79GHz high-gain millimeter wave liquid level meter antenna based on dielectric lens

Abstract

The invention relates to the technical field of millimeter wave antennas, and provides a dielectric-lens-based 79GHz high-gain millimeter wave liquid level meter antenna, which comprises a dielectric substrate, a radiation patch, a parasitic patch, an annular directional coupler and a dielectric lens, and is characterized in that the radiation patch is arranged at the central position of the surface of the dielectric substrate; the parasitic patch is arranged on the surface of the dielectric substrate and concentrically arranged around the radiation patch; the annular directional coupler is arranged on the dielectric substrate and is electrically connected with the radiation patch through the microstrip transmission line; and the dielectric lens is arranged above the dielectric substrate and is coaxially aligned with the radiation unit formed by the radiation patch and the parasitic patch. According to the millimeter wave antenna, the working bandwidth is expanded and the radiation efficiency is improved by utilizing the electromagnetic coupling effect of the parasitic patch, the receiving and transmitting channel isolation greater than 25dB is realized by combining the annular directional coupler, and the gain and directivity of the millimeter wave antenna are remarkably improved based on the refraction focusing principle of the dielectric lens; and the antenna can be applied to industrial application scenes of high directivity and long-distance ranging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of millimeter wave antenna, and particularly relates to a 79GHz high-gain millimeter wave liquid level meter antenna based on a dielectric lens. BACKGROUND

[0002] As a high-precision non-contact sensing technology, millimeter wave radar is widely used in industrial liquid level measurement, material height detection and intelligent sensing system and other key application scenarios. Millimeter wave radar has extremely high precision in distance measurement, near distance measurement can reach millimeter level, and far distance measurement precision can reach centimeter level. In speed measurement, with the help of Doppler effect and micro-Doppler characteristics, the micro motion change of the target surface can be effectively identified. In azimuth angle measurement, the wavelength of millimeter wave is short, and the antenna volume is small, so multiple transmitting and receiving units can be integrated to obtain a larger radar aperture, thereby realizing high angular resolution. At present, millimeter wave radar liquid level meter usually works in 24GHz, 60GHz or 77-81GHz frequency band. Among them, the 79GHz frequency band has shorter wavelength, allowing the construction of smaller and more directional high-performance antenna systems, which shows obvious advantages in high-precision long-distance liquid level measurement scenarios.

[0003] With the rapid development of industrial automation, intelligent manufacturing and process control technology, higher requirements are put forward for the precision, reliability and real-time performance of the liquid level measurement system. The liquid level meter technology is accelerating from the traditional contact type, mechanical type sensor to the non-contact, high-precision and intelligent type. Among various non-contact measurement schemes, the millimeter wave radar-based liquid level meter is widely adopted due to its high resolution, strong penetration and low environmental sensitivity. It not only has excellent distance measurement and target recognition capability, but also has good anti-environmental interference capability, especially in complex industrial environments with high steam, dust, pressure and temperature changes.

[0004] In the prior art, the millimeter wave liquid level meter antenna is mainly designed by using a traditional microstrip patch antenna structure. However, the radiation efficiency of such an antenna is limited at high frequencies, and it is difficult to provide sufficient far-field gain, resulting in the inability to realize long-distance measurement and complex medium penetration, which seriously affects the measurement accuracy and reliability of the millimeter wave liquid level meter in the industrial environment. SUMMARY

[0005] Therefore, the present application provides a 79GHz high-gain millimeter wave liquid level meter antenna based on a dielectric lens, which solves the problem that in the prior art, the millimeter wave liquid level meter antenna is mainly designed by using a traditional microstrip patch antenna structure. However, the radiation efficiency of such an antenna is limited at high frequencies, and it is difficult to provide sufficient far-field gain, resulting in the inability to realize long-distance measurement and complex medium penetration, which seriously affects the measurement accuracy and reliability of the millimeter wave liquid level meter in the industrial environment.

