Vivaldi slotted yagi antenna based on Alzheimer's disease detection

Abstract

The invention belongs to the field of human body Alzheimer's disease detection, and discloses a Vivaldi slotted yagi antenna based on Alzheimer's disease detection, which comprises a dielectric substrate, a radiation oscillator, a director, a floor (metal plate) and a microstrip line, two rectangular radiation oscillators are symmetrically printed on the front surface of the dielectric substrate; the single arm A and the single arm B are respectively positioned on a negative x axis and a positive x axis on the front surface of the dielectric substrate; and the single arm A and the single arm B are sequentially connected with the reflection floor through the impedance conversion section. The microstrip yagi antenna is simple in structure, impedance matching of the antenna can be improved, meanwhile, high-gain transmission can be achieved, and the use scene of the microstrip yagi antenna is expanded.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of human Alzheimer's disease detection technology, and particularly relates to a Vivaldi slotted Yagi antenna based on Alzheimer's disease detection. Background Technology

[0002] With the continuous development of wireless communication technology, the requirements for antenna bandwidth, gain, and size are becoming increasingly stringent. In the antenna field, the Yagi antenna, also known as a directional antenna, has advantages such as simple structure and strong directivity, and is widely used in wireless communication. However, traditional Yagi antennas are typically too bulky. Furthermore, limitations in antenna size and vibrator material prevent them from conformally fitting to the carrier surface. The operating bandwidth of traditional Yagi antennas is also relatively narrow, generally less than 5%. These limitations significantly restrict their use in mobile communication and in many space-constrained environments. Therefore, it is necessary to appropriately improve upon the shortcomings of traditional Yagi antennas while retaining their many advantages.

[0003] Compared to Yagi antennas, microstrip antennas are not only smaller, lighter, and have a lower profile, but they are also easier to integrate, lower in cost, and suitable for mass production. Combining microstrip and Yagi antennas, and giving full play to their respective advantages, allows microstrip Yagi antennas to have broad application prospects.

[0004] A typical microstrip Yagi antenna generally consists of a dielectric substrate, a ground plane, a reflector, a radiating element, and a director. Due to the metal backing of the microstrip antenna, directly combining a microstrip antenna with a Yagi antenna only achieves quasi-end-fire radiation, meaning the maximum radiation direction of the antenna is diagonally above the dielectric substrate (a normal microstrip antenna ground plane consists of the entire lower surface of the dielectric substrate covered with metal; however, this type of ground plane causes the Yagi antenna's radiation pattern to point towards the space slightly above the upper surface of the dielectric substrate, which is something we need to avoid). To solve this problem, a microstrip quasi-Yagi antenna structure is usually used. This structure does not use a traditional reflecting element but instead utilizes the truncated ground plane at the back of the microstrip antenna as a reflector to achieve end-fire radiation. Common microstrip quasi-Yagi antennas use microstrip line feeding, broadband impedance matching through a broadband balun structure, and a 180-degree phase difference between the two arms of the active array, which can provide better signal reception and transmission performance in some cases.

[0005] However, a drawback of this type of microstrip quasi-Yagi antenna structure is its relatively large antenna size printed on the dielectric substrate, and the relatively complex balun structure. Another common microstrip quasi-Yagi antenna has its two arms of the radiating element printed on opposite sides of the dielectric substrate. One arm on the front side is connected to the feed line via a microstrip line, and the other arm on the back side is connected to a truncated ground plane via a microstrip line. Balanced feeding of the radiating element is achieved through the current distribution on the ground plane. Although this scheme eliminates the need for a complex balun structure, its disadvantages include a narrower bandwidth, affecting the antenna's receiving efficiency within a specific frequency range, and its impedance matching performance. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a Vivaldi slotted Yagi antenna based on Alzheimer's disease detection.

[0007] The present invention is implemented as follows: a Vivaldi slotted Yagi antenna based on Alzheimer's disease detection, characterized in that the Vivaldi slotted Yagi antenna based on Alzheimer's disease detection includes a dielectric substrate, radiating elements, a director, a ground plane (metal plate), and a microstrip line; two rectangular radiating elements are symmetrically printed on the front side of the dielectric substrate; these are respectively a single arm A located on the negative x-axis and a single arm B located on the positive x-axis of the front side of the dielectric substrate; the single arms A and B are connected to the reflective ground plane in sequence through an impedance transformation section.

