A broadband microstrip quasi-yagi antenna

Abstract

The application provides a broadband microstrip quasi-Yagi antenna, which has simple structure, can improve impedance matching of the antenna, can realize high-gain transmission and expand use scenarios of the microstrip Yagi antenna. The broadband microstrip quasi-Yagi antenna comprises a dielectric substrate, an excitation oscillator and a director. One excitation oscillator is printed on each of the front and back surfaces of the dielectric substrate, forming a butterfly-shaped oscillator. The two excitation oscillators are two arms of the butterfly-shaped oscillator, and are single arm A on the front surface of the dielectric substrate and single arm B on the back surface of the dielectric substrate respectively. Single arm A is connected to a feed line through an impedance transformation section and a microstrip line A in sequence. The other end of the front and back surfaces of the dielectric substrate is provided with a director, and the director comprises a plurality of strip-shaped director units arranged in parallel. The central axis of the director unit coincides with the central axis of the dielectric substrate. Slot lines are symmetrically arranged along the central axis at both ends of the length direction of each director unit.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microstrip antennas, and particularly relates to a broadband microstrip quasi-Yagi antenna. BACKGROUND

[0002] With the continuous development of wireless communication technology, people's requirements for the bandwidth, gain and size of antennas are also getting higher and higher. In the field of antennas, Yagi antennas, also known as directional antennas, have the advantages of simple structure and strong directivity, and are widely used in the field of wireless communication. The traditional Yagi antenna is usually too large in size, and due to the limitations of the size of the antenna and the material of the vibrator, the Yagi antenna cannot be conformal with the surface of the carrier, and the working bandwidth of the traditional Yagi antenna is also narrow, and the relative bandwidth is generally within 5%. These greatly limit the use of Yagi antennas in mobile communication and many environments with limited space. Therefore, it is necessary to properly improve the shortcomings of the traditional Yagi antenna while retaining its many advantages.

[0003] Compared with Yagi antennas, microstrip antennas are not only small in size, light in weight, low in profile, easy to conform, but also easy to integrate, low in cost and suitable for mass production. By combining microstrip antennas and Yagi antennas and giving full play to their respective advantages, microstrip Yagi antennas can have broad application prospects.

[0004] Common microstrip Yagi antennas are generally composed of a dielectric substrate, a ground plate, a reflector, an excitation vibrator and a director. Due to the metal back cover of the microstrip antenna, direct use of the microstrip antenna combined with the Yagi antenna can only achieve quasi-end-fire radiation, i.e. the maximum radiation direction of the antenna is in the space above the inclined surface of the dielectric plate (that is, the ground plate of the normal microstrip antenna is composed of the entire lower surface of the dielectric substrate covered with metal, but the ground plate in this case will make the radiation pattern of the Yagi antenna point to the space above the upper surface of the dielectric substrate, which is what we need to avoid). To solve this problem, a microstrip quasi-Yagi antenna structure is usually used, i.e. instead of using a traditional reflector, the truncated ground plate at the back of the microstrip antenna is used as a reflector to realize end-fire radiation of the antenna. Common microstrip quasi-Yagi antennas use microstrip line feeding, and through a broadband balun structure, broadband impedance matching and realization of a 180-degree phase difference between the two arms of the active array can provide better signal receiving and transmitting performance in some cases.

[0005] However, the microstrip quasi-Yagi antenna structure has the defects of large antenna size printed on the dielectric substrate and relatively complex balun structure. Another common microstrip quasi-Yagi antenna has two arms of the excitation dipole printed on two surfaces of the dielectric substrate respectively, one arm on the front surface connected with the feed line through a microstrip line, and one arm on the back surface connected with the truncated ground plane through a microstrip line. The balanced feed of the excitation dipole is realized through the current distribution on the ground plane. Although this scheme eliminates the complex balun structure, it has the defects of narrow frequency band, which affects the receiving efficiency of the antenna in a specific frequency range and the impedance matching performance of the antenna. SUMMARY

[0006] Therefore, the present application provides a broadband microstrip quasi-Yagi antenna, which has a simple structure, can improve the impedance matching of the antenna, realize high-gain transmission, and expand the use scenarios of the microstrip quasi-Yagi antenna.

[0007] The broadband microstrip quasi-Yagi antenna comprises a dielectric substrate, an excitation dipole, and a director.