[0006] The technical solution of this invention is implemented as follows: This invention provides a 79GHz high-gain millimeter-wave level gauge antenna based on a dielectric lens. The antenna includes a dielectric substrate, a radiating patch, a parasitic patch, a ring directional coupler, and a dielectric lens, wherein: The dielectric substrate is made of FR4 epoxy resin glass fiber composite material; The radiating patch is disposed at the center of the surface of the dielectric substrate; The parasitic patch is disposed on the surface of the dielectric substrate and concentrically arranged around the radiating patch. The slits of the parasitic patch are aligned with the long side of the radiating patch, and the parasitic patch forms a radiating unit with the radiating patch through electromagnetic coupling. The ring-shaped directional coupler is disposed on the dielectric substrate and electrically connected to the radiating patch via a microstrip transmission line. It is used to feed the input signal into the radiating patch and the parasitic patch and to isolate the transceiver channel. The dielectric lens is made of polytetrafluoroethylene and is disposed above the dielectric substrate, coaxially aligned with the radiation unit composed of the radiation patch and the parasitic patch.

[0007] Based on the above technical solutions, preferably, the dielectric substrate is a four-layer laminated circuit board, which includes a top copper metal layer and a second wiring layer. The thickness of the top FR4 material is used as a reference indicator when calculating the structural dimensions of the antenna.

[0008] Based on the above technical solutions, preferably, the radiating patch is rectangular in shape; The width of the radiation patch is: ; in, The width of the radiating patch. At the speed of light, For the center frequency, is the dielectric constant of the substrate; The length of the radiation patch is: ; in, The length of the radiating patch, At the speed of light, For the center frequency, is the dielectric constant of the substrate.

[0009] Based on the above technical solutions, preferably, the parasitic patch is a slotted annular shape made of copper. The parasitic patch is arranged concentrically around the radiating patch. The parasitic patch and the radiating patch are not directly electrically connected. Instead, they form a double-layer radiating unit with the radiating patch through spatial electromagnetic coupling, thereby expanding the antenna's operating bandwidth and enhancing its far-field gain characteristics.

[0010] Based on the above technical solutions, preferably, the parasitic patch is a passive structural element, which is disposed coplanarly with the radiating patch on the surface of the dielectric substrate. Through electromagnetic coupling effect, multimode excitation and frequency response optimization are performed, thereby improving the radiation efficiency and operating bandwidth of the antenna in the millimeter-wave band.

[0011] Based on the above technical solutions, preferably, the slit of the parasitic patch is aligned with the long rectangular side of the radiating patch. The slit is used to control the electromagnetic coupling strength between the parasitic patch and the radiating patch, so as to optimize the electromagnetic field distribution and radiation characteristics of the double-layer radiating unit in the 79GHz band.

[0012] Based on the above technical solutions, preferably, the ring directional coupler is a 3dB ring directional coupler, which adopts a closed ring microstrip structure and is composed of a microstrip line with a total length of 1.5 times the wavelength of the pilot wave; Four ports are set on the ring structure: an input port, a coupling port, an isolation port, and a through port. The electrical distance between each port is a quarter wavelength, which enables equal power distribution and directional control of the input signal.

[0013] Based on the above technical solutions, preferably, the isolation of the ring directional coupler is greater than 25dB. When the antenna is in the transmitting state, the input terminal is connected to the feed port, and the through terminal feeds the signal into the radiating patch and the parasitic patch. When the antenna is in receiving mode, the coupling end couples the signal to the signal receiving end, physically isolating the transceiver channel and reducing interference.

[0014] Based on the above technical solutions, preferably, the relative permittivity of the dielectric lens is 2.0 to 2.2, and it is a convex lens structure. The radius of curvature of the dielectric lens is optimized according to the position of the radiation patch and the working wavelength. By utilizing the refraction principle of the lens on the propagation of electromagnetic waves, the electromagnetic beam is converted from a spherical wave to a plane wave.

[0015] Based on the above technical solutions, preferably, the dielectric lens is coaxially aligned and fixed with the dielectric substrate. By adjusting the installation distance of the dielectric lens, the electromagnetic beam emitted by the radiation unit is effectively focused to obtain the best focusing effect and energy concentration.

