Single-layer broadband SIW filter antenna with high out-of-band suppression

Abstract

The present invention discloses a single-layer broadband SIW filter antenna with high out-of-band suppression, comprising a rectangular SIW cavity formed on a dielectric substrate and having multiple resonant modes. A first group of shorting pins is loaded in the rectangular SIW cavity for dividing the rectangular SIW cavity into a left resonant cavity and a right resonant cavity resonating in a first resonant mode; a hexagonal groove is etched on the top surface of the left resonant cavity of the rectangular SIW cavity, and a hexagonal microstrip patch resonating in a second resonant mode is embedded in the hexagonal groove; a second group of shorting pins is loaded in the right resonant cavity for dividing the right resonant cavity into a first resonant cavity resonating in a third resonant mode and a second resonant cavity resonating in a fourth resonant mode; a rectangular groove is etched on the top surface of the second resonant cavity of the rectangular SIW cavity, and a U-shaped groove is etched on the bottom surface of the second resonant cavity of the rectangular SIW cavity at a position corresponding to the rectangular groove, thereby introducing two radiation nulls out of band, achieving filtering characteristics with high out-of-band suppression while improving gain.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a single-layer broadband SIW filter antenna with high out-of-band suppression and a microwave oscillator constructed thereof. Background Art

[0002] With the rapid development of modern communication systems, converged functional devices have become a hot research topic. Antennas and filters are two essential components in the RF front-end, and their performance directly determines the overall performance of the wireless communication system. Filter antennas can combine the radiation performance of an antenna with the filtering performance of a filter into a single RF device.

[0003] Substrate Integrated Waveguide (SIW) is a new type of transmission line structure with high Q value, low loss and easy integration with planes. Combined with the advantages of SIW technology in integrated design, filters and antennas based on SIW technology have received widespread attention. However, due to the high Q value of the SIW structure, the relative bandwidth of the filters and antennas made from it is usually narrow. In order to widen the bandwidth, the prior art discloses a third-order SIW filter antenna, which uses two cavities and carves and etches a groove in the second cavity, and its relative bandwidth is about 8.29%. There is also a SIW antenna with wide bandwidth and highly selective filtering response, which uses circular patches and SIW cavities to construct a multi-mode resonator, with a wide bandwidth of about 9.14% at a center frequency of 3.5 GHz. There are also some antenna structures that etch a folded DGS at the bottom of the half-mode SIW cavity to improve the selectivity of the low stop band. A rectangular groove is etched on the top surface of the SIW cavity, a rectangular groove is etched on the bottom surface, and two U-shaped grooves are etched on the bottom surface, which widens the bandwidth of the antenna and achieves a wide bandwidth of about 11.84% at a center frequency of 11.8 GHz. A broadband fourth-order filtering antenna composed of two SIW dual-mode cavities achieves a wide bandwidth of about 7.64% at a center frequency of 5.4 GHz. A filtering antenna based on a hybrid structure of SIW and artificial localized surface plasmon (SLSP) as feed, due to the rich resonant modes of the SIW-SLSP hybrid structure, achieves a wide bandwidth of about 11.3% at a center frequency of 7.89 GHz.

[0004] In addition to broadband SIW antennas, SIW antennas with high out-of-band suppression have also been a hot topic of research in recent years. The prior art discloses a low-profile SIW filter antenna that uses a multifunctional single slot and five short-circuit pins integrated in a half-mode SIW, with low H-plane cross-polarization and good sideband suppression performance. In other literature, a compact single-layer SIW filter antenna with a parasitic patch is proposed. The first-stage resonant cavity uses a half-mode SIW cavity, and the second-stage resonant cavity is a parasitic patch close to the half-mode SIW cavity, which achieves good sideband suppression. There is also a low-profile, highly selective single-layer SIW filter antenna, which consists of a triangular patch and a SIW cavity. A triangular groove and a U-shaped groove are etched on the upper surface of the substrate integrated waveguide cavity, respectively, and has good frequency selectivity and out-of-band suppression. However, in current research, there are few studies that achieve both broadband and out-of-band suppression. Summary of the Invention

[0005] The present invention aims to provide a microstrip-based, single-layer, broadband SIW filter antenna with high out-of-band rejection. Based on a rectangular SIW cavity, a multimode resonant cavity with multiple resonant modes is constructed, enabling the antenna to exhibit multiple resonant modes and achieve wide bandwidth and high gain. A hexagonal groove is etched in the upper metal layer of the SIW cavity, and a hexagonal patch is loaded into the groove, introducing two out-of-band radiation nulls. This achieves high out-of-band rejection and improved gain.

[0006] In order to achieve the above objectives, the specific solutions of this application are as follows:

[0007] A single-layer broadband SIW filter antenna with high out-of-band suppression includes a rectangular SIW cavity formed on a dielectric substrate and having multiple resonant modes. A first set of shorting pins is loaded in the rectangular SIW cavity for dividing the rectangular SIW cavity into a left resonant cavity and a right resonant cavity. The resonant mode of the left resonant cavity is a first resonant mode.

[0008] A hexagonal groove is etched on the top surface of the left resonant cavity of the rectangular SIW cavity, and a hexagonal microstrip patch is embedded in the hexagonal groove; the resonant mode of the hexagonal microstrip patch is the second resonant mode;

[0009] A second group of short-circuit pins is loaded in the right resonant cavity to divide the right resonant cavity into a first resonant cavity and a second resonant cavity. The resonant mode of the first resonant cavity is the third resonant mode. A rectangular groove is etched on the top surface of the second resonant cavity of the rectangular SIW cavity, and a U-shaped groove is etched on the bottom surface of the second resonant cavity of the rectangular SIW cavity at a position corresponding to the rectangular groove. The resonant mode of the second resonant cavity is the fourth resonant mode.

