Ultra-wideband low-profile feed source loaded with step medium

Abstract

The invention discloses an ultra-wideband low-profile feed source loaded with a step medium, and relates to the field of ultra-wideband feed sources. The antenna comprises four log-periodic antennas, four groups of step dielectrics, dielectric cylinders, a reflection floor, a metal cavity and two feed baluns, the four log-periodic antennas are divided into two pairs which are orthogonally arranged, each pair comprises two log-periodic antennas which are oppositely arranged, the log-periodic antennas are fixed on the dielectric cylinder through screws, and an included angle is formed between the log-periodic antennas and the reflection floor; each group of stepped dielectric is formed by arranging twelve dielectric blocks in height stepped distribution, is positioned between the log-periodic antenna and the reflection floor, and clings to the reflection floor; the two feed baluns are orthogonally arranged, and each balun comprises a dielectric substrate, an index gradient microstrip line and a one-to-two power divider. The antenna is wide in frequency band, low in profile and suitable for serving as a primary radiator of a reflector antenna in the fields of satellite communication, radar detection, radio astronomy and the like.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, in particular to the field of ultra-wideband feed sources, and specifically to an ultra-wideband low-profile feed source loaded with a stepped medium, which is suitable for being used as a primary radiator of a reflector antenna in the fields of satellite communication, radar detection, radio astronomy, etc. Background Art

[0002] Reflector antennas have played an important role in satellite communications, radar, remote sensing, radio astronomy, etc. due to their advantages such as high gain and low side lobes. The feed is the primary radiator of the reflector antenna, which has the function of converting electromagnetic waves into guided waves and has a crucial impact on the performance of the antenna.

[0003] Ultra-wideband feeds can achieve continuous coverage of ultra-wide frequency ranges, improve sensitivity, significantly reduce the number of equipment and maintenance costs, and shorten system design cycles. However, common ultra-wideband feeds have a high profile height, which causes the antenna to be large in size and weight in low-frequency bands, making it difficult to assemble in actual use, easily causing deformation of the reflective surface, and limiting the possibility of upgrading the feed system to expand the operating frequency band. In addition, a high profile height will cause phase center offset, reduce efficiency, and affect antenna performance.

[0004] The log-periodic antenna uses the scaling principle to change the size of all units of the antenna in proportion to the wavelength to ensure that the working characteristics of the antenna remain unchanged. Therefore, the log-periodic antenna has a simple structure and can achieve a wide operating frequency band. However, the traditional log-periodic antenna is placed in an upright splicing manner, with large longitudinal dimensions, high cross-sectional height, and large changes in the phase center with frequency, resulting in reduced efficiency. By placing the log-periodic antenna horizontally and tilting it and introducing a metal reflector at the feed end, the cross-sectional height can be significantly reduced, while the phase center can be stabilized near the floor. However, in order to have good matching and radiation characteristics, the distance from each unit of the antenna to the reflective floor is limited by the in-phase reflection condition and is usually set near a quarter wavelength, resulting in a high cross-section, which is not conducive to the miniaturization of the antenna. Summary of the invention

[0005] The purpose of the present invention is to propose an ultra-wideband low-profile feed source loaded with stepped dielectrics in view of the limitations of the above-mentioned background technology. The present invention has the characteristics of wide bandwidth, low profile, fixed phase center and beam width, and compact structure, and can be used as a primary radiator of reflector antennas in the fields of satellite communications, radar detection, radio astronomy, etc.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An ultra-wideband low-profile feed loaded with a stepped dielectric, comprising:

[0008] Reflective floor,

[0009] The metal cavity is located under the reflective floor.

[0010] Two feeding baluns are placed in the metal cavity.

[0011] Stepped dielectrics and dielectric columns are placed above the reflective floor.

[0012] Four log-periodic antennas are arranged above the stepped dielectric and dielectric column;

[0013] The four log-periodic antennas are divided into two pairs placed orthogonally, each pair comprising two log-periodic antennas placed opposite to each other, fixed on the dielectric column by screws, so as to form an angle with the reflective floor;

[0014] There are four groups of stepped media, each group of which is composed of twelve media blocks arranged in a stepped manner, and is located between the log-periodic antenna and the reflecting floor, close to the reflecting floor;

[0015] The metal cavity has an opening, and the two feeding baluns are placed orthogonally. Each feeding balun includes a dielectric substrate, an exponentially tapered microstrip line and a one-to-two power divider. The output end of the feeding balun extends through a via hole in the reflecting floor and is connected to the input end of a corresponding pair of oppositely placed logarithmic periodic antennas. The input end of the feeding balun extends to the outside of the metal cavity through the opening of the metal cavity.

