CN101950858A

CN101950858A - Broadband binary array antenna based on composite left-handed and right-handed transmission line

Info

Publication number: CN101950858A
Application number: CN2010105007263A
Authority: CN
Inventors: 郑奎松; 吴昌英; 韦高; 许家栋
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2010-09-30
Filing date: 2010-09-30
Publication date: 2011-01-19

Abstract

The invention discloses a broadband binary array antenna with composite left and right-handed transmission lines, which includes a microwave dielectric substrate and upper and lower surface elements, and the upper surface element includes two antenna array units connected by arcuate connecting lines. The source is connected with a microstrip line, and the lower surface element is a grounding plate. Each antenna array unit is composed of N square radiators arranged in sequence, and each radiator is connected to the grounding plate through a short-circuit pin; the outermost A square groove is etched on the radiation sheet, a square tooth-shaped etching line is etched between every two radiation sheets, and a gap of 0.1 mm to 0.3 mm is etched between the arc connecting line and the radiation sheet. The invention enhances the electromagnetic coupling between the radiation sheets, improves the impedance distribution and electromagnetic current distribution of the antenna, and further improves the radiation bandwidth and gain of the antenna array.

Description

Broadband binary array antenna of composite left-right-hand transmission line

Technical Field

The invention relates to an antenna, in particular to a broadband high-gain millimeter wave binary array antenna based on a composite left-right hand transmission line technology.

Background

Left-handed materials (left-handed materials) have been one of the hot spots in research in the fields of materials science and physics in recent years. In classical theory of electrodynamics, the electromagnetic properties of a dielectric material can be described by two macroscopic parameters, permittivity epsilon and permeability mu. In nature, the dielectric constant epsilon and the magnetic permeability mu of the medium are positive numbers, and when electromagnetic waves irradiate the medium materials, the electric field intensity E, the magnetic field intensity H and the propagation direction K of the electromagnetic waves, which describe the propagation characteristics of the electromagnetic waves, satisfy a right-handed spiral relationship, which is a classic "right-handed rule" relationship in physics. The dielectric material satisfying the relation of the right-hand rule is the right-hand material. And through a certain periodic structure design, the artificial left-handed material with negative dielectric constant epsilon and permeability mu can be obtained. When the electromagnetic wave irradiates the left-handed material, the electric field intensity E, the magnetic field intensity H and the propagation direction K of the electromagnetic wave describing the propagation characteristics of the electromagnetic wave satisfy the relationship of 'left-handed helix'. In addition, electromagnetic waves have special electromagnetic characteristics such as inverse snell refraction when propagating through left-handed materials. Based on the theoretical analysis of the transmission line, the transmission line designed by adopting the series capacitance and the parallel inductance has the characteristics of a left-handed material, and the transmission line forms a composite left-handed transmission line because the right-handed effect is also parasitic on the transmission line.

Itoh et al, and related documents, describe methods for designing antennas based on a composite right and left handed transmission line technology. In 2002, the article "Application of the transmission line of the left-handed (LH) material to the reconstruction of a microstrip LH-line" and the article "explicit new zero-order antenna" in 2007, the article "Eye et al both describe antennas designed by using a left-handed and a right-handed transmission line. Such antennas are difficult to meet with practical application requirements. The reason is mainly that when the zero-order resonance mode of the composite left-right-handed transmission line is adopted, in the working state, the transmission constant beta of the transmission line is zero, the wavelength is infinite, and the electric field distribution under the antenna patch has no phase inversion process, so that the problems of low antenna radiation efficiency and poor gain are caused.

Disclosure of Invention

In order to overcome the defects of narrow bandwidth (generally less than 1%) and low gain in the prior art, the invention provides a binary array antenna, which is based on a composite left-hand and right-hand transmission line technology, improves the distribution of series capacitance and parallel inductance which form the left-hand characteristic of the antenna, and reasonably sets an antenna array unit structure consisting of the composite left-hand and right-hand transmission lines, thereby realizing the binary array antenna with small size, wide bandwidth and high gain and meeting the actual requirements of various antenna occasions.

