically transparent base station antenna based on a frequency selective surface is shown in fig. 1 (a), 1 (b) and 1 (c), comprising a rectangular reflective ground 1 and a low frequency antenna 3 arranged overhead above the centre of the reflective ground 1. The low-frequency antenna 3 includes a low-frequency antenna dielectric substrate 41, two Y-shaped feeding structures provided on upper and lower surfaces of the low-frequency antenna dielectric substrate 41, and a frequency selection surface. The two Y-shaped feed structures are arranged orthogonally for exciting the energy of the two polarizations of the low frequency antenna, respectively. The low-frequency antenna 3 further comprises two low-frequency coaxial cables (not shown in the figure) corresponding to the Y-shaped feed structures one by one, wherein the outer conductors of the low-frequency coaxial cables are in contact with square loops at the bottom of the low-frequency antenna dielectric substrate 41, and the inner conductors of the low-frequency coaxial cables are connected with the energy input ends of the corresponding Y-shaped feed structures. In the figure, reference numeral 7 denotes a port 1, and reference numeral 8 denotes a port 2. Port 1 and port 2 are connected to the energy input of the two Y-shaped feed structures of the top layer via first metallized vias 61, respectively. In the embodiment of fig. 1 (a), to keep the current passing, two second metallized vias 62 are used to connect the bottom metal tab and the upper Y-feed line.
The frequency selective surface of the low-frequency antenna 3 in this embodiment is formed by frequency selective surface units arranged in a 2×2 array structure as shown in fig. 1 (a) and 1 (b), where the frequency selective surface units (see scheme F4 in fig. 2) include a square loop, and a rectangular metal sheet disposed inside the square loop and used for improving high-frequency electromagnetic transparency and insulated from the square loop, and the rectangular metal sheet is provided with cross slots (experiments show that the transverse slots or the vertical slots can achieve similar technical effects). As shown, the cross slit is a through length, and the rectangular metal sheet is divided into four small metal sheets by the through length slit. When a transverse slit or a vertical slit solution is used, the rectangular metal sheet is then divided into two small metal sheets. The high-frequency electromagnetic transparency of the low-frequency antenna can be adjusted by adjusting the parameters of the metal sheet. The dimensions of the metal sheet can be obtained by scanning parameters. The specific parameters include the side length of the metal sheet and the width of the opening gap.
In order to improve the high-frequency electromagnetic transparency of the low-frequency antenna, in the present embodiment, the low-frequency antenna further includes a stepped width arm 10 provided at the outer corner of the square loop for improving the low-frequency impedance bandwidth and a crossing vertical strip line 9 provided between adjacent square loops. The low-frequency impedance bandwidth of the low-frequency antenna 3 is adjusted by adjusting the parameters of the stepped width arm 10 and the crossed vertical strip line 9, and the adjustment of the low-frequency impedance bandwidth and the adjustment of the high-frequency electromagnetic transparency are mutually independent and do not interfere with each other. Of course, other methods of expanding the low frequency bandwidth besides the step width arms 10 and the intersecting vertical strip lines 9 may be employed, such as: and nesting square rings and adding parasitic structures.
In order to clearly demonstrate the autonomously controllable electromagnetic transparency characteristics and impedance matching of the LB antenna (i.e. the low frequency antenna in this embodiment), several key parameters (Lw were studied 2 、Lslotw、Lp 1 ) FIGS. 4 (a) and (b) show normalized RCS and |S for LB antennas 11 | a. The invention relates to a method for producing a fibre-reinforced plastic composite. It can be seen that with Lw 2 Is increased (from 6.3mm to 8.3 mm), the nadir shifts to lower frequencies (from 4.2GHz to 3.7 GHz), and the maximum RCS within HB decreases (from 0 to-10.41 dB). Meanwhile, |S 11 The l remains almost unchanged as shown in fig. 4 (b). Thus, lw is selected 2 =8.3 mm. In FIG. 4 (c), as Lslow increases (from 0.1 to 0.5 mm), the minimum RCS moves to higher frequencies (from 3.63 to 3.82 GHz), while |S 11 And | is fixed in fig. 4 (d). Lslotw=0.3 mm was selected in view of machining accuracy. As shown in FIG. 4 (e), when Lp 1 The normalized RCS showed little change when increased (from 10mm to 16 mm). Conversely, |S 11 The second resonance mode in l shifts to lower frequencies and the bandwidth follows Lp 1 Is narrowed by the increase of (a) as shown in fig. 4 (f). Thus, for a wider bandwidth (|s) 11 |<-15dB)，Lp 1 Set to 13mm. The result shows that the electromagnetic transparency of the LB antenna is represented by Lw 2 And Lstw control, the impedance matching of which can be controlled by Lp 1 And (5) adjusting.
