Single-layer broadband SIW filtering antenna with high out-of-band rejection

Abstract

The invention discloses a high out-of-band rejection single-layer broadband SIW filter antenna, which comprises a rectangular SIW cavity which is formed on a dielectric substrate and has a plurality of resonant modes, and a first group of short-circuit needles which are used for dividing the rectangular SIW cavity into a left resonant cavity and a right resonant cavity which resonate in a first resonant mode are loaded in the rectangular SIW cavity; a hexagonal groove is etched in the top surface of a 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 short-circuit pins used 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 are loaded in the right resonant cavity, a rectangular groove is etched in the top surface of the second resonant cavity of the rectangular SIW cavity, and a U-shaped groove is etched in the position, corresponding to the rectangular groove, of the bottom surface of the second resonant cavity of the rectangular SIW cavity; two radiation zero points are introduced out of band, the filtering characteristic of high out-of-band rejection is achieved, and meanwhile the gain is improved.

Description

Technical Field

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

[0002] With the rapid development of modern communication systems, fusion functional devices have become a hot topic in current research. Antennas and filters are two indispensable components of the RF front end, and their performance directly determines the performance of the entire wireless communication system. Filter antennas can integrate the radiation performance of antennas and the filtering performance of filters into one 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 plane. 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 therefrom is usually narrow. In order to broaden the bandwidth, a third-order SIW filter antenna is disclosed in the prior art. The antenna uses two cavities and a groove is engraved and etched 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 a circular patch and an SIW cavity to construct a multi-mode resonator, and has 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 the center frequency of 11.8GHz. A broadband fourth-order filtering antenna composed of two SIW dual-mode cavities achieves a wide bandwidth of about 7.64% at the center frequency of 5.4GHz. A filtering antenna based on a hybrid structure of SIW and artificial localized surface plasmon (Spoof 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 the center frequency of 7.89GHz.

[0004] In addition to broadband SIW antennas, SIW antennas with high out-of-band suppression are also a hot topic of research in recent years. The prior art discloses a low-profile SIW filter antenna, which uses a multifunctional single slot and five short-circuit pins integrated in a half-mode SIW, and has low H-plane cross-polarization and good sideband suppression performance. In other literatures, 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 better 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 level. However, in current research, there are few studies that can achieve both broadband and out-of-band suppression. Summary of the invention

[0005] The purpose of the present invention is to provide a single-layer broadband SIW filter antenna with high out-of-band suppression based on microstrip. Based on a rectangular SIW cavity, a multi-mode resonant cavity with multiple resonant modes is constructed, so that the antenna can have multiple resonant modes and achieve the characteristics of wide bandwidth and high gain. A hexagonal groove is etched on the upper metal of the SIW cavity and a hexagonal patch is loaded in the hexagonal groove, so that two radiation zero points are introduced out of the band, and the filtering characteristics of high out-of-band suppression are achieved while improving the gain.

[0006] In order to achieve the above purpose, the specific scheme of this application is:

[0007] A single-layer broadband SIW filter antenna with high out-of-band suppression comprises a rectangular SIW cavity with multiple resonance modes formed on a dielectric substrate, a first group of short-circuit pins for dividing the rectangular SIW cavity into a left resonance cavity and a right resonance cavity are loaded in the rectangular SIW cavity, and the resonance mode of the left resonance cavity is a first resonance 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 for dividing 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. A U-shaped groove is etched at the position corresponding to the rectangular groove on the bottom surface of the second resonant cavity of the rectangular SIW cavity. The resonant mode of the second resonant cavity is the fourth resonant mode.

[0010] In some specific embodiments, 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 groove, and the second short-circuit pin is arranged close to the hexagonal groove.

[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 implementations, 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 implementations, 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.

[0014] In some specific implementations, a sixth shorting pin is loaded in the hexagonal groove, 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 short-circuit needle and the feeding point of the rectangular SIW cavity; 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.

[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 interval between two adjacent metallized through holes is less than twice the diameter of the metallized through hole.

