A Phased Array Antenna Based on Interdigital Capacitor Loading and an RCS Reduction Method
By adopting an interdigital capacitance loading design in phased array antennas, adjusting the interdigital gap to change mode term scattering, the problem that existing phased array antennas are difficult to reduce RCS while maintaining radiation efficiency and gain, achieving more efficient stealth performance.
Patent Information
- Application Number
- CN202210471620.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-04-29
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2042-04-29
AI Technical Summary
While existing phased array antennas achieve high gain, wide band and low RCS, it is difficult to maintain radiation efficiency and gain, and the stealth performance is not enough to deal with the threat of enemy active detection systems.
The phased array antenna design based on the interdigital capacitance loading is adopted. By adjusting the interdigital gap on the interdigital capacitance, the mode term scattering is changed, thereby reducing the RCS of the antenna while keeping the structural term scattering unchanged.
The RCS of the phased array antenna is reduced on the basis of ensuring radiation characteristics. It has a simple structure and is easy to implement, which improves the stealth performance of the antenna.
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Figure CN114759361B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of radar, and relates to a method for reducing the RCS of a phased array antenna based on interdigital capacitor loading. Background Art
[0002] As a representative of the new generation of systems, the multi-functional active phased array radar system not only needs to have a long operating range, high sensitivity, and large information capacity, but also must have stealth characteristics in order to effectively enhance the ability to counter enemy reconnaissance and subsequent interference on the premise of ensuring its basic tactical performance, so as to gain the initiative in future battlefields; otherwise, simply relying on increasing the radiation power of the phased array radar system and increasing the aperture of the phased array antenna in accordance with traditional concepts to improve the operating range will only make itself more easily exposed. At the same time, in order to cope with the threat of enemy active detection systems, the requirements for the stealth performance of combat aircraft are getting higher and higher. The active phased array radar antenna installed on it is an important part of modern fighter jets, and as one of the three major strong scattering sources on the fighter jet's nose, its stealth performance directly affects the overall stealth performance of the fighter jet and plays a crucial role.
[0003] The electromagnetic scattering control of phased array antennas has its particularity. Phased array radars must first have a powerful detection ability in complex electromagnetic environments. The radiation characteristics of their phased array antennas need to achieve high gain, wide bandwidth, ultra-low sidelobes, etc., while at the same time achieving low RCS characteristics. Controlling the scattering characteristics of phased array antennas without reducing the antenna radiation efficiency and gain is the key technical difficulty in the design of phased array antennas. Summary of the Invention
[0004] To solve the problems existing in the prior art, the present invention provides a phased array antenna based on interdigital capacitor loading. The phased array antenna includes a metal substrate 3 and a dielectric substrate 2 located above the metal substrate 3. Two symmetrical radiation patches 1 are provided on the upper surface of the dielectric substrate 2. Interdigital capacitors 11 are provided on the outer edges of each radiation patch 1. The metal substrate 3, the dielectric substrate 2, and the radiation patch 1 are fed through a coaxial line 4 provided inside the phased array antenna.
[0005] Further, the coaxial line 4 includes a first inner conductor 41 passing through the dielectric substrate 2, a second inner conductor 42 passing through the dielectric substrate 2 and the metal substrate 3, and a second outer conductor 43 wrapping the lower end of the second inner conductor 42 and passing through the metal substrate 3; the lower end of the first inner conductor 41 is located at the interface between the dielectric substrate 2 and the metal substrate 3, and the lower end of the second inner conductor 42 is located at the bottom surface of the metal substrate 3; the upper ends of the first inner conductor 41 and the second inner conductor 42 are respectively connected to the inner edges of the radiation patch 1.
[0006] The present invention also provides an RCS reduction method for a phased array antenna, which is implemented by using any one of the above phased array antennas based on interdigital capacitor loading; the RCS of the phased array antenna is reduced by adjusting the interdigital gap of the interdigital capacitor, that is, the phased array antenna changes the mode term scattering while keeping the structural term scattering of the RCS theoretical model unchanged through interdigital capacitor loading.
