Broadband microstrip quasi-yagi antenna

Abstract

The invention provides the broadband micro-strip quasi-yagi antenna, the broadband micro-strip quasi-yagi antenna is simple in structure, the impedance matching of the antenna can be improved, meanwhile, high-gain transmission can be realized, and the use scene of the micro-strip yagi antenna is expanded. The broadband micro-strip quasi-yagi antenna comprises a dielectric substrate, an excitation oscillator and a director, one excitation oscillator is printed at one end of each of the front surface and the back surface of the dielectric substrate to form a butterfly-shaped oscillator; the two excitation oscillators are two arms of a butterfly-shaped oscillator, namely a single arm A positioned on the front surface of the dielectric substrate and a single arm B positioned on the back surface of the dielectric substrate; the single arm A is connected with the feeder line through the impedance conversion section and the microstrip line A in sequence; directors are arranged at the other ends of the front surface and the back surface of the dielectric substrate; each director comprises a plurality of strip-shaped director units which are arranged in parallel; the central axis of the director unit coincides with the central axis of the dielectric substrate. Groove lines are symmetrically arranged at the two ends of each director unit in the length direction along the central axis of the director unit.

Description

Technical Field

[0001] The invention belongs to the technical field of microstrip antennas, and in particular relates to a broadband microstrip quasi-Yagi antenna. Background Art

[0002] With the continuous development of wireless communication technology, people have higher and higher requirements for the bandwidth, gain and size of antennas. 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 communications. Traditional Yagi antennas are usually too large. At the same time, due to the limitations of antenna volume and vibrator material, Yagi antennas cannot conform to the surface of the carrier, and the working bandwidth of traditional Yagi antennas is also narrow, with the relative bandwidth generally within 5%. These greatly limit the use of Yagi antennas in mobile communications and many environments with limited space. Therefore, it is necessary to retain the many advantages of traditional Yagi antennas while making appropriate improvements to their shortcomings.

[0003] Compared with Yagi antenna, microstrip antenna is 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. Combining microstrip antenna and Yagi antenna, giving full play to their respective advantages, microstrip Yagi antenna can obtain broad application prospects.

[0004] Common microstrip Yagi antennas are generally composed of a dielectric substrate, a ground plane, a reflector, an excitation oscillator, and a director. Because the microstrip antenna is covered with a metal plate on the back, directly using a microstrip antenna in combination with a Yagi antenna can only achieve quasi-end-fire radiation, that is, the maximum radiation direction of the antenna is in the space obliquely above the dielectric plate (that is, the floor of a normal microstrip antenna is composed of the entire lower surface of the dielectric substrate covered with metal, but the floor 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 we need to avoid). To solve this problem, a microstrip quasi-Yagi antenna structure is usually used, that is, instead of using a traditional reflector oscillator, the floor truncated at the back of the microstrip antenna is used as a reflector to achieve end-fire radiation of the antenna. Common microstrip quasi-Yagi antennas use microstrip line feeding, broadband impedance matching through a broadband balun structure, and a 180-degree phase difference between the two arms of the active array, which can provide better signal reception and transmission performance in some cases.

[0005] However, the disadvantage of this type of microstrip quasi-Yagi antenna structure is that the antenna printed on the dielectric substrate is large in size and the balun structure is relatively complex. Another common microstrip quasi-Yagi antenna has two arms of the excitation oscillator printed on the two sides of the dielectric substrate, one arm on the front side is connected to the feeder through a microstrip line, and the other arm on the back side is connected to the truncated floor through a microstrip line. The balanced feeding of the excitation oscillator is achieved through the distribution of current on the floor. Although this solution eliminates the complex balun structure, the disadvantage is that the frequency band is narrow, which affects the receiving efficiency of the antenna in a specific frequency range and the impedance matching performance of the antenna. Summary of the invention

[0006] In view of this, the present invention provides a broadband microstrip quasi-Yagi antenna, which has a simple structure and can improve the impedance matching of the antenna, while achieving high-gain transmission and expanding the use scenarios of the microstrip Yagi antenna.