[0010] In some specific embodiments, the first group of shorting pins includes a first shorting pin, a second shorting pin, and a third shorting pin. The first shorting pin, the second shorting pin, and the third shorting pin are arranged in a triangle. The first shorting pin and the third shorting pin are on the same straight line and the straight line is parallel to the long side of the rectangular slot. The second shorting pin is arranged close to the hexagonal slot.

[0011] In some specific embodiments, the second group of shorting pins includes a fourth shorting pin and a fifth shorting pin, and the fourth shorting pin and the fifth shorting pin are installed on the same straight line, and the straight line is parallel to the long side of the rectangular slot.

[0012] In some specific embodiments, a straight-line distance between the first shorting pin and the third shorting pin is smaller than a straight-line distance between the fourth shorting pin and the fifth shorting pin.

[0013] In some specific embodiments, the diameters of the first shorting needle, the second shorting needle, the third shorting needle, the fourth shorting needle, and the fifth shorting needle are all the same.

[0014] In some specific embodiments, a sixth shorting pin is loaded in the hexagonal slot, and a diameter of the sixth shorting pin is smaller than a diameter of the first shorting pin.

[0015] In some specific embodiments, the coupling strength between the feeding point and the hexagonal microstrip patch is changed by adjusting the distance between the sixth shorting needle and the feeding point of the rectangular SIW cavity; and the coupling strength between the first resonant mode and the third resonant mode is changed by adjusting the distance between the sixth shorting needle and the second shorting needle.

[0016] In some specific embodiments, the opening direction of the U-shaped groove is perpendicular to the long side of the rectangular groove, and the bottom of the U-shaped groove is parallel to the long side of the rectangular groove, the length of the bottom of the groove is smaller than the length of the long side of the rectangular groove, and the width of the U-shaped groove is smaller than the width of the rectangular groove.

[0017] In some specific embodiments, a plurality of metallized through holes are arranged at equal intervals along the four edges of the rectangular SIW cavity. The diameters of the metallized through holes are the same and the spacing between two adjacent metallized through holes is less than twice the diameter of the metallized through holes.

[0018] In some specific embodiments, the first resonance mode is TE 102 mode, the second resonance mode is TM 11 mode, the third resonance mode is TE 101 mode, the fourth resonance mode is half TE 102 model.

[0019] The present invention has the beneficial effects:

[0020] The single-layer broadband SIW filter antenna with high out-of-band suppression proposed in the present invention comprises a rectangular SIW cavity, a first set of shorting pins, a second set of shorting pins, a hexagonal microstrip patch, a hexagonal slot, a rectangular slot and a U-shaped slot on the bottom. 104 A hexagonal groove is etched in the metal layer of the SIW cavity of the mode, and a radiation zero point appears on the left side of the passband. Then, a hexagonal patch is loaded in the hexagonal groove, adding a radiation zero point on the right side of the passband and improving the gain at the same time. By loading the first set of short-circuit needles and the second set of short-circuit needles, the TE of the SIW cavity is increased. 104 The mode is divided into a TE 102 mode and two TE 101 mode, which improves the antenna bandwidth and gain.

[0021] Furthermore, by loading short-circuit pins in the hexagonal patch, 101 Rectangular grooves were etched into the mode cavity to rationally shift the resonance point, increasing bandwidth and gain. Finally, a U-shaped groove was etched at the cavity bottom to adjust the antenna's impedance matching. Coupling matrix theory was used to analyze the principle behind the antenna's filtering characteristics, and the physical mechanism behind the two adjustable nulls was further explained using the coupling coefficient.

[0022] The single-layer, broadband SIW filter antenna with high out-of-band rejection proposed in this invention achieves a -10dB impedance bandwidth of 9.5%, out-of-band rejection of 19dB on the left side of the passband, 15.5dB on the right side of the passband, and a peak gain of 7.6dBi. Compared to existing single-layer SIW filter antennas, this achieves the design goals of excellent out-of-band rejection and wide bandwidth while maintaining high gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A top view of a high out-of-band suppression broadband SIW filter antenna structure provided by an embodiment of the present invention;

[0024] Figure 2 A bottom view of a high out-of-band suppression broadband SIW filter antenna structure provided by an embodiment of the present invention;

[0025] Figure 3 A side view of a high out-of-band suppression broadband SIW filter antenna structure provided by an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of antenna structure evolution during the design process provided by an embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of a rectangular SIW cavity. Figure 4 (b) is a schematic diagram of the structure of antenna 1, Figure 4 (c) is a schematic diagram of the structure of antenna II. Figure 4(d) is a schematic diagram of the structure of antenna III. Figure 4 (e) is a schematic diagram of the structure of antenna IV. Figure 4 (f) is a schematic diagram of the structure of a broadband SIW filter antenna with high out-of-band suppression;

[0027] Figure 5 Based on Figure 4 Simulation results of the designed antenna structure; Figure 5 (a) is |S 11 | Schematic diagram of the comparison curve, Figure 5 (b) is a schematic diagram of the gain comparison curve;

[0028] Figure 6 Schematic diagram of the relationship between the actual length l and actual width w of a rectangular SIW cavity at a resonant frequency of 16.5 GHz for different resonant modes provided by an embodiment of the present invention;

[0029] Figure 7 Based on Figure 4 Schematic diagram of the electric field distribution of antenna I; Figure 7 (a) is a schematic diagram of the electric field distribution at 16.16 GHz. Figure 7 (b) is a schematic diagram of the electric field distribution at 16.02 GHz;