[0007] Further, the RCS theoretical model is specifically:
[0008]
[0009] Where E out is the total RCS of the phased array antenna, is the mode term scattering, is the structural term scattering, represents the scattering field when and m≠n, represents the scattering field when ; represents that the nth unit is in an open state, represents that the scattering energy of the mth unit is 0; N represents the total number of units of the antenna; represents the passive reflection coefficient of the nth unit, represents the transmission coefficient of the energy re-radiated from the port incident signal of the pth unit coupled to the nth unit under the action of an incident field; represents the transmission coefficient of the energy re-radiated from the port incident signal of the pth unit of the antenna coupled to the qth unit under the action of an incident field; T nq represents T nq is the element in the nth row and qth column of the matrix T, where the matrix T = [P] -1
[0010] P = R -1 +S
[0011]
[0012] Where R np is the load transmission coefficient of the array reception (n≠p) / passive reflection coefficient (n = p), represents the transmission coefficient of the energy re-radiated from the port incident signal of the pth unit coupled to the nth unit in the case of a pure radiation problem.
[0013] Further, the interdigital gap of the interdigital capacitor is adjusted to 0.1 mm.
[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0015] A phased array antenna based on interdigital capacitor loading and an RCS reduction method proposed by the present invention can reduce RCS while ensuring radiation characteristics, with a simple structure and easy implementation. Description of the Drawings
[0016] Figure 1 It is a schematic diagram of the model of the phased array antenna based on interdigital capacitor loading in the first embodiment.
[0017] Figure 2 It is a schematic diagram of the interdigital gap of the model of the phased array antenna based on interdigital capacitor loading in the second embodiment.
[0018] Figure 3 It is a comparison diagram of the standing wave of the full-wave simulation of the model of the phased array antenna based on interdigital capacitor loading in the second embodiment
[0019] Figure 4 It is a comparison diagram of the gain of the full-wave simulation in the second embodiment.
[0020] Figure 5 It is a comparison diagram of the RCS of the full-wave simulation in the second embodiment.
[0021] Figure 6 It is a comparison diagram of the calculated RCS change amount results in the second embodiment. Detailed Embodiment
[0022] The present invention will be further described in detail below in conjunction with the embodiments and with reference to the drawings.
[0023] First Embodiment
[0024] As Figure 1 shown, this embodiment provides a phased array antenna based on interdigital capacitor loading. The phased array antenna includes a metal substrate 3 and a dielectric substrate 2 located above the metal substrate 3. Two symmetric radiation patches 1 are provided on the upper surface of the dielectric substrate 2. Interdigital capacitors 11 are provided on the outer edges of each radiation patch 1. The metal substrate 3, the dielectric substrate 2, and the radiation patch 1 are fed through a coaxial line 4 provided inside the phased array antenna.
[0025] The coaxial line 4 includes a first inner conductor 41 passing through the dielectric substrate 2, a second inner conductor 42 passing through the dielectric substrate 2 and the metal substrate 3, and a second outer conductor 43 wrapping the lower end of the second inner conductor 42 and passing through the metal substrate 3; the lower end of the first inner conductor 41 is located at the interface between the dielectric substrate 2 and the metal substrate 3, and the lower end of the second inner conductor 42 is located at the bottom surface of the metal substrate 3; the upper ends of the first inner conductor 41 and the second inner conductor 42 are respectively connected to the inner edges of the radiation patch 1.
[0026] Second Embodiment:
[0027] This embodiment is based on Embodiment 1 and provides a method for reducing the RCS of a phased array antenna. By adjusting the interdigital gap on the interdigital capacitor, the RCS of the phased array antenna is reduced, that is, the phased array antenna changes the mode term scattering while keeping the structural term scattering in the RCS theoretical model unchanged through the loading of the interdigital capacitor.
[0028] In the study of conventional antenna scattering problems, people often decompose the RCS into two categories: the structural scattering term and the mode scattering term, and consider that the sum of the structural scattering term and the mode scattering term is the total RCS of the antenna.
[0029] However, in the research process of this embodiment, we found that the scattering problem of the array antenna is much more complex than that of the single antenna, and the total RCS of the antenna cannot be simply decomposed into the structural mode term and the antenna mode term composed of isolated units.