[0008] Furthermore, a director is provided on the front side of the dielectric substrate, the director comprising two parallel director units arranged in a strip shape; the central axis of the director unit coincides with the central axis of the dielectric substrate; and grooves are symmetrically arranged at both ends of each director unit along its central axis in the length direction.

[0009] Furthermore, the number of director units is two sets, with the first director unit being the one closest to the radiating oscillator, and the second director units being the ones closest to the radiating oscillator. The length of the first director unit increases from the first director unit to the second director unit. The length of the first director unit is 12 mm, and the length of the second director unit is 20 mm.

[0010] Furthermore, the distance between the first director unit and the vertex of the radiating oscillator is 6 mm; the distance between the second director unit and the first director unit is 4 mm.

[0011] Furthermore, symmetrically arranged metal vivoldi grooves are provided on both sides of the impedance transformation section on the front side of the dielectric substrate to achieve bandwidth expansion.

[0012] Furthermore, the length e of the single arm A and the single arm B is 0.21 dielectric wavelengths.

[0013] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0014] The broadband microstrip quasi-Yagi antenna provided by this invention eliminates the complex balun structure, featuring a simple and easy-to-implement structure. Simultaneously, the inclusion of a rectangular dipole and director unit enables the antenna to achieve a return loss of over 20dB across the entire frequency band and an impedance bandwidth of 71.52%, significantly higher than that of ordinary microstrip Yagi antennas. The antenna gain exceeds 4.43dBi, achieving broadband microstrip Yagi antenna performance while maintaining high gain.

[0015] The rectangular vibrator of this invention can improve the impedance matching of the antenna by rotating it at a certain angle, thereby achieving high-gain transmission and expanding the application scenarios of the microstrip quasi-Yagi antenna.

[0016] The present invention has two sets of director units, and the length and adjacent spacing of each set are set according to a predetermined size. There is a trade-off between optimizing the working bandwidth and improving the antenna gain, thereby reducing the impact of expanding the working bandwidth on the antenna gain.

[0017] The Vivaldi slot design of this invention serves to expand the bandwidth on both sides of the operating frequency.

[0018] In this invention, the length e of the single arm A and the single arm B is 0.21 times the dielectric wavelength. Under these conditions, the vibration effect of the radiating oscillator is optimal, allowing for more efficient signal radiation or reception.

[0019] Currently, the main diagnostic methods for Alzheimer's disease both domestically and internationally include neuropsychological tests, neuroimaging examinations, blood tests, and electroencephalography (EEG). While these methods have achieved significant success in clinical medicine, they still have considerable limitations. Neuropsychological tests are easily influenced by factors such as education level, cultural background, and socioeconomic status. Neuroimaging examinations, such as MRI and CT scans, can detect and display brain images at different stages of Alzheimer's disease, indicating the presence of Alzheimer's through brain atrophy; PET (Positron Emission Tomography) can reveal the activity level of brain metabolism. However, these imaging methods are expensive and have fixed structures, making them inconvenient for some patients. Blood tests, EEG, and genetic testing are only used as auxiliary methods. Furthermore, in vivo Aβ and tau protein imaging often uses visible light, which cannot penetrate the skull. Therefore, if in vivo detection is desired, an alternative method urgently needs to be developed. Currently, there is no effective treatment for advanced Alzheimer's disease; however, research has found that early detection and diagnosis of Alzheimer's lead to better intervention outcomes. Therefore, finding non-invasive and more accurate detection methods is urgently needed.

[0020] Economic value: Due to the low cost of the equipment, the cost of a single test can be effectively reduced (the cost of a PET scan for amyloidosis is usually around 10,000 yuan and is not covered by medical insurance).

[0021] Clinical value: Due to its portability and ease of manufacture, the device can effectively improve the screening coverage rate of community hospitals.

[0022] There are few studies on early Alzheimer's disease detection from the perspective of Aβ detection. The technical solution of this invention specifically addresses the high gain and bandwidth requirements of Aβ protein detection by designing a Vivaldi slotted Yagi antenna.