[0030] Figure 8 Based on Figure 4 The a2 parameter of antenna II in |S 11 |Schematic diagram of the impact;

[0031] Figure 9 Based on Figure 4 Schematic diagram of the surface current distribution of the middle antenna II at 17.32 GHz;

[0032] Figure 10 Based on Figure 4 The electric field distribution diagram of antenna III, Figure 10 (a) is a schematic diagram of the electric field distribution at 15.62 GHz. Figure 10 (b) is a schematic diagram of the electric field distribution at 16.68 GHz. Figure 10 (c) is a schematic diagram of the electric field distribution at 17.12 GHz. Figure 10 (d) is a schematic diagram of the electric field distribution at 15.3 GHz; Figure 11 Based on Figure 4 Half TE of middle antenna IV at 15.78 GHz 101 Electric field distribution diagram of the mode;

[0033] Figure 12 Based on Figure 4 Current distribution diagram of antenna IV at 15.48 GHz;

[0034] Figure 13Antenna current distribution diagram of the antenna, where Figure 13 (a) is the antenna current distribution diagram at 15.48GHz. Figure 13 (b) is the antenna current distribution diagram at 17.7 GHz;

[0035] Figure 14 The equivalent coupling topology diagram of the high out-of-band suppression broadband SIW filter antenna provided by the embodiment of the present invention;

[0036] Figure 15 Based on Figure 14 Schematic diagram of ideal S-parameter simulation results of the coupling matrix;

[0037] Figure 16 Schematic diagram of the effect of adjusting the coupling coefficient in the coupling matrix on the S parameters. Figure 16 (a) is the coupling coefficient M 23 Impact on S parameters; Figure 16 (b) is the coupling coefficient M S2 Impact on S parameters;

[0038] Figure 17 is the S parameter of the coupling matrix (CM) and the antenna S 11 and gain comparison chart;

[0039] Figure 18 is the influence of structural parameters on the zero point. Figure 18 (a) is the effect of l3 on the zero point on the right side; Figure 18 (b) The effect of l4 on the left zero point

[0040] Figure 19 S parameter |S 11 |Comparison of measured and simulated sum gain results;

[0041] Figure 20 is the normalized radiation pattern of the antenna at 15.98 GHz, 16.60 GHz and 17.12 GHz, where

[0042] (a) 15.98 GHz, (b) 15.98 GHz,

[0043] (c) 16.60 GHz, (d) 16.60 GHz,

[0044] (e) 17.12 GHz, (f)17.12GHz,

[0045] The corresponding names of the numbers in the accompanying drawings are:

[0046] 1-dielectric substrate, 2-left resonant cavity, 3-right resonant cavity, 31-first resonant cavity, 32-second resonant cavity, 4-hexagonal slot, 5-hexagonal microstrip patch, 6-rectangular slot, 7-U-shaped slot, 8-metallized through hole, 9-feeding point, pin1-first shorting pin, pin2-second shorting pin, pin3-third shorting pin, pin4-fourth shorting pin, pin5-fifth shorting pin, pin6-sixth shorting pin. DETAILED DESCRIPTION

[0047] In order to reflect the creativity and novelty of the present invention, the following will be described with reference to the accompanying drawings and specific embodiments, but the embodiments of the present invention are not limited thereto.

[0048] Example 1:

[0049] like Figure 1-Figure 3 As shown, this embodiment provides a single-layer broadband SIW filter antenna with high out-of-band suppression, including a rectangular SIW cavity with multiple resonant modes formed on a dielectric substrate 1. A plurality of metallized through holes 8 are arranged at equal intervals along the four edges of the rectangular SIW cavity. The metallized through holes 8 have the same diameter and the spacing between two adjacent metallized through holes 8 is less than twice the diameter of the metallized through holes 8.

[0050] A first group of short-circuit pins is loaded in the rectangular SIW cavity for dividing the rectangular SIW cavity into a left resonant cavity 2 and a right resonant cavity 3. The resonant mode of the left resonant cavity 2 is the first resonant mode; specifically, the first resonant mode is the TE102 mode.

[0051] A hexagonal groove 4 is etched on the top surface of the left resonant cavity 2 of the rectangular SIW cavity, and a hexagonal microstrip patch 5 is embedded in the hexagonal groove 4; the resonant mode of the hexagonal microstrip patch 5 is the second resonant mode, which is the TM11 mode;

[0052] A second group of short-circuit pins is loaded in the right resonant cavity 3 to divide the right resonant cavity into a first resonant cavity 31 and a second resonant cavity 32. The resonant mode of the first resonant cavity 31 is the third resonant mode, which is the TE101 mode.

[0053] A rectangular groove 6 is etched on the top surface of the second resonant cavity 32 of the rectangular SIW cavity, and a U-shaped groove 7 is etched on the bottom surface of the second resonant cavity 32 at a position corresponding to the rectangular groove 6. The resonant mode of the second resonant cavity 32 is the fourth resonant mode, which is a half-TE102 mode. By adding the rectangular groove 6, the TE101 mode in the cavity is perturbed, a new resonant point is generated, and impedance matching is improved.

[0054] Specifically, the opening direction of the U-shaped groove 7 is perpendicular to the long side of the rectangular groove 6, and the bottom of the U-shaped groove 7 is parallel to the long side of the rectangular groove 6. The length of the bottom of the groove is smaller than the length of the long side of the rectangular groove 6, and the width of the U-shaped groove 7 is smaller than the width of the rectangular groove 6.

