An off-axis quiet zone compact field device for array feeding

Abstract

The present invention discloses an array-fed off-axis quiet zone compact field device. Based on the compact field feed source defocus control and array feeding, the quiet zone beam realized by the defocus is compensated by the array feeding, thereby improving the quality of the off-axis plane wave quiet zone field, and is used for physical simulation and precise simulation testing of mobile communication base stations, terminals, radar targets or radar antennas in a far-field multi-beam electromagnetic environment. By controlling the defocus of the feed source, the direction of the electromagnetic beam reflected by the reflection surface can be changed, so that the plane wave quiet zone is off-axis; by the array feeding technology that can individually weight the amplitude and phase of the feeding unit, the amplitude and phase fluctuations caused by the off-axis ray path distortion can be compensated, and a high-quality plane wave field is synthesized in the quiet zone, thereby improving the quiet zone performance of the off-axis compact field system. The device of the present invention can achieve that when the feed source of the reflective surface compact field system is not in focus or the quiet zone is not on the axis, the system can still synthesize a high-quality plane wave quiet zone off-axis.

Description

Technical Field

[0001] The present invention relates to a compact field and array feeding technology, and in particular to an off-axis quiet zone compact field device for array feeding. The direction of the electromagnetic wave beam reflected by the reflection surface is controlled by feed source defocusing, so that the plane wave quiet zone is off-axis; the amplitude and phase fluctuations caused by the off-axis ray path distortion are compensated by array feeding with feed source amplitude and phase weighting, thereby improving the quality of the off-axis plane wave quiet zone field. It is mainly used in high-frequency antenna (such as millimeter wave antenna) testing, and provides a plane wave electromagnetic environment for simulation testing of equipment working in a far-field electromagnetic environment. Background Art

[0002] In order to test, debug and verify the performance of antenna equipment, it is necessary to accurately measure its far-field pattern. However, the far field of electrically large-sized antennas is often long, especially in high-frequency bands (such as millimeter wave bands), which can reach several kilometers or even tens of kilometers, making direct far-field measurement difficult to achieve in engineering. Compact field technology can directly test the far-field pattern of the antenna in a compact space, meeting the requirements of the controllable test distance and far-field electromagnetic environment for the radiation characteristics test of electrically large-sized antennas. The reflector compact field is a type of compact field with mature technology and the most widely used technology. It uses a precision parabola (the processing accuracy is generally 1 / 100 wavelength) to collimate and correct the spherical wave emitted by the feed source into a high-quality quasi-plane wave. In the design of the reflector compact field system, there are generally two problems: 1. Due to some special reasons, the feed source cannot be placed at the focus position of the reflector or the geometric center of the plane wave quiet zone cannot be placed on the system axis; 2. Due to the off-axis ray path distortion, the plane wave quiet zone field has large amplitude and phase unevenness. Summary of the invention

[0003] In view of the above problems, the present invention proposes an off-axis quiet zone compact field device for array feeding, which adopts compact field defocus control technology and array feeding device to realize plane beam direction control and plane wave field compensation, so as to make the feed source defocused or the quiet zone off-axis and synthesize a high-quality plane wave quiet zone field. It has the advantages of flexible feed source and quiet zone positions and high quiet zone field quality, solves the problems of compact field feed source defocusing, quiet zone off-axis and large amplitude and phase unevenness of the plane wave quiet zone field, and provides more favorable test conditions for antenna measurement.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an array-fed off-axis quiet zone compact field device, the device includes a compact field reflection surface, a feed source, a feed source defocus control system, and an equivalent electromagnetic environment quiet zone, wherein:

[0005] The compact field reflection surface is a parabola, the central solid part is a rotating parabola or a spherical surface, and the edge is processed by sawtooth or curling, which is used to reflect the electromagnetic wave emitted by the excitation source and compactly form the required plane wave front in the specified area;

[0006] The feed source is a feed source array in which the amplitude and phase of the feed units are independently controllable. By independently assigning predetermined amplitude and phase weights to each unit of the feed source array, a high-quality plane wavefront is synthesized in the quiet zone.

