Directional antenna suitable for UWB radar product

Abstract

The invention discloses a directional antenna suitable for a UWB radar product, and relates to the technical field of wireless microwave antennae, the directional antenna comprises a substrate, and the substrate is provided with a reflector, an excitation unit, a guiding unit, a driving unit and a signal feed-in point; the driving unit and the signal feed-in point are arranged on one surface of the substrate; the reflector, the excitation unit and the guide unit are arranged on the other surface of the substrate; the driving unit is connected to a signal pin of the signal feed-in point, the reflector and the excitation unit are both connected to a ground pin of the signal feed-in point, and the guiding unit is not connected with the outside. In a controllable size range, the contradiction between the bandwidth and the size of the PCB antenna, the difficulty in gain and efficiency improvement and the problem of multi-antenna mutual coupling are overcome; while the directional performance and the gain are reserved, the size and the cost are greatly reduced, the impression that the UWB antenna is high in price and large in size is changed, and producibility is really achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless microwave antennas, and in particular to a directional antenna. Background Art

[0002] With the rapid development of modern communication technology, the demand for high-speed, low-power, high-precision positioning, and high-resolution imaging capabilities is growing. Ultra-Wideband (UWB), an emerging wireless communication technology, has become a focus of current research and application due to its unique technical advantages and broad application prospects in multiple fields.

[0003] In UWB systems, antennas are key components for transmitting and receiving electromagnetic waves. Their performance directly determines core system metrics such as communication quality, positioning accuracy, and range. Given the ultra-wide bandwidth of UWB signals, UWB antennas must possess excellent broadband characteristics, enabling efficient and stable signal radiation and reception across the entire UWB frequency band. Furthermore, to meet the diverse needs of different application scenarios, UWB antennas must precisely meet specific performance requirements, including radiation patterns, gain, and polarization characteristics.

[0004] Compared to traditional narrowband antennas, UWB antenna design faces numerous challenges. For example, achieving good impedance matching across an ultra-wide frequency band to ensure efficient signal transmission; controlling the antenna's radiation pattern to maintain relative stability at different frequencies to avoid beam distortion and pattern splitting; and improving antenna gain to meet the demands of long-distance communication and high-precision positioning. Furthermore, miniaturizing, lightweighting, and reducing costs to accommodate diverse and complex application scenarios are also key challenges. Properly addressing these challenges will be of immeasurable importance to the widespread adoption and application of UWB technology.

[0005] In many practical application scenarios, UWB antennas are not only required to have broadband characteristics, but also to have directional radiation capabilities. UWB directional antennas can precisely focus radiated energy in a specific direction, thereby significantly improving the signal transmission distance and anti-interference ability in that direction. However, while achieving these functions, the UWB directional antennas currently on the market often face the prominent problems of large size and high cost. The large size limits the use of UWB antennas in some application scenarios with extremely stringent space requirements, such as micro devices and wearable devices; while the high cost makes it difficult to be widely used in some cost-sensitive application fields. These problems have, to a certain extent, restricted the further promotion and application of directional antennas. Therefore, the design of miniaturized, low-cost directional antennas has broad application prospects.

[0006] The utility model patent with application number 202123213324.8 discloses a miniaturized UWB antenna, including a feeding unit, a grounding unit, a radiating unit and an adjustment slot unit. The radiating unit includes a first radiating branch, a second radiating branch, a ground branch, a connecting branch and a third radiating branch. The adjustment slot unit includes a first adjustment slot, a second adjustment slot, a third adjustment slot and a fourth adjustment slot. The connecting branch and the third radiating branch are used to generate signals in the 3GHz~5GHz frequency band. The first radiating branch is used to generate signals in the 5GHz~7GHz frequency band. The first adjustment slot widens the bandwidth of the 3GHz~5GHz band to generate 7GHz~10GHz. The second adjustment slot and the fourth adjustment slot adjust the wavelength of the 3GHz~5GHz band to reduce the wiring length and achieve the purpose of miniaturization. The third adjustment slot adjusts the 5GHz~7GHz band and shortens the length of the first radiating branch to achieve the purpose of miniaturization. The miniaturized UWB antenna provided by the above utility model is small in size and covers all frequency bands required for UWB (3.1GHz~10.6GHz). However, the above patent has the problem that the SWR in the low frequency band (3.1GHz~7GHz) and high frequency band (9.4GHz~10.6GHz) (SWR means standing wave ratio, which is used to express the matching degree between signal transmission and load impedance. The lower the better. The ideal SWR is 1. When SWR is 1, the impedance matching between the signal transmission port and the load is completely matched) is greater than 2, and the omnidirectional antenna has no directional characteristics and cannot be applied to radar products. Summary of the Invention