[0030] Through the detailed and in-depth research of the present invention, we obtained that the RCS theoretical model of the array antenna should be expressed by the following formula, which includes the mutual coupling factor between the array antenna elements.
[0031]
[0032] In the above formula, the summation term is a specific term of the array antenna scattering problem. The structural term of the array indicates that there are large errors in the method previously adopted by people (ignoring the mutual coupling effect between units) when studying the array antenna scattering problem.
[0033] Among them, E out is the total RCS of the phased array antenna. is the mode term scattering. is the structural term scattering. represents the scattering field when and m≠n. represents the scattering field when is satisfied. represents that the nth unit is in the open state. represents that the scattering energy of the mth unit is 0; N represents the total number of antenna units. represents the passive reflection coefficient of the nth unit. represents the transmission coefficient of the energy re-radiated from the port incident signal of the pth unit coupled to the nth unit under the action of the incident field. represents the transmission coefficient of the energy re-radiated from the port incident signal of the pth unit of the antenna coupled to the qth unit under the action of the incident field; T nq represents T nq is the element in the nth row and qth column of the matrix T, where the matrix T = [P]. -1
[0034] P = R -1 + S
[0035]
[0036] Wherein, R np is the load transfer coefficient (n ≠ p) / passive reflection coefficient (n = p) during array reception, representing the transmission coefficient of the re-radiated energy of the incident signal at the p-element port coupled to the n-element under the pure radiation problem.
[0037] Meanwhile, through this model, it can also be concluded that by adopting an appropriate method to regulate the mutual coupling between antenna elements, zero backscattering of the array antenna can be achieved.
[0038] Here, we adopted the form of a strongly coupled antenna array with interdigital capacitor loading to verify the present invention. As Figure 1 shown, after equivalent circuit calculation, the two models selected here are Figure 2 shown, and the corresponding interdigital capacitor slot widths are 0.1 mm (Model 1) and 0.2 mm (Model 2), respectively, which are called the elements of Array 1 and Array 2.
[0039] Since the change in the interdigital capacitor slot width is very small, when a plane wave is incident on this element, the change in the structural scattering term in its scattered field can be ignored. Therefore, the change in the RCS obtained by simulation is all caused by the mode term of the antenna.
[0040] The antenna mode term changes with the standing wave ratio, but the active standing wave ratio of the element can be obtained in the simulation. Therefore, the change in the RCS caused by the change in the standing wave ratio can be calculated through the active reflection coefficient of the antenna. The RCS of the antenna mode term can be calculated by the following formula:
[0041]
[0042] Wherein, σ ant is the RCS of the antenna mode term, λ is the operating wavelength, G is the antenna gain, and Γ is the active reflection coefficient of the antenna. In the simulation, we extracted two states from a large number of simulation results to examine the RCS reduction effect. The two states are:
[0043] Since the unit structures of Array 1 and Array 2 are basically exactly the same, only with a 0.1 mm difference at the interdigital capacitor, they have basically exactly the same structural scattering terms.
[0044] The simulation results of the active standing wave ratios of Array 1 and Array 2 are as Figure 3 shown, and there are a little differences between their active standing wave ratios.
[0045] Due to the almost identical structures, the active element gains (Gain, not RealizedGain) of Array 1 and Array 2 are almost exactly the same, as Figure 4 shown.
[0046] The full-wave simulation results of the RCS of Array 1 and Array 2 are as Figure 5 shown. At 9 GHz, the RCS difference between the two models of Array 1 and Array 2 expressed in dBsm is relatively large. Similarly, here, in addition to the RCS difference caused by the different standing wave ratios of the elements in Array 1 and Array 2, according to the scattering matrix model of the "zero-scattering" array antenna, there is also an RCS difference caused by the coupling factor.
[0047] Similarly, in order to examine the magnitude of the latter, we processed the RCS simulation results of the two models of Array 1 and Array 2 in exactly the same way as Model 1.
