CN204011692U - A kind of broadband high-efficiency high directivity electronically small antenna - Google Patents

Abstract

The utility model relates to a broadband, high-efficiency, and high-directional electric small antenna, which belongs to the technical field of antennas. The antenna includes an excitation unit, an upper parasitic unit, a lower parasitic unit, two thin cylindrical dielectric plates, and a coaxial feeder; the two thin cylindrical dielectric plates have the same radius, are center aligned, and are placed in parallel up and down; the excitation unit, the upper parasitic unit They are respectively arranged on the bottom and top surfaces of the upper thin cylindrical dielectric board, and the lower parasitic unit is arranged on the top surface of the lower thin cylindrical dielectric board; the inner and outer conductors of the coaxial feeder are respectively connected to the two metal sheets of the excitation unit; the coaxial feeder The feed end passes through the lower thin cylindrical dielectric plate and extends to its lower side for a certain distance, and connects with the 50Ω signal source. The antenna has a simple design, a compact structure, and is easy to manufacture, and can be applied to a broadband wireless communication system with an operating frequency near 1 GHz.

Description

A Broadband High Efficiency High Directivity Electrically Small Antenna

technical field

The utility model belongs to the technical field of antennas and relates to a broadband, high-efficiency, and high-directivity electric small antenna.

Background technique

As wireless communication radio frequency front-end equipment continues to advance towards miniaturization, compactness, integration, and multi-function, more and more stringent requirements are put forward for the design of electrically small antennas. In recent years, with the continuous deepening of research, antenna workers try to reduce the overall electrical size of the antenna as much as possible, so as to reach the limit level of physical structure design, and maintain good radiation performance, and have achieved certain research results. First of all, in terms of antenna miniaturization and multi-functional design, currently more popular technologies include: improvement and optimization of its own physical structure, such as slotting and bending antenna; loading technology, such as loading capacitive or inductive elements on the antenna unit ; use artificial electromagnetic metamaterial structures as near-field parasitic resonant units, such as negative dielectric constant dielectric materials, near-field parasitic resonators, etc.; reconfigurable technology, such as expanding the antenna by loading PIN switches, varactor diodes and other lumped components The frequency range used. Secondly, in terms of improving the directional radiation performance of the antenna, such as directivity, gain, efficiency, front-to-back ratio, etc., the technologies currently used include: by constructing a Huygens source composed of basic electric dipoles and magnetic dipoles ; Load capacitive or inductive distribution elements in the near-field region of the excitation unit; integrate resonant reflectors with electromagnetic bandgap structures and grounding plates in other structural forms, etc.

Essentially, according to the design theory of electrically small antennas, the performance indicators of electrically small antennas such as electrical size, efficiency, and operating bandwidth are mutually restricted, making them face design limits in actual research and development, as described in the "Chu limit" theory. It can be seen that the design of an antenna that is electrically small, broadband, high-efficiency, and directional radiation is extremely challenging. It can be seen that its successful design has very important application value in practical engineering applications.

Utility model content

In view of this, the purpose of the present invention is to provide a broadband, high-efficiency, high-directivity electrically small antenna, which can meet the requirements of broadband and high gain on the premise of a small electrical size of the antenna.

In order to achieve the above object, the utility model provides the following technical solutions:

A broadband, high-efficiency, and high-directional electric small antenna, the antenna includes an excitation unit, an upper parasitic unit, a lower parasitic unit, two thin cylindrical dielectric plates, and a coaxial feeder; the two thin cylindrical dielectric plates have the same radius, and the center The excitation unit and the upper parasitic unit are respectively arranged on the bottom and top surfaces of the upper thin cylindrical dielectric board, and the lower parasitic unit is arranged on the top surface of the lower thin cylindrical dielectric board; the inner and outer conductors of the coaxial feeder are respectively connected to The two metal sheets of the excitation unit; the feed end of the coaxial feeder passes through the lower thin cylindrical dielectric plate and extends to its lower side for a distance, and connects with the 50Ω signal source. Such a long coaxial feeder is designed to consider the existence of The influence of the feeder in the near field of the antenna system on the overall performance of the antenna.

Further, the metal sheet of the excitation unit forms a tomahawk shape, and the tomahawk-shaped metal sheet is composed of a straight metal arm connected to two arc-shaped metal sheets, one of the two metal sheets is connected to the inner conductor of the coaxial feeder, and the other side is connected to the inner conductor of the coaxial feeder. The symmetrically arranged metal sheets are connected to the outer conductor of the coaxial feeder.

