A CPW slot line structure based terahertz broadband high gain Vivaldi antenna

Abstract

The application discloses a terahertz broadband high-gain Vivaldi antenna based on a CPW slot line structure and belongs to the field of terahertz communication. The antenna adopts an integrated single-layer metal structure of a top layer of a dielectric substrate, is divided into a radiation arm and a CPW slot line balun along an axial direction, and the inner side edge of the radiation arm is a smooth exponential change curve; a middle exponential gradual change slot forms a broadband traveling wave radiation channel; the outer side edge is loaded with periodic grid choke slots to suppress edge surface waves and improve a directional diagram; a CPW slot line balun structure is adopted in a feeding part to realize conversion from unbalanced to balanced mode; a broadband virtual short-circuit boundary is formed at a feeding point by using a sector radial branch to ensure unidirectional and high-efficient energy transmission; and a group of "string" type director patches are arranged along a central axis in an exponential gradual change slot opening area to guide a beam by phase correction. The application effectively solves the problems of limited bandwidth and insufficient gain of a terahertz planar antenna, and has the characteristics of compact structure, easy integration and excellent radiation performance.

Description

Technical Field

[0001] This invention belongs to the field of terahertz communication technology, specifically a terahertz broadband high-gain Vivaldi antenna based on a CPW (coplanar waveguide) slotted wire structure. Background Technology

[0002] In 2023, the International Telecommunication Union's Radiocommunication Sector, ITU-R, completed the IMT-2030 Global 6G Vision Framework Recommendation. Terahertz wireless communication needs to meet the demands of new application scenarios such as ubiquitous connectivity, integrated communication and sensing, and artificial intelligence.

[0003] As a core component of the entire communication system, antennas are increasingly being developed towards ultra-wideband, high-gain, and integrated technologies. Compared to other antenna types such as lens antennas, horn antennas, or Cassegrain antennas, Vivaldi antennas offer advantages such as small size and ease of integration.

[0004] As a non-frequency-variable antenna, the Vivaldi antenna has a wider operating bandwidth, better pattern symmetry, and stronger directivity compared to terahertz microstrip patch antennas, thus it has broad application prospects in the terahertz band.

[0005] Traditional Vivaldi antennas use a microstrip slotted wire structure, which is a narrowband feed, thus limiting the overall bandwidth of the antenna; moreover, due to the surface wave effect and the influence of edge current distribution, most Vivaldi antennas have low gain in the terahertz band.

[0006] The traditional Vivaldi antenna was first proposed by PJ Gibson in 1979 and has since been widely used in the millimeter-wave band. However, few works have been proposed for Vivaldi antennas in the terahertz band. Therefore, researching new feeding structures to improve bandwidth and employing appropriate methods to enhance gain is of great significance for the integrated antenna design in the terahertz band. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention proposes a terahertz broadband high-gain Vivaldi antenna based on a CPW (Content-Coplanar Waveguide) slotted wire structure. The impedance bandwidth of the antenna is improved through the balun structure of the coplanar waveguide slotted wire. The radiation pattern is improved and the gain is increased by loading slots of gradually varying lengths onto the radiating arms and adding a "string" type director. This invention features a simple and novel structure, is easy to implement, possesses an ultra-wideband impedance bandwidth, good directivity, and high gain, providing a new solution for integrated on-chip terahertz antennas.

[0008] The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted line structure includes: a dielectric substrate and a CPW slotted line balun structure, radiating arms, and director patches located on the top layer of the dielectric substrate.

[0009] Copper is deposited on the top surface of the dielectric substrate using a metal deposition process; the antenna is divided into two parts along the antenna axis: a radiating arm and a CPW-groove balun structure; the two parts form an integrated conductive structure.

[0010] The radiating arms are two symmetrically etched metal foils; the inner edges of the two radiating arms form smooth exponential curves; the two exponential curves are positioned opposite each other, forming a channel of non-metallic region in the middle, which is called the exponential gradient groove. The width of the exponential gradient groove gradually increases along the antenna axis (set as the y-axis), with the starting end being the feed side and the ending end being the radiating side.