[0007] The broadband microstrip quasi-Yagi antenna comprises: a dielectric substrate, an excitation vibrator and a director;

[0008] An excitation vibrator is printed at one end of the front and back of the dielectric substrate to form a butterfly vibrator; the two excitation vibrators are two arms of the butterfly vibrator, namely, a single arm A located on the front of the dielectric substrate and a single arm B located on the back of the dielectric substrate;

[0009] The single arm A is connected to the feeder via the impedance transformation section and the microstrip line A in sequence;

[0010] The back of the dielectric substrate is set on the floor, and the single arm B is connected to the floor through an impedance transformation section;

[0011] Directors are provided at the other ends of the front and back sides of the dielectric substrate, the directors comprising a plurality of strip-shaped director units arranged in parallel, the director units on the front and back sides 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] Grooves are symmetrically arranged along the central axis of each director unit at both ends in the length direction.

[0013] As a preferred embodiment of the present invention, the number of the director units is four groups, the first director unit is the closest to the excitation vibrator, and the second director unit, the third director unit and the fourth director unit are arranged in order from near to far;

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

[0015] As a preferred embodiment of the present invention,

[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 embodiment of the present invention,

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

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

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

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

[0025] As a preferred embodiment of the present invention, the groove depth of the groove line is 1.15 mm, and the distance from the groove line to the central axis of the dielectric substrate is 244 mm.

[0026] As a preferred embodiment of the present invention, parasitic patches 7 made of metal material are symmetrically arranged on both sides of the front and back impedance transformation sections 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 embodiment of the present invention, the distance from the parasitic patch to the wide side of the single arm B is 26.9 mm.

[0030] As a preferred embodiment of the present invention, 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 embodiment of the present invention, the length e of the single arm A and the single arm B is 0.25 medium wavelength.

[0032] Beneficial effects:

[0033] (1) The broadband microstrip quasi-Yagi antenna provided by the present invention eliminates the complex balun structure and has the characteristics of simple structure and easy implementation. At the same time, a butterfly-shaped vibrator is provided and slots are symmetrically provided in the director unit, so that the return loss of the antenna can achieve a full-band above 20dB, 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 above 7.5dBi, and the broadband of the microstrip Yagi antenna is achieved while ensuring high gain.

[0034] (2) The groove lines are symmetrically arranged on the director unit of the present invention, which can improve the impedance matching of the antenna, realize high-gain transmission, and expand the application scenarios of the microstrip quasi-Yagi antenna.

[0035] (3) The number of director units of the present invention is four groups, and the length of each group and the adjacent spacing are set according to set dimensions. There is a trade-off between optimizing the working bandwidth and improving the antenna gain, which reduces the impact of expanding the working bandwidth on the antenna gain.

[0036] (4) The parasitic patch of the present invention and the through hole design thereon play a role in expanding the bandwidth on the left and right sides of the operating frequency.

[0037] (5) The length e of the single arm A and the single arm B of the present invention is 0.25 medium wavelength. In this case, the vibration effect of the exciting oscillator is the best, and the signal can be radiated or received more effectively. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0041] Figure 4 A schematic diagram of the back-side dimensions of the broadband microstrip quasi-Yagi antenna of the present invention;

[0042] Figure 5 A schematic diagram of the spacing between the first director unit and the narrow side of the excitation dipole of the broadband microstrip quasi-Yagi antenna of the present invention, and the spacing between the second to fourth director units;

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

[0044] Figure 7 The radiation pattern of the broadband microstrip quasi-Yagi antenna of the present invention;

