A decoupling method for SIW wide-angle scanning antenna array

Abstract

This invention provides a decoupling method for SIW wide-angle scanning antenna arrays to solve the technical problem of coupling between array elements during phased array antenna scanning. The invention discloses a decoupling method for SIW wide-angle scanning antenna arrays that uses a genetic algorithm to optimize the presence or absence of metal pillars at specific positions between array elements, introducing new coupling to cancel out the original coupling, thereby achieving decoupling. The method includes the following steps: Step 1: Metallize the surfaces of four dielectric substrates and longitudinally slot them to form array elements; Step 2: Slot two array elements on one side and slot the other two array elements on both sides, removing part of the metal wall of the array elements; Step 3: Assemble the four array elements, placing the two array elements with slots on one side at both ends and the two array elements with slots on both sides in the middle, with adjacent array elements having slots facing each other; Step 4: Replace the removed metal walls with several equally spaced metal pillars to ensure good impedance matching in the target frequency band and reduce the active reflection coefficient at the ports; Step 5: Replace the metal pillars with discrete ports.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a decoupling method for SIW wide-angle scanning antenna arrays. Background Technology

[0002] When the scanning angle of a phased array antenna increases, the coupling between elements increases due to the smaller spacing between the antenna array elements. This not only affects the element radiation pattern and array factor but also significantly impacts the scanning capability. The coupling between elements causes significant changes in the impedance of the feed port, affecting the port impedance matching during array scanning and severely degrading the antenna's operating bandwidth. Therefore, decoupling between array elements is crucial for improving array performance.

[0003] Inter-element coupling is mainly classified into surface wave coupling, near-field coupling, and far-field coupling. Surface wave coupling is mainly due to the thickness of the medium between elements or its high dielectric constant; near-field coupling originates from the antenna's near-field spatial radiation; far-field coupling is caused by the antenna's far-field radiation. Because far-field coupling couples antenna elements located in the far field, the coupling is relatively small and is generally not considered.

[0004] Currently, decoupling mainly falls into two categories. The first category decouples at the source of coupling, preventing coupling from occurring and eliminating the coupling path, thus preventing surface waves or near-field waves from reaching nearby antenna elements. This includes DGS (Discrete Gauge) and EBG (Electromagnetic Bandgap) structures, which use filtering-like functions to prevent surface waves from coupling to neighboring elements. For near-field coupling, metal baffles of a certain height can be loaded between elements to block the transmission path. A DGS can be equivalent to an LC (Lithium-Oxide-Semiconductor) array, which can form a resonance to filter waves passing through the structure. When multiple DGS are arranged in a certain order, a certain stopband can be formed, achieving the effect of blocking surface waves. DGS is easy to manufacture, but it occupies a large space and requires a certain amount of space between array elements. It is not suitable for multi-element arrays because the current shunting of other decoupling structures will affect its decoupling effect, and slotting will have a certain impact on the antenna pattern. Electromagnetic bandgap (EBG) structures function similarly to DGS. By periodically arranging a certain amount of metal between antenna elements, the equivalent circuit is also similar to that of an LC array, so it can achieve a filtering function, thereby blocking the transmission of coupled waves between antenna elements. Its disadvantages are that it is cumbersome to manufacture, occupies a large space, and is not suitable for large arrays.

[0005] Another approach starts from the result, introducing new coupling to cancel the initial coupling. A common example is the neutralization line (NL), where the coupling introduced by the NL, if equal in amplitude and opposite in phase to the original coupling, will cancel the original coupling. However, because there is current on the neutralization line, the added structure will also generate radiation, thus affecting the original radiation pattern, impedance, and other performance characteristics. Another method of using external coupling to cancel the original coupling is the array antenna decoupling surface (ADS), proposed in recent years. By loading a periodically arranged metal sheet reflective surface at a certain distance above the antenna array, the electromagnetic waves emitted by each element will be partially reflected to adjacent elements. The spacing between the surface and the array, as well as the surface structure, affect the amplitude and phase of the reflected wave. Adjusting these parameters can make the reflected wave equal in amplitude and opposite in phase to the original coupling, thus canceling the original coupling. However, the added ADS not only increases the difficulty of antenna fabrication but also increases the antenna profile height. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a SIW wide-angle scanning antenna array decoupling method to solve the technical problem of coupling between array elements during phased array antenna scanning, as mentioned in the background art.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0008] A decoupling method for SIW wide-angle scanning antenna arrays uses a genetic algorithm to optimize the presence or absence of metal pillars at specific positions between array elements, introducing new couplings to counteract the original couplings, thereby achieving decoupling.

