Miniaturized wideband high-gain millimeter wave cavity-fed planar filter antenna

Abstract

The application discloses a miniaturized wideband high-gain millimeter wave cavity-fed planar filter antenna. The application realizes the required performance by exciting high-order cavity modes, and reduces the size by using a half-cavity technology. Two long slits are located at the strongest electric field position and are blocked by the long side through-hole wall of cavity C, so as to excite half-TE 120 modes; a pair of metalized through holes VT are arranged in the cavity C, so as to divide the cavity C into left and right two half cavities, and the two half cavities simultaneously excite half-TE 110 modes; the left and right two half-TE 110 modes are opposite in phase, the radiation generated by the long slits SR is offset, so as to introduce a radiation zero point at a low frequency. The antenna has excellent radiation performance and additional filtering characteristics. The filtering characteristics are realized without relying on additional filtering circuits or loading parasitic filtering structures, and therefore have low loss characteristics. The application realizes wideband, high gain and high frequency selectivity by using a simple and compact planar antenna structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas for wireless communication terminals, and relates to a miniaturized broadband, high-gain millimeter-wave cavity-fed planar filtering antenna. The antenna can be used as the antenna for the RF front end of a highly integrated wireless transceiver and is widely used in wireless communication systems such as mobile communications, satellite communications, and radar. Background Art

[0002] Multiple-Input-Multiple-Output (MIMO) technology is a core technology in fifth-generation (5G) mobile communications. One of the unique features of 5G communication systems compared to previous generations is their integration into the millimeter-wave frequency band to address spectrum resource constraints. Therefore, developing antennas suitable for millimeter-wave MIMO systems is of practical significance. One of the challenges with millimeter-wave communications is high transmission loss. Therefore, antennas with high-gain characteristics have attracted widespread attention from both academia and industry, as they can compensate for this loss. In the millimeter-wave frequency band, metal cavity feeding achieves lower insertion loss than traditional microstrip line feeding, facilitating the implementation of high-gain antennas. However, metal cavities are known to be expensive and bulky. The substrate integrated cavity (SIC) structure seamlessly combines the advantages of the low loss of a metal cavity with the ease of integration of microstrip lines. It is also inexpensive and can be mass-produced using PCB processes. Therefore, it is widely used in the construction of high-gain antennas in the millimeter-wave frequency band. However, there are still some urgent problems to be solved in applying SIC structure in millimeter wave MIMO antenna array. The size of SIC structure is generally large, especially for some cavities working in high-order modes, whose length and width are usually greater than 0.7λ. c (λ c is the wavelength at the center frequency in free space). The MIMO antenna array requires the spacing between antenna elements to be less than 0.5λ. c Therefore, miniaturization design is a key scientific issue that needs to be overcome when applying SIC structures to MIMO systems to achieve high-gain millimeter-wave MIMO antennas.

[0003] Modern and future communication systems are moving toward high integration, making filter antennas a research hotspot. Filter antennas are multifunctional devices that combine filters and antennas, two components that are typically essential in RF front-end circuits. Functionally, they enable both wireless signal transmission and reception and target signal selection. Structurally, by eliminating the matching network between the antenna and filter, they achieve lower loss, smaller size, and higher integration. Previous filter antennas were mostly designed based on microstrip structures, which, as open structures, suffer from significant losses in the millimeter-wave band. In recent years, antenna researchers have applied the design methods of microstrip filter antennas to substrate-integrated structures, resulting in several high-performance millimeter-wave filter antennas. However, these design methods generally require complicating the antenna structure or increasing the antenna size, making the realization of substrate-integrated millimeter-wave filter antennas suitable for array design a challenge.

