A slot coupled antenna element, microstrip antenna array and radar system

Abstract

The application relates to a slot coupling antenna unit, a microstrip antenna array and a radar system, which comprises a metal reflecting plate, a first air coupling layer, a metal ground plate, a first dielectric layer, a microstrip feed line, a second air coupling layer, a second dielectric layer and a radiation patch which are sequentially stacked, and the metal ground plate is provided with a coupling slot; the coupling slot is used for changing the current distribution, so that the current in the direction of the microstrip feed line is cut off by the coupling slot to reserve part of the current in the direction of the microstrip feed line in the coupling slot; the microstrip feed line is used for receiving energy and coupling the received energy to the metal bottom plate through the first dielectric layer, and transmitting the energy to the radiation patch through the second air coupling layer and the second dielectric layer; the first air coupling layer is used for adjusting the impedance matching between the microstrip feed line and the metal reflecting plate; and the second air coupling layer is used for adjusting the impedance matching between the radiation patch and the metal ground plate, the application adopts a multilayer structure, realizes compact layout of the antenna unit, and further realizes miniaturization of the antenna array.

Description

Technical Field

[0001] This application relates to the field of electromagnetic antenna technology, and in particular to a slot-coupled antenna element, a microstrip antenna array, and a radar system. Background Technology

[0002] In modern wireless communication, radar detection, and other fields, the requirements for antenna performance are constantly evolving towards higher performance, miniaturization, wider bandwidth, and lower cost. With the continuous increase in the integration of electronic devices, more powerful antenna systems need to be accommodated within limited space, making antenna miniaturization a critical requirement. Simultaneously, to adapt to complex and ever-changing signal environments, antennas must possess a sufficiently wide operating bandwidth to achieve efficient reception and transmission of multi-band signals, improve electromagnetic energy transmission efficiency, and ensure the stability and reliability of communication and detection.

[0003] In radar systems, accurate target detection and tracking rely on the antenna's excellent beamforming capabilities. Precise sum and difference beamforming is crucial for accurately determining target position, velocity, and other parameters, effectively improving the performance and accuracy of the radar system. Traditional antenna designs, when faced with these combined requirements, are increasingly revealing numerous limitations and failing to meet the ever-evolving technological demands, urgently requiring innovative design methods to overcome existing bottlenecks. Summary of the Invention

[0004] In view of this, embodiments of this application propose a slot-coupled antenna element, a microstrip antenna array, and a radar system, aiming to solve the problem that the radiating array and the feed network of traditional antennas are difficult to effectively isolate in spatial arrangement, which makes it impossible to compactly arrange the antenna elements and restricts the miniaturization of antenna arrays.

[0005] To achieve the above objectives, embodiments of this application provide a slot-coupled antenna element, comprising: a metal reflector, a first air coupling layer, a metal ground plane, a first dielectric layer, a microstrip feed line, a second air coupling layer, a second dielectric layer, and a radiating patch, stacked sequentially. The metal ground plane has a coupling slot, and the microstrip feed line is perpendicular to the coupling slot. The coupling slot is used to change the current distribution, such that the current in the direction of the microstrip feed line is cut off by the coupling slot, thereby retaining a portion of the current in the direction of the microstrip feed line within the coupling slot. The microstrip feed line is used to receive energy and couple the received energy to the metal ground plane through the first dielectric layer, and to transfer the received energy to the radiating patch through the second air coupling layer and the second dielectric layer. The first air coupling layer is used to adjust the impedance matching between the microstrip feed line and the metal reflector; the second air coupling layer is used to adjust the impedance matching between the radiating patch and the metal ground plane.

[0006] Optionally, the coupling gap is a rectangular gap.

[0007] Optionally, the thickness of the second air coupling layer is 3.3 mm ± 0.1 mm, the thickness of the first air coupling layer is 3.2 mm ± 0.1 mm, the thickness of the first dielectric layer is 1.524 mm ± 0.01 mm, and the thickness of the second dielectric layer is 4.572 mm ± 0.01 mm.

[0008] Optionally, both the first dielectric layer and the second dielectric layer are PCB boards, wherein the PCB board is composed of Taconic-TMS-DS, the dielectric constant of the PCB board is 2.95, and the loss tangent of the PCB board is 0.0028.