[0007] The feed source defocus control system is to adjust the position of the feed source through mechanical and electronic equipment to make the feed source defocus, thereby adjusting the radiation direction of the electromagnetic beam and controlling the quiet zone position;

[0008] The equivalent electromagnetic environment quiet zone is a plane wave electromagnetic field area formed by secondary radiation after the focused or defocused feed array illuminates the reflecting surface, which includes all on-axis and off-axis conditions and is used for antenna measurement and radar stealth testing.

[0009] Furthermore, the feeding method is feed array feeding. By independently assigning appropriate amplitude and phase weights to each antenna unit of the feed array, a high-quality plane wavefront can be synthesized in a compact field quiet zone. The appropriate amplitude and phase weights refer to weights that can compensate for the path difference caused by feed source defocusing.

[0010] Furthermore, the position of the feed array is regulated by using a compact field focus control system, including focus and defocus, to change the radiation direction of the compact field main beam, thereby controlling the position of the plane wave quiet zone field within a certain range.

[0011] Furthermore, the position of the equivalent electromagnetic environment quiet zone is indirectly controllable by the feed source position, including all situations on-axis and off-axis, that is, the aperture normal line where the geometric center of the quiet zone is located on or deviates from the aperture normal line of the equivalent aperture geometric center of the compact field reflection surface.

[0012] Furthermore, the equivalent electromagnetic environment quiet zone can be applied to the transmission link test, reception link test and transceiver link test of the radio system.

[0013] Furthermore, the realization of the feed array on which the plane wavefront synthesis depends includes a phased array antenna, a reflective array antenna, and a transmission array antenna.

[0014] Furthermore, the compact field reflection surface on which the plane wavefront synthesis depends includes a single reflection surface, a double cylinder, a Gregorian or Cassegrain type, or a multi-reflection surface.

[0015] The technical principles of the present invention are as follows:

[0016] The present invention discloses an array-fed off-axis quiet zone compact field device, comprising a compact field reflection surface, a feed source, a feed source focus control system, and an equivalent electromagnetic environment quiet zone. The feed source focus control system allows the feed source position to be flexibly adjustable within a certain range, and both the lateral focus and longitudinal focus of the feed source can cause the beam to deflect linearly, thereby making the radiation direction of the plane beam synthesized by the compact field controllable, and the position of the electromagnetic environment quiet zone equivalent to the compact field controllable.

[0017] The feed array (in focus or off focus) illuminates the reflecting surface. By independently assigning appropriate amplitude and phase weights to each antenna unit of the feed array, a high-quality plane wavefront can be synthesized in the compact field quiet zone (on axis or off axis). The high quality standard is: the peak-to-peak amplitude of the quiet zone is less than 0.5dB, and the peak-to-peak phase is less than 3.6 degrees. Figure 1 shown.

[0018] In order to control the influence of diffraction at the edge of the reflector and improve the performance of plane wave fields with equal amplitude and phase in the quiet zone, the edge of the reflector is usually serrated or curled. In order to avoid feed source shielding, the compact field system usually adopts an offset feed structure, the single reflector is part of a rotating parabola, and uses virtual vertex technology.

[0019] Among them, the realization of the feed array on which plane wavefront synthesis depends is not limited to phased array antennas, but also includes reflection arrays, transmission arrays, etc.

[0020] Among them, the compact field working principle on which plane wavefront synthesis relies is not limited to the type of reflection surface system scheme, including single reflection surface, double cylinder, Gregorian or Cassegrain type, multiple reflection surfaces, etc.

[0021] The design of the reflective surface of the compact field device is not limited to a specific edge form of the reflective surface, including serration or curling.

[0022] Among them, the working frequency band of the simulated plane wavefront is not limited to specific requirements. The highest frequency is determined based on the reflector surface accuracy and the allowable phase residual error of the quiet zone field. The peak-to-peak value of the plane wave phase after being excited by the antenna unit amplitude-phase-independent weighted feed source array can be controlled within at least 10 degrees. The lowest frequency must at least meet the reflector aperture electrical size greater than 10 to 17 times the wavelength.

