Millimeter wave broadband filtering antenna with large angle beam scanning function and array

Abstract

The application discloses a kind of millimeter wave broadband filtering antennas with wide-angle beam scanning function and array, from top to bottom include broadband radiator, metal ground layer and microstrip line feed layer in sequence, the broadband radiator includes first rectangular patch, second rectangular patch and driving patch;By controlling the size of first metal patch, second metal patch and driving patch, the resonant frequency of broadband radiator is regulated;By adjusting the distance between first rectangular patch, second rectangular patch and driving patch, and the spacing of adjacent first metal patch and adjacent second metal patch, the coupling amount of broadband radiator is regulated, and the bandwidth of broadband radiator is further regulated.The application has simple and compact structure, wide impedance bandwidth, and can cover four millimeter wave frequency bands.

Description

Technical Field

[0001] This invention relates to the field of wireless communication, and in particular to a millimeter-wave broadband filter antenna and array with a large-angle beam scanning function. Background Technology

[0002] With the development of 5G wireless communication, millimeter-wave bands have received widespread attention due to their abundant spectrum resources. Commercial millimeter-wave bands typically include four sub-bands: N258 (24.25-27GHz), N257 (26.5-29.5GHz), N260 (37-40GHz), and N259 (39.5-43.5GHz). In wireless systems, a broadband antenna covering multiple frequency bands is urgently needed to save space. To achieve broadband radiation, antennas typically expand bandwidth by adding additional resonant modes or by reducing the quality factor of the radiator to increase impedance bandwidth. Different radiation modes may not guarantee stable radiation over a broadband range; for example, the radiation pattern may change, or the antenna gain may change abruptly. Therefore, designing a millimeter-wave broadband antenna that simultaneously covers four frequency bands and provides stable radiation over a wide broadband range remains a significant challenge.

[0003] Compared to Sub-6GHz band antennas, millimeter-wave antennas have higher integration density and greater loss, thus typically requiring antenna arrays with beam scanning capabilities to simultaneously provide higher gain and wider coverage. To achieve large-angle beam scanning of an antenna array, antenna elements need to have a large beamwidth. Smaller element sizes also allow for reduced spacing between antenna elements, improving the array's beam scanning capability over a wide bandwidth. Therefore, designing a small, compact broadband antenna can help the antenna array achieve a large beam scanning range over a wide bandwidth.

[0004] Furthermore, millimeter-wave antennas typically need to be connected to other RF components (such as filters) to suppress out-of-band interference. Traditional cascaded antenna and filter solutions result in bulky size, reduced integration density, increased insertion loss, and a decline in overall system performance. Common filtering antenna design methods involve replacing the last resonator of the filter with an antenna or introducing a radiation null in the stopband to suppress antenna radiation and achieve filtering functionality. However, in millimeter-wave antenna design, due to size constraints and manufacturing limitations, realizing millimeter-wave antennas with filtering capabilities is quite challenging. Researching millimeter-wave filtered antennas that do not require additional filtering circuitry is of great significance.

[0005] Therefore, the research on millimeter-wave broadband filter antennas has unique value in the development of 5G wireless communication. Summary of the Invention

[0006] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a millimeter-wave broadband filtering antenna with a large-angle beam scanning function.

[0007] Another objective of this invention is to provide a millimeter-wave broadband filter antenna array with a large-angle beam scanning function.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A millimeter-wave broadband filter antenna with a large-angle beam scanning function includes, from top to bottom, a broadband radiator, a metallic ground layer and a microstrip line feed layer. The broadband radiator includes a first rectangular patch, a second rectangular patch and a driving patch.

[0010] The first rectangular patch is composed of 3×3 first metal patches arranged in an array;

[0011] The second rectangular patch is composed of 2×2 second metal patches arranged in an array, and a long strip parasitic patch is set at the center of the second rectangular patch;

[0012] The metallic stratum includes a metallic ground plane and an H-shaped slot disposed on the metallic ground plane;

[0013] The microstrip feed layer includes a microstrip feed line, the end of which is connected to the metal ground layer through a grounding metal via.

