A low cross-polarization vivaldi antenna

Abstract

The application discloses a low cross-polarization Vivaldi antenna and belongs to the technical field of electromagnetic fields and antennas. The low cross-polarization Vivaldi antenna comprises a dielectric substrate, a pair of radiation arms and a balanced radiation arm are arranged on the dielectric substrate, and the pair of radiation arms and the balanced radiation arm are oppositely arranged. Metal through holes are formed in the dielectric substrate, and the pair of radiation arms and the balanced radiation arm are electrically connected through the metal through holes. A dielectric director is arranged on one side of the dielectric substrate, and a reflecting floor is arranged on the other side of the dielectric substrate. The dielectric director is used for adjusting the phase difference of electromagnetic waves at the opening of the Vivaldi antenna. The reflecting floor is used for improving the front-to-back ratio of electromagnetic waves. Electromagnetic waves are radiated from the reflecting floor to the direction of the dielectric director. The application further reduces the cross-polarization level of the Vivaldi antenna and can be applied to the fields of satellite communication, ground penetrating radar, microwave imaging and UWB ultra-wideband communication.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic field and antenna, and particularly relates to a low cross-polarization Vivaldi antenna. BACKGROUND

[0002] The Vivaldi antenna is a non-periodic, gradually changing, end-fire traveling wave antenna, has the characteristics of small size, low cost, simple structure and easy processing, and the like, and has the characteristics of wide frequency band and theoretically infinite bandwidth due to the fact that the electrical size of the Vivaldi antenna remains unchanged at different working frequencies, and the input impedance and the radiation pattern of the antenna can also remain approximately unchanged in the entire working frequency band.

[0003] The traditional Vivaldi antenna is provided with radiation arms on both sides of a dielectric substrate, and the direction of the electric field is from one side of the radiation arm to the other side during the working of the antenna, and an angle is formed between the electric field and the dielectric substrate due to the thickness of the dielectric substrate, which leads to the deterioration of cross-polarization, and the deterioration of cross-polarization is more obvious with the increase of the frequency, and on the other hand, the opening distance of the Vivaldi antenna cannot be large enough due to the limitation of the size of the dielectric substrate, which affects the low-frequency performance of the Vivaldi antenna, and this problem is also a difficult problem encountered in the current research on the Vivaldi antenna, and how to reduce the size of the Vivaldi antenna while achieving good low-frequency performance is one of the current research hotspots. SUMMARY

[0004] The application aims to provide a low cross-polarization Vivaldi antenna, which can further reduce the cross-polarization level of the electric field and the dielectric substrate and improve the low-frequency performance of the Vivaldi antenna.

[0005] In order to solve the above problems, the application adopts the following technical scheme: a low cross-polarization Vivaldi antenna, comprising a dielectric substrate, the dielectric substrate is provided with a pair of radiation arms and a balanced radiation arm, the pair of radiation arms and the balanced radiation arm are oppositely arranged, a metal through hole is formed in the dielectric substrate, the pair of radiation arms and the balanced radiation arm are electrically connected through the metal through hole, a dielectric director is arranged on one side of the dielectric substrate, and a reflecting floor is arranged on the other side, the dielectric director is used for adjusting the phase difference of electromagnetic waves at the opening of the Vivaldi antenna, the reflecting floor is used for improving the front-to-back ratio of electromagnetic waves, and the electromagnetic waves are radiated from the reflecting floor to the dielectric director.

[0006] Furthermore, the dielectric substrate is provided with two pairs of topological arms; the two pairs of topological arms are respectively a first pair of topological arms and a second pair of topological arms, and the first pair of topological arms and the second pair of topological arms are respectively disposed on both sides of the dielectric substrate.

[0007] Furthermore, the dielectric substrate is provided with two balanced radiation arms; the two balanced radiation arms are a first balanced arm and a second balanced arm, the first balanced arm and a first pair of topological radiation arms are opposite each other, and the second balanced arm and a second pair of topological radiation arms are opposite each other.

[0008] Furthermore, the dielectric director is located behind the dielectric substrate, and the reflective ground plane is located in front of the dielectric substrate.

[0009] Furthermore, the first pair of topographic arms and the second pair of topographic arms have notches on the side near the reflector floor, and the notches are used to adjust the impedance matching of the Vivaldi antenna.

[0010] Furthermore, the first pair of topological arms and the second pair of topological arms are provided with feed points, and electrical signals enter the first pair of topological arms and the second pair of topological arms of the antenna through the feed points respectively.