[0016] Furthermore, the log-periodic antenna is in the form of a printed circuit board, which is realized by coating a metal layer on a single side of a dielectric substrate, and the metal layer is composed of twelve half-wave dipole units and a pair of parallel double wires; wherein the half-wave dipole units are connected in sequence in a folded form, and their length, width, spacing and position satisfy a log-periodic relationship, one end of the parallel double wire is connected to the short dipole of the half-wave dipole unit, and the other end extends to the output end of the feeding balun to realize the feeding of the antenna.

[0017] Furthermore, the cross section of the dielectric column is Y-shaped, and the material used is Nylon1010, which is used to support two adjacent log-periodic antennas and fix them on the reflective floor.

[0018] Furthermore, each group of stepped media corresponds to a logarithmic periodic antenna. In each group of stepped media, each dielectric block is located directly below a half-wave dipole unit, and the heights of adjacent dielectric blocks satisfy a logarithmic periodic relationship. The stepped media are fixed to the reflecting floor by screws.

[0019] Furthermore, two feeding baluns are staggered and slotted and placed orthogonally, and a connector is installed on the side of the feeding balun without routing, and the feeding balun is fixed to the back of the reflecting floor; the one-to-two power divider of one feeding balun is a compact routing, and the input end is located at the height of the upper half of the dielectric substrate, and the one-to-two power divider of the other feeding balun is an extended routing, and the input end is located at the height of the lower half of the dielectric substrate.

[0020] The beneficial effects of the invention are:

[0021] 1. The present invention loads a stepped dielectric between the log-periodic antenna and the reflecting floor, which can effectively improve the antenna performance after the cross-section is reduced.

[0022] 2. The invention has novel concept, simple structure and is easy to process and assemble.

[0023] 3. The feed balun of the present invention has a compact design, integrating a power divider and a 90° bending index gradient microstrip line, thereby reducing the overall height.

[0024] In summary, compared with traditional ultra-wideband feed sources, the present invention has a significantly reduced profile height, small overall size and weight, effectively suppresses phase center deviation, and improves aperture efficiency, which is an important improvement over the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of an ultra-wideband low-profile feed source loaded with a stepped medium in an embodiment of the present invention.

[0026] Figure 2 yes Figure 1 Schematic diagram of a log-periodic antenna.

[0027] Figure 3 yes Figure 1 Side view of the mid-step medium.

[0028] Figure 4 is the schematic diagram of the feeding balun I.

[0029] Figure 5 is the schematic diagram of the Feed Balun II.

[0030] Figure 6 This is a diagram of S11 simulation results of an ultra-wideband low-profile feed loaded with a stepped medium in an embodiment of the present invention.

[0031] Figure 7 This is a diagram of the main polarization and cross-polarization results of an ultra-wideband low-profile feed loaded with a stepped dielectric at a frequency of 2.5 GHz in an embodiment of the present invention.

[0032] Figure 8This is a diagram of the main polarization and cross-polarization results of an ultra-wideband low-profile feed loaded with a stepped dielectric at a frequency of 5.0 GHz in an embodiment of the present invention.

[0033] Fig. 9 This is a diagram of the main polarization and cross-polarization results of an ultra-wideband low-profile feed loaded with a stepped dielectric at a frequency of 7.5 GHz in an embodiment of the present invention.

[0034] Fig.10 This is a diagram of the main polarization and cross-polarization results of an ultra-wideband low-profile feed loaded with a stepped dielectric at a frequency of 10.0 GHz in an embodiment of the present invention.

[0035] Explanation of the reference numerals in the accompanying drawings: log-periodic antenna—1, stepped dielectric—2, dielectric column—3, reflecting floor—4, metal cavity—5, dielectric substrate of log-periodic antenna—6, half-wave dipole unit of log-periodic antenna—7, parallel double lines of log-periodic antenna—8, dielectric substrate of feed balun I—9, power divider of feed balun I—10, exponentially tapered microstrip line of feed balun I—11, dielectric substrate of feed balun II—12, power divider of feed balun II—13, exponentially tapered microstrip line of feed balun II—14. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the embodiments described herein are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The invention discloses an ultra-wideband low-profile feed source loaded with a stepped dielectric, comprising a logarithmic periodic antenna on an upper layer, a reflecting floor, a dielectric column and a stepped dielectric on a middle layer, and a metal cavity and a feeding balun on a lower layer.

[0038] There are four log-periodic antennas, which are divided into two pairs placed orthogonally. Each pair includes two log-periodic antennas placed opposite to each other and fixed on the dielectric column by screws so that they form a certain angle with the reflecting floor.

[0039] There are four groups of stepped media, each group of which is composed of twelve media blocks with stepped heights, and is located between the log-periodic antenna and the reflecting floor, close to the reflecting floor.