[0023] This invention achieves a gain of >5dBi (breaking the Chu limit of 28%) at a maximum size of 0.65λ, compared to only 2.3dBi for traditional patch antennas of the same size. Attached Figure Description

[0024] Figure 1 This is a front view of the antenna model provided in an embodiment of the present invention;

[0025] Figure 2 This is a reverse schematic diagram of the antenna model provided in the embodiment of the present invention;

[0026] Figure 3 This is a simulation diagram of the S-parameters of the antenna provided in an embodiment of the present invention;

[0027] Figure 4 This is a gain simulation diagram of the antenna provided in an embodiment of the present invention;

[0028] Figure 5 This is a 2D radiation effect diagram of the antenna provided in an embodiment of the present invention;

[0029] Figure 6 This is a 3D radiation effect diagram of the antenna provided in an embodiment of the present invention;

[0030] In the diagram: 1. Dielectric substrate; 2. Radiating oscillator; 3. Director; 4. Ground plane (metal plate); 5. Microstrip line. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] like Figure 1-4As shown, this embodiment of the invention provides a Vivaldi slotted Yagi antenna based on Alzheimer's disease detection, which includes a dielectric substrate 1, a radiating element 2, a director 3, a ground plane 4 (metal plate) and a microstrip line 5; a radiating element 2 is printed on the front side of the dielectric substrate 1. The radiating element 2 is the radiating element of the antenna. The excitation element 2 can take various forms, such as rectangular or butterfly shapes.

[0033] Figure 1 The curve segment connected to excitation element 2 is the impedance transformation segment; it does not belong to the excitation element. Only... Figure 2 The part extending upwards from the center is the excitation element. The impedance transformation section and the excitation element 2 together form an L-shaped structure. The rectangular oscillator has a wide side (width denoted by a) and a narrow side (width denoted by b). The narrow side of the rectangular oscillator is connected to the impedance transformation section. In order to reduce reflection, the width of the impedance transformation section is the same as the width of the narrow side of the rectangular oscillator (because if the width of the impedance transformation section changes, there will be more reflection when it is connected to the rectangular oscillator).

[0034] The microstrip line 5 is mounted on the back of the dielectric substrate 1 and connected to the radiating element 2 on the front through solder vias, forming a vertical feed path from bottom to top. The metal ground plane 4 is entirely copper-clad on the back of the substrate, serving as the reference ground for the microstrip line and extending outwards by several millimeters to form an electromagnetic isolation barrier, reducing interference from metal devices on the head. This stacked structure of "microstrip line-substrate-radiating element" ensures a 50Ω reference impedance while allowing the antenna thickness to be controlled at the 1mm level, facilitating its fit to the curved surface of a wearable testing helmet.

[0035] The radiating oscillator 2 is in the form of a rectangular or butterfly plate, with its lower edge (narrow side b) connecting end-to-end with the curved impedance transformation section, forming an L-shaped continuous copper foil. The width of the impedance transformation section is precisely made the same as the narrow side b to eliminate current backflow and additional reflections caused by the step-like width abrupt change at the connection. Along the arc of the impedance transformation section, the characteristic impedance smoothly transitions from 50Ω to the low-impedance region of the radiating plate, and the surface current is uniformly drawn to the outer edge of the radiating plate, ensuring |S| within the 3–10 GHz range. 11 |Stable below -15dB.

[0036] A monolithic director 3 is mounted parallel to the radiating plate at a distance of approximately 0.20λ0 (a quarter wavelength of free space at the center frequency f0) directly in front of its leading edge. This director is printed coplanarly with the radiating plate and maintains the same width longitudinally to form the inductive coupling channel of a classic Yagi array: when the traveling wave radiated by the radiating plate reaches the director, the induced current radiates forward again, superimposing with the main wave to enhance the forward field and suppress backward leakage. Simultaneously, the metal ground plate 4 on the back, spaced approximately 0.065λ0 apart from the radiating plate by a dielectric thickness, provides a mirror current, further enhancing the forward gain and forming unilateral radiation, thereby preventing excessive energy from entering the operator's body during detection.

[0037] At startup, the network analyzer injects sweep pulses via a 5-axis microstrip array; after impedance matching, the energy is emitted from the edge of the gradually expanding slit in a broadband Vivaldi manner, and guided by the director to form a narrow beam that penetrates the skull. The dielectric constant and conductivity of the brain tissue of Alzheimer's patients differ slightly from those of normal individuals. The reflected composite wave is coupled back through the same transceiver converter, causing |S... 11 |、|S 21 Measurable phase and amplitude shifts occur in specific frequency bands. The antenna's low reflection, directional radiation, and tightly mounted multilayer structure work together to ensure that these subtle differences are presented with a high signal-to-noise ratio, providing stable and repeatable bioelectromagnetic feature input for backend machine learning algorithms.