As shown in fig. 1, the dual-band base station antenna array proposed in this embodiment includes a rectangular reflective ground 1, four high-frequency antennas disposed overhead above four corners of the reflective ground 1, and one low-frequency antenna 3 disposed overhead above the center of the reflective ground 1 and located above the high-frequency antennas (see the above low-frequency antenna for structure), where the projection portions of the low-frequency antenna 3 and the high-frequency antenna on the reflective ground 1 overlap (the four corners of the low-frequency antenna 3 respectively block the inner corners of the four high-frequency antennas 2). Wherein the low frequency antenna 3 has a frequency selective surface and two Y-shaped feed structures arranged orthogonally above the frequency selective surface for exciting the energy of the two polarizations of the low frequency antenna, respectively. Surprisingly, the high frequency antenna array may also take other forms, such as a cross.
In this embodiment, the high-frequency antenna 2 includes a high-frequency antenna dielectric substrate 42, four square loops arranged in a 2×2 array structure at the bottom of the high-frequency antenna dielectric substrate 42, and two Y-shaped feeding structures arranged at the top of the high-frequency antenna dielectric substrate 42 for exciting energy in two polarization directions of the high-frequency antenna respectively.
In this embodiment, on the one hand, four small square metal sheets are added into the square loop to improve EM transparency characteristics of the FSS unit at HB. On the other hand, the combination of the stepped wide arms and the crossed vertical strip line improves the impedance bandwidth of the LB antenna. In addition, the 4 HB antennas are all designed into square ring shape, and the center-to-center spacing is fixed to be 0.77 lambda h (λ h Wavelength at the center operating frequency of HB). Both LB and HB antennas were placed on a dielectric substrate (. Epsilon.) with a thickness of 0.8mm r =4.4, tan δ=0.02). Y-shaped feeder lines with good impedance matching effect are printed on the top layer of the same dielectric substrate. Details of the feed structure are shown in fig. 1 (a). The first metallized via 61 is 0.8mm and the second metallized via 62 is 0.6mm in diameter. The detailed parameter values of the low-RCS FSS-based LB antenna array of this example are shown in Table I.
TABLE I
The low-RCS FSS-based LB antenna designed as described above was introduced into the proposed array and its transparency properties were verified as shown in fig. 1. For illustration, the reference antenna array is shown in fig. 5. The specification defines three antenna arrays: antenna array 1 (HB alone), antenna array 2 (reference antenna) and antenna array 3 (the proposed antenna of the present invention). To evaluate the shielding effect of LB antennas on HB antennas, the radiation patterns of LB antennas in the three antenna arrays were almost the same as shown in fig. 6 (a). The result shows that the low-RCS FSS-based LB antenna has good radiation performance. In fig. 6 (b), the HB radiation pattern of the antenna array 2 is distorted with a decrease in the Half Power Beam Width (HPBW), a decrease in gain, and even an increase in cross polarization. By using low-RCS FSS-based LB antennas in antenna array 3, the radiation performance is expected to be improved, almost the same as in antenna array 1. The blocking effect of LB antennas on HB antennas is hardly obvious. In order to finely evaluate the fluctuation level of the HB antenna in the radiation pattern, HPBW is used as an important index. The inventors defined a new metric to measure the maximum HPBW difference (MDHPBW) between antenna array 1 and antenna array 2/3. The smaller the MDHPBW value, the better the electromagnetic transparency of the LB antenna to HB, and the better the radiation performance of HB antenna is recovered. In fig. 7, the HPBW of the three antenna arrays is plotted. The MDHPBW of the antenna array proposed by the present invention is 3.17 ° whereas the MDHPBW of the reference array is 12.38 °. It is apparent that the EM transparent characteristics of the low-RCS FSS-based LB antenna proposed herein are significantly improved and its blocking effect is greatly reduced over the entire HB.
Test results
Fig. 8 shows a prototype of the proposed antenna array. The positions of ports 1-10 are shown in fig. 8 (b). Fig. 9 shows simulated and measured S parameters for LB and HB antennas. It can be seen that the |S of two antenna ports in LB antenna 11 I and S 22 The measurement is less than-15 dB (45%) in the range of 1.7-2.7 GHz. The bandwidth of HB antenna in the measurement covers 3.3-3.8GHz (14%), satisfies the bandwidth requirement of present communication. Further, LB antenna and HB antenna (|s) 21 I and S 43 I) and HB antennas (|s) 35 I) are greater than 25dB.
Fig. 10 shows simulated and measured radiation patterns of an LB antenna (port 1 excitation) and an HB antenna (port 3 excitation) on the H-plane and V-plane, respectively. It was observed that the simulated and measured radiation patterns fit well. Both the LB antenna and the HB antenna have stable radiation performance. The antenna gain and HPBW are shown in fig. 11. The average analog gain of the LB antenna was about 8.96dBi, and the measured gain was 8.69dBi. HPBW was measured to be 62.12 ° ± 8 °. For the HB antenna, the average antenna gain values obtained by simulation and measurement are about 8.32dBi and 8.15dBi. The HPBW measured was 68.88 ° ± 4 °. In summary, the measurement results agree well with the simulation results, and small differences between the two are acceptable.