[0009] Includes the following steps:

[0010] Step 1: Metallize the surfaces of the four dielectric substrates and create longitudinal slots to form array elements;

[0011] Step 2: Groove one side of two array elements and groove both sides of the other two array elements to remove part of the metal wall of the array elements.

[0012] Step 3: Assemble the four array elements. Place the two array elements with slots on one side at both ends, and place the two array elements with slots on both sides in the middle, with the slots of adjacent array elements facing each other.

[0013] Step 4: Replace the removed metal wall with several equally spaced metal columns;

[0014] Step 5: Replace the metal pillars with discrete ports.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] Without changing the antenna's footprint or profile height, and applicable to array fabrication, this decoupling method can maintain the radiation pattern, ensure good impedance matching in the target frequency band, and reduce the active reflection coefficient at the port. Attached Figure Description

[0017] Figure 1(a) is a structural diagram of the array unit of the present invention.

[0018] Figure 1(b) is a top view of the array structure of the present invention.

[0019] Figure 1(c) is a side view of the array structure of the present invention.

[0020] Figure 2 This refers to the port reflection coefficient of the array element in this invention.

[0021] Figure 3 This is a schematic diagram of the optimized region of the present invention.

[0022] Figure 4(a) is a schematic diagram of the antenna structure with metal column array of the present invention.

[0023] Figure 4(b) is a schematic diagram of the dimensions of the metal column used in this invention.

[0024] Figure 5 The flowchart for this invention has been optimized.

[0025] Figure 6 This is a diagram of the optimized array structure of the present invention.

[0026] Figure 7(a) shows S11 before and after array decoupling in this invention.

[0027] Figure 7(b) shows S22 before and after array decoupling in this invention.

[0028] Figure 7(c) shows S33 before and after array decoupling in this invention.

[0029] Figure 7(d) shows S44 before and after array decoupling in this invention.

[0030] Figure 7(e) shows S21 before and after array decoupling in this invention.

[0031] Figure 7(f) shows S31 before and after array decoupling in this invention.

[0032] Figure 7(g) shows S32 before and after array decoupling in this invention.

[0033] Figure 7(h) shows S41 before and after array decoupling in this invention.

[0034] Figure 7(i) shows S42 before and after array decoupling in this invention.

[0035] Figure 7(j) shows S43 before and after array decoupling in this invention.

[0036] Figure 8(a) shows the 0-degree scan S1 before and after array decoupling in this invention.

[0037] Figure 8(b) shows the 0-degree scan S2 before and after array decoupling in this invention.

[0038] Figure 8(c) shows the 0-degree scan S3 before and after array decoupling in this invention.

[0039] Figure 8(d) shows the 0-degree scan S4 before and after array decoupling in this invention.

[0040] Figure 9(a) shows the 30-degree scan S1 before and after array decoupling in this invention.

[0041] Figure 9(b) shows the 30-degree scan S2 before and after array decoupling in this invention.

[0042] Figure 9(c) shows the 30-degree scan S3 before and after array decoupling in this invention.

[0043] Figure 9(d) shows the 30-degree scan S4 before and after array decoupling in this invention.

[0044] Figure 10(a) shows the 45-degree scan S1 before and after array decoupling in this invention.

[0045] Figure 10(b) shows the 45-degree scan S2 before and after array decoupling in this invention.

[0046] Figure 10(c) shows the 45-degree scan S3 before and after array decoupling in this invention.

[0047] Figure 10(d) shows the 45-degree scan S4 before and after array decoupling in this invention.

[0048] Figure 11(a) shows the 0-degree scanning direction before and after array decoupling in this invention.

[0049] Figure 11(b) shows the 30-degree scanning direction before and after array decoupling in this invention.