[0008] One excitation dipole is printed on each of the front and back surfaces of the dielectric substrate at one end to form a butterfly-shaped dipole. The two excitation dipoles are two arms of the butterfly-shaped dipole, which are a single arm A on the front surface of the dielectric substrate and a single arm B on the back surface of the dielectric substrate.

[0009] The single arm A is connected with the feed line through an impedance transformation section and a microstrip line A in sequence.

[0010] The dielectric substrate is provided with a ground plane on the back surface, and the single arm B is connected with the ground plane through an impedance transformation section.

[0011] The dielectric substrate is provided with a director at the other end of the front and back surfaces. The director comprises a plurality of strip-shaped director units arranged in parallel. The director units on the front and back surfaces of the dielectric substrate correspond to each other in position. The central axis of the director unit coincides with the central axis of the dielectric substrate.

[0012] Groove lines are symmetrically arranged along the central axis at both ends of the length direction of each director unit.

[0013] As a preferred mode of the present application, the number of director units is four. The first director unit is the closest to the excitation dipole, and then the second director unit, the third director unit, and the fourth director unit are sequentially arranged from the closest to the farthest.

[0014] The lengths of the first director unit to the fourth director unit decrease in sequence.

[0015] As a preferred mode of the present application,

[0016] The length of the first director unit ranges from 279 mm to 285 mm.

[0017] The length of the second director unit ranges from 260 mm to 270 mm;

[0018] The length of the third director unit ranges from 251 mm to 255 mm;

[0019] The length of the fourth director unit ranges from 235 mm to 240 mm.

[0020] As a preferred mode of the present application,

[0021] The distance between the first director unit and the narrow side of the excitation vibrator ranges from 65 mm to 67 mm;

[0022] The distance between the second director unit and the first director unit ranges from 68 mm to 75 mm;

[0023] The distance between the third director unit and the second director unit ranges from 38 mm to 45 mm;

[0024] The distance between the fourth director unit and the third director unit ranges from 65.7 mm to 70 mm.

[0025] As a preferred mode of the present application, the slot line slotting depth is 1.15 mm.

[0026] As a preferred mode of the present application, metal parasitic patches 7 are symmetrically arranged on both sides of the impedance transformation sections on the front and back surfaces of the dielectric substrate;

[0027] Each of the parasitic patches is provided with a through hole;

[0028] The through holes on the parasitic patches on the same side are connected through the through holes on the dielectric substrate at the corresponding positions.

[0029] As a preferred mode of the present application, the distance from the parasitic patch to the wide side of the single-arm B is 26.9 mm.

[0030] As a preferred mode of the present application, the wide side length of the single-arm A and the single-arm B is 28.6 mm, and the narrow side length is 17.2 mm.

[0031] As a preferred mode of the present application, the length e of the single-arm A and the single-arm B is 0.25 wavelength of the dielectric.

[0032] Beneficial effects:

[0033] (1) The broadband microstrip quasi-Yagi antenna provided by the application omits the complex balun structure, has the characteristics of simple structure and easy realization, and meanwhile, the slot line is symmetrically arranged on the director unit, so that the return loss of the antenna can be more than 20 dB in the full frequency band, and the impedance bandwidth can reach 22%, which is much higher than the impedance bandwidth of the ordinary microstrip Yagi antenna. The gain of the antenna is more than 7.5 dBi, which realizes the broadband of the microstrip Yagi antenna while ensuring high gain.

[0034] (2) The slot line symmetrically arranged on the director unit can improve the impedance matching of the antenna, realize high-gain transmission, and expand the use scenarios of the microstrip quasi-Yagi antenna.

[0035] (3) The number of the director units of the application is four, and the length and adjacent spacing of each group are set according to the set size. There is a trade-off relationship between optimizing the working bandwidth and improving the antenna gain, and the influence of expanding the working bandwidth on the antenna gain is reduced.

[0036] (4) The parasitic patch and the through hole above it of the application play a role in expanding the bandwidth on the left and right sides of the working frequency point.