[0014] The resonant frequency of the broadband radiator is adjusted by controlling the size of the first and second metal patches; the coupling amount of the broadband radiator is adjusted by adjusting the distance between the first rectangular patch, the second rectangular patch and the driving patch, as well as the spacing between adjacent first and second metal patches, thereby further controlling the bandwidth of the broadband radiator.

[0015] Furthermore, it includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate stacked sequentially.

[0016] A first rectangular patch is disposed on the upper surface of the first dielectric substrate, a second rectangular patch is disposed on the lower surface of the first dielectric substrate, and a driving patch is disposed on the lower surface of the second dielectric substrate; a metal ground layer is disposed on the lower surface of the third dielectric substrate, and a microstrip line feed layer is disposed on the lower surface of the fourth dielectric substrate.

[0017] Furthermore, the first metal patch includes a square patch and a rectangular patch, wherein there are three square patches, located in the middle of the first rectangular patch, with rectangular patches on both sides.

[0018] Furthermore, the microstrip feed line is a microstrip line with a gradually changing impedance.

[0019] Furthermore, the elongated parasitic patch is perpendicular to the H-shaped gap. The elongated parasitic patch generates a current opposite to that of the driving patch at its half-wavelength resonant frequency, generating a third radiation null point. Adjusting the length of the elongated parasitic patch further adjusts the position of this radiation null point.

[0020] Furthermore, the driving patch is square, and the four corners of the square are chamfered.

[0021] Furthermore, the thicknesses of the four dielectric substrates are 0.25 mm, 0.2 mm, 0.508 mm and 0.2 mm, respectively.

[0022] Furthermore, a short circuit at the end of the microstrip feed line will prevent the energy from being effectively coupled to the broadband radiator at a specific frequency, resulting in two radiation nulls. The specific frequencies are one-quarter and three-quarter wavelengths of the distance from the end of the microstrip line to the ground plane gap. Adjusting this distance will simultaneously adjust the positions of the two radiation nulls.

[0023] An array composed of the aforementioned millimeter-wave broadband filter antennas includes N millimeter-wave broadband filter antennas arranged in an array, where N is at least one.

[0024] Furthermore, the feed ports of the N millimeter-wave broadband filter antennas are connected to the power divider feed network by connecting phase extension lines of different lengths, so as to assign different phases to each antenna and realize the beam scanning function of the antenna array.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) The broadband radiator of the present invention is composed of three layers of patches stacked together. The antenna structure is simple, the impedance bandwidth is wide, and it can cover four commercial millimeter wave sub-bands.

[0027] (2) The embodiments of the present invention do not include additional filtering circuits, do not increase the antenna volume, and have good engineering application value.

[0028] (3) The embodiments of the present invention have three radiation nulls outside the passband, which have good out-of-band suppression capability, while having good radiation performance within the passband, making them more suitable for high-integration millimeter-wave antenna applications.

[0029] (4) The antenna unit of the present invention is small in size, and the array antenna formed therefrom has broadband radiation capability and large-angle beam scanning function, which can meet the commercial needs of millimeter wave antennas. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is an exploded view of the structure of the millimeter-wave broadband filter antenna according to an embodiment of the present invention;

[0032] Figure 2 This is a structural diagram of the broadband radiator of the millimeter-wave broadband filter antenna according to an embodiment of the present invention;

[0033] Figure 3 This is a structural diagram of the metal ground layer and microstrip line feed layer of the millimeter-wave broadband filter antenna according to an embodiment of the present invention;

[0034] Figures 4-7 These are schematic diagrams illustrating the evolution of the broadband radiator structures in antennas one through four.