Further, the upper parasitic unit is formed by merging two tomahawk-shaped metal sheets, and has a strip-shaped metal arm connecting the two arc-shaped metal sheets at the top. When excited, it is coupled with the tomahawk-shaped excitation unit on the bottom surface to realize LC resonance , resulting in a resonance mode. The form of the radiation field synthesized by the upper parasitic unit and the tomahawk-shaped excitation unit is similar to that of the traditional electric dipole, and the two form a tomahawk-shaped electric dipole.

Further, the center of the lower parasitic unit is an annular metal sheet, and the two sides of the annular metal sheet are connected to a tomahawk-shaped metal sheet formed by a combination of a straight metal arm and an arc-shaped metal sheet, and the annular metal sheet is not in contact with the coaxial feeder; The parasitic unit loaded with this structure has the function similar to the Yagi antenna reflector, so that the total radiation field of the electric small antenna is directed upward, so as to facilitate the good realization of the side-fire characteristics. The LC resonance occurs between the lower parasitic unit, the tomahawk-shaped excitation unit and the upper parasitic unit, and a new adjacent resonance mode is generated, thereby further broadening the working frequency band of the antenna.

Further, the material of the upper and lower thin cylindrical dielectric plates is Rogers Duroid6010, the dielectric constant is 10.2, the relative magnetic permeability is 1.0, the loss tangent angle value is 0.0023, the radius is 30-34mm, and the thickness is 1.20-1.33mm. The thickness of copper is 0.016-0.019mm. The distance between the centers of the two dielectric boards is 27-30mm.

Further, the width of the two tomahawk-shaped metal arms of the excitation unit is 2.56-2.83mm, the length of the arms is 19-21mm, the outer radius of the arc part is 25-27mm, the arc width is 5.5-6.5mm, and the gap between the two arcs is 31- 33mm.

Further, the middle metal arm width of the upper parasitic unit is 4.1-4.7mm, the arm length is 47-49mm, the top arc outer radius is 31-33mm, the arc width is 7.5-8.5mm, and the gap between the two arcs is 31-33mm.

Further, the inner radius of the annular metal sheet in the center of the lower parasitic unit is 2.4-2.7mm, the outer radius is 5.3-5.9mm, the length of the straight metal sheet is 17.5-19.5mm, the width is 3.5-6.9mm, and the outer radius of the top arc is It is 31-33mm, the width is 7.5-8.5mm, and the gap between the two arcs is 27-30mm.

Further, the inner conductor of the coaxial feeder is in the shape of a solid cylinder with a radius of 0.5-0.7mm and a length of 50-55mm, and the outer conductor is in the shape of a thin-walled hollow cylinder with a radius of 1.5-1.7mm and a length of 50-55mm. An insulating layer is filled between the conductors to meet the characteristic impedance of 50 ohms; half of the outer conductor of the coaxial feeder between the upper and lower thin cylindrical dielectric plates is cut off.

The beneficial effects of the utility model are: in the technical scheme, the coaxial feeder is directly connected to the tomahawk-shaped excitation unit, so that the size of the excitation part is small so as to be well matched with the 50Ω signal source; the tomahawk-shaped excitation unit and the upper parasitic unit form a battle The form of the ax-shaped electric dipole approximates the excited unit of the Yagi antenna, and the coupling resonance between them makes the antenna have high radiation efficiency while maintaining an electrically small size. The tomahawk-shaped lower parasitic unit is designed to form the reflector of the Yagi antenna, so that the general radiation direction of the antenna is directly above the antenna, and the directivity of the antenna is improved. At the same time, the working frequency bands of the upper parasitic unit and the lower parasitic unit overlap each other, which obviously expands the working bandwidth of the antenna. The antenna provided by the invention is simple in design, compact in structure and easy to manufacture, and can be applied to a broadband wireless communication system with an operating frequency near 1 GHz.

Description of drawings

In order to make the purpose, technical solutions and beneficial effects of the utility model clearer, the utility model provides the following drawings for illustration:

Fig. 1 is the overall structural diagram of electric small antenna described in the utility model;

Fig. 2 is the front view of the electric small antenna described in the utility model;

Fig. 3 is the plan view of electric small antenna described in the utility model;

Fig. 4 is the side view of electric small antenna described in the utility model;

Fig. 5 is the S parameter curve diagram of simulating the electric small antenna described in the utility model;

Fig. 6 is the E-plane radiation field pattern of simulation electric small antenna described in the utility model;

Fig. 7 is the H plane radiation field pattern of simulating the electric small antenna described in the utility model;

In the figure, 1 is the upper thin cylindrical dielectric plate, 2 is the lower thin cylindrical dielectric plate, 3 is the inner conductor of the coaxial transmission line, 4 is the outer conductor of the coaxial transmission line, 5 is the upper parasitic unit, 6 is the excitation unit, and 7 is the Tomahawk-shaped metal sheet metal arm part, 8 is the lower parasitic unit, and 9 is the ring part in the lower parasitic unit.