[0011] Furthermore, the parameterized equation expression for the exponentially gradient groove is:

[0012] X(_t)=Wmin / 2*exp(alpha1*L*_t),

[0013] Y(_t) = _t * L;

[0014] Where alpha1 = ln(Wmax / Wmin) / Lr, Wmin is the initial width of the exponential gradient groove, Wmax is the width of the end opening of the exponential gradient groove, and L is the length of the exponential gradient groove.

[0015] At the starting end of the radiating arm, rectangular deep grooves arranged in a comb-like pattern are etched inward along the outer edges of the two radiating arms, forming a grid-structured choke groove. The length of each choke groove gradually decreases from the starting end to the ending end, and a fixed spacing is maintained between the grooves.

[0016] The lower part of the radiating arm extends into a CPW-groove balun structure for unbalanced-to-balanced conversion. This structure is divided into left and right sides, with the center and exponentially tapered groove integrally formed. The left ground plane extends directly upward along the axis, smoothly transitioning to the left radiating arm. The right side is the center signal line of the CPW feed port, serving as the signal feed point connected to an external signal source. The CPW center signal line extends smoothly and connects to the right radiating arm. To the right of the center signal line is a groove line of the same width as the left exponentially tapered groove, with a fan-shaped open-circuit slot at the top of the groove line. The fan-shaped open-circuit slot is symmetrical vertically, with the center of the fan (or the starting neck) located at a vertical distance from the bottom edge of the antenna. The outer radius of the sector groove is ,inner radius Zhang Jiao was This creates a broadband virtual short circuit at the power supply point.

[0017] At the top of the radiating arm, in the exponentially tapered groove region, a set of cascaded floating director patches is positioned along the central axis of symmetry. These patches reside in the same metal layer as the radiating arm but are not electrically connected to it. Each director patch consists of six rectangular metal units. The lateral dimension (width) of each unit is perpendicular to the wave propagation direction, while its longitudinal dimension (height) is parallel to the wave propagation direction. The net spacing between adjacent units is fixed. These units are connected in series along the axis by an extremely fine strip, forming a cascaded array structure resembling a "string."

[0018] The working principle of the terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure is as follows:

[0019] Electromagnetic energy is fed in from the bottom CPW feed port. The electric field lines are mainly distributed vertically between the central signal band and the ground planes on both sides, and the magnetic field lines surround the central conductor. At this time, it is an unbalanced mode.

[0020] As the signal propagates upwards to the CPW transfer slot structure area, according to the impedance transformation principle, this sector-shaped open-circuit slot serves as the open-circuit terminal of the right-side slot line. Based on transmission line theory and the Bessel function impedance formula:

[0021]

[0022] in: This represents the input impedance of the open-circuit sector. The characteristic impedance of the sector open-circuit slot; Represents the imaginary unit; A waveguide beam that represents the propagation of electromagnetic waves on a dielectric substrate; Let represent the zeroth and first order Bessel functions of the first kind, respectively; Let represent the zeroth and first order Bessel functions of the second kind, respectively.

[0023] By designing the outer radius of the sector and inner radius This allows for the provision of virtual short-circuit boundary conditions for the feed point over an extremely wide frequency band, forcing electromagnetic energy to be transmitted unidirectionally upwards. The electric field lines, originally confined to the gaps on both sides of the CPW's central signal line, are "stretched" and reoriented. The electric field vector no longer points towards the ground planes on either side, but instead crosses directly across the gradually widening exponentially tapered slot in the middle, pointing towards the opposite radiating arm; this process forcibly transforms the CPW's unbalanced field into a balanced field within the slot lines.