[0004] In summary, in order to realize a miniaturized high-gain millimeter-wave filtering antenna, the present invention proposes a filtering antenna suitable for MIMO communication systems through a fractional-order substrate integrated cavity design for the 5G millimeter-wave n256 / n257 / n261 frequency band (24.25-29.5GHz). The antenna proposed in the present invention utilizes a high-order substrate integrated cavity mode to achieve excellent performance, and then uses half-cavity technology to reduce the structural size. Compared with other filtering antenna designs based on SIC structures, the realization of its filtering characteristics does not require the introduction of complex parasitic structures and does not increase the structural size. In summary, the present invention uses a simple and compact planar antenna structure to achieve excellent performance including broadband, high gain and high frequency selectivity. Summary of the Invention

[0005] The present invention addresses the shortcomings of existing technologies by providing a miniaturized, broadband, high-gain millimeter-wave cavity-fed planar filter antenna. Specifically, the antenna and filter are integrated using a substrate-integrated cavity (SIC). Power is fed via a coaxial probe (SMA), thereby exciting the resonant modes of the SIC and microstrip patch to generate radiation and introduce a radiation null. The proposed antenna structure is remarkably simple, utilizing only two dielectric substrates, a substrate-integrated cavity, and a microstrip patch. Its processing is straightforward and its production cost is low. Furthermore, despite its simple and compact structure, the antenna also exhibits excellent radiation and filtering performance.

[0006] Technical solutions to achieve the purpose of the present invention:

[0007] Miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna, including:

[0008] Upper dielectric substrate S1;

[0009] Lower dielectric substrate S2;

[0010] An upper metal surface P, which covers the upper surface of the upper dielectric substrate S1;

[0011] A middle metal surface M1 covering the lower surface of the upper dielectric substrate S1 and the upper surface of the lower dielectric substrate S2;

[0012] A lower metal surface M2, which covers the lower surface of the lower dielectric substrate S2;

[0013] in:

[0014] The upper metal surface P is a microstrip patch.

[0015] Two long slits SR are etched on the middle metal surface M1; the two long slits SR are arranged symmetrically about the length of the upper metal surface P and toward the center line;

[0016] The lower dielectric substrate S2 includes a substrate integrated cavity C formed by periodic metallized through-holes V extending through the lower dielectric substrate S2, as well as a middle metal surface M1 and a lower metal surface M2. Within the substrate integrated cavity C are a pair of metallized through-holes VT and a non-metallized through-hole VP for loading the SMA.

[0017] A circular hole for SMA feeding is etched on the lower metal surface M2.

[0018] The distance dvy between the metallized through hole VT and the long side through hole wall of the substrate integrated cavity C which is farther away from the metallized through hole VT satisfies 0.51Wc≤dvy≤0.53Wc, where Wc is the width of the substrate integrated cavity C.

[0019] The two long slits SR are respectively located on the two long side through-hole walls of the substrate integrated cavity C.

[0020] Preferably, the center of the upper metal surface P, the center of the substrate integrated cavity C, the center of the upper dielectric substrate S1, and the center of the lower dielectric substrate S2 are located on the same straight line.

[0021] Preferably, the length and width of the substrate integrated cavity C are each less than 0.5λ c .

[0022] Preferably, the length Ls of the long gap SR satisfies 0.95Lc≤Ls≤Lc, where Lc represents the length of the substrate integrated cavity C.

[0023] Preferably, the width Ws of the long gap SR satisfies d≤Ws≤1.5d, where d represents the diameter of the metallized through hole V.

[0024] Preferably, the distance df between the long side of the substrate integrated cavity C which is closer to the through hole VT and the through hole VP satisfies df≤0.4Wc.

[0025] Preferably, the center of the through hole VP is located on the width center line of the substrate integrated cavity C.

[0026] Preferably, the metallized through hole V, the metallized through hole VT, and the non-metallized through hole VP have the same diameter, which is 0.026-0.028λ0, wherein λ0 is the wavelength at 27 GHz in free space.

[0027] Preferably, the center of the circular hole coincides with the center of the non-metallized through hole VP, and the diameter of the circular hole Ds is greater than the diameter of the through hole VP.