The technical scheme adopted by the invention for solving the technical problems is as follows: a broadband binary array antenna based on a left-right hand transmission line technology comprises a microwave dielectric substrate coated with copper foil, and an upper surface element and a lower surface element which are respectively formed on the upper surface and the lower surface of the microwave dielectric substrate by etching the copper foil, wherein the upper surface element comprises two antenna array units with the same structure, and the antenna array units are connected through an arch-shaped connecting line; the middle of the arched connecting line is connected with one end of a microstrip line, the distance between the connecting point and two ports of the arched connecting line is different from lambda/2, lambda is the working wavelength of the antenna array unit, the other end of the microstrip line is connected with a feed source, and the lower surface element is a ground plate. Each antenna array unit is composed of N square radiating fins which are sequentially arranged, and the number of N can be 2-10. Each radiation piece penetrates through the microwave medium substrate through the short-circuit pin to be conducted with the grounding plate; a square groove is etched on the radiation sheet on the outermost side (the side far away from the arch-shaped connecting line is taken as the outer side) of the antenna array unit, so that the electromagnetic current distribution on the radiation sheet on the outermost side is improved; a square tooth-shaped etching line is etched between every two radiating sheets to form one or more square tooth-shaped interdigital so as to form interdigital capacitors, and electromagnetic coupling between the radiating sheets is enhanced, so that distributed capacitors required by left-hand and right-hand transmission lines can be formed between the radiating sheets; gaps are etched between the arch connecting wires and the radiation sheets, electromagnetic coupling between the arch connecting wires and the radiation sheets is enhanced, and the distance between the gaps can be 0.1-0.3 mm.

The microwave dielectric substrate is made of Teflon materials, has low price and excellent ageing resistance, and can also be made of FR4 epoxy glass cloth or other microwave dielectric materials such as expanded polystyrene.

The bow-shaped connecting line is a microstrip line with the shape similar to a bow.

The width of the interdigital capacitor formed by the square tooth-shaped etching line is smaller than that of the radiation sheet.

The invention has the beneficial effects that: by changing the capacitance part playing the left-hand effect in the composite left-hand and right-hand transmission line technology into an interdigital capacitance mode, the electromagnetic coupling between the radiation pieces is enhanced, the impedance distribution condition of the antenna is improved, and the bandwidth of the antenna is improved; the phase difference between the two antenna array units is adjusted by utilizing the optimized arrangement of the position of the connection point between the bow-shaped connecting line and the microstrip line with one end connected with the feed source, thereby improving the electromagnetic current distribution of the whole binary array antenna, further improving the radiation bandwidth and the gain of the antenna array and obtaining the wavelet binary array millimeter wave antenna with high gain and broadband.

The invention is further illustrated with reference to the following figures and examples.

Drawings

Fig. 1 is a schematic view of the overall structure of a broadband binary array antenna according to embodiment 1 of the present invention.

Fig. 2 is a schematic diagram of an upper surface element structure of a broadband binary array antenna according to embodiment 1 of the present invention.

Fig. 3 is an equivalent diagram of the resonance characteristics of the antenna array elements according to the present invention.

Fig. 4 is a return loss/frequency graph of the broadband binary array antenna according to embodiment 1 of the present invention.

Fig. 5 is a Voltage Standing Wave Ratio (VSWR)/frequency graph of the broadband binary array according to embodiment 1 of the present invention.

Fig. 6 is a schematic diagram of an upper surface element structure of a broadband binary array antenna in embodiment 2 of the present invention.

In the figure, 10-microwave dielectric substrate, 20-upper surface element, 21-radiating plate, 22-interdigital capacitor, 23-gap, 24-square groove, 25-bow connecting line, 26-microstrip line, 30-grounding plate and 41-short circuit pin.