[0009] To achieve the above objectives, the application also provides multiple slot-coupled antenna elements as described in the preceding embodiment, and a sum-difference device and two sets of 16-way power dividers; each of the two sets of 16-way power dividers has a T-junction, and the two sets of power dividers are cascaded through the T-junction; the sum-difference device includes a 3dB bridge and a 90° phase shifter, the 3dB bridge has two input terminals and two output terminals, wherein the two output terminals of the sum-difference device are respectively connected to the T-junctions of the cascaded sets of 16-way power dividers, and the two input ports respectively perform one-dimensional sum-difference processing on the input beam, and the two sets of 16-way power dividers and the sum-difference device form a feeding network; the microstrip feed lines of each of the multiple slot-coupled antenna elements are respectively connected to the output terminals of the 16-way power dividers; wherein, after the input beam is processed by the sum-difference device, a first sum-difference signal and a second sum-difference signal are obtained, and the first sum-difference signal and the second sum-difference signal are respectively transmitted outward as different radiation signals through the slot-coupled antenna elements at the ends of the two sets of 16-way power dividers.

[0010] Optionally, it also includes: two microstrip to coaxial structures, which are respectively connected to the two input terminals of the sum and difference device. The microstrip to coaxial structure includes a boss fixed to a metal platform by screws. A coaxial structure is provided in the middle of the boss. One end of the coaxial structure is connected to one input terminal of the sum and difference device, and the other end is connected to the energy transmitting device.

[0011] To achieve the above objectives, this application also provides a radar system equipped with a slot-coupled microstrip antenna array with one-dimensional sum and difference functions as provided in the foregoing embodiments.

[0012] To achieve the above objectives, embodiments of this application also provide a slot-coupled antenna element.

[0013] This application provides an embodiment of a slot-coupled antenna element, a microstrip antenna array, and a radar system. The slot-coupled antenna element comprises a metal reflector, a first air coupling layer, a metal ground plane, a first dielectric layer, a microstrip feed line, a second air coupling layer, a second dielectric layer, and a radiating patch, stacked sequentially. The metal ground plane has a coupling slot, and the microstrip feed line is perpendicular to the coupling slot. The coupling slot is used to change the current distribution, so that the current in the direction of the microstrip feed line is cut off by the coupling slot, so as to retain a portion of the current in the direction of the microstrip feed line within the coupling slot. The microstrip feed line is used to receive energy and couple the received energy to the metal ground plane through the first dielectric layer, and transfer the received energy to the radiating patch through the second air coupling layer and the second dielectric layer. The application employs a multi-layer structure, which effectively isolates the radiating surface from the feed network in terms of spatial arrangement, achieving a compact layout of antenna elements and thus miniaturizing the antenna array. Furthermore, by adding an air coupling layer, the resonant points are increased, widening the bandwidth of the array antenna and improving electromagnetic energy transmission efficiency. The microstrip antenna array achieves excellent sum-difference beamforming performance while maintaining a compact structure through a sum-difference design. This application realizes a low-profile, small-size broadband array antenna, providing a high-performance, low-cost solution for radar antenna systems. Attached Figure Description

[0014] Figure 1 This is a diagram of a slot-coupled antenna element stack-up structure provided in an embodiment of the present invention;

[0015] Figure 2 This is a top view of a slot-coupled antenna element structure provided in an embodiment of the present invention;

[0016] Figure 3 This is a graph showing the reflection coefficient of an antenna element and the corresponding peak gain curve at a given frequency, provided in an embodiment of the present invention.

[0017] Figure 4 This is a simulation result diagram of the antenna element standing wave ratio provided in the embodiment of the present invention;

[0018] Figure 5 This is the polar coordinate system radiation pattern of the antenna element at 5.3 GHz provided in the embodiment of the present invention;

[0019] Figure 6 This is a structural diagram of the summator provided in an embodiment of the present invention;

[0020] Figure 7 This is a simulation result diagram of the optimized sum-difference S-parameter amplitude provided in the embodiment of the present invention;

[0021] Figure 8This is a simulation result diagram of the optimized sum-difference S-parameter phase of the sum-difference device provided in this embodiment of the invention;

[0022] Figure 9 This is a power splitting network structure diagram provided in an embodiment of the present invention;

[0023] Figure 10 This is a simulation result diagram of the optimized power divider network reflection coefficient provided in the embodiment of the present invention;

[0024] Figure 11 This is a diagram showing the optimized coupling degree of the power splitting network provided in this embodiment of the invention.

