Broadband Hilbert-like antenna for partial discharge detection

Abstract

The invention provides a broadband Hilbert-like antenna for partial discharge detection, the broadband Hilbert-like antenna adopts a fourth-order Hilbert fractal curve as a basic framework, and each line segment is realized by a parameterized controlled cosine function curve, so that a surface current path of the broadband Hilbert-like antenna extends in a wave shape. According to the technical scheme, the cosine curve and the fractal geometry are organically combined, and the key problem that it is difficult to consider both the broadband and the omni-direction of the partial discharge detection antenna is solved through accurate parameterization control. Practical application proves that the antenna is simple in structure and excellent in performance, and has a good engineering application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage equipment and partial discharge detection, and in particular relates to a broadband Hilbert-like antenna for partial discharge detection. Background Art

[0002] As the scale of the power grid continues to expand, the requirements for the reliability and safety of power equipment are also gradually increasing. Partial discharge detection is an important means of evaluating the insulation condition of power equipment. Antennas, as key components for electromagnetic signal sensing, have a direct impact on detection effectiveness. Traditional partial discharge detection antennas mainly include dipole antennas, horn antennas, and fractal antennas. Among them, fractal antennas have become a research hotspot due to their self-similar properties and space-filling capabilities, which enable multi-band or broadband operation in a compact size.

[0003] As an important branch of fractal antennas, Hilbert fractal antennas are widely used in various communication systems due to their excellent space utilization and self-similarity. Traditional Hilbert antennas consist of multiple straight line segments, which are folded in space to increase their electrical length. However, in partial discharge detection applications, traditional Hilbert antennas have significant shortcomings: first, their bandwidth is relatively limited, making it difficult to cover the wide spectrum characteristics of partial discharge signals; second, the radiation pattern is easily distorted with frequency changes, affecting detection reliability; third, the antenna structure parameters have limited freedom of adjustment, making it difficult to optimize for different application scenarios.

[0004] In recent years, researchers both domestically and internationally have attempted various improvements to the Hilbert antenna. Some have attempted to adjust performance by varying the number of fractal iterations or line width, but the bandwidth improvement has been limited. Others have employed hybrid fractal structures, which increases design complexity. Regarding curved antennas, sine and cosine curves, due to their smooth transition properties, have been used in dipole antenna design, showing potential for improving bandwidth and radiation patterns. However, there have been no reports combining these with fractal structures.

[0005] The electromagnetic pulse signals generated by partial discharges have nanosecond-level rise times and a wide spectrum (typically covering 500 MHz to 2 GHz). This places stringent requirements on detection antennas for both broadband and omnidirectionality. Existing antennas struggle to simultaneously meet these requirements for broadband, stable radiation patterns, and miniaturization, hindering improvements in partial discharge detection accuracy. Therefore, developing a novel broadband, omnidirectional fractal antenna has significant engineering application value. Summary of the Invention

[0006] In view of the above problems in the prior art, the present invention provides a broadband Hilbert-like antenna for partial discharge detection.

[0007] A broadband Hilbert-like antenna for partial discharge detection uses a fourth-order Hilbert fractal curve as a basic framework, wherein each line segment is implemented by a parameterized cosine function curve, so that the surface current path of the broadband Hilbert-like antenna extends in a wavy shape.

[0008] Preferably, the broadband Hilbert-like antenna covers the partial discharge detection requirements of 300 MHz-3 GHz.

[0009] Preferably, the control parameters of the cosine function curve include amplitude and period;

[0010] The amplitude is used to control the fluctuation amplitude of the cosine function curve, and the optimization range is 0.3-1.5;

[0011] The period is used to control the fluctuation density of the cosine function curve, and the optimization range is 0.5-2.0.

[0012] Preferably, it is characterized in that the expression of the cosine function curve is as follows:

[0013]

[0014] Among them, A is the amplitude parameter, K is the period parameter, is the phase parameter.

[0015] Preferably, the broadband characteristics of the broadband Hilbert-like antenna are achieved through multi-resonance point coupling, a current path extending in a wavy line, and an impedance gradient structure; wherein,

[0016] The curvature change introduced by the cosine function curve generates coupled resonance at multiple frequency points, and the coupled resonance points are overlapped to form a wide-band response.

[0017] Preferably, the omnidirectional radiation characteristic of the broadband Hilbert-like antenna is achieved by symmetrical current distribution, phase center stability, and coordinated operation of radiation units;

[0018] The symmetry of the cosine function curve enables the current of each radiation unit to be symmetrically distributed.

