A compact high-isolation dual-frequency dual-polarization filtering antenna

Abstract

The present invention discloses a compact high-isolation dual-frequency dual-polarization filtering antenna, comprising a reflective floor, a low-pass filter patch antenna unit and a high-pass filter dipole antenna unit, wherein the low-pass filter patch antenna unit comprises a first layer of feed patches and a second layer of parasitic patches, wherein the second layer of parasitic patches is located above the first layer of feed patches, the first layer of feed patches is arranged above the reflective floor, and square gaps are provided between the first layer of feed patches and the second layer of parasitic patches; the high-pass filter dipole antenna unit is nested in the middle of the low-pass filter patch antenna, and the centers of the two coincide; the high-pass filter dipole antenna unit comprises two pairs of dipole arms and a pair of baluns, wherein the two pairs of dipole arms are located above the second layer of parasitic patch antennas, and the baluns are vertically inserted into the gaps between the two layers of patch antennas and connected to the reflective floor. The present invention overcomes the problem of strong coupling when dual-band antennas are nested together, and realizes the miniaturization and high performance of dual-band antennas.

Description

Technical Field

[0001] The invention relates to the field of antennas in mobile communications, and in particular to a compact high-isolation dual-frequency dual-polarization filtering antenna. Background Art

[0002] In 5G communication research, massive MIMO antenna technology is a key technical means to improve channel capacity. In massive MIMO antennas, the spacing between antenna arrays must be close enough and the beam width of the array unit must be wide enough to achieve a larger angle beam scanning range. The close spacing between arrays will lead to poor isolation, so miniaturization of antenna units is also necessary. In massive MIMO applications, since the spacing between antenna arrays in the same frequency band is very small, it is difficult to have extra space to embed the antenna array of another frequency band. Even after miniaturization, the antennas of the two frequency bands are embedded together, then the coupling between the antennas of the two frequency bands will be very large, affecting the radiation pattern of the antennas of the two frequency bands, resulting in a decrease in communication quality. If the isolation is improved by cascading filters under each array, the design and installation cost will increase significantly in the scenario of massive MIMO antenna arrays. On the other hand, in high-frequency band application scenarios, the loss of circuits such as filters and microstrip lines is greater, which has a greater impact on the gain of the antenna.

[0003] In recent years, the use of filtering antenna unit decoupling technology to design dual-band antennas with smaller frequency intervals has attracted attention. Specific literature such as "A Compact Dual-band Dual-polarized Antenna with FilteringStructures for Sub-6GHz Base Station Applications" uses the principle of filtering antenna decoupling to design a dual-band dual-polarized antenna (2.5-2.7GHz & 3.3-3.6GHz) for use in the 5G frequency band. However, the polarization states of the two frequency bands are different. It works at 0° and 90° polarization states at 2.5-2.7GHz, and at ±45° polarization states at 3.3-3.6GHz. The 0° and 90° polarization states are not commonly used in actual base station applications. In addition, the low-frequency array of this antenna is composed of a bowl-shaped array with a large caliber and a complex feeding network. If it is used in large-scale MIMO, the cost will also be high.

[0004] In view of the problems existing in the prior art, it is of great research significance and application value to study an antenna with small coupling between dual-frequency base station antennas or a small occupied area. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a compact high-isolation dual-frequency dual-polarization filtering antenna. The antenna is based on the decoupling principle of the filtering antenna, does not require an additional filtering circuit, has a smaller aperture, and has higher isolation. It can be applied to 5G communication dual-frequency dual-polarization antenna units.

[0006] The purpose of the present invention is achieved through the following technical solutions: a compact high-isolation dual-frequency dual-polarization filtering antenna, comprising a reflective floor, a low-pass filter patch antenna unit and a high-pass filter dipole antenna unit, the low-pass filter patch antenna unit comprises a first layer of feed patches and a second layer of parasitic patches, the second layer of parasitic patches is located above the first layer of feed patches, the first layer of feed patches is arranged above the reflective floor, and square gaps are opened between the first layer of feed patches and the second layer of parasitic patches; the high-pass filter dipole antenna unit is nested in the middle of the low-pass filter patch antenna, and the centers of the two coincide; the high-pass filter dipole antenna unit comprises two pairs of dipole arms and a pair of baluns, the two pairs of dipole arms are located above the second layer of parasitic patch antennas, the baluns are vertically inserted into the gaps between the two layers of patch antennas, and are connected to the reflective floor. The present invention overcomes the problem of strong coupling when dual-band antennas are nested together, and realizes the miniaturization and high performance of dual-band antennas.