[0016] The 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens of the present invention has the following advantages over the prior art: (1) By integrating the coupling structure of FR4 epoxy resin glass fiber composite dielectric substrate, rectangular radiating patch and slotted circular parasitic patch, the transmit and receive isolation mechanism of 3dB ring directional coupler, and the electromagnetic wave focusing of polytetrafluoroethylene dielectric lens, the working bandwidth is expanded and the radiation efficiency is improved by utilizing the electromagnetic coupling effect of parasitic patch. Combined with ring directional coupler, transmit and receive channel isolation of more than 25dB is achieved. Based on the refraction focusing principle of dielectric lens, spherical wave is converted into plane wave and the directivity is significantly enhanced, achieving high gain, narrow beamwidth and excellent sidelobe suppression performance in the 79GHz band. (2) By adopting a four-layer laminated circuit board structure and precisely controlling the material thickness of the top copper layer and the top FR4 layer, combined with the dielectric constant of FR4 material and the size parameters of the radiating patch optimized by electromagnetic simulation, the antenna was precisely designed using the theoretical calculation formula of the width and length of the radiating patch, achieving the best impedance matching, high radiation efficiency and stable electrical performance at the 79GHz center frequency. (3) By adopting a passive coupling structure in which a slit circular parasitic patch with an inner radius of 1 mm and a width of 0.25 mm is arranged concentrically around a rectangular radiating patch, a double-layer radiating unit is constructed using spatial electromagnetic coupling and a multi-mode excitation mechanism is realized. Combined with the precise positioning design of aligning the slit direction with the long side of the radiating patch, the electromagnetic coupling strength is controlled. This achieves an effective expansion of the antenna's working bandwidth in the 79 GHz band, an enhancement of the far-field gain characteristics, and a significant improvement in radiation efficiency, providing a wider frequency coverage and better radiation performance for the millimeter-wave level gauge antenna. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens according to the present invention; Figure 2 This is a schematic diagram of lens installation for a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens according to the present invention. Figure 3 This is a schematic diagram illustrating the dielectric lens refraction principle of a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens according to the present invention. Figure 4 The figure shows the S-parameter results of a 79 GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens according to the present invention. Figure 5 The image shows the 79 GHz one-dimensional radiation pattern of a 79 GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens according to the present invention. Figure 6 This invention relates to a 79 GHz one-dimensional radiation pattern of a 79 GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens. Figure 7 The image shows the 79 GHz one-dimensional radiation pattern of a 79 GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens installed at different positions, according to the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 and Figure 2 This invention provides a 79GHz high-gain millimeter-wave level gauge antenna based on a dielectric lens. The antenna includes a dielectric substrate 1, a radiating patch 2, a parasitic patch 3, a ring directional coupler 4, and a dielectric lens 5, wherein: The dielectric substrate 1 is made of FR4 epoxy resin glass fiber composite material; The radiation patch 2 is disposed at the center of the surface of the dielectric substrate 1; The parasitic patch 3 is disposed on the surface of the dielectric substrate 1 and is concentrically arranged around the radiating patch 2. The slits of the parasitic patch 3 are aligned with the long side of the radiating patch 2, and form a radiating unit with the radiating patch 2 through electromagnetic coupling. The ring-shaped directional coupler 4 is disposed on the dielectric substrate 1 and electrically connected to the radiating patch 2 via a microstrip transmission line. It is used to feed the input signal into the radiating patch 2 and the parasitic patch 3 and to isolate the transceiver channel. The dielectric lens 5 is made of polytetrafluoroethylene and is disposed above the dielectric substrate 1, coaxially aligned with the radiation unit composed of the radiation patch 2 and the parasitic patch 3.

[0021] Specifically, this embodiment integrates the coupling structure of an FR4 epoxy resin glass fiber composite dielectric substrate 1, a rectangular radiating patch 2 and a slotted annular parasitic patch 3, the transmit / receive isolation mechanism of a 3dB annular directional coupler 4, and the electromagnetic wave focusing of a polytetrafluoroethylene dielectric lens 5. It utilizes the electromagnetic coupling effect of the parasitic patch 3 to expand the working bandwidth and improve radiation efficiency, and combines the annular directional coupler 4 to achieve transmit / receive channel isolation greater than 25dB. Based on the refraction and focusing principle of the dielectric lens 5, it converts spherical waves into plane waves and significantly enhances directivity. This solves the problems of insufficient gain, poor directivity, limited bandwidth, and poor transmit / receive isolation in traditional millimeter-wave level gauge antennas. It achieves a high gain of 27.5dBi, a narrow beamwidth of 4.1°, and excellent sidelobe suppression performance in the 79GHz band, meeting the application requirements of industrial level measurement systems for high precision, long distance, and strong anti-interference capabilities.