[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 by the present invention comprises a rectangular SIW cavity, a first group of short-circuit pins, a second group of short-circuit 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 upper metal 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 group of short-circuit needles and the second group of short-circuit needles, the TE of the SIW cavity is 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, the TE 101 A rectangular groove is etched in the mode cavity to reasonably move the resonance point, increase the bandwidth and improve the gain. Finally, a U-shaped groove is etched at the bottom of the cavity to adjust the impedance matching of the antenna. The coupling matrix theory is used to analyze the principle of the antenna's filtering characteristics, and the physical mechanism of the two adjustable zero points is further explained through the coupling coefficient.

[0022] The single-layer broadband SIW filter antenna with high out-of-band suppression proposed by the present invention has a -10dB impedance bandwidth of 9.5%, an out-of-band suppression of 19dB on the left side of the passband, an out-of-band suppression of 15.5dB on the right side of the passband, and a peak gain of 7.6dBi. Compared with the single-layer SIW filter antenna in the prior art, the design goals of good out-of-band suppression and wide bandwidth are achieved while maintaining a high gain performance. 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 A schematic diagram of the evolution of the antenna structure 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 I, 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 high out-of-band suppression broadband SIW filter antenna;

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

[0028] Figure 6 A schematic diagram showing the relationship between the actual length l and the actual width w of a rectangular SIW cavity at a resonant frequency of 16.5 GHz for different resonant modes provided in 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 a of middle antenna II 2 Parameter pair |S 11 |Schematic diagram of the impact;

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

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

[0033] Fig.12 Based on Figure 4 The current distribution diagram of antenna IV at 15.48 GHz;

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

[0035] Fig.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] Fig.15 Based on Fig.14 Schematic diagram of ideal simulation results of S parameters of the coupling matrix;

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

[0038] Fig.17 is the S parameter of the coupling matrix (CM) and the antenna S 11 Comparison chart with gain;

[0039] Fig.18 is the influence of structural parameters on the zero point. Fig.18 (a) is l 3 Impact on the right zero point; Fig.18 (b) is l 4 Impact on the left zero point

[0040] Fig.19 is the S parameter |S 11 |Comparison chart of measured and simulated results of sum gain;

[0041] Fig. 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) 17.12 GHz,

[0045] The corresponding names in the attached drawings are:

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

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

[0048] Embodiment 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 resonance modes formed on a dielectric substrate 1, and a plurality of metallized through holes 8 arranged at equal intervals are provided along the 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.

[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, and the resonant mode of the left resonant cavity 2 is a first resonant mode; specifically, the first resonant mode is a 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, and the second resonant mode is the TM11 mode;

[0052] 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 the third resonant mode, and the third resonant mode 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 of the rectangular SIW cavity at a position corresponding to the rectangular groove 6. The resonant mode of the second resonant cavity 32 is the fourth resonant mode, and the fourth resonant mode is a half TE102 mode. By loading the rectangular groove 6, the TE101 mode in the cavity is perturbed, a new resonant point is generated, and the 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] In order to increase the bandwidth of the antenna, multiple short-circuit pins can be set in the SIW cavity to construct a multi-mode resonant cavity in the SIW cavity to increase the bandwidth. Specifically, the first group of short-circuit pins includes the first short-circuit pin pin1, the second short-circuit pin pin2 and the third short-circuit pin pin3, which are arranged in a triangle, and the first short-circuit pin pin1 and the third short-circuit pin pin3 are on the same straight line and the straight line is parallel to the long side of the rectangular slot 6, and the second short-circuit pin pin2 is arranged close to the hexagonal slot 4. The second group of short-circuit pins includes the fourth short-circuit pin pin4 and the fifth short-circuit pin pin5, and the fourth short-circuit pin pin4 and the fifth short-circuit pin pin5 are installed on the same straight line and the straight line is parallel to the long side of the rectangular slot 6.

[0056] Specifically, the structural parameters of the short-circuit pins are as follows: the straight-line distance between the first short-circuit pin 1 and the third short-circuit pin 3 is smaller than the straight-line distance between the fourth short-circuit pin 4 and the fifth short-circuit pin 5. The diameters of the first short-circuit pin 1, the second short-circuit pin 2, the third short-circuit pin 3, the fourth short-circuit pin 4 and the fifth short-circuit pin 5 are the same.