[0025] Figure 12 This is a diagram showing the array layout of a slot-coupled microstrip antenna provided in an embodiment of the present invention;

[0026] Figure 13 These are the simulation results of the antenna array E-plane and radiation pattern provided in the embodiments of the present invention;

[0027] Figure 14 These are the simulation results of the antenna array H-plane and radiation pattern provided in the embodiments of the present invention;

[0028] Figure 15 These are the simulation results of the antenna array differential radiation pattern provided in the embodiments of the present invention;

[0029] Figure 16 This is a simulation result diagram of the antenna array S-parameters provided in the embodiment of the present invention;

[0030] Figure 17 This is a diagram of the antenna outlet microstrip to coaxial structure provided in an embodiment of the present invention;

[0031] Figure 18 This is a simulation result diagram of the antenna outlet microstrip to coaxial converter provided in an embodiment of the present invention;

[0032] Figure 19 This is a physical image of the antenna printed circuit board provided in an embodiment of the present invention;

[0033] Figure 20 This is a diagram showing the measured results of the antenna S-parameters provided in an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this application to enable readers to better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0035] In the field of electromagnetic field radomes, existing technologies have many shortcomings in the design and implementation of slot-coupled microstrip antenna arrays. These shortcomings limit the further application and development of antennas in modern communication and radar systems. This invention proposes an innovative solution to these pain points, including:

[0036] 1. Existing technologies face numerous challenges in miniaturizing antenna arrays. Traditional designs struggle to effectively isolate the spatial arrangement of the radiating array and the feed network, resulting in a loose and uncompacted layout of antenna elements. This not only occupies excessive space but also increases the difficulty and cost of system integration, severely hindering the development of antenna arrays towards miniaturization and lightweight design, and failing to meet the stringent requirements of modern electronic devices for compact structures.

[0037] 2. Bandwidth and electromagnetic energy transmission efficiency are also shortcomings of existing technologies. Ordinary antenna array designs have narrow bandwidth, which cannot meet the needs of multi-band, wide-band signal transmission. At the same time, electromagnetic energy suffers significant losses during transmission, resulting in low transmission efficiency. This limits the performance of the antenna in receiving and transmitting signals, failing to guarantee the stability and efficiency of communication and detection. In complex electromagnetic environments, signal distortion and interruptions are prone to occur.

[0038] 3. The design of the sum and difference converter also has significant shortcomings in existing technologies. Previous solutions have struggled to achieve excellent sum and difference beamforming performance while maintaining a compact structure. The amplitude balance and phase consistency of the sum and difference converter are poor, resulting in large phase deviations and amplitude fluctuations in the output signal, high return loss, and difficulty in achieving accurate sum and difference signal output. This significantly impacts the accuracy and reliability of target detection and tracking for radar systems that rely on precise beamforming.

[0039] In summary, existing technologies struggle to effectively achieve miniaturization, sufficient bandwidth and efficient power transmission, as well as ideal summer performance, making it difficult to design high-performance antenna arrays with low profile, small size, and wide bandwidth. Therefore, designing high-performance, low-cost antenna arrays to meet the practical application needs of radar antenna systems and other fields has become a critical problem that urgently needs to be solved.

[0040] In existing technologies, various implementation schemes exist for slot-coupled microstrip antenna designs. Common antenna element designs also consist of multi-layered dielectric structures, including radiating patches, dielectric substrates, and feed lines. However, these designs often fail to effectively address the spatial isolation problem between the radiating array and the feed network. Interference between the radiating array and the feed network makes it difficult to achieve a compact antenna element layout, thus hindering the miniaturization of antenna arrays. Furthermore, due to the lack of effective bandwidth expansion methods, their operating bandwidth is relatively narrow, and electromagnetic energy transmission efficiency needs improvement.

[0041] In the design of sum and difference converters, previous solutions have struggled to achieve ideal sum and difference beamforming performance while maintaining a compact structure. While some sum and difference converters can perform signal sum and difference functions, they perform poorly in key indicators such as amplitude balance, phase consistency, and return loss. For example, some sum and difference converters based on traditional circuit structures exhibit significant input return loss within the operating frequency band, failing to achieve good impedance matching and resulting in severe energy loss during signal transmission. Furthermore, uneven energy distribution at the output ports, unstable coupling, large phase deviations between the two output ports, and amplitude fluctuations exceeding acceptable limits make it difficult to meet the requirements of high-precision sum and difference beamforming.

[0042] In the design of power divider networks, existing solutions struggle to balance high-precision power distribution characteristics with good impedance matching performance. While some power dividers can achieve a certain proportion of power distribution, their input port return loss is high across the entire operating frequency band, making stable impedance matching impossible. Simultaneously, the power distribution characteristics at each output port are unsatisfactory, with large fluctuations in coupling coefficients and poor amplitude balance and phase consistency, impacting the overall stability and reliability of the antenna array.

[0043] In existing technologies, antenna arrays face challenges in miniaturization. Traditional antennas struggle to effectively isolate the radiating surface and feed network in spatial arrangement, hindering compact antenna element placement and limiting miniaturization. This invention employs a multi-layer structure, successfully achieving effective spatial isolation between the radiating surface and feed network. This creates conditions for compact antenna element placement, thereby promoting the miniaturization of antenna arrays and meeting the demands of modern electronic devices for miniaturized antennas.

