Stepped reverse ridge structure short axial length dual-polarized compact field feed antenna

Abstract

The present application relates to a kind of stepped inverted ridge structure short axial length dual-polarized compact range feed antenna, wherein inverted ridge fin part adopts stepped fin, cooperate with small angle of aperture conical waveguide structure can effectively expand working bandwidth, compress horn axial length, reduce voltage standing wave ratio;Feed probe adopts four standard coaxial connector connected coaxial cable;Feed uses horn design with axial slot, can realize beam with wideband equalization, stable phase center and low cross polarization, after optimization, feed full-band realizes voltage standing wave ratio less than 1.5.The four-ridge horn feed has the outstanding advantages of simple structure, small size, light weight and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compact range feed, in particular to a stepped inverted ridge structure short axial length dual-polarized compact range feed antenna. BACKGROUND

[0002] With the continuous development of compact range technology, the demand for compact range miniaturization of feed is increasing. The original standard waveband feed adopts the scheme of waveguide coaxial transition and then through the rectangular circular transition to connect the feed radiation section. This scheme cannot meet the demand of compact range measurement due to the large physical size at low frequency. In the future, the miniaturization of wideband feed is the inevitable direction of development.

[0003] The feed is the core component of the reflector antenna. The reflector antenna has the advantages of simple system, low cost and easy to achieve super high gain. With the increasing demand for wideband and high-efficiency reflector antenna systems in the national economic field and the military defense field, it has great theoretical and engineering significance to study the ultra-wideband feed.

[0004] The feed capable of realizing dual polarization mainly includes corrugated horn and four-ridge horn, etc. The corrugated horn has the advantages of rotationally symmetric pattern, low sidelobe, low voltage standing wave ratio, low cross polarization, and stable phase center, etc. However, due to the existence of many high-order modes at high frequency, the working bandwidth is low and cannot meet the current application demand. The four-ridge horn feed is inserted with two pairs of perpendicular ridges inside the traditional horn, and has the characteristics of wide working bandwidth and simple feeding mode. However, when it is used as a feed to irradiate the reflector antenna at high frequency, the aperture efficiency of the antenna is low, which cannot meet the urgent demand of ultra-wideband high-efficiency antenna. When it is used as a feed, similar to the traditional horn feed, the widening of the working frequency band will cause the beam width to narrow sharply, which seriously affects the performance of the antenna. SUMMARY

[0005] The present application solves the problem of overcoming the shortcomings of the prior art and providing a stepped inverted ridge structure short axial length dual-polarized compact range feed antenna. The inverted four-ridge stepped horn feed is used to significantly improve the wideband standing wave matching, ensure the wide beam radiation of the entire feed in the wide frequency band, and has the advantages of simple structure, low return loss, small size, low cost, etc.

[0006] The technical scheme adopted by the present application is: a stepped inverted ridge structure short axial length dual-polarized compact field feed source antenna, comprising a stepped four-ridge, an axial circular waveguide single-slot corrugated horn, four semi-rigid coaxial cable feed joints connected by SMA joints, a bottom support block and a short circuit plate; the axial circular waveguide single-slot corrugated horn is divided into a single-slot corrugated horn section and a feed cavity section, and the single-slot corrugated horn can realize a wideband equalized beam, a stable phase center and low cross-polarization; the stepped inverted four-ridge, the axial circular waveguide single-slot corrugated horn, the bottom support block and the short circuit plate are sequentially connected to form a horn feed source, and the four semi-rigid coaxial cable feed joints connected by SMA joints sequentially pass through the feed cavity of the axial circular waveguide single-slot corrugated horn and the four ridge plates of the stepped four-ridge to realize conductive connection, the four ridge plates correspond to four feed ports respectively, the currents of a pair of opposite feed coaxial lines are equal in amplitude and opposite in phase, the radiation leakage and coupling of the currents are mutually offset, the generation of high-order modes is suppressed, and the cross-polarization and port isolation are improved; the axial length of the stepped inverted ridge structure short axial length dual-polarized compact field feed source antenna is 1.1-1.3 times the lowest working frequency.

