Planar compact broadband millimeter wave filtering quasi-yagi antenna

Abstract

The invention discloses a planar compact broadband millimeter wave filtering quasi-yagi antenna, which is characterized in that a horizontal metal strip pair and a half-wavelength strip resonator of a center loading short-circuit branch knot can be excited by a biased coplanar waveguide transmission line at the same time in a parallel position relation; three radiation modes, namely an equivalent LC resonance mode, an odd coupling half-wave mode of a horizontal metal strip pair and an odd symmetry half-wave mode of a half-wavelength strip resonator of which the center is loaded with a short-circuit stub, can be obtained; according to two radiation zero points generated by an even symmetrical half-wave mode of the half-wavelength strip resonator of which the center is loaded with the short-circuit stub and an even coupling half-wave mode of the horizontal metal strip pair, the antenna not only can realize stable broadband end-direction radiation and obtain good filtering performance, but also can take the characteristics of a planar structure and compact size into account.

Description

Technical Field

[0001] The invention relates to a microwave communication device, in particular to a broadband millimeter wave filtering quasi-Yagi antenna. Background Art

[0002] As an important planar end-fire antenna, the quasi-Yagi antenna has won wide attention due to its simple structural design, convenient manufacturing process and easy installation method. When the planar quasi-Yagi antenna is integrated with the filtering function, it not only effectively reduces the number of independent filters used in the system, thereby reducing the overall system loss, but also improves the frequency selectivity of the antenna and the ability to suppress out-of-band interference, which has important research value.

[0003] There are several methods for implementing filtered quasi-Yagi antennas. One is to use dielectric resonators and near-zero materials as drivers and directors in quasi-Yagi antennas. At this time, the end-fire direction size will reach 1.1 λ0, where λ0 is the free space wavelength corresponding to the center frequency. The second method is to cascade the filtering structure in the feeding structure of the quasi-Yagi antenna or between the reflector and the driver of the quasi-Yagi antenna. Although this method can effectively introduce the filtering function, it will also lead to an increase in the size of the antenna, especially in the end-fire direction, which must be at least 0.6 λ0. The third is to add parasitic structures to the quasi-Yagi antenna, such as inserting double lateral parallel lines (DSPSL) between the driver and the reflector, or loading a ring structure in front of the director. These designs can provide filtering functions and improve frequency selectivity without significantly increasing the size of the antenna. At present, the end-fire direction of the filtered quasi-Yagi antenna based on this method can be reduced to 0.37 λ0, which needs further improvement, and all use probe feeding perpendicular to the antenna structure, so it is not easy to design in the millimeter wave band. In addition, by adding a resistively loaded microstrip branch between the reflector and the driver, the filtering function can be realized without increasing the extra size. At this time, the end-fire dimension is reduced to 0.13λ0, but the bandwidth is only 22.9% and the horizontal dimension is larger.

[0004] In order to achieve both compact structure and wide bandwidth in a planar filtering quasi-Yagi antenna, it is necessary to propose a new type of millimeter-wave filtering quasi-Yagi antenna. Summary of the invention

[0005] Purpose of the invention: In view of the above-mentioned prior art, a planar compact broadband millimeter-wave filtering quasi-Yagi antenna is proposed to solve the problem that bandwidth, compact structure and millimeter-wave application cannot be taken into account at the same time.