[0023] Among them, the feed array control system on which plane wavefront synthesis depends is not limited to a specific implementation method, including manual control or electric control.

[0024] Among them, the radiation direction of the plane wave beam synthesized by the compact field can be adjusted within a certain range, and the adjustment range depends on the allowable error of the quiet zone.

[0025] Among them, the layout of the compact antenna test field of the integrated plane wavefront is not limited to indoors or outdoors. In order to put the background electromagnetic environment under controllable test conditions, it is recommended that the simulator be set up in a microwave darkroom.

[0026] The relationship between the angle offset of the radiation direction of the plane wave beam in the compact field and the feed source focus deviation is shown in the following formula:

[0027]

[0028]

[0029] Where: Δθ is the angular offset of the radiation direction of the compact field plane wave beam, H is the height of the geometric center of the equivalent aperture of the reflector or the system axis, F is the focal length of the reflector, Δx is the lateral focus offset of the feed source, which is positive when it is far away from the virtual vertex of the reflector and negative when it is close to the virtual vertex of the reflector, Δy is the longitudinal focus offset of the feed source, which is positive when it is far away from the system axis and negative when it is close to the system axis, θ 2 is the angle between the incident beam and the reflected beam when the feed is in focus, θ 1 It is the angle between the incident beam or reflected beam and the normal to the midpoint of the reflecting surface when the feed is in focus.

[0030] It should be pointed out that the constraint relationship of formula (1) is a paraxial approximation in the sense of geometric optics. When the edge diffraction is serious in the low-frequency band (such as the aperture is less than 30 times the wavelength) and the defocus is large (such as), the conditions for the optical ray theory and the paraxial approximation are not met, and more sophisticated methods are required for accurate calculation and evaluation, such as physical optics or computational electromagnetic algorithms such as the method of moments.

[0031] The advantages of the present invention compared with the prior art are:

[0032] (1) The multi-quiet zone compact field device with array compensation feeding can realize flexible displacement of the feed source within a certain range through the feed source focus control system, which is convenient for comprehensive consideration of the layout of facilities near the focus of the compact field system.

[0033] (2) The multi-quiet zone compact field device with array compensation feed can control the direction of the plane wave beam by adjusting the defocus of the feed source, thereby controlling the position of the quiet zone of the compact field equivalent electromagnetic environment, which is convenient for antenna measurement or radar electromagnetic scattering testing and the arrangement of equipment near the axis quiet zone.

[0034] (3) The multi-quiet zone compact field device with array compensation feeding can reduce the amplitude and phase unevenness of the plane wave quiet zone field by independently assigning appropriate amplitude and phase weights to each antenna unit of the feed source (on-focus or off-focus) array, and compensate for a plane wavefront of higher quality (high quality index: peak-to-peak value of quiet zone amplitude is less than 0.5dB, and peak-to-peak value of phase is less than 3.6 degrees) in the compact field quiet zone (on-axis or off-axis). The appropriate amplitude and phase weights can be obtained by amplitude and phase weighting by means of geometric optical path compensation method, inverse method, etc., which can compensate for the amplitude and phase unevenness caused by the wave path difference.

[0035] (4) The multi-quiet zone compact field device with array compensation feeding can work in a more controllable natural environment or electromagnetic environment, which is conducive to improving the test conditions of electromagnetic simulation debugging, reducing test costs and improving test efficiency. It is better than the outdoor field which is greatly affected by natural climate.

[0036] (5) The multi-quiet zone compact field device with array compensation feeding can operate in a wider radio frequency band and can be used in commonly used microwave and millimeter wave bands. For example, the 2m-level compact field reflector and 1m-level quiet zone can cover the S (2-4GHz), C (4-8GHz), X (8-12GHz), Ku (12-18GHz), K (28-27GHz), Ka (27-40GHz), U (40-60GHz), V (60-80GHz) bands and W (75-110GHz) bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the system working principle of the present invention, wherein 1 is the compact field reflection surface, 2 is the feed source array, 3 is the quiet zone offset range, 4 is the on-axis equivalent electromagnetic environment quiet zone, 5 is the off-axis equivalent electromagnetic environment quiet zone, 6 is the plane wave quiet zone field, 7 is the geometric center of the feed source array, 8 is the focus of the compact field reflection surface, 9 is the virtual vertex of the compact field reflection surface, 10 is the midpoint of the compact field reflection surface, 11 is the compact field system axis, 12 is the electromagnetic wave beam, and 13 is the normal to the midpoint of the compact field reflection surface.