[0028] Working principle:

[0029] The two long gaps SR are located at half-TE 120 The electric field of the mode is the strongest position, and it is blocked by the long side through-hole wall of the substrate integrated cavity C, thereby stimulating the half-TE 120 model;

[0030] A pair of metallized through holes VT are provided inside the substrate integrated cavity C, dividing the substrate integrated cavity C into two half cavities, the left and right half cavities, and the two half cavities simultaneously excite the half-TE 110 Mode; and because of the two half-TE 110 The modes are in opposite phase, so the radiation generated by the long SR slot will cancel each other out, introducing a radiation null at low frequency.

[0031] And because of half-TE 120 Field distribution characteristics of the mode and the fundamental mode TM of the microstrip patch 01 The field distribution characteristics of the substrate are similar, so a microstrip patch P is placed above the substrate integrated cavity C to introduce a new resonance point to widen the working bandwidth; in addition, the loading of the microstrip patch P also introduces a new coupling path, which promotes the occurrence of cross-coupling, thereby a new radiation zero point appears at high frequency.

[0032] Compared with the prior art, the present invention has the following significant advantages:

[0033] 1) Small size: Normally works in TE 120 The size of the substrate integrated cavity of the mode is usually larger than 0.7λ c The length and width of the substrate integrated cavity used in the present invention are less than 0.5λ c , which is much smaller than the commonly used substrate integrated cavity, mainly operates in the fractional-order resonant mode, so it can meet the needs of most miniaturized applications.

[0034] 2) No complex filtering structure: The introduction of the filtering characteristics of the present invention does not rely on the loading of the parasitic filtering structure, but utilizes the resonance characteristics of the structure itself. Therefore, the structural complexity and design complexity are much lower than those of existing designs.

[0035] 3) Simple feeding structure: The present invention only requires a coaxial probe for feeding, and the feeding structure does not occupy additional space and does not introduce additional loss.

[0036] 4) Low loss and high gain: The present invention utilizes substrate-integrated waveguide technology, which offers low loss in the millimeter-wave frequency band compared to existing microstrip technology. Furthermore, since it does not contain additional filtering circuitry, the present invention does not introduce filtering performance at the expense of additional insertion loss, as is the case with most existing designs.

[0037] 5) Wide bandwidth: The present invention introduces multiple resonance points through multi-mode resonance, and the bandwidth achieved is better than most planar antennas of the same type. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the three-dimensional structure decomposition of the present invention;

[0039] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention;

[0040] Figure 3 It is a top view of the upper dielectric substrate of the present invention, including the upper metal surface and the middle metal surface;

[0041] Figure 4 It is a top view of the lower dielectric substrate of the present invention, including the lower metal surface and the middle metal surface;

[0042] Figure 5 It is a simulation diagram of the S parameter curve of the present invention;

[0043] Figure 6 It is a simulation diagram of the gain curve of the present invention;

[0044] Figure 7 This is the simulated radiation pattern of the present invention at 24.5 GHz under the right-hand circular polarization working state;

[0045] Figure 8 This is the simulated radiation pattern of the present invention at 26.7 GHz under the right-hand circular polarization working state;

[0046] Figure 9 This is the simulated radiation pattern of the present invention at 29.1 GHz under the right-hand circular polarization working state. DETAILED DESCRIPTION

[0047] The present invention will be further analyzed below with reference to specific embodiments.

[0048] Combine Figure 1 and Figure 2 The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna includes two layers of upper dielectric substrate S1 with a thickness of 0.508 mm and model number Rogers5880, a lower dielectric substrate S2, and an upper metal surface P with the same size as the dielectric substrate covering the upper surface of the upper dielectric substrate S1, a middle metal surface M1 covering the lower surface of the upper dielectric substrate S1 and the upper surface of the lower dielectric substrate S2, and a lower metal surface M2 covering the lower surface of the lower dielectric substrate S2.