[0044] The bandwidth and electromagnetic energy transmission efficiency of an antenna are also key issues. In existing technologies, antennas have narrow bandwidths and low electromagnetic energy transmission efficiency, affecting their performance. This invention, by adding an air coupling layer, increases the resonant point, effectively widening the bandwidth of the array antenna while improving electromagnetic energy transmission efficiency. This allows the antenna to operate stably over a wider frequency range with more efficient energy transmission, laying the foundation for improving the overall system performance.

[0045] The performance of the sum and difference converter is equally important. Previously, it was difficult to achieve excellent sum and difference beamforming performance while maintaining a compact structure in the design of sum and difference converters. This invention achieves a breakthrough in sum and difference converter design, realizing outstanding sum and difference beamforming performance while maintaining a compact structure, providing strong support for the accurate detection and tracking of targets by radar antenna systems.

[0046] Furthermore, antennas designed with existing technologies often struggle to achieve low profile and small size while simultaneously maintaining broadband characteristics, failing to adequately meet the high-performance requirements of radar antenna systems. This invention, through a series of optimized designs, realizes a low-profile, small-size broadband array antenna. Experimental results verify the effectiveness of this design, providing a high-performance, low-cost solution for radar antenna systems. It effectively addresses the difficulty in balancing antenna size, bandwidth, and performance in existing technologies, thus driving technological advancements in the field of electromagnetic field radomes.

[0047] Existing technologies have varying degrees of deficiencies in the design of each key component of slot-coupled microstrip antenna arrays, making it difficult to meet the comprehensive requirements of modern technology for antennas in terms of high performance, miniaturization, and wide bandwidth. This highlights the necessity and urgency of the innovative design method proposed in this invention.

[0048] To address the shortcomings of existing technologies, this invention aims to comprehensively overcome their deficiencies. By employing a multi-layered structure, effective spatial isolation between the radiating array and the feed network is successfully achieved, creating conditions for a compact layout of antenna elements, thereby miniaturizing the antenna array and significantly reducing system space occupation and integration costs. The introduction of an air coupling layer increases the number of resonant points, broadens the bandwidth of the array antenna, and improves electromagnetic energy transmission efficiency, ensuring stable and efficient signal transmission over a wide frequency band. Breakthroughs have been achieved in the design of the sum and difference converter, realizing excellent sum and difference beamforming performance within a compact structure, ensuring high precision of the sum and difference signal output. Finally, through a series of innovative designs, a low-profile, small-size broadband array antenna has been realized. Practical testing has verified the effectiveness of the solution, providing a high-performance, low-cost, high-quality solution for radar antenna systems, and powerfully promoting technological progress and practical application expansion in the field of electromagnetic field radomes.

[0049] The slot-coupled antenna unit proposed in this embodiment includes: a metal reflector, a first air coupling layer, a metal ground plane, a first dielectric layer, a microstrip feed line, a second air coupling layer, a second dielectric layer, and a radiating patch stacked sequentially. The metal ground plane has a coupling slot, and the microstrip feed line is perpendicular to the coupling slot. The coupling slot is used to change the current distribution, so that the current in the direction of the microstrip feed line is cut off by the coupling slot, thus retaining a portion of the current along the direction of the microstrip feed line within the coupling slot. The microstrip feed line is used to receive energy and couple the received energy to the metal ground plane through the first dielectric layer, and to transfer the received energy to the radiating patch through the second air coupling layer and the second dielectric layer. The first air coupling layer is used to adjust the impedance matching between the microstrip feed line and the metal reflector; the second air coupling layer is used to adjust the impedance matching between the radiating patch and the metal ground plane.

[0050] Specifically, the slot-coupled microstrip antenna structure comprises multiple layers. The top layer is a radiating patch, below which are a second dielectric layer and a second air coupling layer. Next are a microstrip feed line and a first dielectric layer. Below the first dielectric layer is a metal ground plane containing coupling slots located at the center of the projection of the radiating patch onto the metal ground plane. By loading slots onto the metal ground plane, the current distribution can be altered, causing the current along the feed line direction to be interrupted by the slots, thus retaining only a small amount of current along the feed line direction within the rectangular slots. The areas between the upper radiating patch and the metal ground plane, and between the microstrip feed line and the reflector, are used to adjust the matching air layers. Energy is coupled from the microstrip feed line through the air layers to the ground plane, and then, through the second dielectric layer and the second air layer, finally transfers the energy to the upper radiating patch.