[0011] Furthermore, the medium guide is trapezoidal in shape.

[0012] Furthermore, the dielectric substrate is an FR-4 dielectric substrate with dimensions of 92mm × 74mm × 0.65mm.

[0013] Furthermore, the surfaces of the top radiation arm, the balance radiation arm, and the inner surface of the metal through hole are plated with copper.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the dielectric substrate is provided with a pair of topological arms and a balanced radiating arm, which are arranged opposite to each other to increase the current path of the antenna at low frequencies and reduce the cross-polarization generated at high frequencies; the dielectric substrate is provided with metal vias, through which the pair of topological arms and the balanced radiating arms are electrically connected; a dielectric director is provided on one side of the dielectric substrate, and a reflector is provided on the other side; the dielectric director is used to adjust the phase difference of electromagnetic waves at the opening of the Vivaldi antenna; the reflector is used to improve the front-to-back ratio of electromagnetic waves; electromagnetic waves are radiated from the reflector towards the dielectric director; when the antenna is in a high-frequency state, the second pair of topological arms couples with the second balanced arm on the other side to generate an electric field in the opposite direction to that between the second pair of topological arms and the first pair of topological arms, canceling out part of the cross-polarized electromagnetic waves, further reducing the cross-polarization level of the Vivaldi antenna, and can be applied to satellite communication, ground penetrating radar, microwave imaging, UWB ultra-wideband communication and other fields. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the Vivaldi antenna structure in the prior art provided by the embodiments of the present invention;

[0016] Figure 2 This is a schematic diagram of a low cross-polarization Vivaldi antenna structure provided in an embodiment of the present invention;

[0017] Figure 3 This is a front view of a low cross-polarization Vivaldi antenna provided in an embodiment of the present invention;

[0018] Figure 4 This is a back-side structure diagram of a low cross-polarization Vivaldi antenna provided in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the return loss of a Vivaldi antenna topology provided in the embodiments of the present invention.

[0020] Figure 6 This is a schematic diagram of the gain of a Vivaldi antenna topology provided in the prior art according to the embodiments of the present invention;

[0021] Figure 7 This is a schematic diagram of the return loss of the low cross-polarization Vivaldi antenna provided in an embodiment of the present invention;

[0022] Figure 8 This is a schematic diagram showing the variation of the return loss of the low cross-polarization Vivaldi antenna with the length L1 of the topological radiating arm provided in this embodiment of the invention.

[0023] Figure 9 This is a schematic diagram of the current distribution of the low cross-polarization Vivaldi antenna provided in an embodiment of the present invention at 2.5 GHz;

[0024] Figure 10 This is a schematic diagram of the current distribution of the low cross-polarization Vivaldi antenna at 4 GHz provided in an embodiment of the present invention;

[0025] Figure 11 This is a schematic diagram of the current distribution of the low cross-polarization Vivaldi antenna at 8 GHz provided in an embodiment of the present invention;

[0026] Figure 12 This is the radiation pattern of the low cross-polarization Vivaldi antenna EH surface at 4 GHz under current conditions provided in this embodiment of the invention.

[0027] Figure 13 This is the radiation pattern of the low cross-polarization Vivaldi antenna EH surface at 8 GHz under current conditions provided in this embodiment of the invention.

[0028] Figure 14 This is a schematic diagram of the gain of the low cross-polarization Vivaldi antenna provided in an embodiment of the present invention;

[0029] In the figure: 01-substrate; 02-radiating arm; 03-opening; 1-dielectric substrate; 2-first pair of topological radiating arms; 3-second pair of topological radiating arms; 4-first balancing arm; 5-second balancing arm; 6-metal through-hole; 7-dielectric director; 8-reflective ground plane; 9-notch; 10-feed point. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] like Figure 1 As shown, in the prior art, when the Vivaldi antenna is in operation, the direction of the electric field is from one side of the radiating arm 02 to the other side of the radiating arm. Because the substrate 01 has a thickness, an angle is formed between the electric field and the substrate 01, which leads to the deterioration of cross-polarization. As the frequency increases, the deterioration of cross-polarization becomes more obvious. On the other hand, the opening 03 of the Vivaldi antenna is small, which affects the low-frequency performance of the Vivaldi antenna.