[0022] The dielectric substrate 1 is a four-layer laminated circuit board with a thickness of 1.6 mm. The dielectric substrate 1 includes a top copper metal layer and a second wiring layer. The thickness of the top copper metal layer is 0.035 mm. The thickness of the FR4 material between the top copper metal layer and the second wiring layer is 0.0994 mm. The thickness of the top FR4 material is used as a reference indicator when calculating the structural dimensions of the antenna.

[0023] The dielectric substrate 1 has a dielectric constant of 4.1. The radiating patch 2, after optimization through electromagnetic simulation and actual measurement, has a length of 1.16 mm and a width of 0.88 mm to achieve impedance matching and radiation efficiency optimization in the 79 GHz band. The radiating patch 2 is rectangular in shape and is made of copper with a thickness of 0.035 mm. The width of the radiation patch is: ; in, The width of the radiating patch. At the speed of light, For the center frequency, is the dielectric constant of the substrate; The length of the radiation patch is: ; in, The length of the radiating patch, At the speed of light, For the center frequency, is the dielectric constant of the substrate.

[0024] In one specific embodiment, it is necessary to consider the presence of a capacitive component in the equivalent admittance, which should be: ; ; in, This refers to the actual length of the radiating patch. To achieve an equivalent shortening of length, For the effective dielectric constant, For FR4 material thickness, This refers to the width of the radiating patch.

[0025] The optimal length and width of a rectangular radial patch on an FR4 substrate can be calculated as follows: ; Through relevant electromagnetic simulation software and actual measurements, the optimal length of the rectangular radiating patch is 1.16 mm and the width is 0.88 mm. The rectangular patch antenna has a main lobe radiation direction in its vertical direction, with a narrow beam and stable direction, which facilitates electromagnetic energy focusing and matching with the subsequent dielectric lens 5, thereby achieving the goal of high gain and narrow beam of the antenna as a whole. It is particularly suitable for long-distance, highly directional liquid level ranging scenarios.

[0026] While the bandwidth of a single rectangular patch antenna is limited, its structural parameters (such as aspect ratio and grounding spacing) can be flexibly adjusted, and it is easy to form a coupling structure with the parasitic patch 3 to expand the bandwidth and improve the gain. The combination of the rectangular patch and the parasitic structure has good high-frequency stability in the millimeter-wave band, which can meet the dual requirements of liquid level radar for wideband anti-interference and frequency selectivity. To improve the antenna's gain and bandwidth performance, a slotted circular ring structure, also made of copper, is set around the main radiating patch 2. It is not directly connected to the feed structure, but enhances the radiation efficiency of the radiating element through spatial electromagnetic coupling. The coupling effect of the parasitic patch 3 can effectively broaden the antenna's operating frequency band and enhance far-field gain characteristics, making it particularly suitable for the concentrated millimeter-wave band. Through relevant theoretical calculations and test optimization, the preferred width of the parasitic patch 3 is 0.25 mm, and its inner radius is 1 mm with the center of the radiating patch 2 as the reference point. As a passive structural component, the parasitic patch 3 does not increase the power supply complexity and manufacturing cost of the antenna system, and is suitable for conventional PCB processes. It can be processed coplanarly with the radiating patch 2, and has excellent process compatibility and reliability.

[0027] The parasitic patch 3 has an inner radius of 1 mm, is a slit ring shape, is made of copper, and has a width of 0.25 mm. The parasitic patch 3 is arranged concentrically around the radiating patch 2. The parasitic patch 3 and the radiating patch 2 are not directly electrically connected, but form a double-layer radiating unit with the radiating patch 2 through spatial electromagnetic coupling, thereby expanding the antenna's operating frequency band and enhancing its far-field gain characteristics.

[0028] The parasitic patch 3 is a passive structural element, which is coplanar with the radiating patch 2 on the surface of the dielectric substrate 1. Through electromagnetic coupling effect, it performs multimode excitation and frequency response optimization, thereby improving the radiation efficiency and operating bandwidth of the antenna in the millimeter wave band.

[0029] The slits in the parasitic patch 3 are aligned with the long rectangular side of the radiating patch 2. The slits are used to control the electromagnetic coupling strength between the parasitic patch 3 and the radiating patch 2, so as to optimize the electromagnetic field distribution and radiation characteristics of the double-layer radiating unit in the 79GHz band.