[0035] Figure 8 Comparison of mode importance results for broadband radiators corresponding to antennas one through four;

[0036] Figure 9 This is a top view of a millimeter-wave broadband filter antenna array according to an embodiment of the present invention;

[0037] Figure 10 This is a bottom view of a millimeter-wave broadband filter antenna array according to an embodiment of the present invention;

[0038] Figure 11 The figure shows the simulation results of the return loss of the millimeter-wave broadband filter antenna according to an embodiment of the present invention.

[0039] Figure 12 The figure shows the gain simulation results of the millimeter-wave broadband filter antenna according to an embodiment of the present invention.

[0040] Figure 13 The figure shows the simulation results of the return loss of the millimeter-wave broadband filter antenna array according to an embodiment of the present invention.

[0041] Figure 14 This is a simulation result of the gain of the millimeter-wave broadband filter antenna array according to an embodiment of the present invention;

[0042] Figure 15 The simulation results of the radiation pattern of the millimeter-wave broadband filter antenna array in this embodiment of the invention when scanned to 0°, 30° and 60° at a frequency of 34 GHz are shown. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0044] Example

[0045] like Figure 1 As shown, a millimeter-wave broadband filter antenna with large-angle beam scanning capability comprises, from top to bottom, a broadband radiator 1, a metallic ground layer 2, and a microstrip line feed layer 3, with each functional layer connected by a dielectric substrate. The dielectric substrate is made of low-loss material to reduce losses in the millimeter-wave frequency band.

[0046] Furthermore, the dielectric substrate comprises four layers stacked sequentially. The first dielectric substrate 41 and the second dielectric substrate 42 control the coupling of the broadband radiator 1. In this embodiment, the thicknesses of the first dielectric substrate and the second dielectric substrate are 0.25 mm and 0.2 mm, respectively. The third dielectric substrate 43 mainly controls the height between the broadband radiator 1 and the antenna reference ground, i.e., the metal ground layer 2, thereby satisfying the antenna's good radiation characteristics. In this embodiment, the thickness of the third dielectric substrate is 0.508 mm. The fourth dielectric substrate 44 mainly controls the distance between the microstrip line feed layer 3 and the metal ground layer 2 to ensure the RF signal transmission of the microstrip line feed layer. To prevent noise in the transmission line, the thickness of the fourth dielectric substrate is thinner; in this embodiment, the thickness is 0.2 mm.

[0047] This embodiment uses a relatively mature PCB process to laminate a multilayer dielectric substrate with various metal functional layers, and on this basis, provides an antenna array.

[0048] like Figure 2 As shown, the broadband radiator includes, from top to bottom, a first rectangular patch 13, a second rectangular patch 121, and a driving patch 11, with the three patches arranged coaxially.

[0049] The first rectangular patch 13 is disposed on the upper surface of the first dielectric substrate 41. A second rectangular patch 121 is disposed on the lower surface of the first dielectric substrate 41, and a driving patch 11 is disposed on the lower surface of the second dielectric substrate; a metal ground layer 2 is disposed on the lower surface of the third dielectric substrate 43, and a microstrip line feed layer 3 is disposed on the lower surface of the fourth dielectric substrate 44.

[0050] Further explanation: the first rectangular patch 13 is composed of 3×3 first metal patches arranged in an array; the first metal patches include two sizes, namely three square patches and six rectangular patches, with the middle column being square metal patches and the two side columns being rectangular patches. The purpose of using rectangular patches on the sides is to reduce the current in the cross-polarization direction, thereby improving polarization purity. In this embodiment, the size of the three middle square patches is 0.8mm×0.8mm, the size of the six rectangles is 0.8mm×0.4mm, and the patch spacing is 0.2mm.

[0051] The second rectangular patch 121 is composed of 2×2 second metal patches arranged in an array. Each second metal patch is rectangular in shape, with a long, vertically positioned parasitic patch at the center. The overall size of the second rectangular patch is larger than the size of the driving patch to achieve better coupling. In this embodiment, the second metal patch has dimensions of 0.65mm × 0.55mm, a patch spacing of 0.5mm, and the long, vertically positioned parasitic patch has dimensions of 1.4mm × 0.2mm.