[0019] Compared with existing technologies, the present invention offers the following advantages: it effectively extends the current path on the antenna surface, increasing design freedom and achieving a more stable omnidirectional pattern and reduced signal distortion across a wide frequency band compared to conventional Hilbert antennas. Results show that the antenna exhibits excellent broadband characteristics within the 300MHz-3GHz frequency band, with a voltage standing wave ratio (VSWR) of less than 4.0, making it particularly suitable for capturing broadband electromagnetic signals used in partial discharge detection of power equipment. The antenna boasts a compact structure and stable performance, resolving the narrow bandwidth and high pattern distortion associated with conventional partial discharge detection antennas, providing a more reliable detection tool for power equipment condition monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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.

[0021] Figure 1 Schematic diagram of the structure of a traditional fourth-order Hilbert fractal antenna according to an embodiment of the present invention;

[0022] Figure 2 This is the directional pattern of a conventional fourth-order Hilbert fractal antenna at a frequency of 2.0 GHz according to an embodiment of the present invention;

[0023] Figure 3 This is the directional pattern of a conventional fourth-order Hilbert fractal antenna at a frequency of 2.5 GHz according to an embodiment of the present invention;

[0024] Figure 4 Schematic diagram of the broadband Hilbert-like antenna structure with A=1.0 and K=1 according to an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the broadband Hilbert-like antenna structure with A=1.5 and K=1 according to an embodiment of the present invention;

[0026] Figure 6 Schematic diagram of the broadband Hilbert-like antenna structure with A=0.5 and K=2 according to an embodiment of the present invention;

[0027] Figure 7 VSWR schematic diagram of an embodiment of the present invention;

[0028] Figure 8 The three-dimensional radiation pattern of the broadband Hilbert-like antenna according to an embodiment of the present invention;

[0029] Figure 9 This is the directional pattern of the broadband Hilbert-like antenna with a frequency of 0.3 GHz according to an embodiment of the present invention;

[0030] Figure 10 This is the directional pattern of the broadband Hilbert-like antenna with a frequency of 0.5 GHz according to an embodiment of the present invention;

[0031] Figure 11 This is the directional pattern of the broadband Hilbert-like antenna with a frequency of 0.7 GHz according to an embodiment of the present invention;

[0032] Figure 12 This is the directional pattern of the broadband Hilbert-like antenna at a frequency of 1.0 GHz according to an embodiment of the present invention;

[0033] Figure 13 This is the directional pattern of the broadband Hilbert-like antenna of an embodiment of the present invention at a frequency of 1.5 GHz;

[0034] Figure 14 This is the directional pattern of the broadband Hilbert-like antenna at a frequency of 2.0 GHz according to an embodiment of the present invention;

[0035] Figure 15 This is the directional pattern of the broadband Hilbert-like antenna at a frequency of 2.5 GHz according to an embodiment of the present invention;

[0036] Figure 16 This is the directional pattern of the broadband Hilbert-like antenna of an embodiment of the present invention at a frequency of 3.0 GHz. DETAILED DESCRIPTION

[0037] 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] like Figure 1 As shown in FIG, a broadband Hilbert-like antenna for partial discharge detection is constructed. The broadband Hilbert-like antenna uses a fourth-order Hilbert fractal curve as its basic framework, wherein each line segment is implemented by a parameterized cosine function curve, so that the surface current path of the broadband Hilbert-like antenna extends in a wavy shape. That is, the straight line segments of the traditional Hilbert fractal antenna are replaced with cosine curve segments while maintaining the self-similarity of the fractal structure. Specifically, the nth-order cosine Hilbert curve is as follows: Figure 1 shown. Figure 2This is the directional pattern of a conventional fourth-order Hilbert fractal antenna at a frequency of 2.0 GHz according to an embodiment of the present invention; Figure 3 This is the directional pattern of a traditional fourth-order Hilbert fractal antenna at a frequency of 2.5 GHz in an embodiment of the present invention.

[0041] By replacing straight lines with cosine curves, the surface current path is effectively extended, achieving a wider impedance bandwidth. A further implementation involves a broadband Hilbert-like antenna covering partial discharge detection requirements from 300MHz to 3GHz. The smooth nature of the cosine curve improves current distribution and reduces phase differences in high-frequency bands, resulting in a more stable omnidirectional radiation pattern. The new curved fractal structure optimizes the current path and improves radiation efficiency by adjusting the curve curvature while maintaining miniaturization.

[0042] A further implementation involves controlling the cosine function curve with amplitude and period, providing greater design freedom and enabling optimization of antenna performance for specific applications. The parameter range is primarily optimized through multi-step optimization, i.e., correlation. The value of A has a greater impact on the directivity pattern across a wide bandwidth, while the feed position has a greater impact on VSWR.

