An ultra-wideband planar helical antenna for microwave stroke detection

Abstract

The invention discloses an ultra-wideband planar spiral antenna based on microwave stroke detection, and relates to the field of microwave antennas. The type of the ultra-wideband planar spiral antenna is a planar Archimedean spiral antenna; the ultra-wideband planar spiral antenna includes an antenna radiator, a feeding balun and a feeding port; the balanced end of the feeding balun is connected to the antenna radiator; the unbalanced end of the feeding balun is connected to the feeding port; the antenna radiator is an Archimedean spiral line radiator loaded with a dodecagonal fold line, and the radiator is a self-complementary antenna; the self-complementary antenna is an Archimedean spiral antenna of a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap; the Archimedean spiral line radiator loaded with a dodecagonal fold line is a radiator in which each spiral arm of the Archimedean spiral antenna is designed to be a dodecagon as a radiator. The volume of the invention is relatively small, and it can meet the needs of attaching multiple patch antennas to the brain for signal collection, which is more conducive to microwave stroke detection.

Description

Technical Field

[0001] The invention relates to the technical field of microwave antennas, and in particular to an ultra-wideband planar spiral antenna based on microwave stroke detection. Background Art

[0002] When performing microwave imaging of stroke, the characteristics of the received electromagnetic waves will have a great impact on its imaging effect. Since the human brain is a multi-layered complex tissue, when it is close to the head, the head plays both a reflective and an absorbing role. Therefore, how to select the appropriate structure and working frequency will directly affect the effect of stroke detection. In the existing microwave stroke detection (microwave detection of stroke) research, there is no clear regulation on the working frequency of the detection antenna. The detected electromagnetic waves must have both strong penetration and high detection accuracy. If it works in a lower working frequency band, it has higher penetration, but it will also reduce its spatial resolution; at high frequencies, although it can obtain high resolution, it lacks sufficient penetration. Existing research has mainly focused on the frequency range of 0.5-4GHz. Especially in the low-frequency band, the size of the antenna is an important issue. Therefore, the use of low-frequency ultra-wideband antennas is more in line with the needs of microwave detection. Ultra-wideband antennas have the characteristics of miniaturization, circular polarization, light weight, wide bandwidth, and easy conformality. Planar spiral antennas are a common ultra-wideband antenna with extremely high working bandwidth. In the research of microwave detection of cerebral hemorrhage, the antenna performance directly affects the accuracy of cerebral hemorrhage detection results. Ultra-wideband antennas are widely used in communication systems and biomedical detection due to their strong anti-interference ability, high transmission rate, and high precision positioning.

[0003] At present, the existing ultra-wideband antennas used for low frequencies are relatively large in size, and it is difficult to meet the needs of attaching multiple patch antennas to the brain for signal collection, which is not conducive to microwave stroke detection. Summary of the invention

[0004] The purpose of the present invention is to provide an ultra-wideband planar spiral antenna based on microwave stroke detection, which has a relatively small size and can meet the needs of attaching multiple patch antennas to the brain for signal collection, which is more conducive to microwave stroke detection.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] An ultra-wideband planar spiral antenna based on microwave stroke detection, wherein the type of the ultra-wideband planar spiral antenna is a planar Archimedean spiral antenna; the ultra-wideband planar spiral antenna comprises an antenna radiator, a feeding balun and a feeding port;

[0007] The balanced end of the feed balun is connected to the antenna radiator; the unbalanced end of the feed balun is connected to the feed port;

[0008] The antenna radiator is an Archimedean spiral radiator loaded with a dodecagonal zigzag line; the Archimedean spiral radiator loaded with a dodecagonal zigzag line is a self-complementary antenna; the self-complementary antenna is an Archimedean spiral antenna with a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap; the Archimedean spiral radiator loaded with a dodecagonal zigzag line is an Archimedean spiral antenna in which each spiral arm is designed to be a dodecagon as a radiator.