[0007] In response to the technical problems of large size and high cost of existing directional antennas used in UWB radar products, the present invention proposes a directional antenna for UWB radar products, which makes the UWB antenna a standard device packaging module applied to the integrated circuit of the radar product, improves the integration of the radio frequency circuit, and reduces the structural complexity and hardware cost of the product.

[0008] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] A directional antenna suitable for UWB radar products includes a substrate, on which a reflector, an excitation unit, a steering unit, a driving unit and a signal feeding point are arranged; the driving unit and the signal feeding point are arranged on one side of the substrate; the reflector, the excitation unit and the steering unit are all arranged on the other side of the substrate; the driving unit is connected to the signal pin of the signal feeding point, the reflector and the excitation unit are both connected to the ground pin of the signal feeding point, and the steering unit is not connected to the outside.

[0010] Preferably, the reflector is arranged behind the excitation unit; the excitation unit includes a first active vibrator and a second active vibrator, and the first active vibrator and the second active vibrator are both L-shaped structures;

[0011] The first active vibrator and the second active vibrator are both half-wave vibrators.

[0012] Preferably, the reflector has a groove-shaped structure, consisting of a bottom reflective block and side wall reflective blocks perpendicular to both sides of the bottom reflective block, and the side wall reflective blocks are rectangular; a rectangular notch recessed inward is provided in the middle of the bottom reflective block, and the rectangular notch extends along the length direction of the bottom reflective block.

[0013] Preferably, the guiding unit includes N directors, where N≥2.

[0014] Preferably, when N=2, the guiding unit includes a first director and a second director, the first director and the second director are both rectangular, the long sides of the first director and the second director are parallel to the transverse central axis of the substrate, and the second director is arranged parallel to the first director in an upper and lower direction;

[0015] The long side of the first director is greater than the long side of the second director.

[0016] Preferably, the spacing between the first director and the second director is 0.1-0.3λ; the spacing between the first director and the first active oscillator and the second active oscillator is 0.1-0.3λ, where λ is the signal operating wavelength.

[0017] Preferably, the driving unit includes a microstrip line and an impedance converter, the microstrip line is connected to a signal pin of a signal feeding point, and the impedance converter is connected to the signal pin of the signal feeding point through the microstrip line.

[0018] Preferably, the impedance converter adopts a stepped gradient structure, the width of the stepped gradient structure increases stepwise from one end to the other end, and the narrowest end of the stepped gradient structure is connected to the signal pin of the signal feeding point through a microstrip line.

[0019] Preferably, the calculation formula for the width of the microstrip line is:

[0020]

[0021] Where w is the width of the microstrip line, A is the intermediate calculation parameter, Z0 is the characteristic impedance, ∑r is the relative dielectric constant, and h is the substrate thickness;

[0022] The calculation formula of the length of the microstrip line is:

[0023]

[0024] Where L is the length of the microstrip line, λ is the signal operating wavelength, and ∑eff is the effective dielectric constant.

[0025] Preferably, the driving unit receives a high-frequency current signal from the transmitter through a signal feeding point, and couples the high-frequency current signal to the excitation unit, matches the impedance of the input port and the output port through an impedance converter, reduces the reflection loss between the ports, and reduces the transmission loss during the transmission process through the microstrip line. The excitation unit converts the high-frequency current signal into electromagnetic wave radiation in space through the first active vibrator and the second active vibrator to generate a radiation field; when the excitation unit radiates electromagnetic waves outward, the energy originally radiated backward is reflected to the front through the reflector, and the director in the director unit generates an induced current through electromagnetic induction, and the director becomes a secondary radiation source, radiating electromagnetic waves outward, thereby causing the electromagnetic waves to be concentratedly radiated in the direction pointed by the director.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Based on the antenna principle of directional antenna, this invention designs a directional antenna in the form of PCB antenna. Compared with traditional directional antenna, it greatly reduces the size and cost while retaining the directional performance and gain.