[0007] Preferably, the centers of the low-pass filtering patch antenna unit and the high-pass filtering dipole antenna unit coincide with the center of the reflective floor.

[0008] Preferably, the first layer of feeding patches and the second layer of parasitic patches are both square, and a square gap is opened in the middle of the two layers of patches, and the vertical balun of the high-pass filter dipole antenna unit passes through the square gap and is connected to the reflective floor, thereby achieving a low profile and miniaturization of the dual-band antenna unit.

[0009] Preferably, the low-pass filter patch antenna unit adjusts the frequency selectivity of the high frequency band by controlling the size of the second layer parasitic patch.

[0010] Preferably, the low-pass filter patch antenna unit improves out-of-band suppression performance by changing the height between the first layer of feeding patches and the reflective floor.

[0011] Preferably, a pair of baluns of the high-pass filtering dipole antenna unit are orthogonally placed, and the feeding network of the balun structure has filtering characteristics in the low frequency band.

[0012] Preferably, the high-pass filtering dipole antenna unit specifically loads a quarter-wavelength branch on the balun feed network line to achieve filtering performance, and improves the out-of-band suppression effect by parasitizing a ring-shaped microstrip line under the dipole arm.

[0013] Preferably, the low-pass filter patch antenna operates in a low frequency band, and the high-pass filter dipole antenna operates in a high frequency band, and the two frequency bands are spaced 1.2-1.8 times apart.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] The present invention uses a filtering antenna unit without an external loss circuit as the basic unit of the dual-band base station antenna, which can achieve efficient radiation within the band and effective suppression outside the band. The passband edge of the gain rolls off very quickly. Therefore, by utilizing this filtering characteristic, the mutual coupling between multiple basic units with similar working frequency bands can be reduced. At the same time, the antenna units of the two frequency bands use two different antenna arrays, namely patches and dipoles. This facilitates the arrangement of the dipole array in an embedded manner in the patch array, saving occupied space and ensuring stable radiation patterns of the two frequency bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a front structural diagram of the present invention;

[0017] Figure 2 It is a three-dimensional exploded structural diagram of the present invention;

[0018] Figure 3 It is a structural diagram of the dipole arm and parasitic metal ring of the filtering dipole antenna unit of the present invention;

[0019] Figure 4 is a structural diagram of a balun and a feeding network of the filtering dipole antenna unit of the present invention;

[0020] Figure 5 is a structural diagram of the first metal sheet layer of the filtering patch antenna unit of the present invention;

[0021] Figure 6 is a structural diagram of the second metal sheet of the filtering patch antenna unit of the present invention;

[0022] Figure 7 is a structural diagram of the reflective floor and the feeding network of the filter patch antenna of the present invention;

[0023] Figure 8 It is a simulation result diagram of reflection coefficient & polarization isolation-frequency of the filtering antenna unit of the present invention working in the frequency band of 2500-2700MHz and 3300-3800MHz;

[0024] Fig. 9 It is a gain result diagram of the filtering antenna of the present invention working in the frequency bands of 2500-2700MHz and 3300-3800MHz;

[0025] Fig.10It is a simulation result diagram of the frequency isolation of the filtering antenna of the present invention working in the frequency bands of 2500-2700MHz and 3300-3800MHz;

[0026] Fig.11 It is a simulation result diagram of the directional diagram of the present invention working at 2600MHz;

[0027] Fig.12 It is a simulation result diagram of the directional diagram of the present invention working at 3550MHz. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] Example

[0030] like Figure 1-7 As shown, the present embodiment is a compact high-isolation dual-frequency dual-polarization filtering antenna, comprising a filtering patch antenna unit 1 working in a low frequency band and a filtering dipole antenna unit 2 working in a high frequency band, and the two share a reflector 3. The two units adopt different array structures, one adopts a patch form and the other adopts a dipole form, so that when the working frequency bands are close to each other, the space can be fully utilized, and the dipole is nested in the middle of the patch, so that the antennas of the two frequency bands are integrated and designed at a phase center point, and the two working frequency bands are close to each other. The patch antenna working in the low frequency band can achieve a low-pass filtering response effect, and filter out the signal of the array antenna working in the high frequency band, and the filtering dipole antenna working in the high frequency band can achieve a high-pass filtering response effect, and filter out the signal of the patch antenna working in the low frequency band, thereby reducing the influence between the two working frequency bands, wherein the dual-frequency dual-polarization filtering antenna array does not add an additional filtering circuit, so that the feeding network is simpler, the insertion loss is greatly reduced, and the overall efficiency of the antenna is improved.

