A flat, compacted field device with arbitrary aperture-to-height ratio

Abstract

This invention discloses a flat, compact field device with arbitrary aperture-to-height ratio. The device mainly consists of a flat, compact field aperture, a collimated flat plane wave quiet zone, and a feed source. The aperture-to-height ratio is arbitrary, but is recommended to be greater than or equal to 2. This invention also discloses a low-frequency limit design formula for arbitrary flat, compact fields. The low-frequency limit is determined by the aperture type, narrow-side electrical dimensions, and aperture-to-height ratio. A diagonal feed layout is recommended for flat reflector compact fields, which reduces the three-dimensional angle of the reflector towards the feed source, lowers the illumination level of the feed source on the reflector, thereby reducing the taper of the quiet zone amplitude and improving the aperture utilization rate of ultra-large flat, compact fields to 67%. The flattened compact field aperture reduces the aperture size and the height of the shielded anechoic chamber, reduces the self-weight deformation of the high-precision reflector, facilitates the engineering implementation and cost control of ultra-large compact fields, and ensures high-frequency and low-frequency limit performance.

Description

Technical Field

[0001] This invention belongs to the field of compression fields, and specifically relates to a flat compression field device with arbitrary aspect ratio. Background Technology

[0002] Modern aerospace equipment, such as aircraft and missiles, mostly exhibits flat geometric structures. Therefore, obtaining the scattering characteristics of these full-size radar targets is increasingly urgent, as it directly relates to the electromagnetic signature quality of large-scale equipment. Measuring radar target scattering characteristics is typically accomplished through a compacted field test. Traditional compacted field test apertures are mostly square or near-square rectangular structures, with a quiet zone utilization rate of approximately 40%–50%. Solving the technical challenges of testing full-size flat targets presents two main challenges: 1) If the traditional technical approach is adopted, testing aerospace equipment exceeding 20m in size would require a square or near-square reflector exceeding 40m × 40m in size, increasing the development risk, difficulty, and manufacturing cost of the reflector. The 40m height, in particular, poses a significant challenge to controlling the deformation of the precision reflector due to its own weight. 2) If the flat reflector is designed by directly scaling it proportionally to the flat structure of the target under test, the aperture faces the problem of width-to-height imbalance, making it difficult to guarantee low-frequency performance in the quiet zone, especially along the short side of the reflector. Therefore, current traditional compact field solutions are not conducive to meeting the engineering requirements of ultra-large quiet zones for full-scale testing of aerospace equipment, and are difficult to meet the technical requirements of excellent performance in low-frequency and high-frequency quiet zones. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a flat, compact field device with an arbitrary aperture aspect ratio. The aspect ratio is recommended to be greater than or equal to 2. A diagonal feed layout is employed to increase the uniformity of the feed beam's illumination of the reflector surface, and edge processing is used to control the impact of diffraction on the quiet zone. The flattened aperture reduces the reflector height, minimizing the self-weight deformation of the reflector surface caused by its forward tilting. The improved feed beam uniformity from the diagonal offset feeding enhances the lateral high-aperture utilization of the compact field. Optimized edge diffraction control techniques, particularly edge curling or aperture-phase weighting, improve the quiet zone quality. These techniques will facilitate the improvement of the quiet zone quality of the compact field in ultra-large quiet zones, especially its low-frequency and high-frequency limiting performance, while controlling the aperture size. This invention discloses low-frequency limiting design criteria and formulas while ensuring that the low-frequency limiting performance meets typical performance requirements.

[0004] The main purposes of adopting a flat aperture and diagonal offset layout are: 1. To reduce the engineering difficulty caused by the increased height of large precision compact field apertures; 2. To improve the aperture utilization rate of the compact field without increasing the size of the compact field device (including the height of the compact field reflector, the area and volume occupied by the anechoic chamber); 3. To control the development risks and costs of ultra-large compact field devices, including large anechoic chambers, including the construction risks and costs caused by the increased space occupied by the anechoic chamber, the increased height of the test target, and the increased area of ​​the absorbing material; 4. To reduce the impact of the reflector's self-weight structure on the accuracy of the compact field reflector while ensuring the high-frequency performance in the quiet zone; 5. To improve the low-frequency limit performance of the compact field device.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0006] A flat, compact field device with arbitrary aperture-to-height ratio comprises a flat, compact field aperture, a collimated flat plane wave quiet zone, and a feed source. The flat plane wave quiet zone is a finite three-dimensional spatial region where the electromagnetic waves radiated by the feed source meet specific far-field testing requirements after being corrected by a reflecting surface. The width-to-height ratio of the compact field aperture is an arbitrary value. The flat, compact field device adopts a diagonal feed layout, which, under the same focal length constraint, reduces the three-dimensional angle of the reflecting surface towards the feed source, increases the uniformity of the feed source beam irradiation onto the reflecting surface, and helps to reduce the amplitude taper of the plane wave quiet zone and improve aperture utilization.