[0009] Optionally, the ultra-wideband planar helical antenna further includes a dielectric substrate;

[0010] The Archimedean spiral radiator loaded with a dodecagonal fold line is supported by the dielectric substrate;

[0011] The balanced end of the feeding balun passes through the dielectric substrate and is connected to the Archimedean spiral radiator loaded with the dodecagonal fold line.

[0012] Optionally, the dielectric substrate is in a rectangular shape.

[0013] Optionally, the thickness of the dielectric substrate is 0.5 mm.

[0014] Optionally, the dielectric substrate is made of epoxy glass fiber board.

[0015] Optionally, the dielectric constant of the dielectric substrate is 4.4.

[0016] Optionally, the material of the dodecagonal fold line loaded Archimedean spiral radiator is an ideal electrical conductor.

[0017] Optionally, the unbalanced end of the feed balun is provided with a waveguide port;

[0018] The unbalanced end of the feed balun is connected to the feed port through the waveguide port.

[0019] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] The invention discloses an ultra-wideband planar spiral antenna based on microwave stroke detection, the antenna type of which is a planar Archimedean spiral antenna, and the antenna radiator thereof adopts an Archimedean spiral antenna of a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap. The Archimedean spiral antenna, due to its characteristics, well compensates for the defect that "the existing ultra-wideband antennas applied to low frequencies are relatively large in size, and it is difficult to meet the requirement of attaching multiple patch antennas to the brain for signal collection", and can meet the requirement of attaching multiple patch antennas to the brain for signal collection; at the same time, by designing each spiral arm of the Archimedean spiral antenna into a dodecagonal form as a radiator, a dodecagonal fold line loaded Archimedean spiral line radiator is formed, and the dodecagonal fold line loaded Archimedean spiral line radiator is adopted as the antenna radiator, so that the planar structure is further reduced, the volume is relatively small, the current path is significantly increased, and the antenna resonance frequency is further reduced, which is more conducive to microwave stroke detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative labor.

[0022] Figure 1 It is a structural diagram of an embodiment of an ultra-wideband planar helical antenna for microwave stroke detection according to the present invention;

[0023] Figure 2 The present invention is a flowchart of the specific steps of designing an ultra-wideband planar spiral antenna based on microwave stroke detection;

[0024] Figure 3 A schematic diagram of an Archimedean spiral loaded with a dodecagonal fold line according to the present invention;

[0025] Figure 4 Schematic diagram of the starting radius of the ultra-wideband planar helical antenna based on microwave stroke detection of the present invention;

[0026] Figure 5 It is a schematic diagram of the outer radius of the ultra-wideband planar spiral antenna based on microwave stroke detection of the present invention;

[0027] Figure 6 This is a schematic diagram of the modeling of the ultra-wideband planar spiral antenna balun structure based on microwave stroke detection of the present invention;

[0028] Figure 7 This is a schematic diagram of the front structural dimensions of the balun structure of the present invention;

[0029] Figure 8This is a schematic diagram of the reverse structural dimensions of the balun structure of the present invention;

[0030] Fig. 9 It is a structural diagram of the balun structure of the present invention after being connected to the antenna radiator;

[0031] Fig.10 The return loss curve diagram of the balun structure and the whole antenna of the present invention;

[0032] Fig.11 The balun structure and the voltage standing wave ratio curve of the antenna of the present invention are shown in FIG.

[0033] Fig.12 The balun structure and the antenna gain curve of the present invention are shown in FIG.

[0034] Fig.13 It is the directional pattern measured at intervals of 0.5 GHz in the frequency band of 0.8 GHz to 9.2 GHz of the present invention;

[0035] Fig.14 This is a schematic diagram of attaching an antenna to a brain model to simulate stroke detection in CST in the present invention;

[0036] Fig.15 This is a diagram of the antenna structure model established in CST according to the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide an ultra-wideband planar spiral antenna based on microwave stroke detection, which has a relatively small size and can meet the needs of attaching multiple patch antennas to the brain for signal collection, which is more conducive to microwave stroke detection.

[0039] 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.