[0024] After electromagnetic waves are fed into the two radiating arms through exponentially tapered slots, the characteristic impedance of the slot lines rises smoothly as the slot width increases exponentially, achieving impedance matching between the transmission line and the free-space wave. Electromagnetic wave components of different frequencies break free from the metal constraint at positions where the slot width is approximately half the wavelength, transforming from "traveling waves" into "radiated waves" that diffuse outwards. During transmission and radiation, some current tends to flow around to the outer edges of the radiating arms, leading to increased sidelobes. At this point, the choke slots on both sides effectively cut off the surface current at the outer edges, thereby suppressing sidelobe radiation and optimizing the radiation pattern.

[0025] When the electromagnetic wave propagates to the antenna aperture, it couples with the string director patch. Based on the principle of mutual impedance, an induced current is generated on the director patch. The excited element generates an induced current through non-contact excitation via main radiation source and spatial electromagnetic coupling. ;

[0026] in The main radiation source is the equivalent excitation current at the opening of the slot. For the groove line and the first The mutual impedance between individual metal units characterizes the strength of coupling. For the first The self-impedance of each metal unit This represents the mutual impedance between metallic units.

[0027] The excited director patch array forms a secondary radiation source, increasing the total radiation field of the antenna in the far-field region. The total field distribution is calculated by vector superposition of the main channel radiation field and the secondary radiation field of the director patch, according to the principle of mode superposition:

[0028]

[0029] in The free-space wavenumber represents the number of electromagnetic waves propagating through the air. The spacing of the metal units in the director patch. The angle between the far-field observation direction and the antenna tip-fire axis. The inherent radiation characteristics of a single metallic unit; For the first The total phase lag of the current in each metal unit.

[0030] By optimizing the geometry of the director patch to exhibit capacitive reactance characteristics, the generation of the induced current is delayed, thus correcting the wavefront propagation constant. This ensures that, in the end-firing direction, the primary and secondary radiation fields satisfy the Hansen-Woodyard condition.

[0031]

[0032] in The phase difference between adjacent units; 2.94 is the total number of metal units in the director patch; 2.94 is the Hansen-Woodyard constant.

[0033] This condition can effectively cancel out the radiation component in the off-axis direction, further concentrate the energy in the axial direction, and ensure that the synthesized beam has the maximum energy density in the axial direction, thereby significantly compressing the beamwidth, improving the antenna gain, and ultimately forming a highly directional end-fire radiation beam.

[0034] The advantages of the terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure of this invention are as follows:

[0035] 1. This invention proposes a CPW-slot-line balun structure, utilizing a fan-shaped open-circuit slot to achieve a low reflection coefficient transition from CPW to slot line over a wide bandwidth; simultaneously, an exponentially graded slot structure is employed to achieve a smooth transition from transmission line impedance to free-space impedance. The combination of these two features ensures good impedance matching in antenna simulation results within the 350G-800G range, providing an ultra-wide impedance bandwidth.

[0036] 2. This invention suppresses side radiation and improves antenna gain by loading a choke slot with a gradually varying length on the outer edge of the radiating arm;

[0037] 3. This invention optimizes the radiation pattern and further improves the gain by loading a "string" type director patch between the two radiating arms;

[0038] 4. The antenna proposed in this invention adopts a single planar integrated design, which eliminates the need for air bridges or multi-layer interconnection structures, thereby reducing processing costs and process complexity. Attached Figure Description

[0039] Figure 1 This is a perspective view of the terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure of the present invention.

[0040] Figure 2 This is a side view of the terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure of the present invention.

[0041] Figure 3 The curve showing the variation of S11 in the terahertz broadband high-gain Vivaldi antenna proposed in this invention.

[0042] Figure 4 The simulated gain curve of the terahertz broadband high-gain Vivaldi antenna proposed in this invention is shown.

[0043] Figure 5The simulated 3D radiation pattern of the terahertz broadband high-gain Vivaldi antenna proposed in this invention;

[0044] Figure 6 The simulated 2D radiation pattern of the terahertz broadband high-gain Vivaldi antenna proposed in this invention. Detailed Implementation

[0045] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0046] This invention provides a terahertz broadband high-gain Vivaldi antenna based on a CPW swivel line structure, which is particularly suitable for high-speed communication, imaging detection, and other scenarios in the 0.35~0.5THz frequency band. It can be integrated into the front end of a terahertz system to achieve wide-bandwidth, high-radiation-efficiency electromagnetic wave radiation and reception. The CPW swivel line structure proposed in this invention improves input matching and expands bandwidth. Two methods are used: loading multi-layer choke slots on the radiating arm and loading a "string" director, which can improve gain.