[0028] The present invention overcomes the contradiction between PCB antenna bandwidth and size, the difficulty in improving gain and efficiency, and the problem of multi-antenna mutual coupling; it changes the impression that UWB antennas are expensive and large in size, and truly achieves commercialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is the basic model of the present invention.

[0031] Figure 2 1 is a Polar gain simulation result of a basic model in one embodiment of the present invention.

[0032] Figure 3 FIG. 4 is a return loss simulation diagram in one embodiment of the present invention.

[0033] In the figure, 1-reflector, 2-excitation unit, 21-first active oscillator, 22-second active oscillator, 3-direction unit, 31-first director, 32-second director, 4-driving unit, 41-impedance converter, 42-microstrip line, 5-signal feeding point. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, a directional antenna suitable for UWB radar products includes a substrate, on which a reflector 1, an excitation unit 2, a steering unit 3, a driving unit 4 and a signal feeding point 5 are arranged; the driving unit 4 and the signal feeding point 5 are arranged on one side of the substrate; the reflector 1, the excitation unit 2 and the steering unit 3 are all arranged on the other side of the substrate; the driving unit 4 is connected to the signal pin of the signal feeding point 5, the reflector 1 and the excitation unit 2 are both connected to the ground pin of the signal feeding point 5, and the steering unit 3 has no external connection.

[0036] The present invention transmits a radio frequency signal to the excitation unit 2 through the driving unit 4. The excitation unit 2 is excited by the radio frequency signal to radiate electromagnetic waves outward. The electromagnetic waves are reflected by the reflector 1 and guided by the guiding unit 3, and finally radiate electromagnetic waves outward in a specific direction in space.

[0037] In order to reduce costs and have the advantages of size, integration and stable performance, in this embodiment, FR-4 board is selected as the substrate to facilitate the subsequent integration of the present invention into the PCB of the product hardware. The relative dielectric constant of FR-4 board is 4.4 and the loss factor is 0.02.

[0038] The excitation unit 2 is used to radiate electromagnetic waves: the excitation unit 2 converts high-frequency current into electromagnetic waves in space and radiates them to the surrounding area. The excitation unit 2 includes a first active vibrator 21 and a second active vibrator 22. The first active vibrator 21 and the second active vibrator 22 both have an L-shaped structure. Compared with a straight line, the L-shape can increase the effective length and reduce the volume.

[0039] The first active vibrator 21 and the second active vibrator 22 are both half-wave vibrators, and the length L of the long part of the first active vibrator 21 and the second active vibrator 22 is a It is about half of the working wavelength λ. Considering the wavelength shortening effect, in this embodiment, the length L of the long part of the first active oscillator 21 and the second active oscillator 22 isa Take 0.47λ, that is, L a =0.47λ.

[0040] The reflector 1 is used to increase the antenna's gain and concentrate the radiated energy in a specific direction. In this case, the reflector 1 is placed behind the excitation unit 2. By utilizing the metal conductor's reflective properties for electromagnetic waves, the reflector reflects energy originally radiated backwards to the front, thereby enhancing the directional antenna's radiation intensity in the front direction and forming a more concentrated beam.

[0041] The reflector 1 has a trough-shaped structure, consisting of a bottom reflector block and side wall reflectors perpendicular to the bottom reflector block. The side wall reflectors are rectangular. In this embodiment, the side wall reflectors are 3 mm long and 1 mm wide. A rectangular inward-concave notch is provided in the middle of the bottom reflector block. The rectangular notch extends along the length of the bottom reflector block. The depth of the rectangular notch is 5.7 mm and the width is 2.6 mm. The trough-shaped structure can effectively increase the reflection length of the ground and reduce the volume required for the ground plane.

[0042] Theoretically, the length of the active oscillator remains unchanged. The longer the reflector 1 is, the better the antenna's directivity and the stronger the gain will be. However, from an engineering design perspective, the length of the reflector 1 needs to be set within a reasonable range. Generally, the length of the reflector 1 is slightly longer than the active oscillator. Therefore, the length of the reflector 1, L r =0.5λ. The length of the reflector 1 refers to the length of the bottom reflector block.

[0043] The steering unit 3 is used to enhance directivity: it can further concentrate the antenna's radiation pattern, focusing electromagnetic waves in a specific direction and enhancing the antenna's signal strength in that specific direction. The steering unit 3 includes N directors. Due to PCB volume limitations, the number N of directors is set to 2 in this embodiment.