[0055] To increase the antenna's bandwidth, multiple shorting pins can be installed within the SIW cavity, creating a multimode resonant cavity within the SIW cavity to increase bandwidth. Specifically, the first group of shorting pins includes a first shorting pin 1, a second shorting pin 2, and a third shorting pin 3. These are arranged in a triangle, with the first and third shorting pins 1 and 3 aligned on the same straight line parallel to the long side of the rectangular slot 6. The second shorting pin 2 is positioned adjacent to the hexagonal slot 4. The second group of shorting pins includes a fourth shorting pin 4 and a fifth shorting pin 5. These pins are aligned on the same straight line parallel to the long side of the rectangular slot 6.

[0056] Specifically, the structural parameters of the shorting pins are as follows: the straight-line distance between the first shorting pin PIN1 and the third shorting pin PIN3 is less than the straight-line distance between the fourth shorting pin PIN4 and the fifth shorting pin PIN5. The diameters of the first shorting pin PIN1, the second shorting pin PIN2, the third shorting pin PIN3, the fourth shorting pin PIN4, and the fifth shorting pin PIN5 are all the same.

[0057] A sixth shorting pin, pin 6, is loaded within the hexagonal slot 4. Its diameter is smaller than that of the first shorting pin, pin 1. Pin 1 is positioned adjacent to the hexagonal slot 4, with the line connecting the two shorting pins perpendicular to the long side of the rectangular slot 6. The sixth shorting pin, pin 6, is loaded within the hexagonal patch area. This perturbs the TE102 mode of the left resonant cavity 2, improving out-of-band suppression to the left of the passband and achieving the design goal of high out-of-band suppression.

[0058] A feeding point 9 is provided near the metal through-hole in the left resonant cavity 2, and a feeding probe is provided in the feeding point 9. In this embodiment, the distance between the sixth shorting needle pin 6 and the feeding point 9 is adjustable, that is, the position of the sixth shorting needle pin 6 is adjustable. By adjusting the distance between the sixth shorting needle pin 6 and the feeding point 9 of the rectangular SIW cavity, the coupling strength between the feeding point 9 and the hexagonal microstrip patch 5 can be changed. Furthermore, the position of the null point on the right side of the antenna can be changed.

[0059] Similarly, in the present application, the distance between the sixth short-circuit pin pin6 and the second short-circuit pin pin2 is adjustable, and the coupling strength between the first resonance mode (TE102 mode) and the third resonance mode (TE101 mode) can be changed by adjusting the distance between the sixth short-circuit pin pin6 and the second short-circuit pin pin2.

[0060] like Figure 1 As shown in the figure, the overall size of the rectangular SIW cavity of the antenna in this application is w1×l1. Hexagonal grooves and rectangular grooves are etched on the top surface of the SIW cavity. The side length of the hexagonal groove is a1 and the width is g1. The size of the rectangular groove is w2×g2. A hexagonal patch is then embedded in the hexagonal groove. The side length of the hexagonal patch is a2. Figure 2 As shown, a U-shaped groove is etched on the bottom surface of the SIW cavity. The length of the U-shaped groove is w5, the length of the two sides of the groove is l6, and the width of the U-shaped groove is g3. Six shorting pins are also loaded into the SIW cavity: the first shorting pin pin1, the second shorting pin pin2, the third shorting pin pin3, the fourth shorting pin pin4, the fifth shorting pin pin5, and the sixth shorting pin pin6. The sixth shorting pin pin6, located on the far left, has a diameter of d2 and is located at a distance of l3 from the feed point. The first, second, and third shorting pins in the middle are arranged in a triangle, with a distance of l4 from the sixth shorting pin on the left. The spacing between the first and third shorting pins is w3. The two shorting pins on the right are the fourth and fifth shorting pins. The distance between the fourth and fifth shorting pins is w4, and the distance from the three shorting pins on the left is l5. The diameters of the first, second, third, fourth, and fifth shorting pins are all d3. Figure 3 The figure shows a side view of the antenna. The dielectric substrate used is Rogers 4350B, with a dielectric constant of 3.66, a loss tangent of 0.04, and a thickness h of 0.762 mm. In one practicable structure, detailed structural parameters of the filtering antenna are shown in Table 1.

[0061] Table 1 Structural parameters of high out-of-band suppression broadband SIW filter antenna (unit: mm)

[0062]

[0063] (1) Principle analysis

[0064] In order to understand the working mechanism of the broadband SIW filter antenna with high out-of-band suppression proposed in this embodiment, the design process will be explained in detail below, and the principle of each antenna in the design process will be analyzed.

[0065] First, the design process of the antenna structure is as follows Figure 4 As shown in (a)-(f). Figure 4 (a) shows a rectangular SIW cavity. Figure 4 Antenna I shown in (b) is a SIW cavity loaded with a hexagonal slot; Figure 4 Antenna II shown in (c) is based on antenna I and loaded with a hexagonal patch; Figure 4 (d) Antenna III shown in Figure 1 is equipped with five short-circuit pins on the basis of antenna II. Figure 4 Antenna IV shown in (e) has a shorting pin loaded into the SIW cavity in the hexagonal patch area of ​​antenna III and a rectangular slot etched on the right side of the antenna; finally, a U-shaped slot is etched in the underlying metal to form Figure 4 (f) The proposed antenna is shown. During the antenna evolution process, a Rogers 4350B dielectric substrate with a thickness of 0.762mm was used. On the one hand, by loading hexagonal patches and short-circuit pins, and etching hexagonal slots, rectangular slots and U-shaped slots to change the antenna structure, the proposed filtering antenna has good radiation performance. On the other hand, the position of the feeding point and the antenna structure parameters are optimized, so that the proposed filtering antenna has good impedance matching. The antenna in the design process is modeled and simulated, and it can be obtained Figure 5 (a) shows |S 11 |Comparison curve and Figure 5 (b) shows the gain comparison curve. The specific process is:

[0066] Step 1: For Figure 4 For the rectangular SIW cavity shown in (a), the resonant frequencies f of each eigenmode of the rectangular SIW cavity can be calculated according to formula (1): TEm0n Where ε and μ represent the dielectric constant and magnetic permeability of the dielectric substrate, respectively. Based on the selected dielectric substrate material, ε = 3.66 and μ = 1. m and n are the number of standing waves along the wide and long sides of the SIW resonant cavity, respectively.