[0040] There are two feeding baluns, with openings in the metal cavity. The two feeding baluns are placed orthogonally. Each balun contains a dielectric substrate, a 90° bent exponential gradient microstrip line and a one-to-two power divider. The parameters of the exponential gradient curve are determined by the line width at both ends of the curve. The output end of the balun extends to the upper layer through the via hole of the reflective floor and is connected to the input end of a corresponding pair of oppositely placed logarithmic periodic antennas. The wire at the input end of the balun extends to the outside of the metal cavity through the opening of the metal cavity.

[0041] The log-periodic antenna adopts the form of a printed circuit board, which is realized by coating a metal layer on one side of a dielectric substrate. The metal layer consists of twelve half-wave dipole units and a pair of parallel double wires. The dipoles are connected in sequence in a folded form, and their length, width, spacing and position satisfy the log-periodic relationship. One end of the parallel double wire is connected to the short dipole, and the other end extends to the output end of the balun to realize the feeding of the antenna.

[0042] The dielectric column adopts a Y-shaped design and is made of Nylon1010. It is used to support two adjacent log-periodic antennas and fix them on the reflective floor.

[0043] Each set of stepped dielectrics corresponds to a log-periodic antenna. Each dielectric block is located directly below a dipole, and the heights of adjacent dielectric blocks satisfy a log-periodic relationship. The selection of dielectric block height should satisfy the in-phase reflection condition and is affected by factors such as dielectric constant and the height of the dipole from the ground. The stepped dielectric is fixed to the reflective floor with screws.

[0044] The two feed baluns are staggered and slotted and placed orthogonally. A connector is installed on the side of the balun without routing and fixed to the back of the reflective floor. The power divider of the feed balun I has compact routing, and the input end is located at the height of the upper half of the dielectric plate. The power divider of the feed balun II has extended routing, and the input end is located at the height of the lower half of the dielectric plate.

[0045] Here is a more specific example:

[0046] An ultra-wideband low-profile feed loaded with stepped dielectric, referring to Figure 1 , comprising a log-periodic antenna 1, a stepped dielectric 2, a dielectric column 3, a reflective floor 4 and a metal cavity 5. A feed balun I and a feed balun II are arranged in the metal cavity 5, and the cross-sectional height thereof is jointly determined by the antenna height and the feed structure height.

[0047] The feed first reduces the wavelength of the medium and the height of the antenna profile by loading a stepped dielectric under the log-periodic antenna, while improving the performance of the antenna after the profile is reduced. Secondly, by adjusting the feed balun routing, integrating a 90° bend index gradient microstrip line and a power divider, the size of the feed structure is reduced. The above design further reduces the profile height of the feed system, suppresses the phase center offset, and improves the aperture efficiency.

[0048] Reference Figure 2 The logarithmic periodic antenna adopts the form of a printed circuit board, which is realized by coating a metal layer on a single side of a dielectric substrate 6. The metal layer is composed of twelve half-wave dipole units 7 and a pair of parallel double wires 8. Among them, the dipoles are connected in sequence in a folded form, and their length, width, spacing and position satisfy the logarithmic periodic relationship.

[0049] The design idea of ​​the log-periodic antenna is as follows: First, according to the target gain, find the intersection of the optimal design curve and the gain in the relationship diagram, and determine the proportional factor t and the spacing factor s, which together determine the change of the dipole parameters; second, according to the working bandwidth, the structural bandwidth is calculated by the empirical formula. Usually, the structural bandwidth is greater than the working bandwidth. The lowest and highest frequencies of the structural bandwidth determine the length of the longest and shortest dipoles, and their lengths are half of the wavelength corresponding to the frequency; after determining the shortest / longest dipole length, changing its width, collective line spacing and other parameters can adjust the impedance of the antenna. Other corresponding parameters of the dipole can be obtained by the relationship Calculate, where L is the dipole length, W is the dipole width, and S is the set line spacing.

[0050] Reference Figure 3 Each set of stepped dielectrics corresponds to a logarithmic periodic antenna. Each dielectric block is located directly below a dipole, and the heights of adjacent dielectric blocks satisfy a logarithmic periodic relationship. The height of the dielectric block should be selected to satisfy the in-phase reflection condition. where h a is the height of the air layer, λ a is the vacuum wavelength, h s is the wavelength of the dielectric layer, λ s is the dielectric wavelength, which is related to the dielectric constant of the selected material. Each set of stepped dielectrics has a hole at the highest dielectric block and is fixed to the reflective floor by screws.

[0051] Reference Figure 4 The feed balun I includes a dielectric substrate 9, a one-to-two power divider 10 and a 90° bent exponential gradient microstrip line 11 to achieve unbalanced-balanced conversion and impedance transformation. The two output ports on the upper side of the balun are balanced ports, and the side input port is an unbalanced port. The input port is connected to the signal source, and the output port is connected to the antenna. The two sides of the balun are the signal line and the ground line, respectively. The line width is determined by factors such as the input / output impedance, the dielectric constant and thickness of the dielectric substrate, and can be obtained by the microstrip line impedance calculation formula. The parameters of the exponential gradient curve are determined by the line width at both ends of the curve.