[0030] The ring directional coupler 4 is a 3dB ring directional coupler 4, which adopts a closed ring microstrip structure and is composed of a microstrip line with a total length of 1.5 times the wavelength of the pilot wave. Four ports are set on the ring structure: an input port, a coupling port, an isolation port, and a through port. The electrical distance between each port is a quarter wavelength, which enables equal power distribution and directional control of the input signal.

[0031] The isolation of the ring directional coupler 4 is greater than 25dB. When the antenna is in the transmitting state, the input terminal is connected to the feed port, and the through terminal feeds the signal into the radiating patch 2 and the parasitic patch 3. When the antenna is in receiving mode, the coupling end couples the signal to the signal receiving end, physically isolating the transceiver channel and reducing interference.

[0032] In one specific embodiment, directional couplers are widely used in microwave and millimeter-wave systems. Their main function is to sample signals for monitoring, measurement, or power distribution. When a signal is input from the input terminal, in addition to a portion of the power being directly output from the through terminal, another portion of the power is coupled to the coupling terminal for output, but not from the isolation terminal; therefore, the isolation is greater than -25dB. The ring directional coupler 4 is disposed in the antenna feed network and is used to directionally couple the RF input signal to the radiating patch 2. The 3dB ring directional coupler 4 adopts a closed ring microstrip structure, consisting of a segment with a total length of It is composed of microstrip lines, with four ports arranged on a ring structure: an input port, a coupling port, an isolation port, and a pass-through port. The wavelength of the guided wave is based on the substrate material. In a 3dB directional coupler, 3dB refers to the coupling degree as follows: ; The scattering matrix of the ring directional coupler 4 can be expressed as: ; The ring-shaped directional coupler 4 is composed of a circumference of It is formed by connecting a closed circular loop and four input / output transmission lines. The characteristic impedance of the four transmission lines connected to the loop is... The characteristic impedance of the ring is The electrical distance between each port is or This structure enables equal power distribution and directional control of the input signal, and is widely used in millimeter-wave antenna feeding and transmit / receive channel isolation designs. The ring directional coupler 4 employs a closed-loop microstrip structure, with structural parameters including ring radius, linewidth, and coupling spacing. Through precise design and optimization, the microstrip line impedance of the central ring is... The system uses ohms to ensure excellent coupling efficiency and directional selectivity in the 79GHz band. This structure enables shared antenna transmission and reception, effectively isolating the transmit and receive channels, reducing the risk of echo interference, and improving system stability and detection accuracy.

[0033] The dielectric lens 5 has a relative permittivity of 2.0 to 2.2 and is a convex lens structure. The radius of curvature of the dielectric lens 5 is optimized according to the position of the radiation patch 2 and the working wavelength. By utilizing the refraction principle of the lens on the propagation of electromagnetic waves, the electromagnetic beam is converted from a spherical wave to a plane wave.

[0034] The dielectric lens 5 is coaxially aligned and fixed with the dielectric substrate 1. The distance between the dielectric lens 5 and the radiation patch 2 is 18mm. By adjusting the installation distance of the dielectric lens 5, the electromagnetic beam emitted by the radiation unit is effectively focused to obtain the best focusing effect and energy concentration.

[0035] Specifically, the structural principle of a lens antenna utilizes the refraction principle of electromagnetic wave propagation by a lens. Adding a lens to the radiation direction of a patch antenna creates a lens antenna. Compared to patch antennas, lens antennas can more easily achieve higher gain and narrower beam angles. The high gain of a lens antenna is achieved by changing the direction of wave propagation. The path length of the wave after passing through the lens is different in each direction, and the lens can compensate for the phase difference through the path difference, thus achieving the conversion of the radiated electromagnetic wave from a spherical wave to a plane wave in a horn feed.

[0036] The structural design of a lens can be analogous to the refraction principle of light propagation in optical lenses. In the propagation path of electromagnetic waves, the electromagnetic waves radiated by the horn antenna feed reach the aperture surface of the lens antenna with equal path lengths; this is also known as Fermat's principle. Figure 3 Along the edge route The electrical length along the central axis Their electrical lengths are the same.

[0037] Assumption , Based on the above relationship, we can conclude that: ; in, The wavelength of electromagnetic waves propagating in space. Let be the wavelength of the electromagnetic wave propagating through the lens. Multiply this formula by... refractive index The formula can be simplified to: ; The simplified form is a hyperbola in the coordinate system. Let be the focal length of the lens, and the refractive index can also be expressed as: , The relative permeability in the dielectric material. is the relative permittivity of the dielectric material.