[0051] Next, based on the equivalent circuit model of the slot-coupled microstrip antenna, this application conducts a theoretical analysis of the slot-coupled microstrip antenna. in This represents the input impedance of the unit structure, as well as the impedance of open-circuit stubs, floor gaps, and radiating patches. The calculation formula is as follows:

[0052]

[0053] Where n1 is the coupling coefficient between the gap and the patch, Y p and Y a Z represents the admittance of the patch and the slot, where n2 is the coupling coefficient between the slot and the feed line; om β is the characteristic impedance. m Let be the wave number, and S be the equivalent radiating aperture of the antenna. The admittance Y of the slot is... a It can be represented as:

[0054] Y a =-j2Y os ctg(β s L a / 2)

[0055] Among them, Y os For characteristic admittance, β s L is the wave number. a Given the length of the antenna element, the equivalent circuit model shown, and the admittance Y of the radiating patch. p The calculation is as follows:

[0056] Z p =1 / Y p = 1 / Y1 + 1 / Y2

[0057]

[0058] In the formula, β open denoted as the wave number in the open circuit state, and x represents the relative position of the gap.

[0059] In microstrip antennas employing a coupled-feed structure, the radiating and feeding parts are typically located on different planes. This layered design can significantly reduce the interference of the feeding network on the radiation pattern.

[0060] It should be noted that before designing the antenna unit, the material and dimensions of the dielectric substrate must first be determined.

[0061] The slot-coupled antenna unit structure consists of two layers of PCB material. The PCB material is made of Taconic-TMS-DS with a dielectric constant of 2.95 and a loss tangent of 0.0028. A dielectric material with a pre-existing thickness must be selected during the design process.

[0062] Figure 1 , Figure 2 The structure of the slot-coupled antenna unit is demonstrated, consisting of two PCB layers. Dielectric layer 1, with a thickness h1 = 4.572 mm, is used for antenna radiation. An air coupling layer with an intermediate spacing d1 = 3.3 mm forms a gradient region of the electromagnetic field; the coupling effect is controlled by adjusting the cavity height. Dielectric layer 2, with a thickness h2 = 1.524 mm, has a microstrip feed line on top and a metal base plate with coupling slots on the bottom, which also serves as the metal ground for the microstrip feed line. An air coupling layer with an intermediate spacing d2 = 3.2 mm and a metal reflector at the bottom form the resonant cavity. The air cavity combined with the metal reflector constitutes the resonant cavity.

[0063] Based on the calculation formula and known antenna specifications, the approximate dimensions of the radiating patch and slots for each element can be calculated. An initial model of the element is then established using the known parameters.

[0064] The various parameters of the structure were optimized and simulated using HFSS simulation software. Figure 3 , Figure 4 , Figure 5The simulation results for the antenna element show that, within the 5.1GHz-5.5GHz application frequency band, the reflection coefficient at port 1 is better than -15dB, the VSWR is less than 1.5, the gain at each frequency point is above 8dBi, and the in-band gain flatness is good.

[0065] In one embodiment of this application, the coupling gap is a rectangular gap.

[0066] In one embodiment of this application, the thickness of the second air coupling layer is 3.3 mm ± 0.1 mm, the thickness of the first air coupling layer is 3.2 mm ± 0.1 mm, the thickness of the first dielectric layer is 1.524 mm ± 0.01 mm, and the thickness of the second dielectric layer is 4.572 mm ± 0.01 mm.

[0067] Specifically, the thickness of the second air coupling layer is 3.28 mm, 3.29 mm, 3.3 mm, 3.301 mm, and 3.302 mm; the thickness of the first air coupling layer is 3.09 mm, 3.08 mm, 3.1 mm, 3.101 mm, and 3.102 mm; the thickness of the first dielectric layer is 1.5242 mm, 1.5243 mm, 1.524 mm, 1.5244 mm, 1.5245 mm, and 1.5246 mm; and the thickness of the second dielectric layer is 4.5720 mm, 4.5721 mm, 4.572 mm, 4.5723 mm, and 4.5724 mm.

[0068] Specifically, both the first dielectric layer and the second dielectric layer are PCB boards, wherein the PCB board is composed of Taconic-TMS-DS, the dielectric constant of the PCB board is 2.95, and the loss tangent of the PCB board is 0.0028.

[0069] Based on the above embodiments, this application also provides a slot-coupled microstrip antenna array with one-dimensional sum-difference functionality, comprising:

[0070] The previously mentioned slot-coupled antenna element, a sum and difference unit, and two sets of 16 equal power dividers;

[0071] Each of the 16 equal-division power dividers has two sets of power dividers, each with a T-junction, and the two sets of power dividers are cascaded through the T-junction. The sum and difference device includes a 3dB bridge and a 90° phase shifter. The 3dB bridge has two input terminals and two output terminals. The two output terminals are respectively connected to the T-junctions of the cascaded 16 equal-division power dividers, and the two input terminals are respectively connected to the two input signals. The sum and difference device is used to perform one-dimensional sum and difference processing on the input beam. The two sets of 16 equal-division power dividers and the sum and difference device form a feeding network. The microstrip feed lines of the multiple slot-coupled antenna elements are respectively connected to the output terminals of the 16 equal-division power dividers. After the input signal is processed by the sum and difference device, a first sum and difference signal and a second sum and difference signal are obtained. The first sum and difference signal and the second sum and difference signal are respectively transmitted outward as different radiation signals through the slot-coupled antenna elements at the ends of the two sets of 16 equal-division power dividers.