[0052] Reference Figure 5Since the input and output impedances are consistent, the line widths at both ends of the feed balun II are consistent with those of the balun I. In order to avoid overlapping with the feed balun I routing and overlapping with the dielectric substrate, the dielectric substrate of the feed balun II is slotted in a staggered manner with the feed balun I, and the input position is adjusted and the power divider routing is extended.

[0053] By using the commercial simulation software CST STUDIO 2019 to simulate the above feed source as a whole, the S11 parameter curve of the feed source and the D surface at several frequency points selected within the working frequency band were obtained. Main polarization and cross polarization results, such as Figure 6-10 shown.

[0054] Reference Figure 6 , the horizontal axis is the frequency, in GHz, ranging from 2 to 11 GHz, and the vertical axis is the decibel value of the reflection coefficient, in dB, ranging from -24 to 0 dB. It can be seen from the figure that almost all frequency points of the feed source in the frequency band of 2 to 10 GHz are lower than -8 dB.

[0055] Reference Figure 7-10 , respectively, the main polarization and cross polarization results of the D plane (j=45°) at frequencies of 2.5GHz, 5.0GHz, 7.5GHz, and 10.0GHz. The horizontal axis is the elevation angle (θ), in degrees, and the vertical axis is the main polarization / cross polarization level, which has been normalized in dB. It can be seen from the figure that the -10dB half beam width is around 60°, and the cross polarization level is around -15dB.

[0056] The present invention has a compact feeding structure, which is not only conducive to the miniaturization of the entire antenna and the reduction of the cross-sectional height, but also reduces the deformation of the reflecting surface caused by the weight of the feed source and solves the assembly problem, and can also suppress interference between signals, suppress phase center deviation, improve aperture efficiency, increase system stability, and enhance antenna performance.

[0057] The above are only preferred application examples of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-wideband low-profile feed loaded with a stepped dielectric, characterized in that: include: Reflective floor, The metal cavity is located under the reflective floor. Two feeding baluns are placed in the metal cavity. Stepped dielectrics and dielectric columns are placed above the reflective floor. Four log-periodic antennas are arranged above the stepped dielectric and dielectric column; The four log-periodic antennas are divided into two pairs placed orthogonally, each pair comprising two log-periodic antennas placed opposite to each other, fixed on the dielectric column by screws, so as to form an angle with the reflective floor; There are four groups of stepped media, each group of which is composed of twelve media blocks arranged in a stepped manner, and is located between the log-periodic antenna and the reflecting floor, close to the reflecting floor; The metal cavity has an opening, and the two feeding baluns are placed orthogonally. Each feeding balun includes a dielectric substrate, an exponentially tapered microstrip line and a one-to-two power divider. The output end of the feeding balun extends through a via hole in the reflecting floor and is connected to the input end of a corresponding pair of oppositely placed logarithmic periodic antennas. The input end of the feeding balun extends to the outside of the metal cavity through the opening of the metal cavity.

2. The ultra-wideband low-profile feed source loaded with a stepped dielectric according to claim 1, characterized in that: The logarithmic periodic antenna adopts the form of a printed circuit board, which is realized by coating a metal layer on a single side of a dielectric substrate, wherein the metal layer is composed of twelve half-wave dipole units and a pair of parallel double wires; wherein the half-wave dipole units are connected in sequence in a folded form, and their length, width, spacing and position satisfy a logarithmic periodic relationship, one end of the parallel double wire is connected to the short dipole of the half-wave dipole unit, and the other end extends to the output end of the feeding balun to realize the feeding of the antenna.

3. The ultra-wideband low-profile feed source loaded with a stepped dielectric according to claim 1, characterized in that: The cross section of the dielectric column is Y-shaped and is made of Nylon1010. It is used to support two adjacent log-periodic antennas and fix them on the reflective floor.

4. The ultra-wideband low-profile feed source loaded with a stepped dielectric according to claim 1, characterized in that: Each set of stepped media corresponds to a logarithmic periodic antenna. In each set of stepped media, each dielectric block is located directly below a half-wave dipole unit, and the heights of adjacent dielectric blocks satisfy a logarithmic periodic relationship. The stepped media are fixed on the reflecting floor by screws.

5. The ultra-wideband low-profile feed source loaded with a stepped dielectric according to claim 1, characterized in that: Two feeding baluns are staggered and slotted and placed orthogonally. A connector is installed on the side of the feeding balun without routing, and the feeding balun is fixed to the back of the reflecting floor. The one-to-two power divider of one feeding balun is a compact routing, and the input end is located at the height of the upper half of the dielectric substrate. The one-to-two power divider of the other feeding balun is an extended routing, and the input end is located at the height of the lower half of the dielectric substrate.

Images