A broadband dual-polarized four-ridge-fed circular waveguide horn feed

Abstract

The present application relates to a kind of broadband dual-polarized four-ridge feed circular waveguide horn feed source, wherein the electric size of feed cavity is small, high-order mode suppression is realized, ridge waveguide part cooperates with the outer wall of feed cavity and adopts the structure of ridge curve and two transition sections, which can effectively expand the working bandwidth and reduce the voltage standing wave ratio;Feed probe adopts coaxial cable connected by two standard coaxial connectors;The transition section of circular waveguide from feed cavity to feed source radiation section adopts smaller horn opening angle, which further reduces the phase difference of high-frequency aperture field;The horn design using axial slot in feed source can realize broadband equalization beam, stable phase center and low cross polarization, and after optimization, the voltage standing wave ratio of the whole frequency range of the feed source is less than 1.5.The four-ridge horn feed source 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 broadband dual-polarized four-ridge waveguide horn feed. BACKGROUND

[0002] With the continuous development of compact range technology, the demand for compact range for the miniaturization of feed is increasing. The original standard waveband feed adopts the scheme of waveguide coaxial transition and then connects the feed radiation section through the rectangular circular transition. This scheme cannot meet the needs of compact range measurement due to the large physical size at low frequency. In the future, the miniaturization of the feed is the inevitable direction of development. Although there are many types of alternative miniaturized feeds, the ridge waveguide feed has a wide impedance bandwidth and has the potential to be used as a compact range feed. However, the ridge waveguide horn feed cannot be directly applied because the compact range requires a feed with a wide enough beam width, and the beam width of the ridge waveguide horn feed decreases with the increase of frequency. Therefore, it is necessary to design the feed according to the requirements of the compact range.

[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 ultra-high gain. With the increasing demand for wideband and high-efficiency reflector antenna systems in the fields of national economy and military defense, it is of great theoretical and engineering significance to study the ultra-wideband feed. The broadband dual-polarized feed proposed in the present application mainly consists of two parts: a corrugated horn and a four-ridge horn. The corrugated horn was first proposed by A.J.Simons and R.E.Lawrie in 1966. Studies on corrugated horn antennas have found that they have low sidelobe level, low cross-polarization, and amplitude-phase symmetry about the antenna structure. The four-ridge horn feed is a traditional horn feed with two pairs of perpendicular ridges inserted inside, which changes the internal field distribution of the horn feed and reduces the main mode cutoff frequency to achieve ultra-wideband operation. The four-ridge horn feed has the characteristics of wide operating bandwidth and simple feeding method. However, the traditional four-ridge horn feed has a large horn cross-sectional size at the mouth position and a small horn cross-sectional size at the feeding position. This is mainly because the four-ridge waveguide must be matched with the increase of the horn size during the opening process to ensure that the main mode is in a non-cut-off state in a wide band. The feed proposed in the present application does not significantly increase the horn mouth size at the end of the four-ridge waveguide transition, which brings great difficulty to the design. SUMMARY

[0004] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a broadband dual-polarized four-ridge feeding circular waveguide horn feed source, which significantly improves the broadband standing wave matching by adding two transition sections on the basis of the ridge waveguide curve, and has the advantages of simple structure, low return loss, small size, low cost and the like.

[0005] The technical scheme adopted by the present application is as follows: a broadband dual-polarized four-ridge feeding circular waveguide horn feed source, comprising a short-circuit plate, a feeding cavity, four ridges adopting specific ridge curves, and two SMA joint and axial circular waveguide double-slot corrugated horns; the front end of the circular wall of the feeding cavity is connected with the axial circular waveguide double-slot corrugated horn; the four ridges adopting specific ridge curves are respectively installed on the circular wall of the feeding cavity; the two SMA joints pass through the feeding cavity and the vertical two ridges of the four ridges adopting specific ridge curves in sequence and are in contact with the other two ridges of the four ridges adopting specific ridge curves; the design of the four-ridge and double-slot horn realizes low standing wave ratio and better beam width (greater than 48°), and the low standing wave ratio refers to the ratio of the amplitude of the voltage of the wave crest to the voltage of the wave trough of the transmission line.