[0006] Technical solution: A planar compact broadband millimeter-wave filtering Yagi antenna, comprising a pair of horizontal metal strips, a half-wavelength strip resonator with a center-loaded shorting stub, a metal ground, an intermediate strip line, and a dielectric substrate; the pair of horizontal metal strips consists of a left horizontal metal strip and a right horizontal metal strip that are symmetric left and right, and are integrally distributed on the upper surface of the dielectric substrate and are located at the forefront in the end-fire direction of the antenna; the half-wavelength strip resonator with a center-loaded shorting stub includes a horizontal metal strip and a shorting stub strip; the horizontal metal strip is located on the upper surface of the dielectric substrate and is located directly behind the pair of horizontal metal strips and is arranged parallel to the pair of horizontal metal strips; the shorting stub strip is located on the lower surface of the dielectric substrate, and the horizontal metal strip and the shorting stub strip are connected by a metal via hole vertically penetrating the dielectric substrate; the intermediate strip line is located on the upper surface of the dielectric substrate, the intermediate strip line is arranged perpendicular to the horizontal metal strip, and the upper end is connected to a position slightly to the right of the center of the horizontal metal strip; the metal ground includes an upper left metal ground, an upper right metal ground, and a lower metal ground; the upper left metal ground and the upper right metal ground are located on the upper surface of the dielectric substrate and are located behind the half-wavelength strip resonator and are respectively located on both sides of the intermediate strip line; the lower metal ground is located on the lower surface of the dielectric substrate, and the lower edge of the shorting stub strip is connected to the upper edge of the lower metal ground; the upper left metal ground and the upper right metal ground are respectively connected to the lower metal ground through metal via holes provided in a circle along their respective edges; wherein, the metal ground and the intermediate strip line form a coplanar waveguide transmission line, which serves as the feeding structure of the antenna.

[0007] Further, the left horizontal metal strip and the right horizontal metal strip have the same length and width, the length is between 0.24λ0 and 0.28λ0, the width is between 0.05λ0 and 0.07λ0, and the distance between the two is between 0.02λ0 and 0.04λ0, where λ0 is the free space wavelength corresponding to the center frequency.

[0008] Further, the length of the horizontal metal strip is between 0.32 and 0.36λ0, the width is between 0.02 and 0.04λ0, the distance from the pair of horizontal metal strips in front is between 0.02 and 0.04λ0, and the distance from the metal ground behind is between 0.01 and 0.03λ0; the length and width of the shorting stub strip are both between 0.04 and 0.08λ0.

[0009] Further, the distance between the contact center point of the intermediate strip line and the horizontal metal strip and the right edge of the horizontal metal strip accounts for 3 / 10 of the length of the horizontal metal strip.

[0010] Beneficial effects: For the existing filtering end-fire antennas implemented based on planar Yagi antennas, it is necessary to cascade a filtering structure outside the antenna, or reserve space inside the antenna to integrate the filtering structure, or use a director with a specific structure, which all result in a relatively large size in the end-fire direction, and some designs cannot be realized in the millimeter-wave band; there are also designs that achieve a filtering response without increasing the size of the Yagi antenna in the end-fire direction, but the bandwidth is relatively narrow.

[0011] In the solution of the present invention, the horizontal metal strip pair and the half-wavelength strip resonator with a centrally loaded shorting stub can be simultaneously excited by the coplanar waveguide transmission line biased under the parallel positional relationship, and equivalent LC resonance, the odd-coupling half-wave mode of the horizontal metal strip pair, the odd-symmetric half-wave mode of the half-wavelength strip resonator with a centrally loaded shorting stub, and the two radiation zeros generated by the even-symmetric half-wave mode of the half-wavelength strip resonator with a centrally loaded shorting stub and the even-coupling half-wave mode of the horizontal metal strip pair can be obtained. The antenna can not only achieve stable broadband end-fire radiation and obtain good filtering performance, but also take into account the characteristics of a planar structure and a compact size.

[0012] Specifically, the horizontal metal strip is connected to the shorting stub strip through a metal via hole from the symmetry center, introducing equivalent LC resonance, generating a low-frequency first resonance point, and when the overall operates in the odd-symmetric half-wave mode, a high-frequency (third) resonance point is generated and effective radiation is provided; when the overall operates in the even-symmetric half-wave mode, a low-end radiation zero is provided, and its frequency can be controlled by adjusting the distance between the horizontal metal strip and the reflective ground.