[0035] like Figure 2As shown, this embodiment of the invention provides a low cross-polarization Vivaldi antenna, including a dielectric substrate 1. The dielectric substrate 1 is an FR-4 dielectric substrate with a diameter of 92mm × 74mm × 0.65mm and a dielectric constant of 4.4 and a loss tangent of 0.027. The dielectric substrate 1 has a pair of topological arms and a balanced radiating arm, both with copper cladding. The topological arms and balanced radiating arms are arranged opposite to each other. The dielectric substrate 1 has two pairs of topological arms, namely a first pair of topological arms 2 and a second pair of topological arms 3, respectively, located on opposite sides of the dielectric substrate 1. The first pair of topological arms 2 and the second pair of topological arms 3 have feed points 10, each with an SMA (Surface Mount Automation) RF interface connected to the antenna input signal. The electrical signal enters the first pair of topological arms 2 and the second pair of topological arms 3 through the feed points 10. Electromagnetic waves radiate from the reflector 8 towards the dielectric director 7.

[0036] The dielectric substrate 1 is provided with two balanced radiating arms, namely a first balanced arm 4 and a second balanced arm 5. The first balanced arm 4 and a first pair of topological radiating arms 2 are opposite each other, and the second balanced arm 5 and a second pair of topological radiating arms 3 are opposite each other. The dielectric substrate 1 is provided with a plurality of metal through holes 6 with the same diameter. The surface of the metal through holes 6 is plated with copper. The first pair of topological radiating arms 2 and the first balanced radiating arm 4, the second pair of topological radiating arms 3 and the second balanced radiating arm 5 are electrically connected through the metal through holes 6.

[0037] A dielectric director 7 is provided on one side of the dielectric substrate 1, and a reflective ground plane 8 is provided on the other side. The dielectric director 7 is located behind the dielectric substrate 1. In this embodiment, the dielectric director 7 is a portion protruding from the dielectric substrate. The dielectric director 7 is trapezoidal in shape. The reflective ground plane 8 is located in front of the dielectric substrate 1. The dielectric director 7 is used to adjust the phase difference of electromagnetic waves at the antenna opening, thereby improving the radiation directivity of the antenna. Specifically, the electromagnetic waves originally radiated backward by the antenna are reflected by the reflective ground plane 8, and the electromagnetic waves radiate in the end-firing direction. After being converged by the trapezoidal dielectric director 7, the overall gain level of the antenna is increased, thereby improving the front-to-back ratio of electromagnetic waves. The first pair of topological radiating arms 2 and the second pair of topological radiating arms 3 have notches 9 on the side near the reflective ground plane 8. The notches 9 are used to adjust the impedance matching of the Vivaldi antenna. The notches 9 are circular. Since the aperture of the Vivaldi antenna increases after adding the balanced radiating arms, the impedance matching of the antenna will be deteriorated. The notches 9 are used to adjust the impedance matching of the Vivaldi antenna.

[0038] like Figure 3 and Figure 4As shown, the antenna radiating section has a length of L1 = 92 mm, a width of W1 = 74.2 mm, a radius of notch 9 of R1 = 10.5 mm, and the center of notch 9 is located at (X = 31 mm, Y = 25 mm) from the origin. The dielectric director 7 is 10 mm from the boundary G2, has a front width of G3 = 34.2 mm, a height of H1 = 25 mm, and a bottom feed width of G1 = 1.5 mm. The topographic radiating arm is composed of two exponentially decreasing curves Y1 and Y2, which are obtained by the following formula:

[0039]

[0040]

[0041]

[0042]

[0043] In the formula, S 1，2 Let r be the initial height of the exponential equation. 1，2 Let be the slope of the curve, x be the variable of the curve, and hs be the slope of the curve. 1， The offset of the curves is as follows: Curve Y1 has an initial height of S1 = 0.05 mm, a curvature of r1 = 0.45, an offset of hs1 = -0.8 mm, and a length of L2 = 89 mm. Curve Y2 has an initial height of S2 = 0.05 mm, a curvature of r2 = 0.95, an offset of hs2 = 0.7 mm, and a length of L3 = 30 mm. The width of the topographic arm is W2 = 34.75 mm, the width of the balanced radiation arm is W3 = 12.2 mm, and the height of the reflective floor is H2 = 11 mm.