[0047] The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure, such as Figure 1 and Figure 2 As shown, it includes: a dielectric substrate and a feed structure, a radiating arm, and a director patch located on the top layer of the dielectric substrate; the feed structure is a CPW-groove balun structure.

[0048] The dielectric substrate is made of polytetrafluoroethylene (PTFE) with a dielectric constant of 2.2, a loss tangent of 0.0009, a length Ls = 2.5 mm, a width Ws = 1.1 mm, and a height Hs = 0.3 mm.

[0049] Copper is deposited on the top surface of the dielectric substrate using a metal deposition process; the antenna is divided into two parts along the antenna axis: a radiating arm and a CPW-groove balun structure; the two parts form an integrated conductive structure.

[0050] The radiating arms consist of two symmetrically etched metal foil sheets. The overall length of the radiating arms is L = 1.92 mm, and the total width is Wmax = 1 mm. The inner edges of the two radiating arms are not straight lines, but rather form smooth exponential curves. These two exponential curves are positioned opposite each other, forming a channel in the middle of a "trumpet-shaped" non-metallic region, i.e., an exponential gradient groove. The width of this exponential gradient groove gradually increases along the antenna axis (set as the y-axis), starting at the feed side with a width of Wmin = 0.06 mm and ending at the radiating side with a width of Wmax = 1 mm.

[0051] Furthermore, the parameterized equation expression for the exponentially gradient groove is:

[0052] X(_t)=Wmin / 2*exp(alpha1*L*_t),

[0053] Y(_t) = _t * L;

[0054] Where alpha1 = ln(Wmax / Wmin) / Lr, Wmin is the initial width of the exponential gradient groove, Wmax is the width of the end opening of the exponential gradient groove, and L is the length of the exponential gradient groove.

[0055] At the starting end of the radiating arm, rectangular deep grooves arranged in a comb-like pattern are etched inward along the outer edges of the two radiating arms, forming a grid-structured choke groove. This is to suppress side currents and optimize radiation characteristics. The width of each choke groove is designed to be Wc1=0.02mm, and the length Lc of the groove gradually decreases from 0.4mm to 0.1mm from bottom to top. The grooves are arranged in a comb-like pattern with a fixed spacing Wc2=0.09mm between them.

[0056] A choke slot is added to the outer edge of the radiating arm to improve current distribution, suppress surface waves at the edge, concentrate energy near the slot line, and reduce energy radiation at the edge of the radiating arm, thereby improving the radiation capability of the exponentially tapered slot and thus increasing antenna gain. The slot direction is perpendicular to the main radiation direction. When current flows along the slot structure, the transverse currents perpendicular to the main radiation direction cancel each other out, while the longitudinal currents parallel to the main radiation direction superimpose each other, reducing the current perpendicular to the main radiation direction.

[0057] The radiating arm is divided into three parts: a rectangular slot section, an exponential curve gradient section, and a rectangular choke section. The rectangular slot section mainly confines energy within the slot line for energy transmission; as the gradient section expands exponentially, the opening width increases, and when the slot line width exceeds half the corresponding wavelength, the energy will break free and radiate outward. The main function of the gradient section is to radiate energy.

[0058] The lower part of the radiating arm extends into a CPW-slotline balun structure to achieve unbalanced-to-balanced conversion; it uses a dielectric substrate as a carrier and contains the CPW input unit and the slotline output unit. During antenna operation, the CPW feeds energy by coupling it to the slotline. The CPW input unit includes a central metallic signal conductor, i.e., the center signal line, and coplanar metallic ground planes located on both sides of the conductor.