[0037] (5) The length e of the single-arm A and the single-arm B of the application is 0.25 wavelength, in which case, the vibration effect of the excitation vibrator is the best, and the signal can be radiated or received more effectively. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a schematic diagram of the three-dimensional structure of the broadband microstrip quasi-Yagi antenna of the application;

[0039] Figure 2 It is a schematic diagram of the front structure of the broadband microstrip quasi-Yagi antenna of the application;

[0040] Figure 3 It is a schematic diagram of the back structure of the broadband microstrip quasi-Yagi antenna of the application;

[0041] Figure 4 It is a schematic diagram of the back size relationship of the broadband microstrip quasi-Yagi antenna of the application;

[0042] Figure 5 It is a schematic diagram of the distance between the first director unit and the narrow edge of the excitation vibrator of the broadband microstrip quasi-Yagi antenna of the application, and the distance between the second to fourth director units;

[0043] Figure 6 It is a simulation result diagram of the dielectric substrate of the broadband microstrip quasi-Yagi antenna of the application;

[0044] Figure 7 It is a radiation pattern diagram of the broadband microstrip quasi-Yagi antenna of the application;

[0045] Among them, 1-dielectric substrate, 2-excitation oscillator, 3-director, 4-reflector, 5-microstrip line A, 6-slot line, 7-parasitic patch, 8-through hole, 21-one arm, 22-the other arm, 31-director unit. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] like Figures 1-5 As shown, this embodiment provides a broadband microstrip quasi-Yagi antenna, which includes a dielectric substrate 1, an excitation element 2, a director 3, a ground plane 4 (metal plate), and a microstrip line A5. An excitation element 2 is printed at one end of each of the front and back surfaces of the dielectric substrate 1. The excitation element 2 is the radiating element of the antenna. The excitation element 2 can take various forms, such as a rectangular form, or, for example, the butterfly form of this invention, i.e., a butterfly element. It should be noted that: Figure 2 , Figure 4 The horizontal segment connected to excitation element 2 is the impedance transformation segment; it does not belong to excitation element 2, but only... Figure 2 The middle front extends downwards and Figure 3 The part extending upwards from the back is the excitation element 2. The impedance transformation section and the excitation element 2 together form an L-shaped structure. The butterfly oscillator has a wide side (width represented by a) and a narrow side (width represented by b). The narrow side of the butterfly oscillator is perpendicularly connected to the impedance transformation section. In order to reduce reflection, the width of the impedance transformation section is the same as the width of the narrow side of the butterfly oscillator (because if the width of the impedance transformation section changes, there will be more reflection when it is connected to the butterfly oscillator).

[0048] The antenna has two excitation elements 2, which are the two arms of a butterfly oscillator, namely single arm A21 and single arm B22. The two arms are symmetrical along the central axis of the dielectric substrate 1. Each single arm is a metal strip, and the total length of the two single arms (e, the length of each single arm) satisfies half-wavelength resonance (half-wavelength resonance means that the excitation element 2 can reach the resonance state with maximum amplitude when the total length of the two single arms of the excitation element 2 is exactly half a wavelength). Therefore, the length e of single arm A21 and single arm B22 is 0.25 dielectric wavelengths. In this case, the vibration effect of the excitation element 2 is optimal, and it can more effectively radiate or receive signals. Single arm A21 is located on the front side of the dielectric substrate 1, and single arm B22 is located on the back side of the dielectric substrate 1. Single arm A21 is connected to the feed line through an impedance transformation section and microstrip line A5.

[0049] The function of the feeder line is to transmit the high frequency signal from the signal source to the microstrip line A5, and then to the positive excitation vibrator 2; when the high frequency signal passes through the excitation vibrator 2 (i.e. the positive excitation vibrator 2), the electrons will move rapidly on the excitation vibrator 2, generating an alternating electromagnetic field, and the electromagnetic field around the excitation vibrator 2 radiates outward to form radio waves.

[0050] The floor 4 is arranged on the back of the dielectric substrate 1 and connected with the single-arm B22 through an impedance transformation section (the floor 4 can be connected with the single-arm B22 through an impedance transformation section, or can be connected with the single-arm B22 through a microstrip line B and an impedance transformation section). The current characteristics on the floor 4 are used to realize the current phase inversion of the two arms of the vibrator, and the length of the floor to the excited microstrip line is adjusted to choke the unbalanced current.

[0051] Since the butterfly-shaped vibrators of the antenna are arranged on the front and back of the dielectric substrate 1, a double-layer microstrip antenna structure is formed; the double-layer microstrip antenna structure can provide a larger electromagnetic field distribution space, thereby reducing the sensitivity of the resonant frequency to the structure size, and further expanding the working bandwidth.