Detailed Description

Example 1:

as shown in fig. 1 and 2, a broadband, high gain binary array antenna based on composite right and left hand transmission line technology comprises a microwave dielectric substrate 10 made of teflon coated copper foil, an upper surface element 20 and a ground plate 30 formed on the upper and lower surfaces of the microwave dielectric substrate by etching the copper foil, and a shorting pin 41 penetrating through the microwave dielectric substrate and connecting the upper surface element and the ground plate, wherein,

the binary array antenna is composed of two antenna array units with the same structure, the number of the radiation sheets 21 of each antenna array unit can be N (N is 3 in the embodiment), and the size of each radiation sheet 21 is set to be 3.5mm × 3.5 mm; the radiation fins 21 of the antenna array unit are respectively conducted with the grounding plate 30 through the short circuit pins 41; the electromagnetic coupling between adjacent radiation pieces 21 of the antenna array unit is performed through an interdigital capacitor 22, in the embodiment 1, the interdigital capacitor is only designed into an interdigital, the physical size of the interdigital is 0.2mm × 0.4mm, and the distance between the interdigital and the corresponding radiation piece is 0.2 mm; the radiation sheet 21 at the outermost side of the antenna array unit is etched with a square groove 24, so that the electromagnetic current distribution on the radiation sheet is changed, and a distributed capacitor is provided; in the present embodiment example 1, the size of the square groove 24 is 0.6mm × 0.4 mm.

The two antenna array units are connected with two ports of an arched connecting line 25, electromagnetic coupling between a radiation sheet 21 of the antenna array units and the arched connecting line 25 is carried out through a rectangular gap 23, and the size of the arched connecting line 25 is 15.5mm multiplied by 1.5 mm;

one end of the microstrip line 26 is connected to a point in the middle of the bow-shaped connection line 25, and the distance between the connection point and the two ports of the bow-shaped connection line 25 in the embodiment 1 is different by half of the operating wavelength; the other end of the microstrip line 26 is connected with the feed source; the size of the microstrip line 26 is 3.8mm × 0.8 mm;

the radiating plate 21, the interdigital capacitor 22, the grounding plate 30 and the shorting pin 41 form a left-right hand transmission line structure on the microwave medium substrate 10.

The theoretical derivation used to determine the above design is as follows:

according to the electromagnetic field theory and the transmission line theory, the resonance characteristics of the antenna array unit of the antenna of the present invention can be equivalent as shown in fig. 3, wherein in fig. 3, the symbol L_R、C_L、C_RAnd L_LRespectively representing a series inductance, a series capacitance, a parallel capacitance and a parallel inductance. According to the theory of lossless transmission line, the propagation constant of transmission line

Where Z and Y are the impedance and admittance, respectively, per unit length of the transmission line.

According to the Bloch theory and the floquet boundary condition of the periodic boundary, the dispersion equation of the periodic unit shown in fig. 3 can be obtained as follows:

wherein,

andβ is the propagation constant of the Bloch wave, and d is the length of the periodic unit. At omega_M＞ω_EIn the case of (3), the dispersion curve of the transmission line can be obtained by calculating equation (1). When β d takes different values, different resonant frequencies of the composite left-right hand transmission line can be obtained, and a specific expression is as follows:

<math><mrow><msub><mi>β</mi><mi>n</mi></msub><mi>d</mi><mo>=</mo><mfrac><mi>nπd</mi><mi>l</mi></mfrac><mo>=</mo><mfrac><mi>nπ</mi><mi>N</mi></mfrac><mrow><mo>(</mo><mi>n</mi><mo>=</mo><mn>0</mn><mo>,</mo><mo>&PlusMinus;</mo><mn>1</mn><mo>,</mo><mo>&PlusMinus;</mo><mn>2</mn><mo>,</mo><mo>·</mo><mo>·</mo><mo>·</mo><mo>,</mo><mrow><mo>(</mo><mi>N</mi><mo>-</mo><mn>1</mn><mo>)</mo></mrow><mo>)</mo></mrow><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow></math>

in the above formula, N (═ l/d) and l represent the number of periodic units and the length of the entire resonator, respectively. Equation (2) also indicates that when n is 0, the resonance unit of the composite left-right hand structure has a resonance frequency of zero order, which is expressed as:

from equation (3), it can be seen that the zeroth order resonant frequency of the composite right and left-handed transmission line is determined by the parallel inductance and the parallel capacitance of the periodic unit, and is independent of the total length of the entire transmission line (which is composed of a plurality of periodic units). Thus, a wavelet antenna may be constructed using a composite right and left handed transmission line according to this idea.