[0059] The center of this structure is integrally formed with the exponentially gradient groove, and its width is... The left side extends directly upwards along the axis, smoothly transitioning to the left radial arm. The right side contains the center signal line of the CPW feed port, with a width set to [width value missing]. The CPW serves as the signal feed point, connected to an external signal source. Its center signal line extends smoothly and connects to the right radiating arm. A slot of the same width as the left exponentially tapered slot is positioned to the right of the center signal line, with a fan-shaped open-circuit slot at the top. The fan-shaped open-circuit slot is symmetrical vertically, with its center (or starting neck) located at a vertical distance from the bottom edge of the antenna. The radius of the sector groove is ,inner radius Zhang Jiao was This creates a broadband virtual short circuit at the power supply point.

[0060] Furthermore, the radius of the fan-shaped open slot is one-quarter wavelength, it is symmetrical from top to bottom, and its arc is Π / 4.

[0061] At the top of the exponentially tapered slot region of the radiating arms, a set of cascaded floating director patches are positioned along the central axis of symmetry between the left and right radiating arms. These patches reside in the same metal layer as the radiating arms but are not electrically connected. The director patches begin at the antenna axial coordinate La3 = 1.22 mm (with the bottom of the radiating arm as the reference origin) and extend in the radiation direction. Each director patch consists of six rectangular metal units. The lateral dimension (width Wa1 = 0.08 mm) of each unit is perpendicular to the wave propagation direction; the longitudinal dimension (height La1 = 0.02 mm) is parallel to the wave propagation direction; the net spacing between adjacent units is fixed at La2 = 0.1 mm; and the direction of director extension is parallel to the transmission direction of the slot line. The units are not independently suspended but are connected in series along the axis by an extremely fine strip with a width of Wa2 = 0.008 mm, forming a cascaded array structure resembling a "string". This structure is functionally similar to the direction-guiding element of a Yagi-Uda antenna, which guides and refocuses the electromagnetic waves transmitted to the opening, thereby improving the antenna's gain and directivity in the end-fire direction.

[0062] By adding a director patch, the slot line electric field will couple to both sides of the patch. At high frequencies, radiation is mainly generated by the coupled field between the two arms, which improves off-axis radiation caused by phase difference and enhances the antenna's end-fire capability.

[0063] The working principle of the terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure is as follows:

[0064] Electromagnetic energy is fed in from the bottom CPW feed port. The electric field lines are mainly distributed vertically between the central signal band and the ground planes on both sides, and the magnetic field lines surround the central conductor. At this time, it is an unbalanced mode.

[0065] As the signal propagates upwards to the CPW transfer slot structure area, according to the impedance transformation principle, this sector-shaped open-circuit slot serves as the open-circuit terminal of the right-side slot line. Based on transmission line theory and the Bessel function impedance formula:

[0066]

[0067] in: This represents the input impedance of the open-circuit sector. The characteristic impedance of the sector open-circuit slot; Represents the imaginary unit; A waveguide beam that represents the propagation of electromagnetic waves on a dielectric substrate; These represent the zeroth and first-order Bessel functions of the first kind, respectively; used to describe the radial standing wave distribution in cylindrical coordinates. These represent the zeroth and first-order Bessel functions of the second kind, which, together with the first-order Bessel functions, constitute the complete solution to the radial transmission line equation.

[0068] By designing the outer radius of the sector and inner radius This allows for the provision of virtual short-circuit boundary conditions for the feed point over an extremely wide frequency band, forcing electromagnetic energy to propagate unidirectionally upwards. The electric field lines, originally confined to the gaps on either side of the CPW's central signal line, are "stretched" and reoriented. The electric field vector no longer points towards the ground planes on either side, but instead crosses directly across the gradually widening exponentially tapered slot in the middle, pointing towards the opposite radiating arm. This process forcibly transforms the CPW's unbalanced field into a balanced field within the slot lines.