[0072] Next, the design of the sum and difference circuit is required. A 3dB bridge is a four-port network that can split the input signal into two outputs, introducing a 90° phase difference. This invention is based on the principle of the 3dB bridge and uses microstrip lines to achieve signal summation and difference.

[0073] Assume the input signal is V in In an ideal scenario, the signals at the two output ports of the 3dB bridge would be: where the 90° phase shifter delays the phase of the input signal by 90°. In microwave circuits, phase shifters can be implemented in various ways, such as by changing the length of the transmission line or using specific circuit structures. Assume the input signal is V. in_phase Then the output signal of the phase shifter is:

[0074] V out_phase =V in_phase e j90°

[0075] The function of a sum and difference circuit is to combine two input signals into a sum signal and a difference signal. Assuming the two input signals are V1 and V2, the sum signal V... sum Sum and difference signals V diff It can be represented as:

[0076] V sum =V1+V2

[0077] V diff =V1-V2

[0078] When a 3dB bridge is combined with a 90° phase shifter, assuming the input signal is V in After passing through a 3dB bridge, two signals V are obtained. out1 and V out2 V out2 After passing through a 90° phase shifter, the final sum and difference signals can be expressed as:

[0079]

[0080] The combination of a 3dB bridge and a 90° phase shifter can achieve signal sum and difference synthesis. With proper circuit design, accurate sum and difference signal output can be achieved.

[0081] Based on the above principles, HFSS was used to simulate and analyze the microstrip sum and difference circuit. Figure 6 This is a diagram of the summator / difference device. Figure 7 , Figure 8 Simulation results for the sum-difference coupler show that, within the 5.1-5.5 GHz operating frequency band, the return loss at both input terminals is better than -20 dB, indicating that the coupler has good impedance matching characteristics. The output power is evenly distributed to ports 3 and 4, with a stable coupling degree of approximately -3 dB. The sum-difference coupler satisfies amplitude balance and phase consistency. The phase deviation between the two output ports does not exceed ±5°, and the amplitude fluctuation is controlled within ±0.5 dB. The sum-difference coupler achieves good sum-difference performance within the applied frequency band.

[0082] The design process of a power distribution network includes the following steps:

[0083] Figure 9 The diagram shows the power divider network structure. The antenna uses a 4×8 element layout, and the corresponding feed network uses a 32-equal-division power divider. The sum and difference device is used to realize the one-dimensional sum and difference of the beam, that is, the sum and difference design is only used for the E-plane radiation pattern. The two output ports of the sum and difference device are connected to a symmetrically distributed 1:16 power distribution network to form a complete feed network.

[0084] The power divider network uses T-junctions as the basic building blocks and achieves a 1:16 power distribution ratio through cascading.

[0085] Figure 10 , Figure 11 Simulation results for the power distribution network show that the feeder network exhibits excellent transmission characteristics within the 5.1-5.5 GHz operating frequency band. The return loss at the input port is better than -20 dB, demonstrating good impedance matching performance. Meanwhile, the power distribution characteristics of the 16 output ports are outstanding, with the coupling coefficient of each channel remaining stable at around -12.5 dB and amplitude fluctuations controlled within ±0.25 dB, achieving high-precision power distribution.

[0086] The power divider network design meets the requirements for amplitude and phase consistency and has good impedance matching characteristics throughout the entire operating frequency band.

[0087] Figure 12The diagram shows the array layout of a slot-coupled microstrip antenna. The antenna array employs a 4×8 element layout. By optimizing the slot coupling structure, feed network design, and element spacing, the beam achieves high gain while maintaining low sidelobe levels, resulting in a good null depth for the difference beam. The slot-coupled microstrip antenna array is simulated and designed using HFSS.

[0088] The array exhibits excellent impedance characteristics within the 5.1-5.5 GHz operating bandwidth, with return loss at the sum and difference ports and port isolation both exceeding -15 dB, demonstrating good impedance matching performance.

[0089] Figure 13 , Figure 14 The radiation characteristics of this multi-layer antenna array are demonstrated. At a center frequency of 5.3 GHz, a peak gain of 19.25 dBi is achieved in the main beam direction. Simultaneously, the maximum sidelobe levels in the E-plane and H-plane are suppressed to below -13.1 dB and -11.05 dB, respectively, indicating that the design achieves effective sidelobe suppression while maintaining high directivity.