[0049] like Figure 3 As shown, an upper metal surface P with a length and width of 5 mm and 2.85 m respectively is placed on the upper surface of the upper dielectric substrate S1. The upper metal surface P adopts a microstrip patch.

[0050] like Figure 4 As shown, within the lower dielectric substrate S2, a substrate-integrated cavity C is designed. Its length and width are 5.7 mm and 4.3 mm, respectively, and it is surrounded by metallized through-holes V. The diameter of the metallized through-holes V is 0.3 mm, less than one-tenth of the air wavelength corresponding to the antenna's operating center frequency. The center-to-center distance between two adjacent metallized through-holes V is 0.5 mm.

[0051] Inside the substrate integrated cavity C, there are a pair of plated through-holes (VT) and a non-metallized through-hole (VP) for loading the SMA. The distance between the two metallized through-holes (V) and VT is 2.1 mm. They are slightly offset from the x-axis of the cavity C, with distances of 2.05 mm and 2.25 mm from the two long sides of the cavity C, respectively. The non-metallized through-hole (VP), reserved for feeding the coaxial probe (SMA), is 1.1 mm away from the adjacent long side of the cavity.

[0052] Two long slits SR are etched into the middle metal surface M1. These slits SR are arranged symmetrically about the length of the upper metal surface P and along the centerline. They are located on the two long side through-hole walls of the substrate integrated cavity C. The length and width of the long slits SP near the long sides of the cavity are 5.2 mm and 0.3 mm, respectively.

[0053] The specific structural geometric parameters are as follows:

[0054] Where h1 and h2 are the thicknesses of the upper and lower dielectric substrates, Lsub and Wsub are the length and width of the dielectric substrates, Lc and Wc are the length and width of the substrate-integrated cavity, Lp and Wp are the length and width of the microstrip patch, Ls and Ws are the length and width of the long slot, dvx and dvy are the spacing between the two metallized through-holes inside the cavity and their distances to the longer side of the cavity farther away, df is the distance from the coaxial probe to the longer side of the adjacent cavity, Ds is the diameter of the circular hole reserved for the coaxial probe installation on the lower metal surface, the diameter of the metallized holes constituting the substrate-integrated waveguide is d, and the hole spacing between adjacent metallized holes is p.

[0055]

[0056]

[0057] The size of the substrate integrated cavity C is conventionally 120 Half of the substrate integrated cavity in the mode. Conventional TE 120 There are two electric field peak regions in the mode. Cutting the cavity from these two electric field peak regions can obtain a mode operating in half-TE 120 This structure can achieve the miniaturization of high-order substrate integrated cavities, but it also has the problem of energy leakage.

[0058] The present invention places a long gap SR at each of the two cutoff points and seals them with periodic metallized through-hole walls, which can also stimulate half-TE 120 mode, and avoids energy leakage while achieving miniaturization.

[0059] A pair of metallized through holes VT is set at a specific position inside the cavity C of the present invention. The pair of metallized through holes VT divides the cavity C into two half cavities, the left and right half cavities, and the two half cavities can simultaneously excite the half-TE 110 Mode. The newly introduced left and right half-TE 110 The modes are in opposite phase, so the radiation generated by the long slot SR is canceled out, thereby introducing a radiation zero point at low frequency, giving the structure low-frequency filtering characteristics.

[0060] And because of half-TE 120 Field distribution characteristics of the mode and the fundamental mode TM of the microstrip patch 01 Because the field distribution characteristics of the cavity C are similar, placing a microstrip patch P above the cavity C introduces a new resonance point, broadening the operating bandwidth. Furthermore, the addition of the microstrip patch P introduces a new coupling path, which promotes cross-coupling and creates a new radiation null at high frequencies. Thus, by introducing three resonance points and two radiation nulls, a miniaturized broadband bandpass filter antenna design is achieved.