[0052] The driving patch is specifically a square patch with chamfered corners at all four sides, used to achieve better impedance matching. In this embodiment, the square patch has dimensions of 1.25mm × 1.25mm, and the four chamfered corners are isosceles right triangles with a leg length of 0.4mm.

[0053] The second rectangular patch, located above the driving patch, adds an additional coupling path, lowers the resonant frequency of the broadband radiator, and simultaneously couples energy from the driving patch to the second rectangular patch array.

[0054] The third rectangular patch, placed above the second rectangular patch, further increases the coupling path of the broadband radiator, thereby further reducing the resonant frequency of the radiator and decreasing its size. At the same time, the increased coupling between the metal patches reduces the Q value of the broadband radiator, increases the bandwidth of the even modes, and enables the radiator to radiate more stably over a wide frequency band.

[0055] The resonant frequency of the radiator can be adjusted by controlling the size of each metal patch; the coupling amount of the radiator can be adjusted by the distance between the three layers of patches (the thickness of the dielectric substrate) and the spacing between the small patches, thereby further controlling the bandwidth of the broadband radiator.

[0056] like Figure 3As shown, the metal ground layer 2 includes a metal ground plane 21 and an H-shaped slot 22 disposed on the metal ground plane. The metal ground plane serves as both a reference ground plane for the broadband radiator and a reference ground for the microstrip feed line. The H-shaped slot is used to improve coupling energy, and the resonance generated by the H-shaped slot can further improve the impedance bandwidth of the antenna at low frequencies. In this embodiment, the H-shaped slot has a slot width of 0.2 mm, a center length of 1.7 mm, and side lengths of 0.5 mm, with a resonant frequency of approximately 25 GHz.

[0057] The driver patch mainly receives the energy transmitted from the microstrip line through the gap in the center of the metal ground plane, causing the broadband radiator to resonate. At the same time, its small size is mainly used to control the radiation performance of the broadband radiator at high frequencies.

[0058] The microstrip feed layer 3 includes a microstrip feed line 31 and a grounding metal via 32 at the end of the microstrip feed line connected to the metal ground layer 2. The H-shaped slot and the elongated parasitic patch are arranged perpendicular to each other.

[0059] The short-circuited microstrip feeder, consisting of the microstrip feeder 31 and the grounding metal via 32, can simultaneously control the energy of two specific frequencies from being effectively transmitted to the broadband radiator 1 by adjusting the path length from the short-circuited end of the microstrip line to the "H"-shaped slot, thereby generating two radiation nulls, Null#1 and Null#2, at the passband edge. The elongated parasitic patch 122 can generate a current opposite to that of the driving patch at its half-wavelength resonant frequency of 51.5 GHz. The radiation caused by the anti-phase current cancels out in the far field, generating a third radiation null, Null#3.

[0060] Specifically, the two specific frequencies refer to a low-frequency point and a high-frequency point outside the operating frequency band. In this embodiment, the values ​​are 17.5 GHz and 52.5 GHz, corresponding to one-quarter and three-quarters of the wavelength of the path length from the short-circuited end of the microstrip line to the "H"-shaped slot.

[0061] To further explain, while traditional rectangular two- or three-layer patch antennas can reduce size and provide additional resonance, the improvement in bandwidth is limited and insufficient to cover multiple frequency bands. This is because the electromagnetic coupling generated between the patches during resonance has a suppression effect on odd-mode radiation, preventing further bandwidth expansion.

[0062] Therefore, in order to obtain a greater bandwidth, this invention utilizes characteristic mode analysis to determine the main radiation modes of the radiator, i.e., the mode bandwidth of even modes. By changing the structure of the stacked patches, the conventional second-layer rectangular patch is changed to a 2×2 patch, which increases the resonant frequency of the second-layer patch and weakens the electromagnetic coupling between it and the first-layer rectangular patch. This reduces the size while preventing the generation of odd modes in the required frequency band, thus preventing the suppression effect from affecting the bandwidth expansion. Similarly, the third-layer rectangular patch is further changed to a 3×3 patch.