[0067]

[0068] Formula (2) and formula (3) describe the a in formula (1) eff and b eff The calculation method of a eff and b eff where d and s represent the equivalent length and width of the SIW resonant cavity, respectively. l and w represent the actual length and width of the SIW resonant cavity, respectively. d and s represent the diameter and spacing of the plated through-holes (PTHs) in the SIW cavity, respectively. Generally, s < 2d. Considering the minimum machining accuracy, we assume s = 1.3 mm and d = 0.8 mm.

[0069] From formula (1), we can see that for TE with determined values ​​of m and n m0n mode, whose resonant frequency is f TEm0n By aeff and b eff Furthermore, from formulas (2) and (3), it can be seen that for a SIW cavity with a determined diameter and spacing of metallized through holes, its resonant frequency f TEm0n It can be determined by the actual length l and actual width w of the SIW resonant cavity. TEm0n =16.5GHz resonant cavity, Figure 6 The relationship between the actual length l and actual width w of the resonant cavity in different modes is shown. Considering that high-order modes can be used to construct a multi-mode resonant cavity to achieve wide bandwidth, the rectangular SIW cavity is selected as TE 104 In this mode, l=23.3 and w=9.1 are used as the initial values ​​of the length and width of the resonant cavity.

[0070] like Figure 4 As shown in (b), antenna I is loaded with a hexagonal slot in a rectangular SIW cavity with initial values ​​of l1 = 23.3 mm and w1 = 9.1 mm. The side length of the hexagonal slot is 3.3 mm. Further analysis of the frequency response of the antenna at this time is as follows: Figure 5 As shown by the curve Ant.Ⅰ in (a), antenna I produces a resonance point at 16.16 GHz. Figure 7 (a) is the electric field distribution diagram of the antenna at 16.16 GHz. It can be seen that the rectangular SIW cavity is in TE 104 Resonance mode, it can be determined that the 16.16GHz resonance point is caused by the TE of the SIW cavity 104 At the same time, it can be seen from Figure 7(a) that antenna I generates radiation at the edge of the hexagonal slot. Figure 5 From the curve Ant.Ⅰ in (b), we can see that the peak gain is only 3.7dBi at this time.

[0071] from Figure 5 From the Ant. I curve in (b), we can see that the out-of-band suppression effect of Antenna I is weak on the left side of the passband, reaching only -3.4 dB. In addition, a radiation null appears at 16.02 GHz. Figure 7 (b) shows the electric field distribution at this frequency. At this time, the overall electric field of the antenna is weak and the radiation characteristics are not obvious, thus forming a radiation null point.

[0072] Step 2: If Figure 4 As shown in (c), antenna II is loaded with a hexagonal patch based on antenna I. For a regular hexagonal microstrip patch with a side length of a, let its area be A, which can be expressed by formula (4).

[0073]

[0074] Hexagonal microstrip patch in TM mnIt is difficult to directly analyze the resonant frequency of the mode. Usually, the hexagonal microstrip patch is equivalent to a circular microstrip patch with the same area. For a regular hexagonal microstrip patch with a radius of r, let its area be A', which can be expressed by formula (5).

[0075] A'=πr 2 (5)

[0076] Assuming the areas of the hexagonal microstrip patch and the circular microstrip patch are equal, we can obtain formula (6). Formula (7) can be obtained by solving formula (6), and it can be seen that the hexagonal microstrip patch with a side length of a can be equivalent to a circular microstrip patch with a radius of 1.15a.

[0077]

[0078] For circular microstrip patches, TM mn Resonant frequency in mode Satisfies formula (8). Where k mn represents the derivative of the Bessel function J′ m (k mn )=0. Assuming that the resonant mode of the hexagonal microstrip patch is similar to that of the circular microstrip patch, substituting formula (7) into formula (8) can obtain formula (9), where Indicates the hexagonal microstrip patch in TM mn The resonant frequency in this mode.

[0079]

[0080] Using formula (9), we can know that the hexagonal patch with a side length of a2 = 2.9 mm is 11 The resonant frequency of the mode resonance is 16.94 GHz. After the hexagonal patch with a side length of a2 = 2.9 mm is embedded in the antenna I, the actual resonant frequency deviates from the calculated one. Figure 8 As shown in the figure, a parameter sweep of a2 is performed. When a2 = 2.6 mm is adjusted, good impedance matching with the SIW cavity is achieved. The resonant frequency of the hexagonal patch with a side length of a2 = 2.6 mm is 16.8 GHz, and the resonance point generated by Antenna I at 16.16 GHz is lowered to 16.02 GHz. These two resonance points form a passband, but the relative bandwidth is very narrow.

[0081] like Figure 5 As shown in the Ant.Ⅱ curve in (b), a second radiation zero point is generated at 17.32GHz. Figure 9As can be seen, at 17.32 GHz, the current flowing through the hexagonal patch is equal in magnitude and opposite in direction to the current flowing through the left side of the hexagonal slot, forming a radiation null. Because the hexagonal patch also radiates, the peak gain reaches 5.84 dBi. At this point, the gain at the radiation null on the right side of the passband is -32 dBi, demonstrating good suppression. However, the radiation null on the left side still exhibits poor suppression, and the gain needs to be further increased.