[0040] Figure 1 FIG. 1 is a structural diagram of an embodiment of an ultra-wideband planar helical antenna for microwave stroke detection according to the present invention. Figure 1As shown, this embodiment provides an ultra-wideband planar spiral antenna based on microwave stroke detection, and the type of the ultra-wideband planar spiral antenna (ultra-wideband planar spiral antenna based on microwave stroke detection) is a planar Archimedean spiral antenna; the ultra-wideband planar spiral antenna includes an antenna radiator 101, a feeding balun 102 and a feeding port (not shown in the figure).

[0041] The balanced end of the feed balun 102 is connected to the antenna radiator 101; the unbalanced end of the feed balun 102 is connected to the feed port. The unbalanced end of the feed balun 102 is provided with a waveguide port; the unbalanced end of the feed balun 102 is connected to the feed port through the waveguide port.

[0042] Antenna radiator 101 is a dodecagonal zigzag-line loaded Archimedean spiral radiator; the dodecagonal zigzag-line loaded Archimedean spiral radiator is a self-complementary antenna; the self-complementary antenna is an Archimedean spiral antenna with a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap; the dodecagonal zigzag-line loaded Archimedean spiral radiator is an Archimedean spiral antenna in which each spiral arm is designed to be a dodecagon as a radiator.

[0043] The ultra-wideband planar helical antenna also includes a dielectric substrate 103; the Archimedean helical radiator loaded with a dodecagonal zigzag line is supported by the dielectric substrate 103; and the balanced end of the feed balun 102 passes through the dielectric substrate 103 and is connected to the Archimedean helical radiator loaded with a dodecagonal zigzag line.

[0044] In this embodiment, the material of the dodecagonal fold line loaded Archimedean spiral radiator is a perfect electric conductor (PEC), the dielectric substrate 103 is made of epoxy glass fiber board, the shape of the dielectric substrate 103 is rectangular, the thickness of the dielectric substrate 103 is 0.5 mm, and the dielectric constant of the dielectric substrate 103 is 4.4.

[0045] The ultra-wideband planar helical antenna based on microwave stroke detection provided by this embodiment is specifically introduced below:

[0046] Figure 2 The specific flow chart of the design steps of the ultra-wideband planar spiral antenna based on microwave stroke detection of the present invention is as follows: Figure 2 The design process of the ultra-wideband planar spiral antenna based on microwave stroke detection provided in this embodiment is as follows:

[0047] For the study of microwave detection of cerebral hemorrhage, based on the results of previous studies, we first determined the specific technical indicators of the antenna, selected the appropriate antenna type, used CST STUDIO SUITE (CST) to design the antenna structure, optimized its performance, and finally determined its structural shape and size.

[0048] Step 1: The specific technical indicators of the reserved antenna are:

[0049] (1) Operating frequency range: 1 to 9 GHz;

[0050] (2) Gain in the entire band: 3~4dBi;

[0051] (3) Standing wave ratio in the whole band: ≤2;

[0052] (4) Antenna size: ≤7cm×7cm;

[0053] Step 2: Determine the antenna type as a planar Archimedean spiral antenna. The main structure of a complete planar Archimedean spiral antenna includes: antenna radiator, feed balun and feed port.

[0054] (1) Determine radiator parameters

[0055] The antenna's operating frequency is 1 to 9 GHz, and its minimum wavelength is λ min =33.33mm, the maximum wavelength is λ max =300mm. The inner and outer diameters of the Archimedean spiral antenna and the minimum wavelength λ of the design frequency min and maximum wavelength λ max The relationship between the two equations, that is, formula (1) and formula (2), shows that the starting radius is r0≤λ min / 8=4.166mm. Among them, r0 and R are the starting radius and outer radius of the antenna respectively.