[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 DESCRIPTION

[0046] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] like Figure 1-5 As shown, this embodiment provides a broadband microstrip quasi-Yagi antenna, which includes a dielectric substrate 1, an excitation oscillator 2, a director 3, a floor 4 (metal plate) and a microstrip line A5; an excitation oscillator 2 is printed on one end of the front and back of the dielectric substrate 1, and the excitation oscillator 2 is the radiation element of the antenna. The excitation oscillator 2 has many forms, such as a rectangular form, and also a butterfly form of the present invention, that is, a butterfly oscillator. It should be noted that: Figure 2 , Figure 4 The horizontal section connected to the excitation array 2 is the impedance transformation section, which does not belong to the excitation array 2. Figure 2 The middle front extends downward and Figure 3 The part extending upward from the middle back surface is the excitation array 2. The impedance transformation section and the excitation array 2 together form an L-shaped structure. The butterfly vibrator has a wide side (width represented by a) and a narrow side (width represented by b). The narrow side of the butterfly vibrator is vertically 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 vibrator (because if the width of the impedance transformation section changes, there will be more reflection when it is connected to the butterfly vibrator).

[0048] The two excitation vibrators 2 in the antenna are two arms of a butterfly vibrator, 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 is the length of each single arm) satisfies half-wavelength resonance (half-wavelength resonance means that when the total length of the two single arms of the excitation vibrator 2 is exactly half a wavelength, the excitation vibrator 2 can reach the resonance state of maximum amplitude); thus, the length e of the single arm A21 and the single arm B22 is 0.25 dielectric wavelength. In this case, the vibration effect of the excitation vibrator 2 is the best, and the signal can be radiated or received more effectively. The single arm A21 is located on the front of the dielectric substrate 1, and the single arm B22 is located on the back of the dielectric substrate 1; the single arm A21 is connected to the feeder through the impedance transformation section and the microstrip line A5.

[0049] The function of the feed 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 (that is, the positive excitation vibrator 2), the electrons will move rapidly on the excitation vibrator 2 to generate 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 is connected to the single arm B22 through an impedance transformation section (the floor 4 can be connected to the single arm B22 through an impedance transformation section, or can be connected to the single arm B22 through a microstrip line B and an impedance transformation section). The current characteristics on the floor 4 are used to achieve the current inversion of the two arms of the oscillator, and the length of the microstrip line from the floor to the excitation is adjusted to choke the unbalanced current.

[0051] Since the butterfly-shaped oscillator of the antenna is distributed on the front and back sides 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, thereby 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 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 provided at the other end of the front and back sides of the dielectric substrate 1, and the director 3 includes a plurality of strip director units 31 arranged in parallel at intervals in sequence, and the strip director units 31 on the front and back sides of the dielectric substrate 1 correspond to each other 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 oscillator, microstrip line A5 and feeder in the antenna is the key to achieving effective energy transmission. Impedance mismatch will lead to signal reflection and reduce antenna efficiency. To further improve impedance matching, as an example, slot lines 6 are symmetrically arranged along the central axis of each director unit 31 on the front and back sides of the dielectric substrate 1 at both ends of the length direction. As an example, the slot depth of the slot line 6 is 1.15 mm; the distance c from the slot line 6 to the central axis of the dielectric substrate 1 is 244 mm.

[0054] As an example, Figure 5 As shown, the number of the director units 31 on the front and back sides of the dielectric substrate 1 is four groups, the first director unit is closest to the excitation vibrator 2, and then the second director unit, the third director unit and the fourth director unit are arranged from near to far.

[0055] The lengths of the first director unit to the fourth director unit decrease gradually, wherein:

[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 is 65 mm to 67 mm;

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

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

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

[0064] In order to expand the bandwidth of the antenna, as an example, parasitic patches 7 made of metal material are symmetrically arranged on both sides of the impedance transformation sections on the front and back sides of the dielectric substrate 1, which are used to expand the bandwidth to the left side of the working frequency point; a through hole 8 is provided at one 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 front and back sides on the same side are connected through the through holes on the dielectric substrate 1 at corresponding positions, which are used to expand the bandwidth to the right side of the working frequency point and optimize various parameters of the antenna.