[0038] The antenna has two radiating elements 2, which are the two arms of a rectangular dipole, namely single arm A21 and single arm B22; the two arms are symmetrical along the central axis of the dielectric substrate 1; thus, the length e of single arm A21 and single arm B22 is 0.21 dielectric wavelengths. In this case, the radiating element 2 has the best vibration effect and can more effectively radiate or receive signals. Single arm A21 and single arm B22 are located on the front side of the dielectric substrate 1, and single arm A21 and single arm B22 are connected to the feed line through an impedance transformation section and microstrip line A5.

[0039] The function of the feeder is to transmit high-frequency signals from the signal source to the microstrip line A5, and then to the front radiating oscillator 2. When the high-frequency signal passes through the radiating oscillator 2 (i.e. the front radiating oscillator 2), electrons will move rapidly on the radiating oscillator 2, generating an alternating electromagnetic field. The electromagnetic field around the radiating oscillator 2 radiates outward, forming radio waves.

[0040] The ground plane 4 is disposed on the front side of the dielectric substrate 1 and is connected to the single arm B22 via an impedance transformation section (the ground plane 4 can be connected to the single arm B22 via an impedance transformation section, or via a microstrip line B and an impedance transformation section). The current characteristics on the ground plane 4 are used to achieve phase reversal of the currents in the two arms of the oscillator, and the unbalanced current is choked by adjusting the length of the microstrip line from the ground plane to the excitation.

[0041] Because the antenna has an exponentially tapered structure, the exponentially tapered structure can provide a larger electromagnetic field distribution space, thereby reducing the sensitivity of the resonant frequency to the structural size and thus expanding the operating bandwidth.

[0042] To reduce the impact of increasing the operating bandwidth on antenna gain (specifically, there is a trade-off between increasing the operating bandwidth and improving antenna gain; typically, increasing the operating bandwidth sacrifices some gain), a director 3 is provided on the front side of the dielectric substrate 1. The director 3 includes several parallel strip-shaped director units arranged at intervals in sequence. The central axis of the director unit 3 coincides with the central axis of the dielectric substrate 1.

[0043] A variety of non-invasive tools, methods, and techniques exist for assessing cognitive, motor, and neuropsychiatric symptoms related to neurodegenerative diseases or cognitive decline in older adults. Studies have shown that early detection of neurodegenerative diseases can be achieved by analyzing the concentrations of biomarkers such as circulating cell-free miRNAs, S100B, and IL-6 in the blood. Furthermore, combining subjective reports, neuroimaging, psychophysiological measurements, and kinematic analysis provides new methods and perspectives for the early detection of neurodegenerative diseases. In recent years, the application of machine learning and deep learning technologies has provided new insights into the differential diagnosis of Alzheimer's and Parkinson's diseases and revealed potential features related to gene expression.

[0044] Research on early detection of neurodegenerative diseases from the perspective of microwave medicine is still in its early exploratory stage and has not yet been fully developed. Microwaves, as non-ionizing radiation, have low energy, insufficient to ionize atoms or molecules, thus making them relatively safe for use in the medical field with minimal harm to humans. Microwave medicine utilizes the differences in the electromagnetic properties of different tissues in the microwave frequency band, analyzing these tissues' different responses to incident electromagnetic waves to create images. Because the electromagnetic wave frequency band used is relatively low (mostly concentrated in the 0.3-3 GHz range), medical imaging equipment using microwave technology does not cause ionizing radiation damage to the human body, has low hardware requirements, low cost, and fast imaging speed, making it very suitable for medical monitoring scenarios such as homes, community hospitals, and nursing homes. In the past decade, microwave technology has been applied to routine health monitoring and initial screening for some diseases such as stroke, breast cancer, COVID-19, and bone fractures, with research directions covering multiple fields including antenna design, phantom fabrication, waveform optimization, imaging algorithms, image processing, and clinical trials.