[0056] 2r0≤0.25λ min (1)

[0057] C=2πR≥1.25λ max (2)

[0058] From formula (2), we can know that R≥1.25λ max / 2π=59.71mm. However, considering the convenience of using the instrument for actual stroke detection, the size of the antenna should be smaller, and the influence of the welding point of the radiator (antenna radiator) and the balun (feed balun) on the high-frequency radiation performance should be minimized. Here, the traditional Archimedean spiral is used as a radiator, and the Archimedean spiral loaded with a dodecagonal fold line is used instead. The Archimedean spiral loaded with a dodecagonal fold line is to design each spiral arm of the Archimedean spiral antenna into a dodecagonal form, such as Figure 3The figure shows the schematic diagram of the Archimedean spiral loaded by the dodecagonal broken line. Figure 3 The hollow spiral is a left-handed dodecagonal line loaded Archimedean spiral, and the solid spiral is a right-handed dodecagonal line loaded Archimedean spiral. Each spiral arm rotates n = 14 times. The final selection of r0 = 1mm, R = 29.5mm, such as Figure 4 and Figure 5 The Archimedean spiral radiator loaded with a dodecagonal fold line is a self-complementary antenna, and the spiral arm line width w = 0.5 mm. At this time, the width of the spiral arm is equal to the width of the air gap.

[0059] (2) Feed balun structure

[0060] In order to achieve impedance matching between the coaxial line and the radiator and conversion from unbalanced signal to balanced signal, a feed balun is introduced between the radiator and the feed line. The microstrip transmission line adopts a gradual transition, that is, an infinite number of step-type impedance transformers are added, and the length of each transformer will be infinitely small. Use CST software to model the antenna balun structure. Figure 6 As shown, the upper part is the front structure of the balun, and the lower part is the back structure of the balun. Figure 7 and Figure 8 As shown, the end of the balun structure connected to the radiator is the balanced end, and the end connected to the feeding port is the unbalanced end.

[0061] (3) Antenna whole device simulation

[0062] CST software is used to model the antenna balun structure and antenna radiator integration. The dielectric substrate of the radiator is composed of a 65mm×65mm×1mm rectangle. Considering the design cost and other issues, the dielectric board (dielectric substrate) is made of FR-4 (epoxy glass fiber board) with a dielectric constant of 4.4; Fig. 9 The structure diagram of the balun structure after being connected to the antenna radiator. The balanced end of the balun is connected to the two arms (spiral arms) of the radiator respectively, and a waveguide port is set at the unbalanced end. The return loss curve, voltage standing wave ratio curve and gain curve of the balun structure and the antenna are shown in the figure. Fig.10 , Fig.11 and Fig.12 shown.

[0063] In the case of 0.8GHz~9.2GHz, most of the return loss is less than -10dB, and the standing wave ratio is less than 2. The gain is greater than 2.5dBi after 1.5GHz. At the same time, the directional pattern measured at intervals of 0.5GHz in the frequency band of 0.8GHz~9.2GHz was tested, such as Fig.13 shown.

[0064] (4) Attaching antennas to brain models in CST to simulate stroke detection

[0065] like Fig.14 As shown, five planar helical antennas designed by the present invention are attached around the brain model.

[0066] Through the above-mentioned design process of the ultra-wideband planar spiral antenna applied to microwave stroke detection, the overall structure of the ultra-wideband planar spiral antenna based on microwave stroke detection of the present invention is obtained. The ultra-wideband planar spiral antenna based on stroke detection of the present invention uses an Archimedean spiral loaded with a dodecagonal zigzag line as a radiator. The radiator material is an ideal conductor, and the radiator is supported by a 65mm×65mm×1mm rectangular dielectric substrate. Considering the design cost and other issues, the dielectric board is made of FR-4 material with a dielectric constant of 4.4. Both sides of the feeding balun structure are attached to a dielectric substrate made of epoxy glass fiber board (FR-4) with a thickness of 0.5mm, and the dielectric constant is 4.4. The feeding balun structure is connected to the balanced end of the radiator, and the Archimedean spiral loaded with the left-handed dodecagonal zigzag line and the Archimedean spiral loaded with the right-handed dodecagonal zigzag line are connected. The model of its antenna structure established in CST is as follows: Fig.15 shown.