[0013] When the horizontal metal strip pair operates in the odd-coupling half-wave mode, a second resonance point will be generated. At this time, the horizontal metal strip pair realizes mutual coupling through the intermediate gap. By adjusting the size and coupling strength of the intermediate gap, the resonance frequency and quality factor can be flexibly controlled. When the quality factor is reduced, the bandwidth of this resonance peak can be increased, so that the antenna can achieve a wider operating frequency band. When the horizontal metal strip pair operates in the even-coupling half-wave mode, the currents on the two horizontal metal strips are equal in amplitude and opposite in phase, so their far fields cancel each other out in the end-fire direction of the antenna, forming a radiation zero, making the antenna generate a filtering response. Description of the drawings

[0014] Figure 1 It is a schematic top-layer structure diagram of the antenna in the embodiment; Figure 2 It is a schematic bottom-layer structure diagram of the antenna in the embodiment; Figure 3 It is the electric field distribution corresponding to the three resonance frequencies of the antenna in the embodiment, where (a) corresponds to the equivalent LCResonance, (b) odd-coupled half-wave mode corresponding to the horizontal metal strip pair, (c) odd-symmetric half-wave mode of the horizontal metal strip corresponding to the center-loaded shorting stub; Figure 4 The electric field distributions of the antenna of the embodiment at two radiation null frequencies, where (a) corresponds to the lower radiation null and (b) corresponds to the higher radiation null; Figure 5 The matching and gain simulation curves of the antenna of the embodiment; Figure 6 For the antenna of the embodiment at E plane and H plane simulation radiation patterns, where (a) corresponds to 29 GHz, (b) corresponds to 33 GHz, and (c) corresponds to 40 GHz. Detailed implementation manners

[0015] The present invention will be further explained below with reference to the accompanying drawings.

[0016] As Figure 1 , Figure 2 shown, a planar compact broadband millimeter-wave filtering Yagi-Uda antenna is composed of a pair of horizontal metal strips 1, a half-wavelength strip resonator 2 with a center-loaded shorting stub, a metal ground 3, an intermediate strip line 4, and a dielectric substrate 5. The pair of horizontal metal strips 1 is composed of a left horizontal metal strip 11 and a right horizontal metal strip 12, and is integrally distributed on the upper surface of the dielectric substrate 5, located at the very front end in the end-fire direction of the antenna, and is symmetric about the midline of the dielectric substrate 5.

[0017] Among them, the left horizontal metal strip 11 and the right horizontal metal strip 12 have the same length and width, the length is between 0.24λ0 and 0.28λ0, the width is between 0.05λ0 and 0.07λ0, and the distance between the two is between 0.02λ0 and 0.04λ0, where λ0 is the free-space wavelength corresponding to the center frequency.

[0018] The half-wavelength strip resonator 2 with a center-loaded shorting stub is composed of a horizontal metal strip 21, a shorting stub strip 22, and a metal through-hole 23. Among them, the horizontal metal strip 21 is located on the upper surface of the dielectric substrate 5, and is located behind the pair of horizontal metal strips 1, is arranged in parallel with the pair of horizontal metal strips 1, and is symmetric about the midline of the dielectric substrate 5. The shorting stub strip 22 is located on the lower surface of the dielectric substrate 5, and is also symmetric about the midline of the dielectric substrate 5. The metal through-hole 23 vertically penetrates the dielectric substrate 5, connecting the horizontal metal strip 21 and the shorting stub strip 22, and the center of its circle coincides with the center of the horizontal metal strip 21.

[0019] The middle strip line 4 is located on the upper surface of the dielectric substrate 5, is arranged perpendicular to the horizontal metal strip 21, and its upper end is connected to the right of the center of the horizontal metal strip 21.

[0020] The metal ground 3 is composed of an upper-layer left metal ground 31, an upper-layer right metal ground 32, a lower-layer metal ground 33, and short-circuit metal vias 34. The upper-layer left metal ground 31 and the upper-layer right metal ground 32 are located on the upper surface of the dielectric substrate 5, are behind the half-wavelength strip resonator 2, and are respectively on both sides of the middle strip line 4. The lower-layer metal ground 33 is located on the lower surface of the dielectric substrate 5, and the lower edge of the short-circuit stub strip 22 is connected to the upper edge of the lower-layer metal ground 33. The short-circuit metal vias 34 are arranged in a circle along the edges of the upper-layer left metal ground 31 and the upper-layer right metal ground 32 for connection to the lower-layer metal ground 33.