[0038] Figure 2 It is a plane wave phase distribution diagram of a certain cross section of the quiet zone of an equivalent electromagnetic environment using the off-axis quiet zone compact field device using the array compensation feeding proposed by the present invention.

[0039] Figure 3 It is a multi-quiet zone compact field device fed by a single feed source (corrugated horn) in conjunction with Figure 2 The plane wave phase distribution diagram of the same section, where the excitation source and Figure 2 Except for the different simulation systems, other system parameters such as the size of the compact field reflection surface and the operating frequency are the same.

[0040] Figure 4 It is intercepted Figure 2 , Figure 3 A comparison chart of the wavefront path of the longitudinal section line on the cross section and the expected wavefront path, as well as a comparison chart of the difference wavelength values ​​between the path of the two sections and the path of the expected path.

[0041] Figure 5 It is intercepted Figure 2 , Figure 3 A comparison chart of the wavefront path of the cross-section line on the cross section and the expected wavefront path, as well as a comparison chart of the path difference ratio of the two cross-section lines to the expected path versus the wavelength value. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work are within the protection scope of the present invention.

[0043] like Figure 1 As shown, 1 is a compact field reflector. When the feed array 2 works at the focus of the reflector, the plane wave quiet zone 4 is on-axis, and the plane wave beam 12 is parallel to the system axis and points to the on-axis quiet zone 4. When the feed array 2 defocuses and illuminates the reflector 1, the plane wave quiet zone 5 is off-axis, and the plane wave beam 12 undergoes an angular offset of Δθ degrees. The angular offset Δθ is determined by formula (1), and the plane wave quiet zone is offset from the on-axis quiet zone 4 to the off-axis quiet zone 5. The plane wave field 6 in the on-axis quiet zone 4 or the off-axis quiet zone 5 is formed by the radiation of the feed array 2 and the reflection of the compact field reflector 1. By performing amplitude and phase weighted compensation on each antenna unit of the feed array 2, appropriate amplitude and phase weights can be used to perform amplitude and phase weighting through geometric optical path compensation method, inverse method, etc., which can reduce the amplitude and phase unevenness of the plane wave field 6, and thus synthesize a high-quality plane wavefront in the quiet zone 4 or 5.

[0044] The compact field reflector is manufactured by machining the reflector designed with edge processing. The reflector includes a working surface and a mounting back frame. The former is used to transform the wavefront emitted by the feed source to the desired wavefront, and the latter plays a role in mechanical support and positioning. In addition, the surface accuracy of the reflector and the control positioning with the feed source need to be guaranteed by the adjustment and positioning mechanism.

[0045] The purpose of the system offset feed design is to avoid the feed system blocking the reflective surface, and the offset feed will inevitably cause inconsistent path attenuation from the feed to the bottom and top of the aperture. The directional characteristics can be used to compensate for the imbalance of the spatial path by adjusting the feed illumination angle. Therefore, the feed offset control system must have the function of adjusting the illumination angle around the feed point (in focus or off focus). The purpose of the system offset feed is to adjust the plane wave beam pointing. Therefore, the feed bracket of the compact field must also have axial and lateral translation functions.

[0046] The function of the reflector entity is to correct the feed source transmission wave into the desired near-field wavefront, and the reflector edge processing is used to form aperture amplitude taper to suppress the influence of edge diffraction on the quiet zone.