[0067] Compared with the prior art, the advantages of the present invention are:

[0068] The existing ultra-wideband antennas used for low frequencies are relatively large in size, and it is difficult to meet the needs of attaching multiple patch antennas to the brain for signal collection. The ultra-wideband planar spiral antenna for microwave stroke detection of the present invention has an antenna type of planar Archimedean spiral antenna, and its antenna radiator adopts an Archimedean spiral antenna of a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap. The Archimedean spiral antenna makes up for the defect that "the existing ultra-wideband antennas used for low frequencies are relatively large in size, and it is difficult to meet the needs of attaching multiple patch antennas to the brain for signal collection" due to its characteristics. In addition, the Archimedean spiral radiator loaded with a dodecagonal fold line mentioned in the design of the present invention further reduces the planar structure, significantly increases the current path, and further reduces the antenna resonant frequency, which is more conducive to the use in the stroke detection system.

[0069] At the same time, the Archimedean spiral antenna loaded with a dodecagonal zigzag line mentioned in the design of the present invention has most of its return losses lower than -10dB at 0.8GHz to 9.2GHz, which is better than the return loss performance of many antennas for stroke detection.

[0070] The ultra-wideband planar spiral antenna based on microwave stroke detection of the present invention can achieve the purpose of miniaturization of the antenna. Although other modeling methods that increase the current path can be used to achieve the purpose of miniaturization of the antenna, such as slotting, folding, power divider and other methods, their cost is relatively high. At the same time, the increased thickness is not conducive to the use of stroke system detection, and it is difficult to implement and has little significance. The ultra-wideband planar spiral antenna based on microwave stroke detection of the present invention has low cost, is conducive to the use of stroke system detection, and is simple to implement, which is of great significance to microwave stroke detection.

[0071] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0072] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An ultra-wideband planar helical antenna based on microwave stroke detection, characterized in that: The type of the ultra-wideband planar spiral antenna is a planar Archimedean spiral antenna; the ultra-wideband planar spiral antenna includes an antenna radiator, a feeding balun and a feeding port; The balanced end of the feed balun is connected to the antenna radiator; the unbalanced end of the feed balun is connected to the feed port; The antenna radiator is an Archimedean spiral radiator loaded with a dodecagonal zigzag line; the Archimedean spiral radiator loaded with a dodecagonal zigzag line is a self-complementary antenna; the self-complementary antenna is an Archimedean spiral antenna of a self-complementary structure in which the width of the spiral arm is equal to the width of the air gap; the spiral arm line width w=0.5mm; the Archimedean spiral radiator loaded with a dodecagonal zigzag line is a radiator in which each spiral arm of the Archimedean spiral antenna is designed in the form of a dodecagon; the number of rotations of each spiral arm n=14 circles; the starting radius r0 of the antenna is 1mm, and the outer radius R of the antenna is 29.5mm; in order to achieve impedance matching between the coaxial line and the radiator and conversion from unbalanced signal to balanced signal, a feed balun is introduced between the radiator and the feed line; the microstrip transmission line adopts a gradual transition, that is, an infinite number of step-type impedance transformers are added, and the length of each transformer will also be infinitely small; the antenna balun structure is modeled using CST software; The ultra-wideband planar helical antenna also includes a dielectric substrate; The Archimedean spiral radiator loaded with a dodecagonal fold line is supported by the dielectric substrate; The balanced end of the feed balun passes through the dielectric substrate and is connected to the Archimedean spiral radiator loaded with the dodecagonal fold line; The dielectric substrate is in a rectangular shape; The thickness of the dielectric substrate is 0.5 mm; The dielectric substrate is made of epoxy glass fiber board; The dielectric constant of the dielectric substrate is 4.4; The material of the Archimedean spiral radiator loaded with the dodecagonal fold line is an ideal electrical conductor; The unbalanced end of the feed balun is provided with a waveguide port; The unbalanced end of the feed balun is connected to the feed port through the waveguide port.

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