[0052] In order to reduce the influence of expanding the working bandwidth on the antenna gain (specific explanation: there is a trade-off relationship between expanding the working bandwidth and improving the antenna gain. Generally, expanding the working bandwidth will sacrifice part of the gain), a director 3 is arranged at the other end of the front and back of the dielectric substrate 1, the director 3 includes a plurality of strip-shaped director units 31 arranged in parallel at intervals, and the strip-shaped director units 31 on the front and back of the dielectric substrate 1 correspond one by one in position; the central axis of the director unit 31 coincides with the central axis of the dielectric substrate 1.

[0053] The impedance matching of the butterfly-shaped vibrators, the microstrip line A5 and the feeder line in the antenna is the key to realize effective energy transmission, and impedance mismatch will cause signal reflection and reduce the antenna efficiency. In order to further improve the impedance matching, as an example, a slot line 6 is arranged symmetrically along the central axis at both ends of the length direction of each of the director units 31 on the front and back of the dielectric substrate 1, and as an example, the slot depth of the slot line 6 is 1.15 mm.

[0054] As an example, as shown in Figure 5 As an example, as shown in

[0055] The lengths of the first to fourth director units decrease, and the lengths of the first to fourth director units are respectively 279 mm, 275 mm, 271 mm and 267 mm.

[0056] The length of the first director unit ranges from 279 mm to 285 mm.

[0057] The length of the second director unit ranges from 260 mm to 270 mm;

[0058] The length of the third director unit ranges from 251 mm to 255 mm;

[0059] The length of the fourth director unit ranges from 235 mm to 240 mm;

[0060] The distance f between the first director unit and the narrow side of the excitation vibrator 2 ranges from 65 mm to 67 mm;

[0061] The distance g between the second director unit and the first director unit ranges from 68 mm to 75 mm;

[0062] The distance h between the third director unit and the second director unit ranges from 38 mm to 45 mm;

[0063] The distance i between the fourth director unit and the third director unit ranges from 65.7 mm to 70 mm.

[0064] To expand the bandwidth of the antenna, as an example, a metal parasitic patch 7 is symmetrically arranged on both sides of the impedance transformation section on the front and back surfaces of the dielectric substrate 1, for expanding the bandwidth to the left of the operating frequency point; a through hole 8 is arranged at the end of each parasitic patch 7 away from the central axis of the dielectric substrate 1, and the through holes 8 on the parasitic patches 7 on the same side of the front and back surfaces are communicated through the through holes on the dielectric substrate 1 at the corresponding positions, for expanding the bandwidth to the right of the operating frequency point and optimizing various parameters of the antenna.

[0065] Moreover, the purpose of the through hole in the dielectric substrate 1 is not only for conduction, because one through hole 8 is equivalent to an inductor in the form of a metal column, and the introduction of electricity can further improve impedance matching. The dielectric substrate 1 itself is conductive, but its impedance is constant, and it needs to introduce external inductance and capacitance components to adjust, so that inductance components can be introduced through the through hole 8. The through hole 8 is located at a position away from the central axis of the dielectric substrate 1 and close to the edge of the parasitic patch 7, and too close to the central axis of the dielectric substrate 1 will affect the transmission effect. There is an optimal region along the length direction of the parasitic patch 7 when the through hole is punched, which can be obtained by optimization in general.

[0066] The distance d between the wide side of the single-arm B22 and the parasitic patch 7 on the corresponding side is 26.9 mm.

[0067] As Figure 6It can be seen that the return loss of the antenna can achieve full-band 20dB or more, and the impedance bandwidth can reach 22%, which is much higher than the impedance bandwidth of ordinary microstrip Yagi antennas. The gain of the antenna is more than 7.5dBi, which realizes the broadbandization of the microstrip Yagi antenna while ensuring high gain.

[0068] As an example, the wide edge width a of the single-arm A21 and the single-arm B22 is 28.6mm, and the narrow edge width b is 17.2mm.

[0069] As an example, the medium substrate 1 is FR4 material, and the medium dielectric constant is 4.4.