[0057] The sixth short-circuit pin pin6 is loaded in the hexagonal slot 4, and the diameter of the sixth short-circuit pin pin6 is smaller than that of the first short-circuit pin pin1; the first short-circuit pin pin1 is arranged close to the hexagonal slot 4, and the line connecting the first short-circuit pin pin1 and the sixth short-circuit pin pin6 is perpendicular to the long side of the rectangular slot 6. A sixth short-circuit pin pin6 is loaded in the area of ​​the hexagonal patch, and by loading the sixth short-circuit pin pin6, the TE102 mode of the left resonant cavity 2 is perturbed. At the same time, the out-of-band suppression on the left side of the passband is improved, achieving the design goal of high out-of-band suppression.

[0058] A feeding point 9 is provided at a position near the metal through hole of the left resonant cavity 2, and a feeding probe is provided in the feeding point 9. In this embodiment, the distance between the sixth short-circuit needle pin6 and the feeding point 9 is adjustable, that is, the position of the sixth short-circuit needle pin6 is adjustable, and the coupling strength between the feeding point 9 and the hexagonal microstrip patch 5 can be changed by adjusting the distance between the sixth short-circuit needle pin6 and the feeding point 9 of the rectangular SIW cavity, and further, 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 of 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, the overall size of the rectangular SIW cavity of the antenna in this application is w 1 × 1 Hexagonal grooves and rectangular grooves are etched on the top surface of the SIW cavity. The side length of the hexagonal groove is a 1 The seam width is g 1 , the size of the rectangular slot is w 2 ×g 2 Then embed a hexagonal patch into the hexagonal slot. The side length of the hexagonal patch is a. 2 .like Figure 2 As shown, a U-shaped groove is etched on the bottom surface of the SIW cavity, and the bottom length of the U-shaped groove is w 5 , the length of the sides of the grooves on both sides is l 6 , the width of the U-shaped slot is g 3 At the same time, six short-circuit pins are loaded in the SIW cavity, namely the first short-circuit pin pin1, the second short-circuit pin pin2, the third short-circuit pin pin3, the fourth short-circuit pin pin4, the fifth short-circuit pin pin5, and the sixth short-circuit pin pin6. The diameter of the sixth short-circuit pin pin6 on the far left is d 2 , the distance from the feeding point is l 3 The first short-circuit pin, the second short-circuit pin and the third short-circuit pin in the middle are arranged in a triangle, and the distance from the sixth short-circuit pin on the left is l 4 , the distance between the first short-circuit pin and the third short-circuit pin is w 3 The two short-circuit pins on the right are the fourth short-circuit pin and the fifth short-circuit pin, and the distance between the fourth short-circuit pin and the fifth short-circuit pin is w 4 , the distance from the three short-circuit pins on the left is l 5 The diameters of the first short-circuit needle, the second short-circuit needle, the third short-circuit needle, the fourth short-circuit needle and the fifth short-circuit needle are all d 3 .like Figure 3 The side view of the antenna is shown in FIG. 1 , and 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 an implementable 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 (b) The antenna I shown is a SIW cavity loaded with a hexagonal slot; Figure 4 Antenna II shown in (c) is a hexagonal patch loaded on the basis of antenna I; Figure 4 (d) Antenna III shown is loaded with 5 short-circuit pins based on antenna II; Figure 4 (e) Antenna IV is shown with 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 0.762 mm was used. On the one hand, by loading hexagonal patches, short-circuit pins, and etching hexagonal slots, rectangular slots, and U-shaped slots to change the antenna structure, the proposed filter 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 filter antenna has good impedance matching. By modeling and simulating the antenna in the design process, it can be obtained Figure 5 (a) shows |S 11 |Comparison curves 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 frequency f of each eigenmode of the rectangular SIW resonant cavity can be calculated according to formula (1): TEm0n . Among them, ε and μ represent the dielectric constant and magnetic permeability of the dielectric substrate, respectively, and are set to ε = 3.66 and μ = 1 according to the selected dielectric substrate material. m and n are the number of changes of standing waves along the wide side and long side directions in 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 effRepresent the equivalent length and equivalent width of the SIW resonant cavity, respectively. l and w represent the actual length and actual width of the SIW resonant cavity, respectively. d and s represent the diameter and spacing of the metallized through holes of the SIW cavity, respectively. Generally, s<2d is set. Considering the limitation of the minimum machining accuracy, it is assumed here that s=1.3mm and d=0.8mm.