Detailed ways

The preferred embodiments of the present utility model will be described in detail below in conjunction with the accompanying drawings.

The overall structure diagram, front view, top view, and side view of the broadband, high-efficiency, and high-directivity electric small antenna described in the utility model are shown in Fig. 1, Fig. 2, Fig. 3, and Fig. 4, respectively. The antenna includes an excitation unit 6 , an upper parasitic unit 5 , a lower parasitic unit 8 , an upper thin cylindrical dielectric plate 1 , a lower thin cylindrical dielectric plate 2 , a coaxial feeder inner conductor 3 , and a coaxial feeder outer conductor 4 . The thickness of the two thin cylindrical dielectric plates is denoted as H1, the material Rogers Duroid6010 is used, the dielectric constant is 10.2, the relative magnetic permeability is 1.0, and the loss tangent is 0.0023. The metal sheets of the excitation unit, the upper parasitic unit and the lower parasitic unit have the same thickness. The optimal size of the antenna obtained by simulation is shown in Table 1, and the electrical size of the composed electric small antenna is small, ka=0.696 (where k=2л/λ _r , k represents the wave number in free space, and λ _r is the resonant frequency f _r =0.94 free-space wavelength at GHz, a is the minimum radius of the sphere surrounding the entire antenna).

The excitation unit 6 is composed of symmetrically placed tomahawk-shaped metal sheets. Its position and structure are shown in FIG. 1 and FIG. The metal arm 7 in the middle of the tomahawk-shaped metal sheet has a length of L1 and a width of W1. The outer radius of the metal arc-shaped structure connected to its top is R1, its width is W2, and the gap between two arcs is L2. The outer conductor 4 of the coaxial feeder is connected to the left tomahawk-shaped metal sheet, and the inner conductor 3 is connected to the right tomahawk-shaped metal sheet. When the antenna is fed, the left and right tomahawk-shaped metal pieces are excited at the same time, generating surface excitation current and generating a radiation field. The two tomahawk-shaped metal sheets have a symmetrical structure, and the middle metal arms are not connected but separated by a gap, which is equivalent to a capacitor in the antenna equivalent circuit analysis, and realizes LC resonance with the loaded inductive unit. The structure of the tomahawk-shaped excitation unit is relatively compact, and the parasitic unit coupled with it also has a compact structure, so that the electrical size of the entire antenna is small, which is beneficial to ensure the miniaturization of the antenna design.

The structure of the upper parasitic unit 5 is shown in Fig. 1 and Fig. 3. It is located on the top surface of the upper dielectric board 1 and is composed of two tomahawk-shaped metal sheets. The middle metal arm has a length of L3 and a width of W3. The outer radius of the arc is R2, and the gap between the two arcs is L4. The upper parasitic unit produces coupled resonance in the near field of the excitation unit. Theoretically, the unit loading can be equivalent to introducing a negative dielectric constant dielectric covering around the antenna to achieve miniaturization, high efficiency, and good matching of the antenna. When the signal source is excited, the arc-shaped metal part of the upper parasitic unit is inductive in the equivalent circuit, and the gap part of the middle straight metal arm is capacitive, and the capacitive tomahawk-shaped excitation unit on the bottom surface realizes the LC resonance mode at low frequencies. Produces an efficient radiation field. The upper parasitic unit and the tomahawk-shaped excitation unit are similar in shape, very close to each other and have good impedance matching. When the tomahawk-shaped excitation unit is excited by near-field coupling, a strong induced current is generated on the middle metal arm of the upper parasitic unit, and its amplitude is larger than the current on the tomahawk-shaped excitation unit, which is the main radiation unit of the designed electric small antenna . The upper parasitic unit is very close to the excitation source, and the two form a tomahawk-shaped electric dipole, and the generated radiation field is similar to the electric dipole radiation field, and acts as a stimulated unit in the equivalent Yagi antenna . The upper parasitic unit, the tomahawk-shaped excitation unit, and the lower parasitic unit are coupled to each other, and together with the coaxial feeder, they match the 50Ω signal source.