[0090] like Figure 15 and 16 As shown, Figure 15 and 16 Simulation results for the differential beamforming of a 4×8 LTCC slot-coupled microstrip antenna array show that, at the same center frequency, the differential beam gain reaches 16.9 dBi, and a null depth of -31 dB is formed in the E-plane with a null level of -14.1 dB. These parameters fully demonstrate the array's excellent differential beamforming capability, fully meeting the technical requirements of modern radar systems for target detection and tracking.

[0091] In this embodiment, the array antenna is designed with a 50Ω microstrip line outlet. The antenna needs to be connected to the radio frequency components for further processing and production. Therefore, a microstrip to coaxial outlet design is used at the feed port.

[0092] Figure 17 The diagram shows the microstrip to coaxial antenna output structure, and the S-parameter simulation results obtained through HFSS are as follows. Figure 18 As shown, the return loss is better than -18dB within the application frequency band, while achieving a transmission efficiency close to the ideal value. Simulation data indicates that the optimized adapter structure has good impedance matching and transmission characteristics throughout the entire operating frequency band, ensuring efficient energy transmission.

[0093] In this embodiment, the final fabricated 4×8 scale slot-coupled microstrip antenna array has physical dimensions of 122mm×242mm×1mm. Figure 19 The images show photographs of the radiating patch layer and feed network layer of the physical antenna sample used for testing.

[0094] The fabricated antenna was assembled, and its S-parameters were tested using a high-performance vector network analyzer. Figure 20 The port S-parameter test results are shown. The measured and simulated S-parameter curves show good consistency. However, due to the influence of antenna manufacturing tolerances and assembly errors, the measured reflection coefficient is slightly higher than the simulated value. Due to the shell structure, the measured port isolation value is lower than the simulated value, and the isolation effect is better.

[0095] This invention employs a multi-layered structure. This multi-layered structure effectively isolates the radiating array from the feed network in space, achieving a compact layout of the antenna elements and representing a key innovation in antenna array miniaturization. This structural design not only solves the spatial layout challenges of traditional designs but also lays the foundation for subsequent performance optimization. It should be considered a core protection point to prevent others from imitating and using similar structures to achieve the same functionality.

[0096] This invention utilizes an air coupling layer to broaden the operating bandwidth. By adding an air coupling layer and increasing the resonant points, the bandwidth of the array antenna is successfully broadened, while significantly improving electromagnetic energy transmission efficiency. This unique design approach overcomes the limitations of traditional antennas in terms of bandwidth and energy transmission, and is a key breakthrough in improving antenna performance. It requires special protection to ensure the invention's uniqueness and innovativeness.

[0097] This invention achieves a high-performance sum and difference converter design. While maintaining a compact structure, it achieves excellent sum and difference beamforming performance. Through a reasonable circuit design using microstrip lines based on the 3dB bridge principle and combined with a 90° phase shifter, the sum and difference converter meets the requirements for amplitude balance and phase consistency within the application frequency band, exhibiting low input return loss and uniform and stable energy distribution at the output port. This unique sum and difference converter design is a key feature distinguishing this invention from existing technologies and should be protected as a critical technical point.

[0098] This invention achieves a high-performance antenna array through overall optimized design. By comprehensively optimizing the slot coupling structure, feed network design, and element spacing, the antenna array exhibits excellent impedance characteristics within the 5.1-5.5 GHz operating bandwidth. The sum beam possesses high gain and low sidelobe level, while the difference beam has good null depth, meeting the technical requirements of modern radar systems for target detection and tracking. This design concept and method of synergistically optimizing various components to achieve overall high performance is the core value of this invention and should be highlighted in patent protection.

[0099] See also Figure 17This invention presents a microstrip-to-coaxial output design. Exemplarily, two microstrip-to-coaxial structures are respectively connected to the two input terminals of a sum and difference device. Each microstrip-to-coaxial structure includes a boss fixed to a metal platform by screws, with a coaxial structure located in the center of the boss. One end of the coaxial structure is connected to one input terminal of the sum and difference device, and the other end is connected to an energy transmitting device.

[0100] The array antenna design incorporates a 50Ω microstrip line output, with a microstrip-to-coaxial output structure at the feed port. This structure, optimized through HFSS simulation, exhibits low return loss and near-ideal transmission efficiency within the application frequency band, ensuring efficient energy transmission. Furthermore, it demonstrates excellent impedance matching and transmission characteristics across the entire operating frequency band. This innovative interface design, tailored to practical application needs, should also be included in the protection scope to safeguard the integrity and uniqueness of the invention in actual production applications.