[0021] Among them, the length of the horizontal metal strip 21 is between 0.32 and 0.36 λ0, the width is between 0.02 and 0.04 λ0, its distance from the front horizontal metal strip pair 1 is between 0.02 and 0.04 λ0, and its distance from the rear metal ground is between 0.01 and 0.03 λ0. The length and width of the short-circuit stub strip 22 are both between 0.04 and 0.08 λ0. The diameter of the metal via 23 is between 0.02 and 0.05 λ0. The distance between the contact center point of the middle strip line 4 and the horizontal metal strip 21 and the right edge of the horizontal metal strip 21 accounts for 3 / 10 of the length of the horizontal metal strip 21.

[0022] The metal ground 3 serves as the reflection ground of the antenna and can also serve as the system metal ground. At the same time, the metal ground 3 and the middle strip line 4 form a coplanar waveguide transmission line, serving as the feeding structure of the antenna.

[0023] For the planar compact broadband millimeter-wave filtering Yagi antenna of this embodiment, the millimeter-wave signal is fed in through the coplanar waveguide transmission line, transmitted to the half-wavelength strip resonator 2 with a center-loaded short-circuit stub, and coupled to the front horizontal metal strip pair 1, exciting Figure 3 the equivalent LC resonance introduced by the loaded short-circuit stub, the odd-coupling half-wave mode of the horizontal metal strip pair, and the odd-symmetric half-wave mode of the half-wavelength strip resonator with a center-loaded short-circuit stub. These three modes form broadband end-fire radiation under the reflection of the metal ground 3.

[0024] In addition, when the antenna operates at Figure 4When the even-symmetric half-wave mode of the horizontal metal strip 2 of the center-loaded shorted stub and the even-coupled half-wave mode of the horizontal metal strip pair 1 are as shown, the electric fields in the horizontal direction are distributed with equal amplitude and opposite phase, causing their far fields to cancel each other out in the end-fire direction of the antenna, thereby generating two radiation nulls at the low and high ends of the operating frequency band and achieving a filtering response. Therefore, with the support of three resonant points and two radiation nulls, the antenna obtains broadband filtering end-fire radiation performance.

[0025] In this embodiment, the planar size of the antenna is 0.65 λ0 × 0.16 λ0 (excluding the metal ground). The lengths of the left horizontal metal strip 11 and the right horizontal metal strip 12 are both 0.26 λ0, the widths are both 0.06 λ0, and the distance between them is 0.03 λ0. The length of the horizontal metal strip 21 is 0.34 λ0, the width is 0.038 λ0, its distance from the front horizontal metal strip pair 1 is 0.03 λ0, and its distance from the rear metal ground is 0.02 λ0. The length and width of the shorted stub strip 22 are both 0.06λ0. The diameter of the metal through-hole 23 is 0.035 λ0. The simulated matching response and gain response curves are as Figure 5 shown. It can be seen that its 10-dB impedance matching bandwidth range is 28.3 - 41.43 GHz, that is, the relative bandwidth is 37.66%; the 3-dB power bandwidth is 32.37% (29.65 - 41.1 GHz). There are two radiation nulls in the gain response curve, corresponding to 26 GHz and 46 GHz respectively. The gain range within the frequency band is 0.1 - 5.31 dBi. Figure 6 The simulated antenna radiation patterns at 29 GHz, 33 GHz, and 40 GHz are shown. From Figure 6 (a), it can be seen that at 29 GHz, the 3-dB beamwidths in the E plane and the H plane are 102.7° and 243.4° respectively, and the cross-polarization levels within the 3-dB beam in the E plane and the H plane are 16.87 dB and 5.32 dB respectively. From Figure 6 (b), it can be seen that at 33 GHz, the 3-dB beamwidths in the E plane and the H plane are 96.1° and 174.9° respectively, and the cross-polarization levels within the 3-dB beam in the E plane and the H plane are 24.03 dB and 10.9 dB respectively. From Figure 6 (c), it can be seen that at 40 GHz, the 3-dB beamwidths in the E plane and the H plane are 68.5° and 118.7° respectively, and the cross-polarization levels within the 3-dB beam in the E plane andH The cross-polarization levels within the 3-dB beam range of the plane are 20.84 dB and 20.28 dB, respectively.