In the present embodiment example 1, each antenna array element is constituted by three periodic elements based on a left-right-hand structure. The interdigital capacitor 22 among the periodic units, the capacitor between the radiation sheet 21 and the grounding plate 30, the inductance generated by the current flowing through the radiation sheet 21 and the inductance generated by the short-circuit pin 41 conducted between the current flowing through the radiation sheet 21 and the grounding plate 30 jointly form a series capacitor C forming a composite right-left-hand transmission line_LParallel capacitor C_RSeries inductor L_RAnd a parallel inductor L_L. It can be seen that the binary array antenna of the present invention has the required conditions for zero order resonance. As an experiment, we designed the frequency f based on the zeroth order resonance₀10.3 GHz. The physical size of the antenna array unit is 0.37 lambda₀×0.12λ₀Wherein λ is₀The zero-order resonance wavelength is shown in fig. 1 of embodiment example 1 of the present invention. The binary array antenna achieves the effect of expected setting, and the physical size of the binary array antenna of the wavelet is far smaller than that of the traditional microstrip antennaThe minimum size value that can be achieved, which illustrates that the invention can be implemented.

Fig. 4 is a return loss/frequency graph of a broadband binary array antenna according to embodiment 1 of the present invention; fig. 5 is a Voltage Standing Wave Ratio (VSWR)/frequency graph of the broadband binary array according to embodiment 1 of the present invention. As can be seen from the figure, the absolute bandwidth of the antenna reaches 480MHz (VSWR < 2), and reaches the design standard of the ultra-wideband antenna. Therefore, the effect of the invention on expanding the frequency bandwidth of the antenna is obvious and remarkable. The peak value Gain of the broadband binary array antenna of the embodiment 1 of the invention reaches 9.7 dBi.

Example 2:

fig. 6 is a schematic diagram of an upper surface element structure of a wideband binary array antenna according to embodiment 2 of the present invention. The interdigital capacitors 22 between adjacent radiation sheets 21 are designed into 5 interdigital capacitors, the microwave dielectric substrate 10 is made of FR4 epoxy glass cloth material, and other structures are the same as those of the embodiment example 1.

Claims

1. A broadband binary array antenna with composite left and right handed transmission lines, comprising a microwave dielectric substrate coated with copper foil and an upper surface element and a lower surface element respectively formed on the upper and lower surfaces of the microwave dielectric substrate by etching the copper foil , characterized in that: the upper surface element includes two antenna array units with the same structure, and the antenna array units are connected by a bow-shaped connection line; somewhere in the middle of the bow-shaped connection line is connected to one end of the microstrip line, and the connection point is to The distance between the two ports of the bow-shaped connecting line differs by λ/2, λ is the working wavelength of the antenna array unit, the other end of the microstrip line is connected to the feed source, the lower surface element is a ground plate, and each antenna The array unit is composed of N square radiators arranged in sequence, and N is 2 to 10. Each radiator is connected to the ground plate through the microwave dielectric substrate through a short-circuit pin; the outermost radiator of the antenna array unit is etched with a square There is a square-tooth-shaped etching line etched between every two radiation sheets to form one or more square-tooth-shaped interdigitated fingers to form an interdigitated capacitor, and there is etched between the bow-shaped connecting line and the radiation sheet Slits, the spacing of the slits may be 0.1 mm to 0.3 mm.

2. The broadband binary array antenna of a composite left-handed transmission line according to claim 1, characterized in that: the microwave dielectric substrate is made of Teflon material, FR4 epoxy glass cloth or expanded polystyrene .

3 . The wideband binary array antenna with composite left and right handed transmission lines according to claim 1 , wherein the arcuate connection line is a curved microstrip line. 4 .

4 . The wideband binary array antenna with composite left and right handed transmission lines according to claim 1 , wherein the width of the interdigitated capacitance formed by the square tooth-shaped etched lines is smaller than the width of the radiation sheet. 5 .