[0063] This invention utilizes a special design for a three-layer patch radiator structure, which effectively reduces the resonant frequency and size compared to traditional patch antennas. At the same time, the three-layer radiator structure composed of multiple small patches introduces additional coupling paths, reducing the quality factor of the radiator and increasing its even-mode bandwidth, enabling it to radiate stably over a wide bandwidth.

[0064] Figures 4-7 The structure of four reference stacked patch antennas is given, and the mode importance results for their corresponding even modes are as follows: Figure 8 As shown. Antenna 1 is a two-layer patch structure, resonating around 37GHz. Its mode bandwidth is relatively narrow, but there is no sudden drop within the band, indicating that the even mode is not affected by the odd mode. Antenna 2, with the addition of a rectangular patch layer to antenna 1, has a resonant frequency around 33GHz, proving that the added third patch layer can reduce the radiator's resonant frequency. Although the even-mode bandwidth of antenna 2 is improved compared to antenna 1, the presence of odd modes and electromagnetic coupling between modes cause the importance of even modes to drop sharply at high frequencies, hindering further bandwidth expansion. Replacing the third rectangular patch in antenna 2 with a 3×3 patch results in antenna 3. The results show that the resonant frequency does not change much, and the influence of odd modes on even modes disappears, while the even-mode bandwidth is further expanded. Further modification of the patch shape optimizes the broadband radiator proposed in this embodiment, namely antenna 4. The resonant frequency of antenna 4 is reduced to 31GHz, and the mode bandwidth is further expanded compared to antenna 3, proving that antenna 4 has better broadband radiation performance.

[0065] like Figure 9 and Figure 10 As shown, this embodiment also provides a millimeter-wave broadband filter antenna array, including a 1×8 antenna array composed of eight millimeter-wave broadband filter antennas. The broadband filter antennas are of the same size, and the spacing between adjacent antennas is generally less than half a wavelength. In this embodiment, it is set to 3.75 mm, which is 0.425 wavelengths at the operating center frequency of 34 GHz. The antenna array is fed from the input port 52 and connected to the microstrip feed lines 31 of the eight millimeter-wave broadband filter antennas through a 1-to-8 power divider network 51 and eight phase extension lines 6, respectively.

[0066] Furthermore, by adjusting the lengths of the eight phase extension lines 6, the phases of the array input port 52 to the eight millimeter-wave broadband filter antennas can be controlled respectively, thereby achieving beam scanning functions at different angles. In this embodiment, the port phase differences for 0°, 30°, and 60° array beam scanning achieved by the phase extension lines are 0°, 75°, and 145°, respectively.

[0067] like Figure 11 The figure shown is a simulation result of the return loss of the millimeter-wave broadband filter antenna according to an embodiment of the present invention. The impedance matching in the passband is good, covering 23-46GHz, and the return loss is below -10dB.

[0068] like Figure 12 The figure shown is a simulation result of the actual gain of the millimeter-wave broadband filter antenna according to an embodiment of the present invention. The gain is greater than 4.5 dBi in the operating frequency band and there are three radiation nulls outside the passband. The suppression of 15-20 GHz is greater than 20 dB and the suppression of 50-55 GHz is greater than 18 dB, which has good filtering function.

[0069] like Figure 13 The figure shown is a simulation result of the return loss of the millimeter-wave broadband filter antenna array according to an embodiment of the present invention. The impedance matching within the passband is good, covering 23.5-46.5GHz, and the return loss is below -10dB.

[0070] like Figure 14 The figure shown is a simulation result of the actual gain of the millimeter-wave broadband filter antenna array according to an embodiment of the present invention. The gain is greater than 9.5 dBi in the operating frequency band, and the gain suppression capability outside the low-frequency and high-frequency passbands is greater than 15 dB.