[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 a eff 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 the 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 a 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), the antenna I has an initial value of l 1 =23.3mm, w 1 =9.1mm rectangular SIW cavity is loaded with a hexagonal slot, the side length of the hexagonal slot is 3.3mm. Further analysis of the frequency response of the antenna at this time, such as 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), it can be seen that the peak gain is only 3.7dBi at this time.

[0071] from Figure 5 From the Ant.Ⅰ curve (b), it can be observed that the out-of-band suppression effect of antenna I on the left side of the passband is weak, reaching only -3.4dB. In addition, the antenna has a radiation null at 16.02GHz. Figure 7(b) shows the electric field distribution diagram 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 zero point.

[0072] Step 2: If Figure 4 As shown in (c), antenna II is loaded with a hexagonal patch on the basis of 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 mn It 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 get 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 Denotes 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) yields formula (9), where Represents a hexagonal microstrip patch in TM mn The resonant frequency in this mode.

[0079]

[0080] Using formula (9), we can see that the side length is a 2 =2.9mm hexagonal patch in TM 11 The resonant frequency of the mode resonance is 16.94 GHz. 2 After the hexagonal patch with a diameter of =2.9mm is embedded in the antenna Ⅰ, the actual resonant frequency has a certain deviation from the calculated one. Figure 8 As shown, for a 2 The value of a is scanned and adjusted.2 =2.6mm, a good impedance matching can be achieved with the SIW cavity. 2 = The resonant frequency of the hexagonal patch with a diameter of 2.6 mm is 16.8 GHz, and the resonance point at 16.16 GHz generated by antenna I is pulled down 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 of (b), a second radiation zero point is generated at 17.32GHz. Fig. 9 It can be seen that at 17.32GHz, the current of the hexagonal patch is equal to the current on the left side of the hexagonal slot and has the opposite direction, forming a radiation zero point. Since the hexagonal patch also has radiation characteristics, the peak gain reaches 5.84dBi. At this time, the gain at the radiation zero point on the right side of the passband is -32dBi, forming a good suppression. However, the radiation zero point on the left still has a poor suppression effect, and the gain needs to be further improved.

[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 TE 104 The mode is divided into two TEs, 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 after the short-circuit pin is loaded, the bandwidth increases significantly. 104 The mode disappears and two new resonance points are generated at 15.62 GHz and 16.68 GHz. Fig.10 As shown in (a), the resonance point at 15.62 GHz is due to TE 102 Mode resonance is generated. Fig.10 As shown in (b), the resonance point at 16.68 GHz is due to TE 101 mode resonance. In addition, Fig.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 It can be seen from the Ant.Ⅲ curve in (a) that the impedance matching of the antenna is poor at this time and further adjustment is needed.

[0084] like Figure 5As shown in the Ant. III curve in (b), due to the increase in bandwidth, the zero point on the left side moves to 15.3 GHz, and the out-of-band suppression on the left side deteriorates. The electric field diagram at 15.3 GHz is shown in Fig.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 zero point on the right side moves to 17.52GHz, and the gain of antenna III is -24dBi at this frequency. At the same time, the out-of-band suppression on the right side of the passband reaches 13dBi. The loading of the short-circuit pin has little effect on the zero point on the right side.

[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 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 102 The mode is perturbed. 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. Fig.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 The coupling of the modes weakens, the original TE 101 The resonant frequency of the TE also changes, and the original resonant frequency at 16.68 GHz is slightly shifted to 16.6 GHz. 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 TE mode produces a perturbation. 102 The cavity resonance frequency of the mode increases from 15.62 GHz to 16.06 GHz, and the resonance frequency of the hexagonal patch increases from 17.12 GHz to 17.22 GHz. 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 enhanced.