[0007] Furthermore, the aspect ratio is recommended to be greater than or equal to 2.

[0008] Furthermore, the low-frequency limit design criteria for the flat plane wave quiet zone are determined by the aperture type, the narrow side electrical dimensions of the aperture, and the aspect ratio.

[0009] Furthermore, the flat and compact field device, through a diagonal feed layout, achieves a lateral aperture utilization rate of ≥65% in the quiet zone.

[0010] Furthermore, the edges of the flattened compact field device employ edge processing technology to control the impact of edge diffraction on the quiet zone, thereby further improving aperture utilization and ensuring quiet zone performance at the low-frequency limit.

[0011] Furthermore, the low-frequency limiting design criteria include:

[0012] The width of the compacted field reflecting surface is N×M×10λ max The height is M×10λ max M represents the coefficient corresponding to the electrical dimensions in the narrow side direction for different types of apertures, where λ maxLet N be the aspect ratio of the flat aperture, corresponding to the maximum operating wavelength corresponding to the desired low-frequency limit. While ensuring the low-frequency limit, the amplitude and phase fluctuations of the quasi-plane wave field in the quiet zone meet the typical requirements of the quiet zone: amplitude ≤ 1dB ± 0.5dB, phase ≤ ± 5 degrees. The coefficient M corresponding to the electrical dimensions in the narrow side direction of different aperture types satisfies:

[0013]

[0014] Under the constraints of typical quiet zone performance indicators, the maximum operating wavelength λ′ corresponding to the practically achievable low-frequency limit is... max for:

[0015]

[0016] Where α is the low-frequency limiting coefficient corresponding to different aperture types:

[0017]

[0018] The advantages of this invention compared to the prior art are:

[0019] (1) Under the requirement of arbitrary aspect ratio of the quiet zone and ensuring the performance of the low-frequency limit quiet zone, the present invention provides the low-frequency limit design criteria and formula for the flat and compact field.

[0020] (2) The flat and compacted field of the present invention reduces the height requirement of the compacted field reflective surface, as well as the additional costs and risks associated with it. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a compacted field of a rolled-edge reflector with an aspect ratio of approximately 2.14:1. In the diagram, 1 is the feed source, 2 is the rolled-edge reflector, 3 is the front section of the quiet zone, 4 is the middle section of the quiet zone, 5 is the rear section of the quiet zone, 6 is the vertex of the reflector, 7 is the rotational symmetry axis of the reflector, and 8 is the electric axis of the compacted field.

[0022] Figure 2 This is a front view of the compressed field of the rolled-edge reflective surface, where 1 is the feed source, 2 is the rolled-edge reflective surface, and 9 is the quiet zone;

[0023] Figure 3 It is the amplitude distribution of the cross-section of the center of the static zone of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz;

[0024] Figure 4 It is the phase distribution of the center cross section of the quiet zone of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz.

[0025] Figure 5It is the amplitude distribution of the longitudinal section of the center of the static zone of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz;

[0026] Figure 6 It is the phase distribution of the longitudinal section of the center of the quiet zone of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0027] Figure 7 It is the amplitude distribution of the cross-section at the center of the static region of the compressed field of the rolled-edge reflector, with the curves corresponding to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0028] Figure 8 It is the phase distribution of the cross-section at the center of the cross section in the quiet region of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz;

[0029] Figure 9 It is the amplitude distribution of the longitudinal section at the center of the cross-section in the quiet zone of the compressed field of the rolled-edge reflector, with the curves corresponding to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0030] Figure 10 It is the phase distribution of the longitudinal section at the center of the cross-section in the quiet region of the compressed field of the rolled-edge reflecting surface, and the curves correspond to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0031] Figure 11 It is the amplitude distribution of the cross-section at the center of the static zone of the compressed field of the rolled-edge reflector, with the curves corresponding to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0032] Figure 12 It is the phase distribution of the center cross-section of the static region of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz.