[0047] Preferred embodiments of the present invention:

[0048] like Figure 1 The schematic diagram of the reflection surface and field distribution of the off-axis quiet zone compact field device of the array feed is shown. The origin of the system coordinate is located at the virtual vertex 9 of the compact field reflection surface. The coordinate system is set as follows Figure 1 As shown. The operating frequency is 1.2GHz, the size of the compact field reflection surface is 20m×16m, the focal length is 21m, and the reflection surface is a part of an infinite parabola whose vertex is (0, 0, 0). The quiet zone simulating the equivalent electromagnetic environment is 62.7m away from the vertex of the reflection surface. The size of the defocused feed array: the interval between each excitation source is approximately half a wavelength, and its projection on the plane with the normal as the vertical axis is a 1m×1m plane feed array with the geometric center point of (3.69m, 0m, 21.32m), which is equivalent to realizing the oblique incident plane wavefront. The simulation results are shown in Figure 2 shown.

[0049] Under the same system parameter layout, the phase distribution simulation results of the multi-quiet zone compact field device fed by a single feed source on this section are as follows Figure 3 As shown. Figure 4 , Figure 5 As shown, respectively Figure 2 and Figure 3 By comparing the longitudinal and transverse sections in the figure with the expected plane wavefront, the path distribution (phase distribution) of the multi-quiet-zone compact field device with array compensation feeding is more consistent with the expected value and has a smaller error. In addition, the peak-to-peak value of the phase of the plane wavefront achieved by the multi-quiet-zone compact field device with array compensation feeding is less than 3.6 degrees, which can meet the application requirements of the plane wavefront quiet zone electromagnetic environment.

[0050] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, and it should be clear that the present invention is not limited to the scope of the specific embodiments, for those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. An array-fed off-axis quiet zone compact field device, characterized in that: The device includes a compact field reflection surface, a feed source, a feed source focus control system, and an equivalent electromagnetic environment quiet zone, wherein: The compact field reflection surface is a parabola, the central solid part is a rotating parabola or a spherical surface, and the edge is processed by sawtooth or curling, which is used to reflect the electromagnetic wave emitted by the feed source and compactly form the required plane wave front in the specified area; The feed source is a feed source array in which the amplitude and phase of the feed units are independently controllable. By independently assigning predetermined amplitude and phase weights to each unit of the feed source array, a high-quality plane wavefront is synthesized in the quiet zone. The feed source defocus control system is to adjust the position of the feed source through mechanical and electronic equipment to make the feed source defocus, thereby adjusting the radiation direction of the electromagnetic beam and controlling the quiet zone position; The equivalent electromagnetic environment quiet zone is a plane wave electromagnetic field area formed by secondary radiation after the focused or defocused feed array illuminates the reflecting surface, which includes all on-axis and off-axis conditions and is used for antenna measurement and radar stealth testing; The feeding method is feed array feeding. By independently assigning appropriate amplitude and phase weights to each antenna unit of the feed array, a high-quality plane wavefront can be synthesized in a compact field quiet zone. The appropriate amplitude and phase weights refer to weights that can compensate for the path difference caused by feed defocus. The position of the feed array is regulated by using a compact field focus control system, including focus and defocus, to change the radiation direction of the compact field main beam, thereby controlling the position of the plane wave quiet zone field within a certain range; The position of the equivalent electromagnetic environment quiet zone is indirectly controllable by the feed position, including all situations on-axis and off-axis, that is, all situations on the aperture normal where the geometric center of the quiet zone is located on or deviates from the aperture normal of the equivalent aperture geometric center of the compact field reflection surface.

2. An array-fed off-axis quiet zone compact field device as claimed in claim 1, characterized in that: The equivalent electromagnetic environment quiet zone can be applied to the transmission link test, the reception link test and the transceiver link test of the radio system.

3. The array-fed off-axis quiet zone compact field device according to claim 1, characterized in that: The realization of the feed array on which the plane wavefront synthesis depends includes a phased array antenna, a reflective array antenna, and a transmission array antenna.

4. The array-fed off-axis quiet zone compact field device according to claim 1, characterized in that: The compact field reflection surface on which the plane wavefront synthesis depends includes a single reflection surface, a double cylinder, a Gregorian or Cassegrain type, or a multi-reflection surface.

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