[0007] The stepped four-ridge is in a cross structure, the stepped inverted four-ridge comprises two opposite ridge plates and two adjacent ridge plates, the two opposite ridge plates are in the same plane, and the two adjacent ridge plates are perpendicular to each other; the total length of the stepped four-ridge ranges from 1.02 to 1.1 lambda c , where lambda c is the wavelength corresponding to the lowest working frequency; each ridge plate is divided into eight steps, the length of each step of the ridge plate ranges from 0.09 to 0.18 lambda c , and the width ranges from 0.01 to 0.006 lambda c . The stepped ridge plate can better realize the matching of the characteristic impedance of the coaxial line and reduce the reflection of the port surface.

[0008] The length of the single-slot corrugated horn section ranges from 0.8 to 0.95 lambda c , the inner wall opening angle of the single-slot corrugated horn section ranges from 1° to 5°, and a smaller opening angle is adopted to reduce the phase difference; the length of the feed cavity section ranges from 0.07 to 0.13 lambda c , the inner diameter of the cavity of the feed cavity section ranges from 0.4 to 0.5 lambda c , and lambda c is the wavelength corresponding to the lowest working frequency. These dimensions are designed to match the stepped inverted four-ridge, so that the final measured result of the simulated and manufactured feed source antenna is that the standing wave ratio is less than 1.5, and the radiation characteristics are good, that is, the 3dB beam width is greater than or equal to 55°, the feed source far field pattern is relatively round, and there is no crack, which indicates that the radiation characteristics are good.

[0009] The stepped four ridges are fixed by support blocks, and the center of the stepped four ridges is connected with the short circuit plate, and the width of the bottom support block is consistent with the length of the feeding cavity section.

[0010] The groove of the single-groove corrugated horn section is circular, and the groove depth ranges from 0.23 to 0.29 lambda c , and the groove width is 0.09-0.13 lambda c .

[0011] Because the 3dB beam width of a general horn feed source is small, it cannot meet the test requirements, and adding a single-groove horn section can widen the beam width and meet the test requirements.

[0012] The stepped inverted ridge structure short-axis length dual-polarized compact range feed source antenna is composed of metal, and the metal is selected from aluminum, iron, tin, copper, silver, gold, platinum and alloys of the above-mentioned metals.

[0013] The principle of the present application is:

[0014] The present application is a kind of wideband feed source for compact range test, which is based on the idea of microwave technology multi-branch matching circuit, and the traditional exponential curve or elliptical curve transition method is evolved into multiple nodes of mutation, and through the control of node position and impedance, short-distance broadband matching is realized. Based on the analysis of the propagation mode characteristics in the waveguide, the impedance is changed by changing the distance between the ridge and the horn wall, and the main mode characteristic impedance of the ridge waveguide and the characteristic impedance of the coaxial line are matched very well through the structure of the stepped inverted four ridges and the horn angle, which effectively reduces the cutoff frequency of the main mode, greatly reduces the return loss of the horn, and improves the standing wave performance of the horn and expands the working bandwidth of the horn. The whole structure is simple, which greatly reduces the cost. By setting the shape of the stepped four ridges, the length of the antenna is minimized, and the volume of the antenna is effectively reduced. The feeding probe adopts a half-steel coaxial cable feeding joint connected by four SMA joints, and the opposite two feeding ports are in phase opposition.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] (1) The present application introduces stepped inverted four-ridge structure and axial single-groove corrugated horn section design in combination with the requirements of tight field for feed antenna, broadens the working frequency band of four-ridge horn feed, compresses the axial length, and greatly reduces the standing wave, laying a foundation for the application of inverted ridge waveguide antenna in the frequency band below 2GHz. The existing low-frequency feed antenna is larger than 400mm in volume, and the axial length is compressed to less than 370mm through the introduction of stepped inverted four-ridge structure in the design of the present application.

[0017] (2) The present application uses the structure of stepped inverted four-ridge to make the two polarizations completely consistent, realizes ultra-wideband, high cross-polarization isolation and high port isolation characteristics, and the feed of the present application is 1-2.4GHz, which is ultra-wideband, and the isolation is less than-50dB, realizing good port isolation.

[0018] (3) The present application introduces inverted four-ridge circular waveguide corrugated horn scheme in the design of feed antenna, realizes dual-polarized low standing wave operation in the frequency range of 1-2.4GHz, and greatly improves the test efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a three-dimensional schematic view of the stepped inverted ridge structure short axial length dual-polarized tight field feed antenna of the present application.

[0020] Figure 2 It is a structure vertical cross-sectional schematic view of the stepped inverted ridge structure short axial length dual-polarized tight field feed antenna of the present application.