[0082] Step 3: If Figure 4 As shown in (d), antenna III is based on antenna II. First, use pin1, pin2 and pin3 to short-circuit the TE 104 The mode is divided into two TE modes: left and right 102 mode, and then use pin4 and pin5 to connect the TE 102 The mode is divided into two TE 101 Mode. Its main function is to construct a multi-mode resonant cavity in the SIW cavity to increase the bandwidth.

[0083] like Figure 5 As shown in the Ant.Ⅲ curve in (a), it can be seen that the bandwidth is significantly increased after the short-circuit pin is loaded. 104 The mode disappears and two new resonance points are generated at 15.62GHz and 16.68GHz. Figure 10 As shown in (a), the resonance point at 15.62 GHz is due to TE 102 Mode resonance is generated. Figure 10 As shown in (b), the resonance point at 16.68 GHz is due to TE 101 mode resonance. In addition, Figure 10 As shown in (c), the resonance point of antenna III at 17.12 GHz is caused by the hexagonal patch loaded by antenna II. Figure 5 From the Ant.III curve in (a), it can be seen that the impedance matching of the antenna is poor at this time and further adjustment is needed.

[0084] like Figure 5 As shown in the Ant.Ⅲ curve in (b), due to the increase in bandwidth, the zero point on the left side moves to 15.3GHz, and the out-of-band suppression on the left side deteriorates. The electric field diagram at 15.3GHz is shown in Figure 10 As shown in (d), we can see that the electric field at this point is similar to the field strength at 15.62 GHz, and there is still TE 102 The mode produces strong radiation. The right null shifts to 17.52 GHz, and at this frequency, Antenna III's gain is -24 dBi. Meanwhile, out-of-band suppression to the right of the passband reaches 13 dBi. The shorting pin loading has little effect on the right null.

[0085] Step 4: If Figure 4 As shown in (e), antenna IV has made further changes to antenna III: a short-circuit pin 6 is loaded in the area of ​​the hexagonal patch, and a rectangular groove is etched on the right. On the one hand, by loading the rectangular groove, the TE in the cavity is 101 The mode is perturbed. A new resonance point is generated and the impedance matching is improved. On the other hand, by loading the short-circuit needle, the TE of the antenna III cavity is 102 At the same time, the out-of-band suppression on the left side of the passband is improved to achieve the design goal of high out-of-band suppression.

[0086] like Figure 5 As shown in the Ant.Ⅳ curve in (a), after etching a rectangular groove in the rightmost cavity, a new resonance point at 15.78 GHz appears. Figure 11 As shown, the etched rectangular groove makes the original TE 101 The mode becomes semi-TE 101 mode, and resonates at 15.78 GHz. 101 Mode separation, two TE 101 Mode coupling weakens, the original TE 101 The resonant frequency of the 16.68GHz has also changed, and the original resonant frequency of 16.6GHz has shifted slightly to 16.6GHz. In addition, a short-circuit pin is loaded in the area of ​​the hexagonal patch, which affects the resonance of the hexagonal patch and the TE 102 The cavity resonance of the mode produces a perturbation. 102 The cavity resonant frequency of the mode increases from 15.62GHz to 16.06GHz, and the resonant frequency of the hexagonal patch increases from 17.12GHz to 17.22GHz. It can be seen that antenna IV basically achieves broadband performance. However, at low frequencies, |S 11 |It has not reached -10dB yet, and the antenna matching needs to be further improved.

[0087] like Figure 5 As shown in the Ant.Ⅳ curve in (b), the peak gain in the band reaches 7.18dBi at this time, and a zero point is generated on the left. Figure 12 As shown, the zero point at 15.48 GHz is due to TE 102 In the cavity, the currents around the hexagonal slots are equal in magnitude and opposite in direction. Out-of-band suppression on the left side of the passband reaches 17dB, demonstrating excellent suppression. The null on the right side of Antenna IV shifts further to the right compared to the null on the right side of Antenna III, appearing at 17.7GHz. At 17.7GHz, the antenna's gain is -26dBi, and out-of-band suppression on the right side of the passband reaches 15dB, also demonstrating excellent suppression.

[0088] Step 5: If Figure 4As shown in (f), the antenna proposed in this paper is based on antenna IV, with a U-shaped groove etched on the bottom metal. 101 On the one hand, this makes up for the problem of poor matching of antenna IV at the low frequency of the passband. Figure 5 As shown in the “proposed antenna” curve in (a), the in-band |S 11 | are all below -10dB, with good matching performance and a relative bandwidth of 9.2%. On the other hand, the loaded U-shaped slot deepens the left null point of antenna IV. Figure 5 As shown in the Ant.V curve in (b), the gain of the proposed antenna is -14dB at 15.48GHz. Figure 13 As shown in (a), at 15.48 GHz, the currents around the hexagonal slot and the rectangular slot are equal in magnitude and opposite in direction. Figure 13 As shown in (b), at 17.7 GHz, the lower edge of the passband, the current in the area to the left of the hexagonal slot is equal in magnitude and opposite in direction to the current within the hexagonal patch, resulting in good out-of-band suppression. Excellent in-band gain is achieved, with a peak gain of 7.73 dBi. Out-of-band suppression is 19 dB on the left side of the passband and 15.5 dB on the right.

[0089] Overall, the single-layer filtering antenna proposed in this embodiment achieves broadband performance, which is mainly due to the TE 102 TE 101 and half TE 101 and hexagonal patches TM 11 modes, thus forming a multi-mode resonant cavity. While maintaining peak gain, the design goals of wide bandwidth and high out-of-band suppression are achieved.