[0069] After electromagnetic waves are fed into the two radiating arms through exponentially tapered slots, the characteristic impedance of the slot lines rises smoothly as the slot width increases exponentially, achieving impedance matching between the transmission line and the free-space wave. Electromagnetic wave components of different frequencies break free from the metal constraint at positions where the slot width is approximately half the wavelength, transforming from "traveling waves" into "radiated waves" that diffuse outwards. During transmission and radiation, some current tends to flow around to the outer edges of the radiating arms, leading to increased sidelobes. At this point, the choke slots on both sides effectively cut off the surface current at the outer edges, thereby suppressing sidelobe radiation and optimizing the radiation pattern.

[0070] When the electromagnetic wave propagates to the antenna aperture, it couples with the string director patch. Based on the principle of mutual impedance, an induced current is generated on the director patch. The excited element generates an induced current through non-contact excitation via main radiation source and spatial electromagnetic coupling. ;

[0071] in The main radiation source is the equivalent excitation current at the opening of the slot. For the groove line and the first The mutual impedance between individual metal units characterizes the strength of coupling. For the first The self-impedance of each metal unit This represents the mutual impedance between metallic units.

[0072] The excited director patch array forms a secondary radiation source, increasing the total radiation field of the antenna in the far-field region. The total field distribution is calculated by vector superposition of the radiation field from the main channel line and the secondary radiation fields from all directors, according to the principle of mode superposition:

[0073]

[0074] in To represent the free-space wavenumber of electromagnetic waves propagating through the air, The spacing of the metal units in the director patch. The angle between the far-field observation direction and the antenna tip-fire axis. The inherent radiation characteristics of a single metallic unit; For the first The total phase lag of the current in each metal unit.

[0075] By optimizing the geometry of the director patch to exhibit capacitive reactive characteristics, the phase delay of the induced current generation is corrected, and the wavefront propagation constant is adjusted, ensuring that the primary and secondary radiation fields satisfy the Hansen-Woodyard condition in the end-firing direction.

[0076]

[0077] in The phase difference between adjacent units; 6 represents the total number of metal patch cells in the guide array; 2.94 is the Hansen-Woodyard constant.

[0078] This condition can effectively cancel out the radiation component in the off-axis direction, further concentrate the energy in the axial direction, and ensure that the synthesized beam has the maximum energy density in the axial direction, thereby significantly compressing the beamwidth, improving the antenna gain, and ultimately forming a highly directional end-fire radiation beam.

[0079] The Vivaldi antenna described in this invention is fed via a coplanar waveguide (CPW) during operation. External unbalanced signals are converted into balanced signals via a CPW-slot balun transition section. During this process, based on transmission line impedance matching theory, the energy coupling efficiency between the CPW and the slot line is determined by the voltage reflection coefficient. Decide:

[0080]

[0081] in, The characteristic impedance of a coplanar waveguide, The characteristic impedance of the slot line input terminal;

[0082] By optimizing the geometric parameters of the balun structure, the impedance matching condition is satisfied: This couples the signal to the tapered slot channel with extremely low reflection loss; the signal is then transmitted in a balanced mode within the slot channel.

[0083] The inner edge contour curve of the radiating arm follows an exponential gradient function, and its slot width... The following relationship applies to the axial distance y: ;

[0084] in The initial slot width, The gradient rate. This geometry creates a gradient impedance characteristic, causing the slotted line to transmit impedance from the input end... Smooth transition to free space wave impedance at the terminal .

[0085] This smooth impedance transformation mechanism effectively eliminates impedance mismatch in the transmission path, thereby significantly widening the operating bandwidth. According to traveling wave antenna theory, the operating frequency band of this antenna is limited by the geometry of the slot line, and its effective operating frequency range satisfies:

[0086] Where c is the speed of light. The diameter width of the end of the gradient groove line. The effective dielectric constant is defined as the spectral components of different frequencies satisfying the resonance condition and radiating outward at different broadband widths of the slot line.

[0087] When the electromagnetic wave propagates to the antenna aperture, it couples with the "string" type director. Its secondary radiation field and the main radiation field are superimposed in phase in the end-fire direction, which guides the wavefront in phase, improves directivity, and ultimately forms a high-gain directional electromagnetic wave radiation into space.