[0021] Figure 3 It is a structure horizontal cross-sectional schematic view of the stepped inverted ridge structure short axial length dual-polarized tight field feed antenna of the present application.

[0022] The meaning of the reference signs in the figure is:

[0023] 1 is a stepped four-ridge, 2 is an axial circular waveguide single-groove corrugated horn, 3 is an SMA joint connected semi-rigid coaxial cable feed joint, 4 is a bottom support block, and 5 is a short-circuit plate. Single-groove corrugated horn section (A) and feed cavity section (B). DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0025] The present application has good impedance bandwidth according to the four-ridge horn antenna, i.e. the designed feed source is 1-2.4GHz, better return loss (less than -13dB), and the key dimensions of the single-slot corrugated horn, the size of the slot of the single-slot horn, the stepped ridge curve size and length of the stepped four-ridge, and the axial length of the single-slot corrugated horn are optimized to make the ridge waveguide horn have as wide as possible impedance bandwidth in the polarization direction, so that the low-frequency cutoff frequency of the ridge waveguide horn is reduced, and the standing wave ratio is effectively reduced under the condition of ensuring the bandwidth by reasonably designing the ridge shape.

[0026] According to the concept of the above-mentioned application, the present application adopts the following technical solutions:

[0027] As shown in Figure 1 , Figure 2 , Figure 3 , taking 1-2.4GHz frequency as an example, the aperture size of the four-ridge horn antenna is first basically determined, i.e. the size of the axial circular waveguide single-slot corrugated horn 2 is determined, and the aperture size is mainly determined by the lowest frequency. The aperture of the traditional four-ridge horn needs to be greater than half of the lowest working frequency, and the aperture should be greater than 150mm. The length of the antenna should be designed according to the principle of optimal horn design, and the aperture phase difference should be as small as possible. The axial circular waveguide single-slot corrugated horn 2 is divided into two parts, i.e. a single-slot corrugated horn segment A and a feeding cavity segment B. The length of the single-slot corrugated horn segment A is between 0.8-0.95λ c , wherein λ c is the wavelength corresponding to the lowest working frequency, and the inner wall opening angle is between 1°-5°. The length of the feeding cavity segment B is mainly designed based on the standing wave optimization of the stepped inverted four-ridge feed source. In one preferred case of the present application (return loss less than 13dB), the length of the feeding cavity is between 0.07-0.13λ c , and the cavity inner diameter is between 0.4-0.5λ c .

[0028] According to the magnetic field integral equation method proposed by BALANIS, the main mode TE 10 of the ridge waveguide is selected. The single-mode working frequency band is 1GHz-2.4GHz, and the ridge thickness is determined to be between 0.01-0.06λ c . Since the general feed source is designed to have a relatively long axial length, the voltage standing wave ratio can be effectively reduced, and the working frequency band can be widened. There are many gradual curves such as exponential curves and parabolic curves for the ridge curve. The stepped four-ridge 1 structure adopted in the present application can effectively reduce the reflection and reduce the standing wave ratio, but the impedance matching design is very complex, and the parameters of each layer of the stepped four-ridge 1 need to be optimized and adjusted to effectively reduce the standing wave ratio. The relative two ridges are in the same plane, the adjacent two ridges are perpendicular to each other, and the whole stepped four-ridge 1 is in a cross structure. The total length of the stepped four-ridge 1 is between 1.02-1.1λc The length of each step of the ridge is between 0.09-0.18 lambda c .

[0029] Since the impedance of the common waveguide is much larger than the impedance of the coaxial line, the feeding interface needs to be far away from the inner wall of the axial circular waveguide single-slot corrugated horn 2, and in order to prevent the joint from being short-circuited and unable to radiate, the joint is connected and fixed with the wall of the axial circular waveguide single-slot corrugated horn 2.

[0030] The stepped inverted four-ridge 1 is different from the loaded ridge structure in the conventional horn, and adopts the structure of the inverted fixed four-ridge, and does not contact the side wall. The center of the bottom supporting block 4, the center of the stepped four-ridge 1 and the center of the short-circuit plate 5 are aligned, so as to ensure the symmetry of the structure. The horn feed generally adopts a 50-ohm radio frequency coaxial line for feeding, and the feed feeding adopts a half-steel coaxial cable feeding interface 3 connected by four SMA joints, and the opposite two feeding ports are in phase opposition. The two pairs of probes perpendicular to each other correspond to the two polarizations of the feed. In actual engineering, there is a certain error in antenna processing, and in the design, the corresponding processing tolerance needs to be given. Due to the existence of processing error, the center of the stepped four-ridge will be deviated, which will affect the performance of the feed. The deviation can be reduced by adding pins and other structures to the short-circuit plate.