[0045] like Figure 3As shown, this embodiment of the invention exhibits dual-band radiation characteristics, with a -10dB impedance bandwidth covering 2.03-4.29GHz (low-frequency band) and 5.42-5.88GHz (high-frequency band). The calculated relative bandwidth is 71.5%, significantly exceeding the 25% threshold standard defined by the IEEE Antennas and Propagation Society for ultra-wideband (UWB) antennas (see standard ITU-R SM.1755), meeting the requirements of medical testing equipment for wideband signal acquisition. The operating center frequency of this embodiment is 3.11GHz, corresponding to a free-space wavelength of 96mm, while the antenna size is 50mm*62mm*1.6mm, significantly smaller than the corresponding wavelength. Its normalized electrical dimensions are 0.53λ×0.65λ×0.016λ. According to the Chu-Harrington limit theory, a miniaturized design is considered to be achieved when the maximum antenna size is less than 0.7λ; therefore, antenna miniaturization can be considered achieved. Furthermore, as... Figure 4 As shown, the gain is 4.43-5.58 dBi within the bandwidth range, indicating a high antenna gain, thus further realizing a high-gain antenna. Finally, as... Figure 5 As shown, the embodiments of the present invention have good directivity at each frequency point and end-fire characteristics, which meet the system design requirements.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A Vivaldi slotted Yagi antenna based on Alzheimer's disease detection, characterized in that, This includes a dielectric substrate, a radiating oscillator, a reflector ground plane, a director, a microstrip feed line, and an impedance transformation section; Two rectangular radiating oscillators are symmetrically arranged along the center line on the front and back sides of the dielectric substrate, forming a single arm A and a single arm B. The single arm A and single arm B are connected to the reflective ground via the impedance transformation section, and the microstrip feed line is electrically connected to the radiating oscillator. The lengths of the single arm A and the single arm B are 0.21 dielectric wavelengths, and the dielectric wavelengths are converted according to the dielectric constant of the substrate.

2. The antenna as described in claim 1, characterized in that, The dielectric substrate has two director units arranged in parallel along the center line on the front side, and each director unit has grooves symmetrically opened at both ends along its own central axis.

3. The antenna as described in claim 1, characterized in that, The director unit consists of two sets: the first director unit is closer to the radiating oscillator and has a length of 12 mm; the second director unit is farther away from the radiating oscillator and has a length of 20 mm.

4. The antenna as described in claim 1, characterized in that, The distance between the first director unit and the vertex of the radiating oscillator is 6 mm; the distance between the second director unit and the first director unit is 4 mm.

5. The antenna as described in claim 1, characterized in that, Metal Vivaldi slots are symmetrically arranged on both sides of the impedance transformation section to extend the operating bandwidth.

6. The antenna as claimed in claim 1, characterized in that, The length of the reflector floor is greater than the length of the radiating oscillator, and its width covers the total width of the two director units.

7. A microwave detection system for Alzheimer's disease, characterized in that, include: The Vivaldi slotted Yagi antenna as described in any one of claims 1–6; The radio frequency excitation and acquisition unit is used to transmit broadband microwave signals to the antenna in the range of 1 to 10 GHz and acquire reflected and transmitted signals; The signal processing module is used to reconstruct images of the dielectric properties of the subject's brain tissue based on scattering parameters and output Alzheimer's disease risk assessment results.

8. The system as described in claim 7, characterized in that, The antenna array consists of N antennas arranged in a ring to form a phased array. The signal processing module performs synchronous sampling and beamforming on each channel to obtain three-dimensional imaging results.

9. A method for diagnosing Alzheimer's disease using microwave scattering imaging, characterized in that, Includes the following steps: S1 Arranges the antenna or array thereof as described in any one of claims 1–6 around the head of the object under inspection; S2 transmits broadband microwaves in a set frequency band and simultaneously collects the S-parameters of each antenna; S3 inverts the S-parameters to obtain the dielectric constant and loss tangent distribution of brain tissue; S4 performs a differential comparison between the distribution and a baseline database of healthy individuals, and outputs the early abnormal region determination results for Alzheimer's disease.

10. A method for manufacturing a Vivaldi slotted Yagi antenna, characterized in that, Includes the following steps: a. Select a double-sided copper-clad dielectric substrate with a dielectric constant of 4.2–4.7 and cut it to the design size; b. The radiating oscillator, director unit, reflective ground plane and microstrip feed line pattern are formed on the front and back sides of the substrate by photolithography and chemical etching processes; c. Vivaldi grooves are simultaneously milled on both sides of the impedance transformation section using CNC milling; d. Weld a coaxial feed point at the connection between the radiating oscillator and the microstrip feed line; e. Perform surface gold plating and passive intermodulation cleaning to complete antenna fabrication.

Images