[0071] like Figure 15 The figure shows the radiation patterns of the millimeter-wave broadband filtered antenna array of this invention when it scans to different angles (0°, 30°, and 60°) at the center frequency of 34 GHz. As can be seen from the figure, the antenna array has good beam scanning capability. The gain drop of the antenna array when scanning to 60° does not exceed 4 dB, and the sidelobe suppression level during scanning is greater than 10 dB.

[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A millimeter-wave broadband filter antenna with large-angle beam scanning capability, characterized in that, From top to bottom, it includes a broadband radiator, a metallic ground layer, and a microstrip line feed layer. The broadband radiator includes a first rectangular patch, a second rectangular patch, and a driving patch. The first rectangular patch is composed of 3×3 first metal patches arranged in an array; The second rectangular patch is composed of 2×2 second metal patches arranged in an array, and a long strip parasitic patch is set at the center of the second rectangular patch; The metallic stratum includes a metallic ground plane and an H-shaped slot disposed on the metallic ground plane; The microstrip feed layer includes a microstrip feed line, the end of which is connected to the metal ground layer through a grounding metal via. The resonant frequency of the broadband radiator is controlled by adjusting the dimensions of the first metal patch, the second metal patch, and the driving patch; the coupling amount of the broadband radiator is controlled by adjusting the distance between the first rectangular patch, the second rectangular patch, and the driving patch, as well as the spacing between adjacent first metal patches and adjacent second metal patches, thereby further controlling the bandwidth of the broadband radiator.

2. The millimeter-wave broadband filtering antenna according to claim 1, characterized in that, It includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate stacked sequentially. A first rectangular patch is disposed on the upper surface of the first dielectric substrate, a second rectangular patch is disposed on the lower surface of the first dielectric substrate, and a driving patch is disposed on the lower surface of the second dielectric substrate. A metal ground layer is disposed on the lower surface of the third dielectric substrate, and a microstrip line feed layer is disposed on the lower surface of the fourth dielectric substrate.

3. The millimeter-wave broadband filtering antenna according to claim 1, characterized in that, The first metal patch includes a square patch and a rectangular patch. There are three square patches, located in the middle of the first rectangular patch, with rectangular patches on both sides.

4. The millimeter-wave broadband filtering antenna according to claim 1, characterized in that, The microstrip feed line is an impedance-gradient microstrip line.

5. The millimeter-wave broadband filtering antenna according to claim 1, characterized in that, The elongated parasitic patch is perpendicular to the H-shaped gap. The elongated parasitic patch generates a current opposite to that of the driving patch at its half-wavelength resonant frequency, generating a third radiation null point. Adjusting the length of the elongated parasitic patch further adjusts the position of the third radiation null point.

6. The millimeter-wave broadband filtering antenna according to any one of claims 1-5, characterized in that, The driver patch is square, and the four corners of the square are chamfered.

7. The millimeter-wave broadband filtering antenna according to claim 2, characterized in that, The thicknesses of the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, and the fourth dielectric substrate are 0.25 mm, 0.2 mm, 0.508 mm, and 0.2 mm, respectively.

8. The millimeter-wave broadband filtering antenna according to claim 1, characterized in that, A short circuit at the end of the microstrip feeder will prevent the energy from being effectively coupled to the broadband radiator at a specific frequency, resulting in two radiation nulls. The specific frequencies are one-quarter and three-quarter wavelengths of the distance from the end of the microstrip feeder to the H-shaped slot. Adjusting this distance will simultaneously adjust the positions of the two radiation nulls.

9. An array composed of the millimeter-wave broadband filter antenna according to any one of claims 1-8, characterized in that, It includes N millimeter-wave broadband filter antennas arranged in an array.

10. The array according to claim 9, characterized in that, The feed ports of N millimeter-wave broadband filter antennas are connected to the power divider feed network by connecting phase extension lines of different lengths, so that each antenna is assigned a different phase and the beam scanning function of the antenna array is realized.

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