[0043] The amplitude controls the fluctuations of the cosine function curve, directly affecting the antenna's equivalent electrical length and radiation resistance. Larger values ​​of A increase the current path and lower the resonant frequency, but increase the overall antenna size. The optimization range is 0.3-1.5. Specifically, due to the optimized design of A, larger values ​​of A increase the current path and lower the resonant frequency, but increase the overall antenna size. The value range of A is 0.3-1.5. This stage primarily ensures minimal pattern distortion and no splitting across a wide frequency band.

[0044] The period controls the fluctuation density of the cosine function curve, affecting the high-frequency characteristics of the antenna. A smaller K value (more fluctuations) improves high-frequency response but increases conductor losses. The optimization range is 0.5-2.0. Specifically, the period parameter K is designed based on the antenna frequency band requirements. A smaller K value (more fluctuations) improves high-frequency response but increases conductor losses. The optimization range of K is 0.5-2.0, with larger values ​​used for low-frequency applications and smaller values ​​used for broadband applications. Since partial discharge primarily operates in the ultra-high frequency and long-wave bands, K is set to 1.

[0045] In this embodiment, the feeding position is optimized. This stage mainly ensures the optimization of the VSWR value.

[0046] Due to the fixed fractal rules, Hilbert antennas are difficult to optimize, resulting in distorted patterns at high frequencies. Pattern splitting can even occur, impacting the reliability of partial discharge. Traditional Hilbert antennas use a "gate" structure composed of straight line segments, but the present invention replaces this with a cosine curve. Assuming the side length of a standard Hilbert element is L, the cosine function curve is expressed as follows:

[0047]

[0048] Among them, A is the amplitude parameter, K is the period parameter, is the phase parameter (usually 0 or π / 2).

[0049] Figure 4 Schematic diagram of the broadband Hilbert-like antenna structure with A=1.0 and K=1;

[0050] Figure 5 Schematic diagram of the broadband Hilbert-like antenna structure with A=1.5 and K=1;

[0051] Figure 6 Schematic diagram of the broadband Hilbert-like antenna structure with A=0.5 and K=2.

[0052] Specifically, during the parameter control and optimization process of the present invention, a multi-stage screening mechanism is first used to preliminarily set reasonable value ranges for the key geometric parameters A and K, avoiding being trapped in local optimality due to inefficient global search. Subsequently, a multi-objective, multi-parameter collaborative optimization mechanism is introduced during the simulation design phase. Taking into account electromagnetic performance, structural continuity, and engineering feasibility, the following three targeted multi-objective tuning strategies are adopted to effectively achieve the precise design of A and K:

[0053] 1. Equivalent electrical length coupling design

[0054] This strategy focuses on the ability to excite multiple resonant modes in an antenna. By jointly adjusting the A and K parameters, it achieves coordinated control of the equivalent electrical lengths of multiple "quasi-resonant units" in the antenna structure. This mechanism enhances energy coupling between resonant frequencies, improving the overall spectral response density and broadening the available bandwidth.

[0055] 2. Pattern equalization control mechanism

[0056] Based on system simulation analysis of the effects of A and K modulation on antenna current distribution and spatial radiation characteristics, this strategy introduces a quantitative assessment model for the impact of spatial curvature on pattern distortion. By selecting an A / K combination that creates a symmetrical current path distribution, this strategy effectively suppresses abnormal patterns such as mainlobe tilt and sidelobe enhancement, achieving stable and balanced radiation pattern control within the operating frequency band.

[0057] 3. VSWR targeted tuning mechanism

[0058] To optimize antenna matching characteristics, this strategy integrates feed point location with AK structural parameter design to create a targeted approach for constructing a VSWR matching region. High-density simulation samples are used to establish a three-parameter "feed-AK" response matrix, avoiding high-reflection areas within the bandwidth and targeting a stable operating range with VSWR < 4.0. This approach balances the broadband stability of the antenna input impedance with the structural manufacturing constraints, ensuring excellent system matching performance while maintaining a compact design.

[0059] High-order fractals are created by rotating, scaling, and connecting low-order curves. Like traditional Hilbert curves, this method maintains the space-filling property but optimizes the extension of the surface current path by varying the curvature of the cosine curve.

[0060] A further embodiment is that the broadband characteristics of the broadband Hilbert-like antenna are achieved through multi-resonance point coupling, a current path extending in a wavy line, and an impedance gradient structure; wherein,

[0061] Multi-resonance coupling: The curvature variation introduced by the cosine function curve generates coupled resonances at multiple frequencies, overlapping the coupled resonances to form a broadband response. Compared to traditional straight-segment fractal antennas, the curved structure produces richer current patterns in higher-order fractals.