[0033] Figure 13 It is the amplitude distribution of the longitudinal section at the center of the static zone of the compressed field of the rolled-edge reflector, with the curves corresponding to frequencies of 0.3 GHz, 0.6 GHz, and 2.0 GHz;

[0034] Figure 14 It is the phase distribution of the longitudinal section at the center of the static zone of the compressed field of the rolled-edge reflector, and the curves correspond to frequencies of 0.3GHz, 0.6GHz, and 2.0GHz. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] The flat, compacted field device with arbitrary aperture-to-height ratio of the present invention mainly consists of a flat compacted field aperture, a collimated flat plane wave still zone, and a feed source.

[0037] The ratio of the width to the height of the compressed field aperture is arbitrary, but it is recommended to be greater than or equal to 2. The low-frequency limit design criteria are determined by the aperture type, the narrow side electrical dimensions of the aperture, and the aspect ratio.

[0038] The plane wave quiet zone is a finite three-dimensional spatial region in which the electromagnetic waves radiated by the feed source meet specific far-field testing requirements after being corrected by the reflecting surface.

[0039] The flat, compact field device adopts a diagonal feed layout. Under the same focal length constraint, the three-dimensional angle of the reflector surface to the feed source is reduced. By reducing the three-dimensional angle of the reflector surface to the feed source, the uniformity of the feed source beam irradiation on the reflector surface is increased, which is beneficial to reduce the amplitude taper of the plane wave in the still zone and improve the aperture utilization rate.

[0040] The edges of the flat, compact field device employ optimized edge processing technology to control the impact of edge diffraction on the quiet zone, further improving aperture utilization and ensuring quiet zone performance at the low-frequency limit.

[0041] The technical principle of this invention is as follows:

[0042] The width of the compacted field reflecting surface is N×M×10λ max The height is M×10λ max M represents the coefficient corresponding to the electrical dimensions in the narrow side direction for different types of apertures, where λ max To determine the maximum operating wavelength corresponding to the desired low-frequency limit, N represents the aspect ratio of the flat aperture, and N ≥ 2 is recommended. Specifically, while ensuring the low-frequency limit, the amplitude and phase fluctuations of the quasi-plane wave field in the quiet zone should meet the typical requirements for the quiet zone: amplitude ≤ 1dB ± 0.5dB, phase ≤ ± 5 degrees. The coefficient M corresponding to the electrical dimensions along the narrow side of different aperture types should satisfy:

[0043]

[0044] Under the constraints of typical quiet zone performance indicators, the maximum operating wavelength λ′ corresponding to the practically achievable low-frequency limit is... max for,

[0045]

[0046] Where α is the low-frequency limiting coefficient corresponding to different aperture types:

[0047]

[0048] The flat-aperture design reduces the height of the compact field reflector, decreases the forward tilt of the precision reflector surface, thereby reducing the stiffness requirements of the reflector mounting frame. It also reduces the height of the darkroom and the height of the target to be measured in the compact field device installation environment.

[0049] The present invention will be further described below with reference to the accompanying drawings and specific examples.

[0050] A preferred embodiment of the present invention:

[0051] like Figure 1 The image shows a compacted field of a rolled-edge reflector with an aspect ratio of approximately 2.14:1, where feed 1 has a focal length of 54m; and rolled-edge reflector 2 has a width of 45m (45λ). max ), 21m high (21λ) max The aspect ratio is N = 2.14, and the height ratio is M = 2.1. Figure 1 The diagram also shows the front section 3 of the quiet zone, the middle section 4 of the quiet zone, and the rear section 5 of the quiet zone. The middle section 4 of the quiet zone is 16m away from the feed source 1. The distances between the front section 3, the rear section 5, and the middle section 4 of the quiet zone are all 15m. The diagram also shows the vertex 6 of the reflecting surface, the rotational symmetry axis 7 of the reflecting surface, and the electric axis 8 of the compacted field.