[0006] In the broadband dual-polarized four-ridge feeding circular waveguide horn feed source, the horn part is an axial circular waveguide double-slot corrugated horn, the length of which is 0.65-0.85 lambda c , wherein lambda c is the wavelength corresponding to the lowest working frequency, and the inner wall diameter of the axial circular waveguide double-slot corrugated horn is 0.65-0.85 lambda c ; the opening angle of the feeding cavity is 3-6°, the width is 2.15-2.35 lambda c , the front end diameter of the cavity wall matched with the horn is the same as that of the horn, and the width of the rear cavity (non-opening angle part) of the feeding cavity is 0.22-0.31 lambda c .

[0007] In the broadband dual-polarized four-ridge feeding circular waveguide horn feed source, the thickness of the ridge waveguide ridge is 0.065-0.085 lambda c mm, the distance between the two ridges of the horn ridge waveguide part is 0.02-0.04 lambda c , and the distance between the two SMA joint connected semi-rigid coaxial cable feed joints and the short-circuit plate is 0.13-0.2 lambda c .

[0008] In the broadband dual-polarized four-ridge feeding circular waveguide horn feed source, the length of the two SMA joint and axial circular waveguide double-slot corrugated horns is 0.65-0.85 lambda Figure 3The ridge shown, wherein the ridge curve is divided into two parts a and b. Wherein a is the exponential curve part, the equation is: y=1.75e^(0.016*x)+0.04x. The b part is the transition section, which is divided into two sections, the total length is between 0.6~0.7 lambda c , wherein c length is between 0.3~0.4 lambda c , d width is between 0.01~0.1 lambda c .

[0009] Wherein, the wideband dual-polarized four-ridge feeding circular waveguide horn feed source, the distance between the ridge (such as Figure 1 4-1 and 4-2 in) and the plane close to the ridge side of the short-circuit plate (1) is between 0.1~0.16 lambda c , the distance between the ridge (such as Figure 2 4-3 and 4-4 in) and the plane close to the ridge side of the short-circuit plate (1) is between 0.11~0.17 lambda c .

[0010] Wherein, the wideband dual-polarized four-ridge feeding circular waveguide horn feed source, the metal is selected from: aluminum, iron, tin, copper, silver, gold, platinum, and alloys of the above metals.

[0011] The principle of the application is that: the application is a kind of wideband feed source for compact range test. The feed source can make the characteristic impedance of the main mode of the ridge waveguide and the characteristic impedance of the coaxial line achieve very good matching effect through the specific ridge curve (including exponential curve and transition section) and the opening angle of the cavity, effectively reduce the cutoff frequency of the main mode, greatly reduce the return loss of the horn, thereby improving the standing wave performance of the horn and expanding the working bandwidth of the horn; and the entire feeding part is a mechanical processing part, which greatly reduces the cost. By setting the ridge curve parameters (ridge curve equation parameters and transition section size), the length of the antenna is minimized, and the volume of the antenna is effectively reduced. The two SMA joint connected half-steel coaxial cable electric joints are used for the feeding probe, and the inner conductor of the feeding probe is improved, the extension diameter and length of the inner conductor are changed, which is convenient for the processing and assembly of the feed source. The two feeding probes are vertically installed and correspond to two polarizations of the feed source.

[0012] Compared with the prior art, the application has the following advantages:

[0013] (1), the application introduces a specific shape (specific ridge curve and transition section) four-ridge curve of the ridge curve according to the requirements of the compact range for the feed antenna, which expands the working frequency band of the four-ridge horn feed source and greatly reduces the standing wave. Most of the feed antennas use exponential curve ridge curve, and the standing wave is relatively high.

[0014] (2), the application realizes the dual-polarized low standing wave operation in the frequency range of 2.6-3.95GHz by introducing the four-ridge circular waveguide corrugated horn scheme in the feed antenna design, greatly improves the test efficiency, and most of the existing feeds are single-polarized, and the standing wave of the dual-polarized cannot meet the test demand. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a vertical cross-sectional schematic view of the structure of the wideband dual-polarized four-ridge feed circular waveguide horn feed source of the application.

[0016] Figure 2 It is a horizontal cross-sectional schematic view of the structure of the wideband dual-polarized four-ridge feed circular waveguide horn feed source of the application.