[0048] First, theoretically calculate the RCS change amount caused by the change in the standing wave ratio, and the result is as Figure 6 shown by Curve 1 in; Secondly, subtract the full-wave simulation results of the RCS of the two models of Array 1 and Array 2 in linear units to obtain the difference in the full-wave simulation results of the RCS of the two models of Array 1 and Array 2, and then convert the result to dBsm units, and the result is as Figure 6 shown by Curve 2 in.
[0049] Figure 6 The difference between Curve 1 and Curve 2 in represents the RCS reduction value caused by the array coupling factor.
[0050] Therefore, from this model, we can also draw the conclusion that the RCS simulation results of the two models of Array 1 and Array 2 reverse around 9.5 GHz. When the frequency is higher than this, the maximum RCS reduction amount caused by the coupling between elements is about 4 dB. In the frequency band of 9.5 - 15 GHz, the average RCS reduction amount is about 2 dB.
[0051] From the comparison between Model 1 and Model 2, we can see that different methods of regulating mutual coupling have a large gap in the effect of reducing RCS. According to the "zero-scattering" array model, this is actually due to the different mutual couplings between elements.
[0052] The present invention first proposes a theoretical model of the scattering field of a phased array antenna including coupling effects. This model is more complete and can more effectively guide the implementation of phased array antenna RCS reduction technology and the design of low-RCS phased array antennas, which is very important for improving the stealth performance of phased array radars. Then, based on this theoretical model, a method for reducing the RCS of a phased array antenna based on interdigital capacitor loading is designed. This method reduces the mode term scattering of the antenna without affecting the structural term scattering of the antenna, and is a new type of RCS reduction technology that is easy to implement and can be applied to existing phased array antenna arrays.
[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for reducing the RCS of a phased array antenna, characterized in that: Realized by using a phased array antenna loaded with interdigital capacitors; the phased array antenna includes a metal substrate (3) and a dielectric substrate (2) located above the metal substrate (3). Two symmetric radiation patches (1) are provided on the upper surface of the dielectric substrate (2). Interdigital capacitors (11) are provided on the outer edges of each radiation patch (1). The metal substrate (3), the dielectric substrate (2), and the radiation patches (1) are fed through a coaxial cable (4) provided inside the phased array antenna; the coaxial cable (4) includes a first inner conductor (41) passing through the dielectric substrate (2), a second inner conductor (42) passing through the dielectric substrate (2) and the metal substrate (3), and a second outer conductor (43) wrapping the lower end of the second inner conductor (42) and passing through the metal substrate (3); the lower end of the first inner conductor (41) is located at the interface between the dielectric substrate (2) and the metal substrate (3), and the lower end of the second inner conductor (42) is located at the bottom surface of the metal substrate (3); the upper ends of the first inner conductor (41) and the second inner conductor (42) are respectively connected to the inner edges of the radiation patches (1). The RCS reduction of the phased array antenna is realized by adjusting the interdigital gap on the interdigital capacitor, that is, the phased array antenna changes the mode term scattering by loading interdigital capacitors while keeping the structural term scattering of the RCS theoretical model unchanged.
2. The RCS reduction method of the phased array antenna according to claim 1, wherein The specific RCS theoretical model is as follows: Among them, is the total RCS of the phased array antenna, is the scattering of the mode term, is the scattering of the structural term, represents the scattering field when is satisfied, represents the scattering field when is satisfied; represents that the nth unit is in an open state, represents that the scattering energy of the mth unit is 0; N represents the total number of units of the antenna; represents the passive reflection coefficient of the nth unit, represents the transmission coefficient of the energy re-radiated by the incident signal at the port of the pth unit coupled to the nth unit under the action of the incident field; represents the transmission coefficient of the energy re-radiated by the incident signal at the port of the pth unit of the antenna coupled to the qth unit under the action of the incident field; represents is the element in the nth row and qth column of the matrix , where the matrix = [P] -1 , where, when n ≠ p, is the load transfer coefficient during array reception, and when n = p, is the passive reflection coefficient, represents the transmission coefficient of the re-radiated energy of the incident signal at the p-element port coupled to the n-element under the pure radiation problem.
3. The RCS reduction method of the phased array antenna according to claim 2, characterized in that, Adjust the interdigital gap on the interdigital capacitor to 0.1 mm.