[0031] The high frequency band and the low frequency band of the dual-polarization filtering antenna are relatively close, about 1.2-1.8 times.

[0032] The filter patch antenna unit includes a first metal sheet 4 and a second metal sheet 5. The first and second metal sheets are separated by a certain distance, and the distance is determined according to the actual situation. The first metal sheet is arranged above the reflective floor 3 and is separated by a certain distance, and the specific distance is determined according to the actual situation. The second metal sheet is located above the first metal sheet. The first metal sheet and the second metal sheet are both square rings, and the specific size depends on the situation.

[0033] The filtering dipole antenna unit comprises two pairs of dipole arms 6, a pair of baluns 7 and a parasitic metal square ring 8. The two pairs of dipole arms 6 are printed on the upper surface of a double-sided PCB circuit board 9, wherein one pair of dipole arms constitutes a +45° linear polarization and the other pair of dipole arms constitutes a -45° linear polarization. The two pairs of dipole arms are connected to the floor 3 through the balun 7 and are fed through the balun 7. A feeding network 10 is provided on the balun, and the feeding network 10 has filtering characteristics. The parasitic metal square ring 8 is printed on the lower surface of the double-sided PCB circuit board 9.

[0034] The filtering dipole antenna unit 2 is nested in the middle of the filtering patch antenna unit 1, and the phase center points of the filtering dipole antenna unit 2, the filtering patch antenna unit 1 and the reflecting plate 3 coincide with each other. Compared with the traditional dual-frequency antenna with close frequencies, this placement of the dual-frequency antenna will make the radiation pattern of the antenna more stable and symmetrical, and will also further improve the space utilization.

[0035] The filtering characteristics of the filtering patch antenna unit in this embodiment are achieved by adjusting the distance from the first metal sheet 4 to the reflector 3 and changing the size of the second metal sheet 5. The size of the second metal sheet can control the size of the zero point, and the out-of-band suppression performance of 3300-3800MHz can be improved by adjusting the distance from the first metal sheet 4 to the reflector 3. The filtering method has a certain degree of universality.

[0036] In this embodiment, the feed network with filtering characteristics in the filtering dipole antenna unit is realized by loading a quarter-wavelength branch on the feed network and parasitizing a metal square ring under the dipole arm. The length of the quarter-wavelength branch controls the position of the zero point, and the metal square ring is mainly used to improve the out-of-band suppression performance at 2500-2700MHz. The filtering technology and parasitic metal square ring used in the feed network are also widely applicable to ordinary antenna units.

[0037] In this embodiment, the frequency interval between the working frequency bands of the two sub-arrays, 2500-2700MHz and 3300-3800MHz, is relatively small. The low-frequency unit radiates efficiently in the 2500-2700MHz band and suppresses radiation in the out-of-band, i.e., 3300-3800MHz band; meanwhile, the high-frequency unit radiates efficiently in its working frequency band, 3300-3800MHz, and suppresses radiation in the out-of-band, i.e., 2500-2700MHz band. Therefore, the radiation of the two units does not interfere with each other, thereby reducing mutual interference and achieving a higher port isolation.

[0038] like Figure 8As shown, it is the reflection coefficient S of the filtering antenna unit without external loss circuit provided by one embodiment of the present invention working in the frequency band of 2500-2700MHz and 3300-3800MHz. 11 & Polarization isolation-frequency simulation results. It can be seen that the echoes in both frequency bands are lower than -14dB. Fig. 9 In the gain curve, the gains of the two frequency bands are both higher than 8.2dBi, the passband edge is steep, the sideband suppression is obvious, the frequency selectivity is good, and the in-band gain is flat. Fig.10 The isolation between the two frequency bands is also higher than 24dB. This is because both antennas have a certain filtering effect, which can produce a zero point at the sideband position of the other frequency band.

[0039] Fig.11 and Fig.12 The radiation patterns of the dual-frequency dual-polarized antenna at 2.6 GHz and 3.55 GHz are given respectively. It can be seen from the result diagram that the antenna array has a stable radiation pattern and is not affected by the insertion of filtering characteristics.