[0088] like Figure 3 The figure shows a simulation diagram of the antenna S11 parameters proposed in this invention. As can be seen from the figure, in the frequency band of 350G-800G, the S11 of the antenna is always below -10dB, and the return loss can be as low as -37dB, with a relative bandwidth of 78%, which meets the requirements of wideband.

[0089] like Figure 4 The figure shows the gain variation curve of the antenna proposed in this invention. As can be seen from the figure, the gain is greater than 9.5 dBi in the 350G-500G frequency band, greater than 12 dBi in the 400G-460G frequency band, and reaches the highest 13.45 dBi at 400G.

[0090] like Figure 5 The image shows the 3D radiation pattern of the antenna simulation proposed in this invention, which demonstrates the far-field performance of the antenna and shows a gain of 13.45 dBi at the 400 GHz frequency.

[0091] like Figure 6 The image shows the simulated 2D radiation pattern of the antenna proposed in this invention, displaying the E-plane and H-plane radiation patterns of the proposed antenna at 400 GHz. It can be seen that the H-plane radiation pattern is almost omnidirectional, and the E-plane radiation pattern has good directivity, which is consistent with the end-fire characteristics of the antenna.

Claims

1. A terahertz broadband high-gain Vivaldi antenna based on a CPW slotted wire structure, characterized in that, include: The dielectric substrate and the CPW-groove balun structure, radiating arms and director patch located on the top layer of the dielectric substrate; Copper is deposited on the top surface of the dielectric substrate using a metal deposition process. The antenna is divided into two parts along its axis: a radiating arm and a CPW-groove balun structure; the two parts together form an integrated conductive structure. The radiating arms are two symmetrically etched metal foils; the inner edges of the two radiating arms form smooth exponential change curves; the two exponential change curves are set opposite each other, forming a channel of non-metallic region in the middle in the shape of a "trumpet mouth", that is, an exponential gradient groove; rectangular deep grooves arranged in a comb pattern are etched inward along the outer edges of the two radiating arms to form a grid structure choke groove. The lower part of the starting end of the radiating arm extends into a CPW-groove balun structure to achieve unbalanced-balanced conversion; the structure is divided into left and right sides, with the center integrally formed with the exponential gradient groove; The ground plane on the left extends directly upward along the axis and smoothly transitions to the left radiating arm; the center signal line of the CPW feed port on the right serves as the signal feed end and connects to the external signal source; the center signal line of the CPW extends smoothly and connects to the right radiating arm; a slot line with the same width as the left exponential gradient slot is left on the right side of the center signal line, and a fan-shaped open-circuit slot with symmetrical upper and lower sides is left at the top of the slot line to form a broadband virtual short circuit at the feed point; At the top of the radiating arm, in the exponentially gradient groove region, there is a set of cascaded floating director patches along the central axis of symmetry. These patches are located in the same metal layer as the radiating arm, but are not electrically connected to it. The director patch consists of 6 rectangular metal units, which are connected in series along the axis by an extremely fine strip, thus forming a cascaded array structure similar to a "string".

2. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 1, characterized in that, The width of the exponentially tapered slot gradually increases along the antenna axis (y-axis), with the starting end being the feed side and the ending end being the radiation side.

3. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 1 or 2, characterized in that, The parametric equation expression for the exponentially gradient groove is: X(_t)=Wmin / 2*exp(alpha1*L*_t), Y(_t) = _t * L; Where alpha1 = ln(Wmax / Wmin) / Lr, Wmin is the initial width of the exponential gradient groove, Wmax is the width of the end opening of the exponential gradient groove, and L is the length of the exponential gradient groove.

4. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 2, characterized in that, The length of each choke groove gradually decreases from the starting end to the ending end, and a fixed distance is maintained between the grooves.

5. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 1, characterized in that, The center or starting neck of the fan-shaped open slot is located at a vertical distance from the bottom edge of the antenna. The outer radius of the sector groove is ,inner radius Zhang Jiao was .

6. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 1, characterized in that, The lateral dimension (width) of each unit of the director patch is perpendicular to the wave propagation direction; the longitudinal dimension (height) is parallel to the wave propagation direction; and the net spacing between adjacent units is fixed.

7. The terahertz broadband high-gain Vivaldi antenna based on the CPW slotted wire structure as described in claim 1, characterized in that, The Vivaldi antenna works as follows: Electromagnetic energy is fed in from the bottom CPW feed port. The electric field lines are mainly vertically distributed between the central signal line and the ground planes on both sides, and the magnetic field lines surround the central conductor. At this time, it is an unbalanced mode. As the signal propagates upwards to the CPW transfer slot structure area, according to the impedance transformation principle, this sector-shaped open-circuit slot serves as the open-circuit terminal of the right-side slot line. Based on transmission line theory and the Bessel function impedance formula: in: This represents the input impedance of the open-circuit sector. The characteristic impedance of the sector open-circuit slot; Represents the imaginary unit; A waveguide beam that represents the propagation of electromagnetic waves on a dielectric substrate; Let represent the zeroth and first order Bessel functions of the first kind, respectively; These represent the zeroth and first-order Bessel functions of the second kind, respectively; By designing the outer radius of the sector and inner radius It can provide virtual short-circuit boundary conditions for the feed point over an extremely wide frequency band, forcing electromagnetic energy to be transmitted unidirectionally upwards; the electric field lines that were originally confined in the gaps on both sides of the CPW center signal line are "stretched" and reoriented; the electric field vector no longer points to the ground planes on both sides, but directly crosses the exponentially tapered slot that gradually widens in the middle, pointing to the opposite radiation arm; this process forcibly transforms the unbalanced field of the CPW into a balanced field within the slot line; After electromagnetic waves are fed into the two radiating arms through the exponentially tapered slots, the characteristic impedance of the slot lines increases smoothly as the slot width increases exponentially, thus matching the transmission line impedance with the free-space wave impedance. Electromagnetic wave components of different frequencies break free from the metal constraint at a position where the slot width is approximately equal to half its wavelength, transforming from "traveling waves" into "radiating waves" and spreading outward. During transmission and radiation, some current tends to flow around to the outer edge of the radiating arm, resulting in increased side lobes. At this time, the choke slots on both sides effectively cut off the surface current at the outer edge, thereby suppressing side lobe radiation and optimizing the radiation pattern. When the electromagnetic wave propagates to the antenna aperture, it couples with the "string" type director patch. Based on the principle of mutual impedance, an induced current is generated on the director patch. The excited element generates an induced current through non-contact excitation via main radiation source and spatial electromagnetic coupling. ; in The main radiation source is the equivalent excitation current at the opening of the slot. For the groove line and the first The mutual impedance between individual metal units characterizes the strength of coupling. For the first The self-impedance of each metal unit The mutual impedance between metal units; The excited director patch array forms a secondary radiation source, increasing the total radiation field of the antenna in the far-field region. The total field distribution is calculated by vector superposition of the main channel radiation field and the secondary radiation field of the director patch, according to the principle of mode superposition: in The free-space wavenumber represents the number of electromagnetic waves propagating through the air. The spacing of the metal units in the director patch. The angle between the far-field observation direction and the antenna tip-fire axis. The inherent radiation characteristics of a single metallic unit; For the first The total phase lag of the current in each metal unit; By optimizing the geometry of the director patch to exhibit capacitive reactance characteristics, the generation of the induced current is delayed, thus correcting the wavefront propagation constant. This ensures that, in the end-firing direction, the primary and secondary radiation fields satisfy the Hansen-Woodyard condition. in The phase difference between adjacent units; This represents the total number of metal units in the director patch. This condition can effectively cancel out the radiation component in the off-axis direction, further concentrate the energy in the axial direction, and ensure that the synthesized beam has the maximum energy density in the axial direction, thereby significantly compressing the beamwidth, improving the antenna gain, and ultimately forming a highly directional end-fire radiation beam.

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