[0026] Compared with the prior art, the planar compact broadband millimeter-wave filtering quasi-Yagi antenna proposed by the present invention can not only obtain a relatively wide millimeter-wave working bandwidth, but also take into account the characteristics of a compact structure and planar integrability.

[0027] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A planar compact broadband millimeter-wave filtering quasi-Yagi antenna, characterized in that, It includes a pair of horizontal metal strips (1), a half-wavelength strip resonator (2) with a centrally loaded shorting stub, a metal ground (3), an intermediate strip line (4), and a dielectric substrate (5); The pair of horizontal metal strips (1) consists of a left horizontal metal strip (11) and a right horizontal metal strip (12) that are symmetric left and right. The whole is distributed on the upper surface of the dielectric substrate (5) and is located at the very front in the end-fire direction of the antenna; The half-wavelength strip resonator (2) with a centrally loaded shorting stub includes a horizontal metal strip (21) and a shorting stub strip (22); the horizontal metal strip (21) is located on the upper surface of the dielectric substrate (5) and is directly behind the pair of horizontal metal strips (1), and is arranged parallel to the pair of horizontal metal strips (1); the shorting stub strip (22) is located on the lower surface of the dielectric substrate (5), and the horizontal metal strip (21) and the shorting stub strip (22) are connected by a metal via hole (23) that vertically penetrates the dielectric substrate (5); The intermediate strip line (4) is located on the upper surface of the dielectric substrate (5). The intermediate strip line (4) is arranged perpendicular to the horizontal metal strip (21), and its upper end is connected to the center of the horizontal metal strip (21) to the right; The metal ground (3) includes an upper left metal ground (31), an upper right metal ground (32), and a lower metal ground (33); the upper left metal ground (31) and the upper right metal ground (32) are located on the upper surface of the dielectric substrate (5) and are behind the half-wavelength strip resonator (2), and are respectively located on both sides of the intermediate strip line (4); the lower metal ground (33) is located on the lower surface of the dielectric substrate (5), and the lower edge of the shorting stub strip (22) is connected to the upper edge of the lower metal ground (33); the upper left metal ground (31) and the upper right metal ground (32) are respectively connected to the lower metal ground (33) through metal via holes arranged along a circle of their respective edges; Among them, the metal ground (3) and the intermediate strip line (4) form a coplanar waveguide transmission line, which serves as the feeding structure of the antenna.

2. The planar compact broadband millimeter-wave filtering quasi-Yagi antenna according to claim 1, wherein The left horizontal metal strip (11) and the right horizontal metal strip (12) have the same length and width. The length is between 0.24λ0 and 0.28λ0, the width is between 0.05λ0 and 0.07λ0, and the distance between the two is between 0.02λ0 and 0.04λ0, where λ0 is the free space wavelength corresponding to the center frequency.

3. The planar compact broadband millimeter-wave filtering quasi-Yagi antenna according to claim 2, characterized in that The length of the horizontal metal strip (21) is between 0.32 and 0.36λ0, the width is between 0.02 and 0.04λ0, the distance from the pair of horizontal metal strips (1) in front is between 0.02 and 0.04λ0, and the distance from the metal ground behind is between 0.01 and 0.03λ0; the length and width of the shorting stub strip (22) are both between 0.04 and 0.08λ0.

4. The planar compact broadband millimeter-wave filtering quasi-Yagi antenna according to any one of claims 1-3, characterized in that, The distance between the contact center point of the intermediate strip line (4) and the horizontal metal strip (21) and the right edge of the horizontal metal strip (21) accounts for 3 / 10 of the length of the horizontal metal strip (21).

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