The structure of the lower parasitic unit 8 is shown in FIG. 1 and FIG. 3 , it is located on the top surface of the lower dielectric plate, and its shape is similar to that of the upper parasitic unit 5 . The center ring 9 has an inner radius R3, an outer radius R4, and the metal arm connected to the ring 9 has a width W5 and a length L5. The arc structure at the top has the same dimensions as the upper parasitic unit 5, and the gap between the two arcs is L6. The coaxial feeder has no contact with the lower parasitic unit 8 . The structure of the lower parasitic unit is similar to that of the tomahawk-shaped excitation unit and the upper parasitic unit, and has a good matching degree. When excited, the surface generates induced currents whose polarization directions are parallel to each other. In terms of the active radiation field, the parasitic unit is similar in shape to the excitation unit and is located at its bottom. This placement method can make the lower parasitic unit have a suitable phase difference and space distance from the upper excitation unit and the upper parasitic unit. In this way, the lower parasitic unit can act like a reflector in a Yagi antenna, so that the total radiation field direction of the designed electrically small antenna is directed upward, which significantly improves the directivity of the antenna system. The unit is not connected to the inner and outer conductors of the coaxial feeder, and is relatively close to the excitation unit. It has the function of a near-field resonator, and the coupling with the tomahawk-shaped excitation source produces a new resonance mode, which makes the electric small antenna operate at a new lower level. It works near the resonant frequency point, thereby broadening the working frequency band of the electrically small antenna.

The coaxial feeder structure is shown in Figure 1, Figure 2, and Figure 4. The inner conductor 3 is in the shape of a solid cylinder with a radius of R5 and a length of L7. The outer conductor 4 is in the shape of a thin-walled hollow cylinder with a radius of R6 and a length of L7. In the section between the upper dielectric plate 1 and the lower dielectric plate 2, the right half of the outer conductor of length L8 is cut off, so that the inner and outer conductors of the feeder are connected to the right and left tomahawk-shaped metal sheets respectively, and the impact of the surface current on the outer conductor is reduced. The influence of antenna radiation characteristics. The outer conductor is in contact with the bottom surface of the lower dielectric thin cylinder, and the inner and outer conductors are not in contact with the metal of the lower parasitic unit.

Using the high-frequency electromagnetic simulation software HFSS13.0 to conduct simulation experiments on the antenna structure model established above, the optimal value of the structure size of the electrically small antenna is shown in Table 1.

Table 1 HFSS13.0 simulation obtained the optimal size of small antenna

H2 in the table is the copper thickness of the excitation unit, the upper parasitic unit and the lower parasitic unit.

In this embodiment, HFSS13.0 is used to simulate the performance parameters of the antenna, and the simulation analysis is carried out on the S parameters and the pattern of the antenna respectively.

Fig. 5 is the curve diagram of the antenna S parameter obtained by simulation. As shown in the figure, the designed electrically small antenna has two resonant frequency points, which are 0.94GHz and 0.99GHz respectively, the bandwidth range of -10dB is 0.93-1.03GHz, and the working frequency bandwidth is 100MHz. The reflection loss value -47.8dB at the resonant frequency point 0.99GHz is lower than the reflection loss value -11.3dB at the resonant frequency point 0.94GHz. The two resonant frequencies are mainly generated by the introduced upper and lower parasitic resonant units respectively. In the equivalent circuit of an electrically small antenna, the parasitic unit is equivalent to a capacitor and an inductor in series, and the tomahawk-shaped excitation unit will provide the corresponding equivalent capacitance for the equivalent circuit, and the two form an LC resonance, so that the antenna can operate at lower frequencies good job. Because the distance between the upper parasitic unit and the tomahawk-shaped excitation unit is very close, the shape is similar and the electrical coupling can be better, and the radiation field radiation efficiency generated by resonance is high. In comparison, the overall polarization current path of the upper parasitic unit is shorter, so that the resonant frequency generated by its action is high. The overall polarization current path of the lower parasitic unit is longer, so that the resonant frequency generated by its action is low.