[0044] like Figure 5 As shown, due to the influence of antenna size, the return loss of the Vivaldi topology antenna is poor at low frequencies (2.8 GHz). This is because the antenna radiating arm cannot form a current loop, thus the low-frequency performance is greatly affected by the antenna size. Figure 6 As shown in the schematic diagram of the Vivaldi antenna gain, the antenna gain is up to 8 dBi in the frequency band. This is because its radiation pattern is wide, and electromagnetic waves leak through both sides of the radiating arm, resulting in poor directivity.

[0045] like Figure 7As shown, this invention, with an antenna lateral dimension W1 = 74mm, possesses superior low-frequency performance, with a minimum bandwidth of 2.3GHz. In contrast, the Vivaldi antenna has a width of 96mm and a minimum bandwidth of 2.8GHz. Due to the addition of a balanced radiating arm structure and short-circuiting to the radiating arm via a metal via 6, a longer current loop can be easily formed in the low-frequency band, thus widening the low-frequency bandwidth. Furthermore, the Vivaldi antenna in this invention has a lower cross-polarization value, and the electromagnetic waves radiated by the antenna are radiated horizontally, which is beneficial for subsequent antenna array formation.

[0046] like Figure 8 As shown, the Vivaldi antenna aperture becomes larger with increasing topological arm length, thus extending its low-frequency bandwidth. For example, when L1 = 94 mm, the lowest bandwidth frequency is 2.15 GHz, while when L1 = 91 mm, the lowest bandwidth frequency is 2.35 GHz. Although the low-frequency bandwidth is extended when L1 = 94 mm or L1 = 93 mm, the impedance matching at 3 GHz deteriorates, with |S11| less than 10 dB, which does not meet communication requirements. Furthermore, when the antenna arm length L1 = 91 mm and L1 = 92 mm, the impedance matching at 3 GHz does not deteriorate, but when L1 = 92 mm, the low-frequency performance is significantly better. Therefore, L1 = 92 mm is chosen as the optimal value for the antenna topological arm length.

[0047] like Figure 9 As shown, when the frequency is 2.5 GHz, the current of the Vivaldi antenna flows through the metal through-hole 6 into the first balancing arm 4 and the second balancing arm 5, increasing the current flow path; Figure 10 As shown, when the current convergence frequency is 4GHz, the current is mainly concentrated on the first pair of topological radiating arms 2 and the second pair of topological radiating arms 3, while the current on the balanced radiating arms is relatively small. Therefore, the antenna can achieve a high gain at 4GHz. Figure 11 As shown, when the frequency is 8GHz, the current distribution on the balanced and topological radiating arms of the Vivaldi antenna is relatively uniform, and the antenna gain reaches 12dBi.

[0048] like Figure 12 As shown, at a frequency of 4 GHz, the Vivaldi antenna pattern is symmetrical, with uniform radiation and a low level of cross-polarization. The dielectric director 7 and the reflector 8 guide the electromagnetic waves towards the end-firing direction, while also improving the gain. Figure 13As shown, at a frequency of 8 GHz, the antenna pattern exhibits increased spikes, but remains generally symmetrical and exhibits uniform radiation. Due to the presence of the balanced radiating arm, cross-polarization is also suppressed. Simultaneously, the dielectric director 7 and the reflecting ground 8 increase the radiation gain of the Vivaldi antenna. The Vivaldi antenna demonstrates excellent radiation performance, with a maximum gain of 13.5 dBi, further satisfying the high-gain requirement of the Vivaldi antenna. Figure 14 As shown, the Vivaldi antenna has an average gain of 9.5 dBi and a peak gain of up to 13.5 dBi, with higher gains at low frequencies, all above 5 dBi.

[0049] The Vivaldi antenna provided in this embodiment of the invention increases the current path of the antenna at low frequencies and reduces cross-polarization at high frequencies by setting a pair of topological radiating arms and a pair of balanced radiating arms on the dielectric substrate 1. A circular notch 9 is opened at the topological radiating arms to adjust the return loss of the Vivaldi antenna. In addition, to address the disadvantage of poor gain of the Vivaldi antenna in the low-frequency band, a dielectric director 7 and a reflector 8 are set on the rear side of the dielectric substrate 1, so that the impedance bandwidth of the antenna is 2.3GHz to 20GHz, and the maximum gain in the frequency band is 13dBi. It can be applied to satellite communication, ground penetrating radar, microwave imaging, UWB ultra-wideband communication and other fields, further improving the gain level of the Vivaldi antenna.