In the present invention, the low-RCS FSS unit is designed as an LB antenna. And then introducing an LB antenna into the 2X 2HB array, and inhibiting the blocking effect of the LB antenna on the HB antenna. The results show that the radiation pattern of the HB antenna is well recovered over the entire HB compared to the reference array. In addition, the electromagnetic transparent characteristic and the impedance matching of the LB antenna can be controlled independently, so that time-consuming optimization is avoided. Therefore, the low-RCS FSS-based antenna has good working performance, good HB antenna radiation pattern recovery capability and great attraction in a dual-frequency shared aperture array.
While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (10)
1. An electromagnetically transparent base station antenna based on a frequency selective surface, comprising:
a rectangular reflective ground (1);
the low-frequency antenna (3) is arranged above the center of the reflecting ground (1) in an overhead manner; the low-frequency antenna (3) comprises a frequency selection surface, a low-frequency antenna medium substrate (41) and two Y-shaped feed structures which are arranged in an orthogonal manner and are used for exciting two polarization energies of the low-frequency antenna, wherein the frequency selection surface, the low-frequency antenna medium substrate and the Y-shaped feed structures are stacked from bottom to top; the frequency selective surface is composed of frequency selective surface units arranged in a 2 x 2 array structure, the frequency selective surface units have square loops, and the frequency selective surface unit is characterized in that:
the low-frequency antenna dielectric substrate (41) is characterized in that a metal sheet which is positioned inside the square loop, used for improving high-frequency electromagnetic transparency and insulated from the square loop is arranged on the lower surface of the low-frequency antenna dielectric substrate (41), and a transverse gap, a vertical gap or a cross gap is formed in the metal sheet.
2. The electromagnetically transparent base station antenna based on a frequency selective surface according to claim 1, wherein: the lower surface of the low-frequency antenna dielectric substrate (41) is also provided with a step width arm (10) which is arranged at the outer corner of the square loop and used for improving the bandwidth of low-frequency impedance, and a crossed vertical strip line (9) which is arranged between adjacent square loops.
3. The electromagnetically transparent base station antenna based on a frequency selective surface according to claim 1, wherein: the metal sheet is rectangular metal sheet, the gap is full length, and the rectangular metal sheet is divided into two or four small metal sheets by the full length gap.
4. The electromagnetically transparent base station antenna based on a frequency selective surface according to claim 1, wherein: the dimensions of the metal sheet are obtained by scanning parameters.
5. The electromagnetically transparent base station antenna based on a frequency selective surface according to claim 1, wherein: the low-frequency coaxial antenna further comprises two low-frequency coaxial cables which are in one-to-one correspondence with the Y-shaped feed structures, wherein the outer conductors of the low-frequency coaxial cables are in contact with square loops at the bottom of the low-frequency antenna medium substrate (41), and the inner conductors of the low-frequency coaxial cables are connected with the energy input ends of the corresponding Y-shaped feed structures.
6. The electromagnetically transparent base station antenna based on a frequency selective surface according to claim 2, wherein: the low-frequency impedance bandwidth of the low-frequency antenna (3) is adjusted by adjusting parameters of the step width arm (10) and the crossed vertical strip line (9); the high-frequency electromagnetic transparency of the low-frequency antenna (3) is adjusted by adjusting parameters of the metal sheet, and the adjustment of the bandwidth of the low-frequency impedance and the adjustment of the high-frequency electromagnetic transparency are mutually independent and do not interfere with each other.
7. A dual-band base station antenna array comprising a high-frequency antenna array, characterized in that: -further comprising an electromagnetic transparent base station antenna based on a frequency selective surface according to any of claims 1-6, said high frequency antenna array being arranged overhead above the reflective ground (1) and below said low frequency antenna (3).
8. The dual-frequency base station antenna array of claim 7, wherein: the projections of the low-frequency antenna (3) and the high-frequency antenna array on the reflection ground (1) are overlapped.
9. The dual frequency base station antenna array of claim 8, wherein: the high-frequency antenna array comprises four high-frequency antennas (2) which are arranged in a 2 multiplied by 2 array structure, and four corners of the low-frequency antenna (3) are respectively used for shielding inner angles of the four high-frequency antennas (2).
10. The dual frequency base station antenna array of claim 8, wherein: the high-frequency antenna (2) comprises a high-frequency antenna dielectric substrate (42), four square loops arranged in a 2X 2 array structure at the bottom of the high-frequency antenna dielectric substrate (42), and two Y-shaped feed structures arranged at the top of the high-frequency antenna dielectric substrate (42) and respectively used for exciting energy in two polarization directions of the high-frequency antenna (2).
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| CN117855863A (en) * | 2024-02-19 | 2024-04-09 | 南通大学 | Electromagnetic transparent base station antenna and array based on grid |
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| CN117855863A (en) * | 2024-02-19 | 2024-04-09 | 南通大学 | Electromagnetic transparent base station antenna and array based on grid |
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