[0087] like Figure 5As shown in the Ant. IV curve in (b), the in-band peak gain reaches 7.18dBi at this time, and a zero point is generated on the left side. Fig.12 As shown, the zero 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. The out-of-band suppression on the left side of the passband reaches 17dB, which has a good suppression effect. The zero point on the right side of antenna IV moves to the right again compared to the zero point on the right side of antenna III, and appears at 17.7GHz. At 17.7GHz, the gain of the antenna is -26dBi, and the out-of-band suppression on the right side of the passband reaches 15dB, which also has a good suppression effect.

[0088] Step 5: If Figure 4 As shown in (f), the antenna finally proposed in this paper is based on antenna IV, with a U-shaped groove etched on the bottom metal. This U-shaped groove is located in the semi-TE 101 In the cavity. On the one hand, this makes up for the problem that antenna IV is poorly matched at the low frequency of the passband. Figure 5 As shown in the “proposed antenna” curve in (a), the 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), at 15.48 GHz, the gain of the proposed antenna is -14 dB. Fig.13 As shown in (a), at 15.48 GHz, the currents around the hexagonal slots and rectangular slots are equal in magnitude and opposite in direction. Fig.13 As shown in (b), at 17.7GHz, the lower edge of the passband, the current in the left area of ​​the hexagonal slot is equal in magnitude and opposite in direction to the current inside the hexagonal patch, forming good suppression outside the band. The in-band gain is good, achieving a peak gain of 7.73dBi. The out-of-band suppression on the left side of the passband is 19dB, and on the right side is 15.5dB.

[0089] Overall, the single-layer filtering antenna proposed in this embodiment achieves broadband performance, which is mainly due to the use of the TE 102 TE 101 and half TE 101 And hexagonal patch TM 11 mode, thus forming a multi-mode resonant cavity. While maintaining the 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 Fig.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 semi-TE of SIW cavity 101 Mode. According to the coupling topology, the normalized coupling matrix [M] can be written as formula (10). Fig.14 The coupling topology and the coupling matrix of formula (5) can be obtained Fig.15 The S-parameter curve is shown.

[0094] like Fig.16 As shown in (a), the coupling coefficient M in the coupling matrix is ​​adjusted. S1 The right zero point movement can be controlled independently. S1 As the frequency increases, the zero point on the right moves toward a higher frequency. Fig.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 zero point on the left 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 Fig.17 The comparison diagram is shown in Figure 1. In the figure, one set of dotted lines and solid lines represent the S11 and S21 parameters of the coupling matrix, respectively, the solid line represents the S11 parameter of the antenna, and the second set of solid lines represents the achieved gain. It can be seen that the coupling matrix fits well with the zero point position and the resonance point position of the proposed antenna.

[0098] Depend on Fig.16 (a) It can be seen that when strengthening Fig.14 Source S and R in the coupling topology diagram 1 The coupling between them can move the zero point on the right side to the low frequency position. Corresponding the coupling topology to the antenna structure, by adjusting Figure 4 (e) The distance from the short-circuit pin 6 to the feeding point l 3 , the coupling strength between the feed probe and the hexagonal patch in the proposed antenna can be changed. Furthermore, the position of the zero point on the right side of the antenna can be changed. Fig.18 As shown in (a), 3Take 4.7mm, 4.9mm and 5.1mm respectively. It can be found that as l 3 As the radiation zero point on the left side moves toward the high frequency position, the radiation zero point on the left side moves toward the high frequency position. 3 , which can realize the independent control of the left radiation zero point.

[0099] Depend on Fig.16 (b) It can be seen that when strengthening Fig.14 In the coupling topology diagram, R 2 and R 3 The coupling between them can make the left zero point move to the low frequency position. Corresponding the coupling topology to the antenna structure, Figure 4 (d) Short-circuit pin 2 to Figure 4 (e) The spacing between the short-circuit pin 6 and the short-circuit pin 6 4 , which 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. Fig.18 As shown in (b), 4 Take 5mm, 5.2mm and 5.4mm respectively. It can be found that as l 4 As the value increases, the radiation zero point on the left moves toward the high frequency position. 4 , to achieve separate control of the left radiation zero point.