[0050] Figure 11(c) shows the 45-degree scanning direction before and after array decoupling in this invention. Detailed Implementation

[0051] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] Example:

[0053] A decoupling method for SIW wide-angle scanning antenna arrays uses a genetic algorithm to optimize the presence or absence of metal pillars at specific positions between array elements, introducing new couplings to counteract the original couplings, thereby achieving decoupling.

[0054] Includes the following steps:

[0055] Step 1: Metallize the surfaces of the four dielectric substrates and create longitudinal slots to form array elements;

[0056] Step 2: Groove one side of two array elements and groove both sides of the other two array elements to remove part of the metal wall of the array elements.

[0057] Step 3: Assemble the four array elements. Place the two array elements with slots on one side at both ends, and place the two array elements with slots on both sides in the middle, with the slots of adjacent array elements facing each other.

[0058] Step 4: Replace the removed metal wall with several equally spaced metal columns;

[0059] Step 5: Replace the metal pillars with discrete ports.

[0060] Figure 1(a) shows a slotted SIW antenna element, and Figure 1(b) shows a four-element slotted SIW antenna array before optimization. The array element is a SIW surface-metallized antenna with longitudinal slots. Each element includes a dielectric substrate and metallized waveguide walls. The dielectric material is ROGERS RO3003 with a dielectric constant of 3 ± 0.04, a loss factor tanδ of 0.0010, and a thickness of 0.50 mm. The element's radiating slot length a is 4.9 mm, the element's radiating slot width b is 1.4 mm, the distance c between the slot and the waveguide wall is 1.65 mm, and the waveguide width d is 4.3 mm, as shown in Figure 1(c). The waveguide thickness e is 0.5 mm. The left side of the array is the waveguide feed port, and each element is separated by a metal wall. The element port reflection coefficient is as follows: Figure 2 As shown.

[0061] like Figure 3 As shown, the metal walls between waveguides are removed to provide a decoupling optimization region, where f is 12 mm, g is 4.95 mm, and h is 2 mm. The value of h can be arbitrary and will not affect the S-parameter amplitude.

[0062] As shown in Figure 4(a), the original Figure 3 The removed metal wall is replaced with equally spaced metal pillars. The diameter of the metal pillars is 0.1 mm and the height is equal to that of the waveguide, as shown in Figure 4(b). Taking a local metal pillar for observation, the distance i between the metal pillar and the metal wall is 0.15 mm, the spacing j between the metal pillars is 0.2 mm, there are 60 metal pillars between adjacent units, and there are 180 metal pillars inside the four-unit array.

[0063] The metal pillars in Figures 4(a) and 4(b) are replaced with discrete ports with a characteristic impedance of 50 ohms. There are a total of 180 internal discrete ports. Adding the four waveguide feed ports of the unit, there are a total of 184 ports. The S-parameters of the total 184 ports are calculated and then converted into Z matrices. ZA is 4*4 and represents the impedance matrix of the four external waveguide ports. ZD is 180*180 and represents the impedance matrix of the 180 internal ports. ZB is 4*180 and represents the mutual impedance between the external waveguide ports and the internal discrete ports. ZC is 180*4 and also represents the mutual impedance between the external waveguide ports and the internal discrete ports.

[0064] In order to simulate the presence or absence of a metal pillar through the internal discrete port during the calculation, we need to add a load to the internal discrete port. Ideally, the load is 0, which means a short circuit, indicating that a metal pillar exists at the internal discrete port. Ideally, the load is infinite, which means an open circuit, indicating that there is no metal pillar at the internal discrete port. In reality, when a metal pillar exists, it is represented by a small reactance, and when a metal pillar does not exist, it is represented by 1e8 to indicate infinity.

[0065] Given the waveguide dimensions and dielectric constant, the characteristic impedance of the waveguide port can be calculated. The characteristic impedance of the discrete port is 50 ohms. Based on the Z matrix and the load state of the internal ports, the Z matrix of the four waveguide feed ports can be calculated using the internal multi-port method. ZL is a 180*180 diagonal matrix, and the diagonal elements are the smaller reactance of the load state of the corresponding internal discrete port or 1e8. Given the Z matrix of the four waveguide feed ports, the S-parameters of the four waveguide feed ports can be calculated.