[0050] A low cross-polarization Vivaldi antenna electromagnetic radiation principle: The first pair of topological arms 2 and the second pair of topological arms 3 are provided with feed points 10. The feed points 10 are provided with SMA radio frequency dedicated interfaces. The SMA radio frequency dedicated interfaces are connected to the antenna of the input signal. The electrical signal enters the first pair of topological arms 2 and the second pair of topological arms 3 through the feed points 10 respectively. The electromagnetic wave radiates along the reflector 8 towards the dielectric director 7.

[0051] The second pair of topological arms 3 are connected to the second balanced arm 5 through the metal through-hole 6. Therefore, when the current reaches the second pair of topological arms 3, it flows into the second balanced arm 5 along the metal through-hole 6, thereby greatly increasing the low-frequency bandwidth of the antenna. On the other side, the radiation of the first pair of topological arms 2 and the first balanced arm 4 is similar. When the antenna is in a high-frequency state, the second pair of topological arms 3, through coupling with the second balanced arm 5 on the other side, generates an electric field with the opposite direction to that between the second pair of topological arms 3 and the first pair of topological arms 2, canceling out some of the cross-polarized electromagnetic waves, giving the antenna low cross-polarization performance. When electromagnetic waves radiate along the end-firing direction through the first pair of topological arms 2 and the second pair of topological arms 3, the end-firing direction is the radiation direction from the reflector 8 to the dielectric director 7. The dielectric director 7 can concentrate the electromagnetic waves in the end-firing direction, thereby improving the antenna directivity and increasing the gain effect of the Vivaldi antenna. Since some electromagnetic waves will radiate backward, by adding the reflector 8, the electromagnetic waves radiated backward are reflected back to the end-firing direction.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low cross-polarization Vivaldi antenna, characterized in that, The device includes a dielectric substrate (1), on which a topological radiating arm and a balanced radiating arm are provided, and the topological radiating arm and the balanced radiating arm are arranged opposite to each other; a metal through-hole (6) is provided on the dielectric substrate (1), and the topological radiating arm and the balanced radiating arm are electrically connected through the metal through-hole (6); a dielectric director (7) is provided on one side of the dielectric substrate (1), and a reflective ground plane (8) is provided on the other side; the dielectric director (7) is used to adjust the phase difference of the electromagnetic wave at the opening of the Vivaldi antenna, and the reflective ground plane (8) is used to improve the front-to-back ratio of the electromagnetic wave; the electromagnetic wave is radiated from the reflective ground plane (8) towards the dielectric director (7); The dielectric substrate (1) is provided with two pairs of topographic arms; the two pairs of topographic arms are respectively the first pair of topographic arms (2) and the second pair of topographic arms (3), and the first pair of topographic arms (2) and the second pair of topographic arms (3) are respectively disposed on the front and back sides of the dielectric substrate (1); The dielectric substrate (1) is provided with two balanced radiation arms; the two balanced radiation arms are a first balanced arm (4) and a second balanced arm (5), the first balanced arm (4) and the first pair of topological radiation arms (2) are opposite to each other, and the second balanced arm (5) and the second pair of topological radiation arms (3) are opposite to each other.

2. The low cross-polarization Vivaldi antenna according to claim 1, characterized in that, The dielectric director (7) is located behind the dielectric substrate (1), and the reflective floor (8) is located in front of the dielectric substrate (1).

3. The low cross-polarization Vivaldi antenna according to claim 1, characterized in that, The first pair of topographic arms (2) and the second pair of topographic arms (3) have notches (9) on the side near the reflector plate (8), and the notches (9) are used to adjust the impedance matching of the Vivaldi antenna.

4. A low cross-polarization Vivaldi antenna according to claim 1, characterized in that, Feed points (10) are provided on the first pair of topographic arms (2) and the second pair of topographic arms (3). Electrical signals enter the first pair of topographic arms (2) and the second pair of topographic arms (3) of the antenna through the feed points (10).

5. A low cross-polarization Vivaldi antenna according to claim 1, characterized in that, The medium guide (7) is trapezoidal in shape.

6. A low cross-polarization Vivaldi antenna according to claim 1, characterized in that, The dielectric substrate (1) is an FR-4 dielectric substrate (1) with a diameter of 92mm × 74mm × 0.65mm.

7. A low cross-polarization Vivaldi antenna according to claim 1, characterized in that, The surfaces of the top radiation arm, the balance radiation arm, and the inner surface of the metal through hole (6) are plated with copper.

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