[0052] Figure 2 This is a front view of the compacted field of the rolled-edge reflector, showing feed 1, rolled-edge reflector 2, quiet zone 9, and a diagonal feed layout. The desired minimum operating frequency for the compacted field is 0.3 GHz, λ max =1m. To reduce the taper of the quiet zone amplitude, a diagonal feed layout is adopted. To reduce edge diffraction, according to equations (1) to (3), under the limited reflector height and aperture aspect ratio (N=2.14, M=2.1), to ensure the quiet zone performance at the desired lowest operating frequency, the reflector edge needs to be rolled. Full-wave simulation calculations were performed on the rolled-edge reflector, and three typical frequency points of 0.3GHz (45λ) were selected for low, medium, and high frequencies. max ×21λ max ), 0.6GHz (90λ) max ×42λ max ), 2GHz (300λ) max ×140λ max The quiet zone field is used to demonstrate the quiet zone performance. The quiet zone fields at three frequency points are shown below. Figures 3 to 14 .in, Figure 3 , Figure 4These are the amplitude and phase distributions of the center cross-section of the static zone of the compressed field of the rolled-edge reflecting surface; Figure 5 , Figure 6 These are the amplitude and phase distributions of the longitudinal section at the center of the static zone of the compressed field of the rolled-edge reflecting surface; Figure 7 , Figure 8 These are the amplitude and phase distributions of the central cross-section of the static region of the compressed field of the rolled-edge reflecting surface; Figure 9 , Figure 10 These are the amplitude and phase distributions of the longitudinal section at the center of the static region of the compressed field of the rolled-edge reflecting surface; Figure 11 , Figure 12 These are the amplitude and phase distributions of the center cross-section of the static region of the compressed field of the rolled-edge reflecting surface; Figure 13 , Figure 14 These are the amplitude and phase distributions of the longitudinal section at the center of the static zone of the compressed field of the rolled-edge reflecting surface; Figures 3 to 14 The results show that, based on the typical indexes of a compact field with a quiet zone amplitude tapered ripple of less than 1dB±0.5dB and a phase peak-to-peak value of less than ±5°, including the desired minimum operating frequency of 0.3GHz, the rolled-edge reflective surface can achieve a quiet zone range of 30m×10.5m×30m (horizontal direction×vertical direction×depth direction), with aperture utilization rates of 66.7% in the horizontal direction and 50% in the vertical direction. Therefore, the compact field device with the desired minimum operating frequency can be achieved using equations (1) to (3).

[0053] The parts of this invention not described in detail are well-known in the art. Those skilled in the art will readily understand that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A flat, compacted field device with an arbitrary aspect ratio, characterized in that: It consists of a flat, compact aperture, a collimated flat plane wave quiet zone, and a feed source. The flat plane wave quiet zone is a finite three-dimensional spatial region where the electromagnetic waves radiated by the feed source meet specific far-field testing requirements after being corrected by the reflecting surface. The width-to-height ratio of the compact aperture is a width-to-height ratio, which can be any value. The flat, compact aperture device adopts a diagonal feed layout, which, under the same focal length constraint, reduces the three-dimensional angle of the reflecting surface towards the feed source, increases the uniformity of the feed source beam irradiation onto the reflecting surface, and helps to reduce the amplitude taper of the plane wave quiet zone and improve the aperture utilization rate. The low-frequency limit design criteria for the flat plane wave quiet zone are determined by the aperture type, the narrow side electrical dimensions of the aperture, and the aspect ratio. The low-frequency limiting design criteria include: The width of the compacted field reflector is N × M ×10 The height is M ×10 , M Here are the coefficients corresponding to the electrical dimensions in the narrow side direction for different types of apertures, where The desired low-frequency limit corresponds to the largest maximum operating wavelength. N The aspect ratio is for a flat aperture; where, while ensuring the low-frequency limit, the amplitude and phase fluctuations of the quasi-plane wave field in the quiet zone meet the typical requirements of the quiet zone: amplitude ≤ 1dB ± 0.5dB, phase ≤ ± 5 degrees; the coefficients corresponding to the electrical dimensions in the narrow side direction of different types of apertures. M satisfy: （1） Under the constraints of typical quiet zone performance indicators, the maximum operating wavelength corresponding to the practically achievable low-frequency limit is... for: （2） in, Low-frequency limiting coefficients for different aperture types: （3）。 2. The flat, compacted field device with arbitrary aspect ratio according to claim 1, characterized in that: The aspect ratio is greater than or equal to 2.

3. A flat, compacted field device with arbitrary aspect ratio as described in claim 1, characterized in that: The flat, compact field device, with its diagonal feed layout, achieves a lateral aperture utilization rate of ≥65% in the quiet zone.

4. A flat, compacted field device with an arbitrary aspect ratio according to claim 1, characterized in that: The edges of the flat, compact field device employ edge processing technology to control the impact of edge diffraction on the quiet zone, further improving aperture utilization and ensuring quiet zone performance at the low-frequency limit.

Images