[0038] To further enhance the antenna's far-field performance, a dielectric lens 5 is placed in the antenna's radiation direction. This lens is made of polytetrafluoroethylene (PTFE), which has a dielectric constant of 2.1 and an extremely low loss factor, making it suitable for high-frequency microwave and millimeter-wave applications. The lens has an overall convex lens structure; by adjusting the lens curvature and installation distance, effective focusing of the electromagnetic beam can be achieved, thereby significantly improving the antenna's directivity and main lobe gain. Through simulation optimization, the distance between the lens and the radiating patch 2 is set to 18 mm from the surface of the radiating antenna to obtain the best focusing effect and energy concentration.

[0039] This embodiment solves the problems of insufficient gain, poor directivity, and limited bandwidth of traditional patch antennas through the synergistic design of patch structure and lens focusing technology. Experimental and simulation results show that the antenna operates stably near the 79GHz center frequency, with a main lobe gain improvement of up to 27.5dBi and a 3dB beamwidth of 4.1°, meeting the requirements for long-distance, high-precision liquid level monitoring. Furthermore, this embodiment's 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens has a compact structure, and the selected materials possess good engineering feasibility and cost control capabilities, facilitating large-scale integration and manufacturing. It is particularly suitable for applications requiring non-contact real-time liquid level monitoring, such as smart factories, hazardous liquid tanks, and sealed reaction vessels.

[0040] In one specific embodiment, to verify the performance of the antenna structure proposed in this invention, a full-wave electromagnetic simulation of the 79GHz millimeter-wave patch antenna with loaded dielectric lens 5 was performed using CSTMicrowave Studio. The simulation considered the actual electrical parameters of the materials: the dielectric constant of the FR4 substrate was 4.1, and the loss tangent was 0.011; the dielectric constant of the PTFE lens was 2.1, with extremely low loss. Key performance parameters such as antenna gain, radiation pattern, VSWR, and bandwidth were evaluated.

[0041] Figure 4 The S-parameter results of a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens 5 proposed in this invention are shown. This antenna exhibits good impedance matching performance near the 79GHz center frequency, with a reflection coefficient S11 less than -10dB in a bandwidth range of 72.26-81.91GHz, and an absolute bandwidth of 9.65GHz, meeting the frequency band application requirements of existing millimeter-wave chips. Within the 76-81GHz frequency band, the S11 parameter is less than -20dB, indicating sufficiently low return loss for the surface antenna, and excellent radiation efficiency and performance.

[0042] Figure 5 The 79GHz one-dimensional radiation pattern of a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens 5 proposed in this invention is shown. The unloaded dielectric antenna has a gain of 8.58dBi and a 3dB beamwidth of 41.7° at 79GHz, but the sidelobe suppression is weak, which will cause dummy position when used for ranging, affecting the ranging performance.

[0043] Figure 6 The present invention provides a 79GHz one-dimensional radiation pattern of a 79GHz high-gain millimeter-wave liquid level gauge antenna based on a dielectric lens 5. After loading the lens, the antenna gain reaches 27.5dBi, which is a significant improvement over the unloaded lens. At the same time, the 3dB beamwidth is only 4.1°, exhibiting excellent directivity and significantly suppressing sidelobe levels, which is beneficial for the stable identification of liquid level targets at both near and far distances, improving ranging accuracy, and further enhancing measurement accuracy and anti-interference capability.

[0044] Figure 7 This paper presents one-dimensional radiation patterns at different installation positions of the dielectric lens 5 in a 79GHz high-gain millimeter-wave liquid level gauge antenna based on the proposed invention. The radiation patterns of the dielectric lens 5 at different heights are also shown. Overall, different heights significantly affect the antenna's radiation directivity and gain distribution. In comparison, the solid line corresponding to a height of 18mm exhibits the best performance in the main lobe direction, with a gain close to 28.5dBi, far exceeding the gain at other distances. Furthermore, the side lobes on both sides of the main lobe are small, effectively suppressing radiation in undesirable directions. Simultaneously, this curve shows minimal fluctuation across the entire angular range, indicating good sidelobe control and demonstrating excellent directivity and stability. In practical applications, it effectively improves signal strength and reduces interference, representing the most balanced choice in terms of overall performance.

[0045] 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 within the protection scope of the present invention.