[0017] Figure 3 It is a schematic view of the ridge piece structure of the wideband dual-polarized four-ridge feed circular waveguide horn feed source of the application.

[0018] The meaning of the reference signs in the figure is:

[0019] 1 is a short-circuit plate, 2-1 and 2-2 are two SMA joints respectively, 3 is a feed cavity, 4-1, 4-2, 4-3 and 4-4 are four ridges adopting specific ridge curves respectively, and 5 is an axial circular waveguide double-slot corrugated horn. Figure 3 It is the outer shape of the ridge, the four ridge piece outer shapes are as shown in Figure 3 4-1, 4-2, 4-3 and 4-4 are the same. DETAILED DESCRIPTION

[0020] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0021] The application has good impedance bandwidth and better return loss according to the four-ridge horn antenna, through the design of key dimensions such as the mouth size of the ridge waveguide horn, the axial length, the ridge spacing, the ridge waveguide thickness, the ridge curve, the ridge waveguide size, the distance between the ridge and the rear cavity, the designed ridge waveguide horn can obtain the widest possible impedance bandwidth in the polarization direction, the low-frequency cutoff frequency of the ridge waveguide horn is reduced, the ridge piece shape is reasonably designed, and the standing wave ratio is effectively reduced under the condition of ensuring the bandwidth.

[0022] According to the concept of the above-mentioned application, the application adopts the following technical scheme:

[0023] As Figure 1 and Figure 2As shown, taking 2.6-3.95GHz as an example, the mouth size and length of the four-ridged horn antenna are basically determined first. The mouth size is mainly determined by the lowest frequency. The traditional four-ridged horn mouth needs to be greater than half of the lowest working frequency. The mouth size should be greater than 58mm. The length of the antenna should be determined according to the principle of optimal horn design, and the phase difference of the mouth should be as small as possible. The inner wall diameter of the axial circular waveguide double-slot corrugated horn 5 is between 0.65-0.85λ c ; and the angle of the feeding cavity 3 is between 3°-6°.

[0024] 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-6GHz. The thickness of the four ridges 4-1, 4-2, 4-3, 4-4 adopting a specific ridge curve is between 0.065-0.085λ c mm. The distance between the two ridges of the horn ridge waveguide part is between 0.02-0.04λ c . The distance between the two semi-rigid coaxial cable feed connectors 2-1, 2-2 connected by the SMA joint and the short circuit plate is optimized to minimize the standing wave ratio. The distance between the two semi-rigid coaxial cable feed connectors 2-1, 2-2 connected by the SMA joint and the short circuit plate is between 0.13-0.2λ c .

[0025] The ridge curve adopts an exponential curve and a transition section, as shown in Figure 3 . The exponential curve part adopts the curve equation y=Ae (B*x) +c*x, where the value of A is half of the distance between the two ridges. Through simulation, the ridge curve equation is finally determined as y=1.75e^(0.016*x)+0.04x. The b part is determined as a transition section through simulation optimization. The total length of the transition section is between 0.6-0.7λ c , the length c is between 0.3-0.4λ c , and the width d is between 0.01-0.1λ c . In order to cooperate with the feeding cavity 3, the four ridges need to be rounded with the feeding cavity 3. In actual engineering, there is a certain error in antenna processing. In the design, the corresponding processing tolerance needs to be given. Due to the processing error, it is difficult to ensure good electrical contact between the four ridges 4-1, 4-2, 4-3, 4-4 adopting a specific ridge curve and the rear cavity. Simulation and experiments have proved that if the four ridges 4-1, 4-2, 4-3, 4-4 adopting a specific ridge curve do not have good electrical contact with the rear cavity, it will have a great impact on the standing wave of the ridge horn. Therefore, in the design, multiple screws are used to connect the four ridges 4-1, 4-2, 4-3, 4-4 adopting a specific ridge curve with the feeding cavity, so that the ridges have good electrical contact with the cavity.

[0026] The cavity size is mainly based on the optimization of the standing wave of the axial circular waveguide double-slot corrugated horn, and in a preferred embodiment of the present application, the feeding cavity 3 has an angle of 3°-6° and a width of 2.15-2.35λ c The front end of the wall of the feeding cavity 3 is matched with the front end of the axial circular waveguide double-slot corrugated horn 5, and the diameter of the front end of the horn is the same as that of the horn, and the rear cavity width of the feeding cavity 3 is 0.22-0.31λ c .