[0062] Optimized current path: The cosine curve creates a wavy surface current path, effectively increasing the equivalent electrical length compared to a straight-line structure. Measurements show that, with the same dimensions, the current path length of the antenna of this invention is increased by 30-50%, which reduces the low-frequency cutoff frequency. The smooth curve transition reduces current fluctuations in the high-frequency range, improving high-frequency response.

[0063] Impedance Gradient: The continuous curvature of the cosine curve creates a natural impedance gradient, enabling better broadband impedance matching. By adjusting the A and K parameters, this gradient can be controlled to achieve impedance matching with a VSWR < 4.0 in the 300MHz-3GHz range.

[0064] Partial discharge antennas are categorized as external or internal, depending on their installation method and location. This invention primarily targets internal installations, typically placed inside a transformer or GIS device. Because the GIS or transformer itself is a metal cavity structure, it's close to the discharge source, resulting in a strong signal and high sensitivity. Furthermore, the shielding provided by the transformer casing makes it difficult for external interference signals to reach the internal antenna, resulting in improved interference resistance. Currently, the industry requires retrofitting transformer casings by pre-installing windows filled with insulating media to ensure a tight seal, allowing the signal to escape.

[0065] The present invention also has advantages in terms of planar and miniaturized structure. The spiral antenna is also a partial discharge antenna, but the three-dimensional structure antenna is difficult to be built-in.

[0066] The present invention not only has a planar structure, but also adopts a curved wire design, which is smaller in size and easier to embed.

[0067] A further embodiment is that the omnidirectional radiation characteristic of the broadband Hilbert-like antenna is achieved by symmetrical current distribution, phase center stability, and coordinated operation of the radiation units;

[0068] Symmetrical current distribution: The symmetry of the cosine function curve makes the current of each radiating unit symmetrically distributed, maintaining good omnidirectional characteristics even in the high frequency band.

[0069] Phase center stability: The smooth transition of the curved structure reduces phase center drift in high-frequency bands, which is the key to pattern stability. Actual measurements show that at 3 GHz, the phase center offset of the antenna of this invention is only one-third of that of traditional designs.

[0070] Radiating unit collaboration: The cosine curve units in the multi-level fractal structure work together in different frequency bands. Low frequencies are mainly radiated by large-size units, while high frequencies are dominated by small-size units. This natural frequency division characteristic ensures radiation stability across the entire frequency band.

[0071] Existing Hilbert antennas typically use straight line segments to construct a two-dimensional recursive curve to extend the current path and reduce the antenna footprint. However, due to the numerous right-angle turning points in the structure, the current undergoes a sharp turn between the straight line segments, which can easily form standing waves at the turning points. This leads to uneven current distribution, limiting bandwidth performance and causing current hotspots.

[0072] In contrast, the present invention introduces a microscopic path control mechanism based on the macroscopic path of the Hilbert fractal structure: by replacing each level of recursive line segment with a parameterized cosine function curve, the current can smoothly transition along the path, thereby effectively suppressing standing wave reflections and improving the uniformity of current distribution, thereby significantly expanding the working bandwidth and maintaining good omnidirectional radiation characteristics.

[0073] Unlike existing methods that control the current path by loading gaps, branches, patches, etc., this scheme directly introduces continuous function perturbations in the main path without the need for additional loading structures. The design is simpler, the principle is clearer, and the shape is more regular.

[0074] Furthermore, the introduction of a cosine path effectively increases the equivalent length of the antenna's current path, effectively embedding more resonant paths within a limited space. This increases the number and density of resonant points. By adjusting the period parameter K, the frequency distribution of the resonant points can be precisely controlled, achieving a uniform response from low to high frequencies and improving the antenna's broadband performance and spectral adaptability.

[0075] In terms of manufacturing, the cosine curve has good regularity and continuity. Compared with irregular loading structures, it is more suitable for standardized processing technology and is easy to implement on flexible materials. It has good practical manufacturability and engineering adaptability.

[0076] In summary, while maintaining the miniaturization advantages of traditional fractal antennas, the present invention solves the design limitation of needing to increase the order to expand the bandwidth, and significantly improves problems such as standing wave concentration, current hot spots, and radiation distortion caused by structural mutations (such as sharp corners and inflection points). It is a broadband omnidirectional antenna solution with strong structural innovation, high electrical performance adjustability, and good manufacturing friendliness.