Claims

1. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens characterized in that, The antenna comprises a dielectric substrate (1), a radiation patch (2), a parasitic patch (3), a ring-shaped directional coupler (4) and a dielectric lens (5), wherein: The dielectric substrate (1) is made of FR4 epoxy glass fiber composite material; The radiation patch (2) is arranged at the center of the surface of the dielectric substrate (1); The parasitic patch (3) is arranged on the surface of the dielectric substrate (1) and concentrically arranged around the radiation patch (2), the slit of the parasitic patch (3) is aligned with the long side direction of the radiation patch (2), and the radiation patch (2) forms a radiation unit through electromagnetic coupling; The ring-shaped directional coupler (4) is arranged on the dielectric substrate (1) and electrically connected to the radiation patch (2) through a microstrip transmission line, for feeding input signals into the radiation patch (2) and the parasitic patch (3), and isolating the transmitting and receiving channels; The dielectric lens (5) is made of polytetrafluoroethylene material and arranged above the dielectric substrate (1) and coaxially aligned with the radiation unit composed of the radiation patch (2) and the parasitic patch (3).

2. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 1 characterized in that, The dielectric substrate (1) is a four-layer laminated circuit board, and the dielectric substrate (1) includes a top layer of metal copper and a second layer of wiring layer, and the thickness of the top layer of FR4 material is used as a reference index when calculating the structure size of the antenna.

3. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 2, wherein, The radiation patch (2) is rectangular in shape; The width of the radiation patch is: ； wherein, is the width of the radiation patch, is the speed of light, is the center frequency, is the dielectric constant of the dielectric substrate; The length of the radiation patch is: ； wherein, is the length of the radiating patch, is the speed of light, is the center frequency, is the dielectric constant of the dielectric substrate.

4. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 1 characterized by, The parasitic patch (3) is a slotted circular ring made of metal copper, which is concentrically arranged around the radiation patch (2), and the parasitic patch (3) is not directly electrically connected to the radiation patch (2), but forms a double-layer radiation unit with the radiation patch (2) through spatial electromagnetic coupling, thereby expanding the working frequency band of the antenna and enhancing the far-field gain characteristics.

5. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 4, wherein, The parasitic patch (3) is a passive structural element arranged on the surface of the dielectric substrate (1) coplanarly with the radiation patch (2), and is excited by multi-mode and optimized in frequency response through electromagnetic coupling effect, thereby improving the radiation efficiency and working bandwidth of the antenna in the millimeter wave frequency band.

6. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 5 characterized in that, The slit of the parasitic patch (3) is aligned with the long side direction of the radiation patch (2), and the slit is arranged to control the electromagnetic coupling strength between the parasitic patch (3) and the radiation patch (2) to optimize the electromagnetic field distribution and radiation characteristics of the double-layer radiation unit in the 79GHz frequency band.

7. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 1 characterized by, The ring-shaped directional coupler (4) is a 3dB ring-shaped directional coupler (4) adopting a closed ring-shaped microstrip structure and composed of a microstrip line with a total length of 1.5 times the guided wave wavelength; Four ports are arranged on the ring-shaped structure, which are input end, coupling end, isolation end and through end, and the electrical distance between each port is one-quarter wavelength, which performs equal power distribution and directionality control on the input signal.

8. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 7 characterized by, The isolation of the ring-shaped directional coupler (4) is greater than 25dB, when the antenna is in the transmitting state, the input end is connected to the feeding port, and the through end feeds signals into the radiation patch (2) and the parasitic patch (3). When the antenna is in a receiving state, the coupling end couples signals to the signal receiving end, physically isolates the transceiving channel and reduces interference.

9. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 1 characterized by, The relative dielectric constant of the dielectric lens (5) is 2.0-2.2, and the dielectric lens (5) is a convex lens structure. The curvature radius of the dielectric lens (5) is designed according to the position and working wavelength of the radiation patch (2). By using the refraction principle of the lens for electromagnetic wave propagation, the electromagnetic wave beam is converted from spherical wave to plane wave.

10. A 79 GHz high gain millimeter wave liquid level meter antenna based on dielectric lens as claimed in claim 9, wherein, The dielectric lens (5) is coaxially aligned and fixed with the dielectric substrate (1). By adjusting the mounting distance of the dielectric lens (5), the electromagnetic wave beam emitted by the radiation unit is effectively focused, and the best focusing effect and energy concentration are obtained.

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