[0031] The wideband horn feed of the stepped inverted four-ridge 1 can adopt good conductive metals such as aluminum and copper, and as an optimal embodiment, hard aluminum is used as the processing material.

[0032] The wideband horn feed based on the stepped inverted four-ridge of the application realizes the characteristics of super wideband, high cross-polarization isolation and high port isolation in the frequency band of 1GHz-2.4GHz, and the standing wave ratio in the frequency band is less than 1.5.

[0033] The application can be used as a transmitting feed of a compact range and also as a receiving feed of a compact range. It is mainly used for conventional testing of a compact range, and can be used as a feed of an antenna and an RCS measurement system of a compact range, and also can be used as a static zone detection probe of a compact range, so as to realize efficient static zone detection.

Claims

1. A stepped inverted ridge structure short axial length dual-polarized compact range feed antenna, characterized in that: The application relates to a short-axial-length dual-polarized compact-field feed source antenna, which realizes dual-polarized low standing wave operation in a 1-2.4GHz frequency range and comprises a stepped inverted four-ridge (1), an axial circular waveguide single-slot corrugated horn (2), four semi-rigid coaxial cable feed joints (3) connected through SMA joints, a bottom supporting block (4) and a short-circuit plate (5); the axial circular waveguide single-slot corrugated horn (2) is divided into a single-slot corrugated horn section (A) and a feed cavity section (B); the stepped inverted four-ridge (1), the axial circular waveguide single-slot corrugated horn (2), the bottom supporting block (4) and the short-circuit plate (5) are sequentially connected to form a horn feed source, the four semi-rigid coaxial cable feed joints (3) connected through SMA joints are sequentially threaded through the feed cavity section (A) of the axial circular waveguide single-slot corrugated horn (2) and four ridge plates of the stepped inverted four-ridge (1) to realize electrically conductive connection; the stepped inverted ridge structure adopts a reverse fixed four-ridge structure, does not contact the side wall, and the axial length of the stepped inverted ridge structure short-axial-length dual-polarized compact-field feed source antenna is 1.1-1.3 times the axial length of the lowest working frequency.

2. The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed antenna of claim 1, wherein: The stepped inverted quadruple ridge (1) is in a cross structure, the stepped inverted quadruple ridge (1) includes two opposite ridge pieces and two adjacent ridge pieces, the two opposite ridge pieces are in the same plane, and the two adjacent ridge pieces are perpendicular to each other; the total length of the stepped inverted quadruple ridge (1) ranges from 1.02 to 1.1 λ c , λ c is the wavelength corresponding to the lowest working frequency; each ridge piece is divided into eight steps, and the length of each step of the ridge piece ranges from 0.09 to 0.18 λ c , and the width ranges from 0.01 to 0.006 λ c .

3. The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed antenna of claim 1, wherein: The length of the single-groove corrugated horn section (A) ranges from 0.8 to 0.95λ c The inner wall angle of the single-groove corrugated horn section (A) ranges from 1° to 5° c The length of the feed cavity section (B) ranges from 0.07 to 0.13λ c The cavity inner diameter of the feed cavity section (B) ranges from 0.4 to 0.5λ c λ is the wavelength corresponding to the lowest working frequency.

4. The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed antenna of claim 1, wherein: The stepped inverted four-ridge (1) is fixed through the bottom supporting block (4), and the center of the stepped inverted four-ridge (1) is connected with the short-circuit plate (5); the width of the bottom supporting block (4) is consistent with the length of the feed cavity section (B).

5. The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed antenna of claim 1, wherein: The single groove corrugated horn segment (A) has a groove depth ranging from 0.23λ to 0.29λ c , and a groove width of 0.09λ to 0.13λ c .

6. The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed antenna of claim 1, wherein: The stepped inverted ridge structure short-axial-length dual-polarized compact-field feed source antenna is composed of metal, and the metal is selected from the group consisting of aluminum, iron, tin, copper, silver, gold, platinum and alloys of the above-mentioned metals.

Images