[0044] The guiding unit 3 includes a first guide 31 and a second guide 32. The first guide 31 and the second guide 32 are both rectangular. The long sides of the first guide 31 and the second guide 32 are parallel to the transverse central axis of the substrate. The long side of the first guide 31 is larger than that of the second guide 32. The second guide 32 is arranged parallel to the first guide 31. The parallel arrangement allows the guiding angle to be concentrated in one direction.

[0045] In this embodiment, the long side L of the first director 31 d1 is 0.45λ, the long side L of the second director 32 d2 The radiation angle of the signal can be effectively reduced by gradually reducing the length of the director.

[0046] The distance between the director unit and the excitation unit is set based on the signal's operating wavelength. If the director is too far away, it will not radiate the signal, while if it is too close, it will shield the signal. Therefore, the spacing between the first director 31 and the second director 32 is 0.1-0.3λ; the spacing Dd between the first director 31 and the active oscillator is also 0.1-0.3λ. In this embodiment, the spacing between the first director 31 and the second director 32 and the spacing between the first director 31 and the active oscillator are both 0.2λ.

[0047] The functions of the first director 31 and the second director 32 are the same. When the excitation unit 2 radiates electromagnetic waves outward, the director is in the electromagnetic field of the excitation unit 2, and will generate induced current through electromagnetic induction, thereby becoming a secondary radiation source, radiating electromagnetic waves outward, and thus allowing the electromagnetic waves to be concentratedly radiated in the direction pointed by the director.

[0048] The driving unit 4 is used to generate a radiation field: the driving unit 4 receives a high-frequency current signal from the transmitter through the signal feed point 5, and then couples the high-frequency current signal to the excitation unit 2. The excitation unit 2 converts the high-frequency current signal into electromagnetic wave radiation in space, generating a radiation field. The driving unit 4 includes a microstrip line 42 and an impedance transformer 41. The microstrip line 42 is connected to the signal pin of the signal feed point 5, and the impedance transformer 41 is connected to the signal pin of the signal feed point 5 through the microstrip line 42. In this embodiment, the method for calculating the size of the microstrip line 42 on the FR-4 substrate is as follows:

[0049] Free space wavelength Where c is the speed of light (3×10 8 m / s), f is the center frequency.

[0050] In this embodiment, the center frequency f is 8 GHz, and the free space wavelength λ0 = 37.5 mm.

[0051] The calculation formula of the width of the microstrip line 42 is as follows:

[0052]

[0053] w is the width of the microstrip line 42 , A is an intermediate calculation parameter, Z0 is the characteristic impedance, ∑r is the relative dielectric constant, and h is the substrate thickness.

[0054] The effective dielectric constant calculation process of microstrip line 42 under FR-4 substrate is as follows:

[0055]

[0056] ∑eff is the effective dielectric constant.

[0057] Then the length of the microstrip line 42 is:

[0058]

[0059] Wherein, L is the length of the microstrip line 42, and λ is the signal operating wavelength.

[0060] In summary, when the center frequency is 8 GHz, the length L of the microstrip line 42 on the FR-4 substrate is 5.11 mm, and the width w is 1.92 mm.

[0061] The impedance converter 41 employs a stepped gradient structure, achieving impedance transformation through multiple steps to reduce unnecessary reflection loss. Specifically, the width of the stepped gradient structure increases in steps from one end to the other. The smallest end of the impedance converter 41, i.e., the narrowest end of the stepped gradient structure, is connected to the signal pin of the signal feed point 5 via a microstrip line 42.

[0062] In summary, in this embodiment, the finished product size of the entire directional antenna is 26.6mm*30mm, and a common FR-4 dielectric substrate with a thickness of 1mm is used. Figure 2 and Figure 3 As shown, the present invention has good antenna gain and directivity, with a maximum gain of 7.24dBi; S11 <-10dB bandwidth covers 4.4GHz-9.8GHz, and the relative bandwidth is 78.8%, perfectly covering the 6.5GHz and 8GHz required by the existing UWB commercial frequencies CH5 and CH9.