Figure 6-7 is the antenna radiation field E-plane and H-plane pattern at the frequency points 0.94GHz, 0.96GHz, and 1.00GHz obtained by simulation. It can be observed from the figure that the radiation field of the electrically small antenna E and H-plane has a direction directly above the antenna. The radiation direction of the H surface has a characteristic similar to omnidirectional radiation, and the E surface radiation field is an asymmetric "8" shape. At the frequency point of 0.94GHz, the maximum gain value of the radiation field of the E and H planes of the electrically small antenna is 4.38dBi, facing the direction of the side beam. With the increase of the frequency, the gain value of the E and H surface radiation field decreases in the direction directly above. There is a certain asymmetry in the backward radiation of the pattern of the E-plane radiation field (especially in the low frequency band), mainly because the antenna adopts the direct feeding method of the unbalanced structure of the coaxial cable. When the frequency is low, the gain of the radiation field directly above the antenna is large. The reason is that in the low frequency band, mainly due to the coupling resonance between the lower parasitic unit and the tomahawk-shaped excitation unit, the phase difference and space distance between them make the radiation The pattern is in the form of a broadside. Relatively speaking, in the high frequency band, mainly due to the coupling resonance between the upper parasitic unit and the tomahawk-shaped excitation unit, when they are at an extremely short distance, the pattern formed is in the form of a traditional dipole. Because the two resonant frequency bands overlap each other, the antenna also exhibits certain side-firing characteristics at high frequencies.

Finally, it is noted that the above preferred embodiments are only used to illustrate the technical solutions of the present utility model without limitation. Although the utility model has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in the form Various changes can be made in the above and in the details without departing from the scope defined by the claims of the present invention.

Claims (9)

1. a broadband high-efficiency high directivity electronically small antenna, is characterized in that: comprise exciting unit, upper parasitic element, lower parasitic element, two thin column shape dielectric-slabs, coaxial feeder;

Described two thin column shape dielectric-slab radiuses are identical, and center is aimed at, upper and lower parallel placement; Exciting unit, upper parasitic element are arranged at respectively thin column shape dielectric-slab bottom surface and end face, and lower parasitic element is arranged at lower thin column shape dielectric-slab end face; The inner and outer conductor of coaxial feeder connects respectively two sheet metals of exciting unit; The feed end of coaxial feeder prolongs to its downside one segment distance through lower thin column shape dielectric-slab, joins with 50 Ω signal sources.

2. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 1, it is characterized in that: the sheet metal of described exciting unit forms battleax shape, this battleax shape sheet metal connects two arc metal plates by vertical bar metal arm and forms, one in two sheet metals connects coaxial feeder inner wire, and the symmetrically arranged sheet metal of another side connects coaxial feeder outer conductor.

3. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 1, it is characterized in that: described upper parasitic element is merged and formed by two battleax shape sheet metal, be a bullion arm and connect top two curved metal chip architectures, in excited target situation, be coupled with bottom surface battleax shape exciting unit, realize LC resonance, produce a mode of resonance.

4. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 1, it is characterized in that: the center of described lower parasitic element is an annular sheet metal, the both sides of annular sheet metal connect the battleax shape sheet metal being combined to form by vertical bar metal arm and arc metal plate, and annular sheet metal does not contact with coaxial feeder; There is LC resonance in lower parasitic element and battleax shape exciting unit, upper parasitic element, produces new mode of resonance.

5. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 1, it is characterized in that: the material of described upper and lower thin column shape dielectric-slab is Rogers Duroid6010, electric medium constant 10.2, relative permeability is 1.0, loss tangent angle value 0.0023, radius is 30-34mm, thickness is 1.20-1.33mm, the thickness that copper is applied on surface is 0.016-0.019mm, and two dielectric-slab centre distances are 27-30mm.

6. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 2, it is characterized in that: described exciting unit two battleax shape metal arm width are 2.56-2.83mm, arm lengths is 19-21mm, arch section outer radius is 25-27mm, arc width is 5.5-6.5mm, and two arc gaps are 31-33mm.

7. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 3, it is characterized in that: described upper parasitic element intermetallic metal arm width is 4.1-4.7mm, arm lengths is 47-49mm, top arc outer radius is 31-33mm, arc width is 7.5-8.5mm, and two arc gaps are 31-33mm.

8. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 4, it is characterized in that: described lower parasitic element center annular sheet metal inside radius is 2.4-2.7mm, outer radius is 5.3-5.9mm, vertical bar sheet metal length is 17.5-19.5mm, width is 3.5-6.9mm, top arc outer radius is 31-33mm, and width is 7.5-8.5mm, and two arc gaps are 27-30mm.

9. a kind of broadband high-efficiency high directivity electronically small antenna according to claim 1, it is characterized in that: described coaxial feeder inner wire is real cylindrical, radius is 0.5-0.7mm, length is 50-55mm, outer conductor is thin-walled hollow cylindrical, and radius is 1.5-1.7mm, and length is 50-55mm, between internal and external conductor, fill insulating barrier, to meet 50 ohm characteristic impedance; One side of something of coaxial feeder outer conductor between upper and lower thin column shape dielectric-slab is pruned.