[0100] (3) Test results

[0101] In order to further verify the accuracy of the design of the above high out-of-band suppression broadband SIW filter antenna, the antenna model was physically processed and tested for performance. The physical production was made of Rogers RO4350B sheet with a thickness of 0.762mm. After the physical production was completed, the microwave darkroom test environment of the antenna was arranged, and the 50Ω SMA adapter was welded to the feed port of the antenna. The 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 pattern parameters. |S 11 |Comparison curve between test and simulation results of gain Fig.19 shown.

[0102] Depend on Fig.19 |S 11|Comparison of simulation and test curves shows that the SIW filter antenna has four in-band resonant points, with resonant frequencies of 15.94GHz, 16.16GHz, 16.68GHz and 17.34GHz. The -10dB impedance bandwidth of the antenna reaches 9.5% (15.89GHz-17.47GHz). From the test results, the antenna matching performance is good. Due to factors such as assembly deviation and manufacturing error, the measured bandwidth is slightly shifted to higher frequencies compared with the simulation results.

[0103] Depend on Fig.19 From the comparison of the gain simulation and test curves, we can see that due to the loss of the dielectric substrate, test line and RF connector, the measured in-band peak gain is about 7.6dBi, which is slightly lower than the simulation result. At the same time, the antenna produces two radiation nulls at the stopband positions of 15.54GHz and 17.92GHz, making its out-of-band suppression on the left and right sides of the passband reach about 18dB and 17dB respectively.

[0104] Fig. 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 the plane. By comparing the radiation patterns at different frequencies and angles, it can be observed that the antenna is in a stable radiation state throughout the entire operating frequency band. In the broadside direction, the measured cross-polarization discrimination ratio (XPD) is basically higher than 25dB, which shows a good cross-polarization suppression effect.

[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] It can be seen from Table 2 that the antenna structure proposed in this application shows significant advantages in overall performance compared with other single-layer antenna structures. Compared with the existing planar quasi-isotropic antenna, this application achieves a wider bandwidth under similar gain conditions, and the two zero points can form a better out-of-band suppression effect; compared with the low-profile single-layer half-mode SIW filter antenna with a short parasitic patch and a defective grounding structure, this application achieves a higher gain under similar bandwidth conditions and has a higher out-of-band suppression effect; compared with the low-profile third-order half-mode SIW filter antenna with low H-plane cross-polarization and good sideband suppression and the single-layer substrate integrated waveguide filter with parasitic patches, this application has greatly reduced the size and has significant advantages in gain, bandwidth and out-of-band suppression; compared with the single-layer filter antenna with two controllable radiation zero points based on patches and SIW multimode resonators, this design achieves a wider bandwidth under similar gain conditions. Overall, this design has good 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 TM of hexagonal patches 11 The multi-mode resonant cavity is constructed to achieve the characteristics of 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 embodiments listed above are intended to illustrate that the single-layer broadband SIW filter antenna with high out-of-band suppression described in the present invention has the characteristics of wide bandwidth and high gain, and has significant technical progress. Those of ordinary skill in the art will appreciate that the embodiments described here are intended to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific variations and combinations based on the technical inspirations disclosed in the present invention without departing from the essence of the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. Single-layer broadband SIW filter antenna with high out-of-band suppression, characterized in that: It comprises a rectangular SIW cavity having multiple resonance modes formed on a dielectric substrate (1), a first group of short-circuit pins for dividing the rectangular SIW cavity into a left resonance cavity (2) and a right resonance cavity (3) being loaded in the rectangular SIW cavity, and the resonance mode of the left resonance cavity (2) is a first resonance 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 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; 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 comprises a first short-circuit pin, a second short-circuit pin and a third short-circuit pin, which 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 groove (6), and the second short-circuit pin is arranged close to the hexagonal groove (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. 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 resonance mode and the third resonance 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), 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 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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