[0027] In order to realize better beam characteristics of the feed source, the axial circular waveguide double-slot corrugated horn 5 is used, so that the beam width of the feed source is larger.

[0028] The improved four-ridge horn feed source can be made of aluminum, copper and other good conductive metals, and as a preferred embodiment, hard aluminum is used as the processing material.

[0029] The present application relates to a kind of broadband dual-polarized four-ridge feed circular waveguide horn feed source, which can be used as transmitting feed source of tight field and receiving feed source of tight field. It is mainly used for the conventional test of tight field, and can be used as the feed source of antenna and RCS measurement system of tight field, and also can be used as tight field quiet zone detection probe, so as to realize high-efficiency quiet zone detection.

Claims

1. A broadband dual-polarized quad-ridged feed circular waveguide horn feed source, characterized by: It comprises a short-circuit plate (1), a feeding cavity (3), four ridges (4-1, 4-2, 4-3, 4-4) with specific ridge curves, two SMA joints (2-1, 2-2) and an axial circular waveguide double-slot corrugated horn (5); the front end of the circular wall of the feeding cavity (3) is connected with the axial circular waveguide double-slot corrugated horn (5); the four ridges (4-1, 4-2, 4-3, 4-4) with specific ridge curves are respectively installed on the circular wall of the feeding cavity (3), the two SMA joints (2-1, 2-2) pass through the feeding cavity (3) and the vertical two ridges (4-1, 4-2) of the four ridges (4-1, 4-2, 4-3, 4-4) with specific ridge curves in sequence, and are in contact with the other two opposite ridges (4-3, 4-4) of the four ridges (4-1, 4-2, 4-3, 4-4) with specific ridge curves. The ridge curve of the four ridges with specific ridge curve is divided into two parts, including an exponential curve part and a straight transition section, the equation of the exponential curve part is: y=1.75e^(0.016 x)+0.04x; the transition section is divided into two sections, the total length ranges from 0.6 to 0.7 lambda c , wherein the length of one section ranges from 0.3 to 0.4 lambda c , the width ranges from 0.01 to 0.1 lambda c , lambda c is the wavelength corresponding to the lowest working frequency; the combination of the exponential curve and the straight transition section effectively reduces the standing wave ratio of the feed antenna.

2. The wideband dual-polarized quad-ridged feed circular waveguide horn feed according to Claim 1, wherein: The length of the axial circular waveguide double-slot corrugated horn (5) ranges from 0.65λ to 0.85λ c The diameter of the inner wall of the axial circular waveguide double-slot corrugated horn ranges from 0.65λ to 0.85λ c λ c is the wavelength corresponding to the lowest working frequency.

3. The wideband dual-polarized quad-ridged feed circular waveguide horn feed according to Claim 1, wherein: The opening angle of the feeding cavity (3) ranges from 3° to 6°, and the length ranges from 2.15λ to 2.35λ c , λ c is the wavelength corresponding to the lowest operating frequency.

4. The wideband dual-polarized quad-ridged feed circular waveguide horn feed of Claim 1, wherein: The thickness of the four ridges (4-1, 4-2, 4-3, 4-4) with specific ridge curves ranges from 0.065λ to 0.085λ c The distance between the two vertical ridges (4-1, 4-2) ranges from 0.02λ to 0.04λ c The minimum distance between the two opposite ridges (4-3, 4-4) ranges from 0.11λ to 0.17λ c .

5. The wideband dual-polarized quad-ridged feed circular waveguide horn feed of Claim 1, wherein: Of the four ridges with specific ridge curves, the distance between the four ridges and the short-circuit plate is 0.1-0.16λ c .

6. The wideband dual-polarized quad-ridged feed circular waveguide horn feed of Claim 1, wherein: The distance between the two SMA joints (2-1, 2-2) and the short circuit plate (1) is 0.13~0.2λ c .

7. The wideband dual-polarized quad-ridged feed circular waveguide horn feed according to claim 1, wherein: The wideband dual-polarized four-ridge-fed circular waveguide horn feed source is made of metal, and the metal is selected from aluminum, iron, tin, copper, silver, gold, platinum and alloys of the above metals.

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