[0070] Working principle:

[0071] The communication device or signal source transmits the generated high-frequency signal from the feed line to the microstrip line A5, and the microstrip line A5 transmits the signal to the exciter vibrator 2 on the front surface of the medium substrate 1 through the impedance transformation section. The microstrip line A5 is usually connected to the exciter vibrator 2 and transmits signals to the exciter vibrator 2, when the signal passes through the exciter vibrator 2, the electrons on the exciter vibrator 2 move quickly, generating alternating current, and in turn generating alternating electromagnetic field. The ground on the back surface of the medium substrate 1 acts as a reflector, mainly serving as a reflector for electromagnetic waves, which can enhance the radiation directivity of the antenna and concentrate more energy in a specific direction.

[0072] In order to ensure that the signal can be effectively transmitted to the butterfly-shaped vibrator and converted into electromagnetic wave, impedance matching needs to be performed on the entire system. The antenna not only adopts the butterfly-shaped vibrator of the double-layer microstrip antenna, but also slots the director 3 and holes 8 on the parasitic patch 7, so as to improve the impedance matching performance of the antenna and the high gain transmission of the signal.

[0073] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A broadband microstrip quasi-Yagi antenna, characterized in that, include: Dielectric substrate (1), excitation oscillator (2) and director (3); An excitation oscillator (2) is printed at one end of the front and back sides of the dielectric substrate (1) to form a butterfly oscillator; the two excitation oscillators (2) are the two arms of the butterfly oscillator, namely the single arm A (21) located on the front side of the dielectric substrate (1) and the single arm B (22) located on the back side of the dielectric substrate (1). The single arm A (21) is connected to the feeder in sequence through the impedance transformation section and the microstrip line A (5); A ground plane (4) is provided on the back of the dielectric substrate (1), and the single arm B (22) is connected to the ground plane (4) through an impedance transformation section; A director (3) is provided at the other end of both the front and back sides of the dielectric substrate (1). The director (3) includes several parallel director units (31) arranged in a strip shape. The director units (31) on the front and back sides of the dielectric substrate (1) correspond one-to-one in position. The central axis of the director unit (31) coincides with the central axis of the dielectric substrate (1). Slots (6) are symmetrically arranged at both ends of the length direction of each director unit (31) along its central axis.

2. The broadband microstrip quasi-Yagi antenna according to claim 1, characterized in that, The number of director units (31) is four groups, with the first director unit being the one closest to the excitation oscillator (2), and then the second, third, and fourth director units being the ones closest to the excitation oscillator (2). The lengths of the first director unit to the fourth director unit decrease.

3. The broadband microstrip quasi-Yagi antenna according to claim 2, characterized in that, The length of the first director unit ranges from 279 mm to 285 mm; The length of the second director unit ranges from 260 mm to 270 mm; The length of the third director unit ranges from 251 mm to 255 mm; The length of the fourth director unit ranges from 235 mm to 240 mm.

4. The broadband microstrip quasi-Yagi antenna according to claim 2, characterized in that, The distance between the first director unit and the narrow side of the excitation oscillator (2) is 65 mm to 67 mm; The distance between the second director unit and the first director unit is 68 mm to 75 mm; The distance between the third director unit and the second director unit is 38 mm to 45 mm; The distance between the fourth director unit and the third director unit is 65.7 mm to 70 mm.

5. The broadband microstrip quasi-Yagi antenna according to any one of claims 1-4, characterized in that, The groove depth of the groove (6) is 1.15 mm.

6. The broadband microstrip quasi-Yagi antenna according to any one of claims 1-4, characterized in that, Parasitic patches (7) made of metal are symmetrically disposed on both sides of the impedance transformation section on the front and back sides of the dielectric substrate (1). Each of the parasitic patches (7) is provided with a through hole (8); The through-hole (8) on the parasitic patch (7) located on the same side is connected through the through-hole on the dielectric substrate (1) at the corresponding position.

7. The broadband microstrip quasi-Yagi antenna according to claim 6, characterized in that, The distance from the parasitic patch (7) to the wide side of the single arm B (22) is 26.9 mm.

8. A broadband microstrip quasi-Yagi antenna according to any one of claims 1-4, characterized in that, The wide side length of the single arm A (21) and the narrow side length of the single arm B (22) are 28.6 mm and 17.2 mm respectively.

9. A broadband microstrip quasi-Yagi antenna according to any one of claims 1-4, characterized in that, The length e of the single arm A (21) and the single arm B (22) is 0.25 times the dielectric wavelength.

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