[0090] (2) Parameter analysis

[0091] The parameters of the antenna structure constructed above are analyzed, including:

[0092] 1. Coupling matrix analysis

[0093] The overall antenna can be equivalent to Figure 14 The coupling topology shown in the figure, where R1 represents the TM of the hexagonal patch 11 mode, R2 represents the TE of the SIW cavity 102 mode, R3 represents the TE of the SIW cavity 101 mode, R4 represents the half TE of the SIW cavity 101 Mode. According to the coupling topology, the normalized coupling matrix [M] can be written as formula (10). Figure 14 The coupling topology and the coupling matrix of formula (5) can be obtained Figure 15 The S-parameter curve is shown.

[0094] like Figure 16 As shown in (a), adjust the coupling coefficient M in the coupling matrix S1 It is possible to independently control the right zero point movement. S1 As increases, the zero point on the right moves toward a higher frequency. Figure 16 As shown in (b), adjust the coupling coefficient M 23 The left zero point movement can be controlled independently. 23 As the frequency increases, the left zero moves toward a lower frequency.

[0095]

[0096] 2. Structural parameter analysis

[0097] The S parameters of the coupling matrix are compared with the proposed filtering antenna |S 11 |Compared with the gain, we can get Figure 17 The comparison graph is shown in Figure 1. In the figure, one set of dashed and solid lines represents the S11 and S21 parameters of the coupling matrix, respectively. The solid line represents the antenna's S11 parameter, and the second set of solid lines represents the achieved gain. It can be seen that the coupling matrix fits well with both the null and resonant point locations of the proposed antenna.

[0098] Depend on Figure 16 (a) It can be seen that when strengthening Figure 14 The coupling between source S and R1 in the coupling topology diagram can move the zero point on the right side to the low frequency position. Figure 4 The distance l3 between the short-circuit pin 6 and the feeding point in (e) can change the coupling strength between the feeding probe and the hexagonal patch in the proposed antenna. Furthermore, the position of the null point on the right side of the antenna can be changed. Figure 18 As shown in (a), l3 is set to 4.7mm, 4.9mm, and 5.1mm, respectively. It can be seen that as l3 increases, the radiation null on the left side moves toward higher frequencies. By adjusting l3, the radiation null on the left side can be independently controlled.

[0099] Depend on Figure 16 (b) It can be seen that when strengthening Figure 14 The coupling between R2 and R3 in the coupling topology diagram can move the zero point on the left to the low frequency position. Figure 4 (d) Short-circuit pin 2 to Figure 4 (e) The spacing l4 of the short-circuit pin 6 can change the TE of the SIW cavity in the proposed antenna. 102 Mode and TE 101 The coupling strength of the mode can be further changed. Figure 18 As shown in (b), l4 is set to 5mm, 5.2mm, and 5.4mm, respectively. It can be seen that as the l4 value increases, the radiation null on the left side moves toward the high-frequency position. By adjusting l4, the radiation null on the left side can be independently controlled.

[0100] (3) Test results

[0101] To further verify the accuracy of the high out-of-band rejection broadband SIW filter antenna design, the antenna model was fabricated and tested. The antenna was fabricated using 0.762mm thick Rogers RO4350B sheet metal. After fabrication, a microwave anechoic chamber test environment was set up for the antenna. A 50Ω SMA adapter was soldered to the antenna's feed port, and a ROHDE & SCHWARZ ZNA network analyzer was used for testing. 11 |Performance test. Place the antenna in a microwave darkroom and use a spherical near-field test system to perform performance tests on gain and radiation pattern parameters. |S 11 |Comparison curve between test and simulation results of gain Figure 19 shown.

[0102] Depend on Figure 19 |S 11 The comparison of simulation and test curves shows that the SIW filter antenna has four in-band resonant points at 15.94 GHz, 16.16 GHz, 16.68 GHz, and 17.34 GHz. The antenna's -10 dB impedance bandwidth reaches 9.5% (15.89 GHz to 17.47 GHz). Test results indicate good antenna matching performance. Due to factors such as assembly deviations and manufacturing errors, the measured bandwidth shifts slightly higher than the simulated result.

[0103] Depend on Figure 19 Comparing the simulated and measured gain curves, we can see that due to losses in the dielectric substrate, test leads, and RF connectors, the measured in-band peak gain is approximately 7.6dBi, slightly lower than the simulated result. Furthermore, the antenna generates two radiation nulls at the 15.54GHz and 17.92GHz stopbands, resulting in out-of-band suppression of approximately 18dB and 17dB to the left and right of the passband, respectively.

[0104] Figure 20 The normalized radiation patterns of the antenna at 15.98 GHz, 16.60 GHz and 17.12 GHz are shown, respectively. and Radiation distribution on a plane. By comparing the radiation patterns at different frequencies and angles, we can observe that the antenna radiates stably across the entire operating frequency band. In the broadside direction, the measured cross-polarization discrimination ratio (XPD) is generally above 25dB, demonstrating excellent cross-polarization suppression.