[0077] Example 2

[0078] This embodiment takes an actual designed partial discharge detection antenna as an example:

[0079] Substrate material: FR-4(ε r =4.4, thickness 1.5mm);

[0080] Fractal order: 4th order;

[0081] Overall dimensions: 100mm×100mm;

[0082] Cosine parameters: A=0.5, K=1, line width 0.6mm, copper thickness 0.05mm;

[0083] Feeding mode: 50Ω coaxial feeding;

[0084] Impedance bandwidth: 300MHz-3.0GHz (VSWR<4.0); Figure 7 shown.

[0085] Gain: -32dBi@0.5GHz;

[0086] Figure 8 is the three-dimensional radiation pattern of the broadband Hilbert-like antenna.

[0087] like Figures 9-16 As shown, similar fractal antennas have poor pattern stability over frequency, particularly at high frequencies, prone to splitting and distortion, which impacts detection reliability. The smooth cosine curve of the present invention improves current distribution and reduces phase differences at high frequencies, resulting in a more stable omnidirectional radiation pattern.

[0088] The technical solution of the present invention can also be extended to the following variant designs:

[0089] (1) Dual-polarization version: By arranging two cosine Hilbert antennas orthogonally, dual-polarization reception is achieved, improving detection reliability.

[0090] (2) Array configuration: Multiple units are combined into an array to improve gain while maintaining broadband characteristics, which is suitable for monitoring large equipment.

[0091] (3) Flexible version: It uses a flexible substrate and special curve parameter design to make it into a conformable antenna for partial discharge detection on complex surfaces.

[0092] According to the technical solution of the present invention, the following technical problems are effectively solved:

[0093] 1. Bandwidth limitation: The effective bandwidth of traditional Hilbert antennas and most fractal antennas usually does not exceed 30% of the center frequency, making it difficult to cover the wide spectrum range of partial discharge signals, resulting in incomplete signal acquisition.

[0094] 2. Pattern distortion: As the frequency changes, the pattern stability of existing fractal antennas is poor. In particular, splitting and distortion are prone to occur in high-frequency bands, affecting detection reliability.

[0095] 3. Low design freedom: Adjustments to the structural parameters of traditional fractal antennas (such as the number of iterations and line width) have limited impact on performance, making it difficult to accurately optimize for different application scenarios.

[0096] 4. Fixed current path: The traditional fractal antenna composed of straight segments has limited optimization space for the surface current path, which restricts the improvement of radiation efficiency.

[0097] In summary, the innovation of this invention lies in its organic combination of cosine curves and fractal geometry. Through precise parameterized control, this approach solves the critical challenge of achieving both broadband and omnidirectional characteristics in partial discharge detection antennas. Practical applications have demonstrated the antenna's simple structure and superior performance, demonstrating promising engineering applications.

[0098] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A broadband Hilbert-like antenna for partial discharge detection, characterized in that: The broadband Hilbert-like antenna adopts a fourth-order Hilbert fractal curve as a basic framework, wherein each line segment is realized by a parameterized cosine function curve, so that the surface current path of the broadband Hilbert-like antenna extends in a wavy shape.

2. The broadband Hilbert-like antenna for partial discharge detection according to claim 1, characterized in that: The broadband Hilbert-like antenna covers the partial discharge detection requirements of 300MHz-3GHz.

3. The broadband Hilbert-like antenna for partial discharge detection according to claim 1, characterized in that: The control parameters of the cosine function curve include amplitude and period; The amplitude is used to control the fluctuation amplitude of the cosine function curve, and the optimization range is 0.3-1.5; The period is used to control the fluctuation density of the cosine function curve, and the optimization range is 0.5-2.

0.

4. The broadband Hilbert-like antenna for partial discharge detection according to claim 3, characterized in that: The expression of the cosine function curve is as follows: y(x)=A·cos(2πxK+φ), Among them, A is the amplitude parameter, K is the period parameter, and φ is the phase parameter.

5. The broadband Hilbert-like antenna for partial discharge detection according to claim 1, characterized in that: The broadband characteristics of the broadband Hilbert-like antenna are achieved through multi-resonance point coupling, a current path extending through a wavy line, and an impedance gradient structure; wherein, The curvature change introduced by the cosine function curve generates coupled resonance at multiple frequency points, and the coupled resonance points are overlapped to form a wide-band response.

6. The broadband Hilbert-like antenna for partial discharge detection according to claim 1, characterized in that: The omnidirectional radiation characteristics of the broadband Hilbert-like antenna are achieved by symmetrical current distribution, phase center stability and coordinated operation of radiation units; The symmetry of the cosine function curve enables the current of each radiation unit to be symmetrically distributed.

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