[0065] Moreover, the purpose of drilling a through hole in the dielectric substrate 1 is not only for conduction, because a through hole 8 is equivalent to an inductor, which is in the form of a metal column. The introduction of an inductor can further improve impedance matching. The dielectric substrate 1 itself is conductive, but its impedance is a constant. If you want to adjust it, you need to introduce external inductance and capacitance components, so the inductance component can be introduced through the through hole 8. The through hole 8 is located away from the central axis of the dielectric substrate 1 and close to the edge of the parasitic patch 7. If it is too close to the central axis of the dielectric substrate 1, it will affect the transmission effect. When drilling a through hole, there is an optimal area along the length of the parasitic patch 7, which can generally be obtained through optimization.

[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] like Figure 6It can be seen that the return loss of the antenna can achieve more than 20dB in the full frequency band, and the impedance bandwidth can reach 22%, which is much higher than the impedance bandwidth of ordinary microstrip Yagi antenna. The gain of the antenna is above 7.5dBi, which achieves the broadband of microstrip Yagi antenna while ensuring high gain.

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

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

[0070] Working principle:

[0071] The communication device or signal source transmits the generated high-frequency signal from the feeder to the microstrip line A5. The microstrip line A5 transmits the signal to the excitation vibrator 2 on the front of the dielectric substrate 1 through the impedance transformation section. The excitation vibrator 2 effectively converts the electrical signal into an electromagnetic wave. The microstrip line A5 is usually connected to the excitation vibrator 2 and transmits the signal to the excitation vibrator 2. When the signal passes through the excitation vibrator 2, the electrons on the excitation vibrator 2 move rapidly, generating an alternating current, and then generating an alternating electromagnetic field. The ground on the back of the dielectric substrate 1 acts as a reflector, mainly reflecting 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 vibrator and converted into electromagnetic waves, the entire system needs to be impedance matched. The antenna not only uses the butterfly vibrator of the double-layer microstrip antenna, but also slots the director 3 and opens a through hole 8 on the parasitic patch 7 to achieve the purpose of improving the impedance matching performance of the antenna and high-gain signal transmission.

[0073] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A broadband microstrip quasi-Yagi antenna, characterized in that: include: A dielectric substrate (1), an excitation vibrator (2) and a director (3); An excitation vibrator (2) is printed on one end of the front and back sides of the dielectric substrate (1) to form a butterfly vibrator; the two excitation vibrators (2) are respectively two arms of the butterfly vibrator, namely a single arm A (21) located on the front side of the dielectric substrate (1) and a single arm B (22) located on the back side of the dielectric substrate (1); The single arm A (21) is connected to the feeder via an impedance transformation section and a microstrip line A (5) in sequence; The back of the dielectric substrate (1) is arranged on the floor (4), and the single arm B (22) is connected to the floor (4) via an impedance transformation section; A director (3) is provided at the other end of the front and back sides of the dielectric substrate (1), the director (3) comprising a plurality of parallel-arranged strip-shaped director units (31), the director units (31) on the front and back sides of the dielectric substrate (1) corresponding to each other in position; the central axis of the director unit (31) coincides with the central axis of the dielectric substrate (1); Grooves (6) are symmetrically arranged along the central axis of each director unit (31) at both ends in the length direction.

2. The broadband microstrip quasi-Yagi antenna according to claim 1, characterized in that: The number of the director units (31) is four groups, with the first director unit being the closest to the excitation vibrator (2), followed by the second director unit, the third director unit and the fourth director unit in order from near to far; The lengths of the first director unit to the fourth director unit decrease gradually.

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 vibrator (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 to 4, characterized in that: The groove line (6) has a groove depth of 1.15 mm, and the distance from the groove line (6) to the central axis of the dielectric substrate (1) is 244 mm.

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

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 to 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) is 28.6 mm, and the narrow side length is 17.2 mm.

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

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