[0105] As shown in Table 2, the performance comparison between the single-layer broadband SIW filter antenna with high out-of-band suppression proposed in this application and the existing single-layer SIW filter antenna is summarized:

[0106] Table 2 Comparison between the SIW filter antenna proposed in this application and the existing single-layer SIW filter antenna

[0107]

[0108] Table 2 shows that the antenna structure proposed in this application demonstrates significant advantages in overall performance over other single-layer antenna structures. Compared to existing planar quasi-isotropic antennas, this application achieves a wider bandwidth with similar gain, and the two nulls provide better out-of-band suppression. Compared to low-profile single-layer half-mode SIW filter antennas with short parasitic patches and a defective ground structure, this application achieves higher gain and higher out-of-band suppression with similar bandwidth. Compared to low-profile third-order half-mode SIW filter antennas with low H-plane cross-polarization and good sideband suppression and single-layer substrate integrated waveguide filters with parasitic patches, this application significantly reduces size and offers significant advantages in gain, bandwidth, and out-of-band suppression. Compared to single-layer filter antennas with two controllable radiation nulls based on patches and SIW multimode resonators, this design achieves a wider bandwidth with similar gain. Overall, this design demonstrates excellent performance in wide bandwidth, high gain, and high out-of-band suppression.

[0109] It is understood that the present application can be realized by the TE of the SIW cavity. 102 Mode, TE 101 Mode, Semi-TE 101 Mode and hexagonal patch TM 11 The multi-mode resonant cavity is constructed to achieve wide bandwidth and high gain. By introducing two radiation zero points outside the band, the filtering characteristics of high out-of-band suppression are achieved.

[0110] The examples listed above illustrate the wide bandwidth and high gain characteristics of the single-layer, wideband SIW filter antenna with high out-of-band suppression described in the present invention, representing a significant technological advancement. Those skilled in the art will appreciate that the examples described herein are intended to help readers understand the principles of the present invention and should be understood as not limiting the scope of protection of the present invention to these specific descriptions and examples. Based on the technical teachings disclosed herein, those skilled in the art may devise various other specific variations and combinations that do not depart from the essence of the present invention, and such variations and combinations remain within the scope of protection of the present invention.

Claims

1. Single-layer broadband SIW filter antenna with high out-of-band suppression, characterized by: Including a plurality of different A rectangular SIW cavity with a resonant mode, wherein a first group of short-circuit pins is loaded in the rectangular SIW cavity for dividing the rectangular SIW cavity into a left resonant cavity (2) and a right resonant cavity (3), and the resonant mode of the left resonant cavity (2) is a first resonant mode; A hexagonal groove (4) is etched on the top surface of the left resonant cavity (2) of the rectangular SIW cavity, and a hexagonal microstrip patch (5) is embedded in the hexagonal groove (4); the resonant mode of the hexagonal microstrip patch (5) is the second resonant mode; a sixth short-circuit needle pin 6 is loaded in the region of the hexagonal patch, and by loading the sixth short-circuit needle pin 6, the first resonant mode of the left resonant cavity (2) is perturbed; A second group of short-circuit pins is loaded in the right resonant cavity (3) for dividing the right resonant cavity into a first resonant cavity (31) and a second resonant cavity (32); the resonant mode of the first resonant cavity (31) is a third resonant mode; a rectangular groove (6) is etched on the top surface of the second resonant cavity (32) of the rectangular SIW cavity; the rectangular groove (6) perturbs the third resonant mode to generate a resonant point; a U-shaped groove (7) is etched on the bottom surface of the second resonant cavity (32) of the rectangular SIW cavity at a position corresponding to the rectangular groove (6); and the resonant mode of the second resonant cavity (32) is a fourth resonant mode.

2. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 1, characterized in that: The first group of short-circuit pins includes a first short-circuit pin, a second short-circuit pin, and a third short-circuit pin. The first short-circuit pin, the second short-circuit pin, and the third short-circuit pin are arranged in a triangle. The first short-circuit pin and the third short-circuit pin are on the same straight line and the straight line is parallel to the long side of the rectangular slot (6). The second short-circuit pin is arranged close to the hexagonal slot (4).

3. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 2, characterized in that: The second group of short-circuit pins includes a fourth short-circuit pin and a fifth short-circuit pin, and the fourth short-circuit pin and the fifth short-circuit pin are installed on the same straight line and the straight line is parallel to the long side of the rectangular slot (6).

4. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 3, characterized in that: A straight-line distance between the first shorting pin and the third shorting pin is smaller than a straight-line distance between the fourth shorting pin and the fifth shorting pin.

5. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 3, characterized in that: The diameters of the first shorting pin, the second shorting pin, the third shorting pin, the fourth shorting pin and the fifth shorting pin are all the same.

6. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 2, characterized in that: A sixth short-circuit needle is loaded in the hexagonal groove (4), and the diameter of the sixth short-circuit needle is smaller than the diameter of the first short-circuit needle.

7. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 6, characterized in that: The coupling strength between the feeding point (9) and the hexagonal microstrip patch (5) is changed by adjusting the distance between the sixth short-circuit needle and the feeding point (9) of the rectangular SIW cavity; and the coupling strength between the first resonant mode and the third resonant mode is changed by adjusting the distance between the sixth short-circuit needle and the second short-circuit needle.

8. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 1, characterized in that: The opening direction of the U-shaped groove (7) is perpendicular to the long side of the rectangular groove (6), and the groove bottom of the U-shaped groove (7) is parallel to the long side of the rectangular groove (6), the length of the groove bottom is smaller than the length of the long side of the rectangular groove (6), and the slit width of the U-shaped groove (7) is smaller than the width of the rectangular groove (6).

9. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 1, characterized in that: A plurality of metallized through holes (8) are arranged at equal intervals along the four edges of the rectangular SIW cavity. The diameters of the metallized through holes (8) are the same, and the spacing between two adjacent metallized through holes (8) is less than twice the diameter of the metallized through holes (8).

10. The single-layer broadband SIW filter antenna with high out-of-band suppression according to claim 1, characterized in that: The first resonance mode is the TE102 mode, the second resonance mode is the TM11 mode, the third resonance mode is the TE101 mode, and the fourth resonance mode is the half TE102 mode.

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