[0040] The present invention uses a filter antenna unit without an external loss circuit as the basic component unit of a compact high-isolation dual-band dual-polarization filter antenna, and can use its filtering characteristics to reduce the mutual coupling between the two frequency band antennas, improve the isolation between the two working frequency bands, eliminate the insertion loss introduced by the filter, and thus improve the gain of the antenna, and achieve stable radiation pattern performance in two working frequency bands in the same volume as a single array of a single frequency band. The use of this arrangement of the filter dipole antenna unit nested in the filter patch antenna unit can greatly reduce the occupied space, overcome the defect that the traditional non-filter antenna can only be embedded in the case of frequency doubling, and realize a miniaturized dual-band dual-polarization antenna unit when the frequencies are very close.

[0041] The compact high-isolation dual-frequency dual-polarization filtering antenna described in this embodiment has the following advantages:

[0042] (1) Integrated filtering and radiation characteristics. The antenna basic unit itself has filtering performance, steep passband edge, obvious sideband suppression, and good frequency selection characteristics. No external duplexer or decoupling network circuit is required, which overcomes the disadvantages of large loss and large volume caused by using external duplexers or decoupling networks.

[0043] (2) The antenna array is suitable for frequency bands with very close frequency intervals. Without the need for decoupling circuits, it achieves high port isolation, suppresses adjacent frequency interference, and improves the performance of base station transceivers.

[0044] (3) This design uses two different antenna elements and embeds the dipole antenna unit into the patch antenna unit, which reduces the size and space occupied. In addition, the phase centers of the patch antenna unit and the dipole antenna unit are consistent, and the directional pattern of each frequency band is very stable, which can be applied to MIMO antenna technology.

[0045] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A compact high-isolation dual-frequency dual-polarization filtering antenna, characterized in that: It comprises a reflective floor, a low-pass filter patch antenna unit and a high-pass filter dipole antenna unit, wherein the low-pass filter patch antenna unit comprises a first layer of feed patches and a second layer of parasitic patches, wherein the second layer of parasitic patches is located above the first layer of feed patches, the first layer of feed patches is arranged above the reflective floor, and square gaps are provided between the first layer of feed patches and the second layer of parasitic patches; the high-pass filter dipole antenna unit is nested in the middle of the low-pass filter patch antenna, and the centers of the two coincide; the high-pass filter dipole antenna unit comprises two pairs of dipole arms and a pair of baluns, wherein the two pairs of dipole arms are located above the second layer of parasitic patch antennas, and the baluns are vertically inserted into the gap between the two layers of patch antennas and connected to the reflective floor; The low-pass filter patch antenna unit adjusts the frequency selectivity of the high frequency band by controlling the size of the second layer of parasitic patches; The low-pass filter patch antenna unit improves the out-of-band suppression performance by changing the height between the first layer of feeding patches and the reflective floor.

2. The compact high-isolation dual-frequency dual-polarization filtering antenna according to claim 1, characterized in that: The centers of the low-pass filtering patch antenna unit and the high-pass filtering dipole antenna unit coincide with the center of the reflecting floor.

3. The compact high-isolation dual-frequency dual-polarization filtering antenna according to claim 1, characterized in that: The first layer of feeding patches and the second layer of parasitic patches are both square, and a square gap is opened in the middle of the two layers of patches. The vertical balun of the high-pass filtering dipole antenna unit passes through the square gap and is connected to the reflecting floor.

4. The compact high-isolation dual-frequency dual-polarization filtering antenna according to claim 1, characterized in that: A pair of baluns of the high-pass filtering dipole antenna unit are placed orthogonally, and the feeding network of the balun structure has filtering characteristics in the low frequency band.

5. The compact high-isolation dual-frequency dual-polarization filtering antenna according to claim 4, characterized in that: The high-pass filtering dipole antenna unit specifically realizes filtering performance by loading a quarter-wavelength branch on the balun feed network line, and improves the out-of-band suppression effect by parasiticizing a ring-shaped microstrip line under the dipole arm.

6. The compact high-isolation dual-frequency dual-polarization filtering antenna according to claim 1, characterized in that: The low-pass filter patch antenna operates in a low frequency band, and the high-pass filter dipole antenna unit operates in a high frequency band, and the two frequency bands are spaced 1.2-1.8 times apart.

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