[0066] Given the S-parameters, each optimization frequency point is taken as the optimization target. The optimization frequency band is 30.8-31.8GHz, and the optimization variable is the load state. In order to ensure that the metal pillar state is the same between every two adjacent units, we variableize the load state of 60 discrete ports between the first and second units. When we change the load state of the discrete ports inside the first and second units, the changes in the load state of the discrete ports between the second and third units and between the third and fourth units are consistent with the changes in the load state of the discrete ports inside the first and second units. We optimize through a genetic algorithm to ensure that the port reflection coefficient is less than -10dB at each optimization frequency point within the optimization frequency band, and the transmission coefficient between ports is reduced as much as possible.

[0067] Optimize the flowchart as follows Figure 5 As shown, the final optimized state of the metal column is as follows: Figure 6 As shown, the S-parameters of the waveguide feed port before and after optimization are as follows: Figures 7(a) to 7(j) As shown, the active reflection coefficient of the port when the array is scanned at 0 degrees is as follows: Figures 8(a) to 8(d) As shown, the active reflection coefficient at the port when the array is scanned at a 30-degree angle is as follows: Figures 9(a) to 9(d) As shown, the active reflection coefficient of the port when the array is scanned at a 45-degree angle is as follows: Figures 10(a) to 10(d) As shown, the array scanning pattern is as follows Figures 11(a) to 11(c) As shown, the target frequency band port reflection coefficient and inter-port transmission coefficient were improved before and after optimization. The active reflection coefficient of the target frequency band was improved when the array scanned at 0 degrees, 30 degrees and 45 degrees and operated below -10dB. The directivity coefficient of the array did not change when scanning before and after optimization.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A decoupling method for a SIW wide-angle scanning antenna array, characterized in that: Genetic algorithms are used to optimize the presence or absence of metal pillars at specific positions between array elements, introducing new couplings to counteract the original couplings and thus achieving decoupling. Includes the following steps: Step 1: Metallize the surfaces of the four dielectric substrates and create longitudinal slots to form array elements; Step 2: Groove one side of two array elements and groove both sides of the other two array elements to remove part of the metal wall of the array elements. Step 3: Assemble the four array elements. Place the two array elements with slots on one side at both ends, and place the two array elements with slots on both sides in the middle, with the slots of adjacent array elements facing each other. Step 4: Replace the removed metal wall with several equally spaced metal columns; Step 5: Replace the metal pillar with a discrete port. Simulate the presence or absence of the metal pillar using the internal discrete port. The characteristic impedance of the discrete port is 50 ohms. Calculate the Z-matrix of the four waveguide feed ports using the internal multi-port method. Calculate the S-parameters of the four waveguide feed ports based on the Z-matrix. After knowing the S-parameters, use each optimization frequency as the optimization target and optimize using a genetic algorithm to ensure that the port reflection coefficient is less than -10dB at each optimization frequency within the optimization band.

2. The SIW wide-angle scanning antenna array decoupling method according to claim 1, characterized in that: The dielectric substrate is made of ROGERS RO3003, with a dielectric constant of 3±0.04, a loss factor tanδ of 0.0010, and a thickness of 0.50 mm.

3. The SIW wide-angle scanning antenna array decoupling method according to claim 1, characterized in that: The slot length a is 4.9 mm, the distance c between the slot and the waveguide wall is 1.65 mm, the waveguide width d is 4.3 mm, and the waveguide thickness e is 0.5 mm.

4. The SIW wide-angle scanning antenna array decoupling method according to claim 1, characterized in that: The lengths of the removed metal wall are f = 12 mm, g = 4.95 mm, and h = 2 mm.

5. The SIW wide-angle scanning antenna array decoupling method according to claim 1, characterized in that: The metal pillars have a diameter of 0.1 mm and a thickness equal to that of the waveguide. The distance i between the metal pillars and the metal wall is 0.15 mm, and the spacing j between the metal pillars is 0.2 mm. There are 60 metal pillars between adjacent units, and there are 180 metal pillars inside the four-unit array.

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