[0061] Figures 5 to 9 The simulation results of the compact high-gain single-fed millimeter-wave cavity-backed patch filter antenna are shown in Figure 2. Figure 5 It can be seen that the -10dB|S of the antenna 11 | is 20.3% (29.64-24.17GHz). Figure 6 It can be seen that the maximum gain of the antenna is 7.3dBi, the in-band gain is relatively flat, and obvious rapid roll-off can be seen outside the operating frequency band on both sides. Figures 7-9 This shows that the antenna has stable and good directional radiation in the entire operating frequency band.

Claims

1. Miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna, including: Upper dielectric substrate S1; Lower dielectric substrate S2; An upper metal surface P, which covers the upper surface of the upper dielectric substrate S1; A middle metal surface M1 covering the lower surface of the upper dielectric substrate S1 and the upper surface of the lower dielectric substrate S2; A lower metal surface M2, which covers the lower surface of the lower dielectric substrate S2; Its characteristics are: The upper metal surface P is a microstrip patch; Two long slits SR are etched on the middle metal surface M1; the two long slits SR are arranged symmetrically about the length of the upper metal surface P and toward the center line; the two long slits SR are respectively located on the two long side through-hole walls of the substrate integrated cavity C; The lower dielectric substrate S2 is provided with a substrate integrated cavity C formed by periodic metallized through holes V penetrating the lower dielectric substrate S2, a middle metal surface M1, and a lower metal surface M2; inside the substrate integrated cavity C there are a pair of metallized through holes VT and a non-metallized through hole VP for loading the SMA; The distance dvy between the metallized through hole VT and the long side through hole wall of the substrate integrated cavity C which is farther away from the metallized through hole VT satisfies 0.51Wc≤dvy≤0.53Wc, where Wc is the width of the substrate integrated cavity C; A circular hole for SMA feeding is etched on the lower metal surface M2.

2. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The center of the upper metal surface P, the center of the substrate integrated cavity C, the center of the upper dielectric substrate S1, and the center of the lower dielectric substrate S2 are located on the same straight line.

3. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The length and width of the substrate integrated cavity C are each less than 0.5λ c .

4. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The length Ls of the long gap SR satisfies 0.95Lc≤Ls≤Lc, where Lc represents the length of the substrate integrated cavity C.

5. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The width Ws of the long slit SR satisfies d≤Ws≤1.5d, where d represents the diameter of the metallized through hole V.

6. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The distance df between the long side of the substrate integrated cavity C that is closer to the through hole VT and the through hole VP satisfies df≤0.4Wc.

7. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The center of the through hole VP is located on the width center line of the substrate integrated cavity C.

8. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The metallized through hole V, the metallized through hole VT, and the non-metallized through hole VP have the same diameter, which is 0.026-0.028λ0, where λ0 is the wavelength at 27 GHz in free space.

9. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to claim 1, characterized in that The center of the circular hole coincides with the center of the non-metallized through hole VP, and the diameter of the circular hole Ds is greater than the diameter of the through hole VP.

10. The miniaturized broadband high-gain millimeter-wave cavity-fed planar filtering antenna according to any one of claims 1 to 9, characterized in that: The two long gaps SR are located at half-TE 120 The electric field of the mode is the strongest position, and it is blocked by the long side through-hole wall of the substrate integrated cavity C, thereby stimulating the half-TE 120 model; A pair of metallized through holes VT are provided inside the substrate integrated cavity C, dividing the substrate integrated cavity C into two half cavities, the left and right half cavities, and the two half cavities simultaneously excite the half-TE 110 Mode; and because of the two half-TE 110 The modes are in opposite phase, so the radiation generated by the long SR slot will cancel each other out, introducing a radiation null at low frequency. And because of half-TE 120 Field distribution characteristics of the mode and the fundamental mode TM of the microstrip patch 01 The field distribution characteristics of the substrate are similar, so a microstrip patch P is placed above the substrate integrated cavity C to introduce a new resonance point to widen the working bandwidth; in addition, the loading of the microstrip patch P also introduces a new coupling path, which promotes the occurrence of cross-coupling, thereby a new radiation zero point appears at high frequency.

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