[0063] In summary, the present invention overcomes the contradiction between PCB antenna bandwidth and size, the difficulty in improving gain and efficiency, and the problem of multi-antenna coupling within a controllable size range; it changes the impression that UWB antennas are expensive and large in size, and truly achieves commercialization.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A directional antenna suitable for UWB radar products, comprising a substrate, characterized in that: A reflector (1), an excitation unit (2), a guiding unit (3), a driving unit (4) and a signal feeding point (5) are provided on the substrate; the driving unit (4) and the signal feeding point (5) are provided on one side of the substrate; the reflector (1), the excitation unit (2) and the guiding unit (3) are all provided on the other side of the substrate; the driving unit (4) is connected to the signal pin of the signal feeding point (5), the reflector (1) and the excitation unit (2) are both connected to the ground pin of the signal feeding point (5), and the guiding unit (3) has no external connection.

2. The directional antenna suitable for UWB radar products according to claim 1, characterized in that: The reflector (1) is arranged behind the excitation unit (2); the excitation unit (2) comprises a first active vibrator (21) and a second active vibrator (22), and both the first active vibrator (21) and the second active vibrator (22) are L-shaped structures; The first active vibrator (21) and the second active vibrator (22) are both half-wave vibrators.

3. The directional antenna suitable for UWB radar products according to claim 2, characterized in that: The reflector (1) has a groove-shaped structure, consisting of a bottom reflective block and side wall reflective blocks perpendicular to both sides of the bottom reflective block, wherein the side wall reflective blocks are rectangular; an inwardly recessed rectangular notch is provided in the middle of the bottom reflective block, and the rectangular notch extends along the length direction of the bottom reflective block.

4. The directional antenna suitable for UWB radar products according to claim 3, characterized in that: The guiding unit (3) comprises N directors, where N is greater than or equal to 2.

5. The directional antenna suitable for UWB radar products according to claim 4, characterized in that: When N=2, the guiding unit (3) comprises a first director (31) and a second director (32), the first director (31) and the second director (32) are both rectangular, the long sides of the first director (31) and the second director (32) are parallel to the transverse central axis of the substrate, and the second director (32) and the first director (31) are arranged in parallel up and down; The long side of the first director (31) is greater than the long side of the second director (32).

6. The directional antenna suitable for UWB radar products according to claim 5, characterized in that: The spacing between the first director (31) and the second director (32) is 0.1-0.3λ; the spacing between the first director (31) and the first active oscillator (21) and the second active oscillator (22) is 0.1-0.3λ, where λ is the signal operating wavelength.

7. The directional antenna suitable for UWB radar products according to claim 6, characterized in that: The driving unit (4) comprises a microstrip line (42) and an impedance converter (41), the microstrip line (42) being connected to a signal pin of a signal feeding point (5), and the impedance converter (41) being connected to the signal pin of the signal feeding point (5) via the microstrip line (42).

8. The directional antenna suitable for UWB radar products according to claim 7, characterized in that: The impedance converter (41) adopts a stepped gradient structure, the width of which increases stepwise from one end to the other end, and the narrowest end of the stepped gradient structure is connected to the signal pin of the signal feeding point (5) via a microstrip line (42).

9. The directional antenna suitable for UWB radar products according to claim 7, characterized in that: The calculation formula for the width of the microstrip line (42) is: Where w is the width of the microstrip line (42), A is the intermediate calculation parameter, Z0 is the characteristic impedance, ∑r is the relative dielectric constant, and h is the substrate thickness; The calculation formula of the length of the microstrip line (42) is: Wherein, L is the length of the microstrip line (42), λ is the signal operating wavelength, and ∑eff is the effective dielectric constant.

10. The directional antenna suitable for UWB radar products according to any one of claims 7 to 9, characterized in that: The driving unit (4) receives a high-frequency current signal from a transmitter through a signal feeding point (5), and couples the high-frequency current signal to the excitation unit (2). The impedance of the input port and the output port are matched through an impedance converter (41), thereby reducing the reflection loss between the ports and reducing the transmission loss during the transmission process through a microstrip line (42). The excitation unit (2) converts the high-frequency current signal into electromagnetic wave radiation in space through a first active oscillator (21) and a second active oscillator (22), thereby generating a radiation field. When the excitation unit (2) radiates electromagnetic waves outward, the energy originally radiated backward is reflected forward through the reflector (1). The director in the director unit (3) generates an induced current through electromagnetic induction, and the director becomes a secondary radiation source, radiating electromagnetic waves outward, thereby causing the electromagnetic waves to be concentratedly radiated in the direction pointed by the director.

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