[0101] In another embodiment of this application, while maintaining the overall functionality of the antenna array, the 4×8 element layout can be replaced with other forms, such as an 8×8 element layout or a circular array layout. Different layouts will affect the radiation characteristics of the antenna. For example, an 8×8 element layout may change the beamwidth and directivity in some directions, while a circular array layout may exhibit unique advantages in omnidirectional radiation characteristics. By reasonably adjusting the element layout and correspondingly optimizing the feed network and element spacing, it is also possible to achieve the inventive objective of high gain and low sidelobe level in the sum beam, as well as good null depth in the difference beam. Furthermore, this invention implements one-dimensional sum and difference functionality. By adjusting the sum and difference device, similar two-dimensional sum and difference beam performance can be achieved in the same way, thus fulfilling the inventive objective.

[0102] In another embodiment of this application, different feeding methods can be employed. Besides the 32-power divider combined with a sum / differential feed network design used in this invention, Wilkinson power dividers can be used to construct the feed network. Wilkinson power dividers have good isolation and power distribution characteristics, and can effectively reduce mutual interference between ports in some application scenarios. By rationally designing the number of stages and parameters of the Wilkinson power divider to cooperate with the sum / differential feeder, the antenna array can be fed, potentially simplifying the feed network structure while meeting antenna performance requirements. Furthermore, the use of distributed feed networks can also be explored. This feeding method can allocate power more flexibly according to the location and characteristics of antenna elements, potentially further optimizing the radiation performance of the antenna array and achieving the purpose of the invention.

[0103] In another embodiment of this application, circular patch elements can be used instead of the rectangular patch elements in this invention. Circular patch elements have different current distributions and radiation characteristics, and may exhibit better bandwidth characteristics or lower cross-polarization in certain frequency ranges. By optimizing the size, position, and coupling method with the feed network of the circular patch elements, combined with adjustments to the slot coupling structure and element spacing, it is expected to achieve sum-difference beam performance similar to the technical solution of this invention, thus fulfilling the invention's objective. Similarly, ring patch elements, due to their unique structure, may have different advantages in generating sum-difference beams and can also be further studied and explored as an alternative.

[0104] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0105] 1. In terms of antenna miniaturization, existing technologies are often limited by the difficulty in effectively isolating the radiating array and the feed network in spatial arrangement, resulting in a loose antenna element layout and difficulty in achieving compactness. This invention, however, cleverly employs a multi-layer structure to effectively separate the radiating array and the feed network in space, successfully achieving a compact antenna element layout and thus miniaturizing the antenna array. For example, the final fabricated 4×8 slot-coupled microstrip antenna array has a physical size of only 122mm×242mm×1mm. Such a small size is highly competitive among similar products, providing an ideal solution for the miniaturized antenna requirements of modern electronic devices, effectively reducing the overall space occupation and integration difficulty of the equipment.

[0106] 2. Bandwidth and electromagnetic energy transmission efficiency are key indicators for evaluating antenna performance. Existing antenna arrays generally suffer from narrow bandwidth and low electromagnetic energy transmission efficiency. This invention innovatively incorporates an air coupling layer, increasing the number of resonant points and effectively widening the bandwidth of the array antenna. Within the 5.1GHz-5.5GHz application frequency band, the antenna of this invention exhibits excellent performance, meeting the needs of multi-band signal transmission. Simultaneously, electromagnetic energy transmission efficiency is significantly improved, ensuring signal stability and efficiency during transmission, reducing signal distortion and loss, and strongly guaranteeing the quality of communication and detection.

[0107] 3. In existing technologies, it is difficult to achieve excellent sum-difference beamforming performance while maintaining a compact structure. This invention, based on the 3dB bridge principle, employs a microstrip line combined with a 90° phase shifter for meticulous design, achieving high-precision sum-difference beamforming within a compact structure. Within the 5.1-5.5GHz operating frequency band, HFSS simulation analysis shows that the return loss at both inputs of the microstrip sum-difference device is better than -20dB, exhibiting excellent impedance matching characteristics. The output energy is evenly distributed to ports 3 and 4, with a stable coupling of approximately -3dB. Furthermore, the sum-difference device satisfies amplitude balance and phase consistency, with a phase deviation between the two output ports not exceeding ±5° and amplitude fluctuations controlled within ±0.5dB. This precise sum-difference signal output capability provides strong support for the radar system's accurate target detection and tracking, significantly improving the radar system's performance and accuracy.

[0108] 4. From the perspective of overall antenna array performance, this invention achieves a low-profile, small-size broadband array antenna through comprehensive optimization of the slot coupling structure, feed network design, and element spacing. Within the 5.1-5.5 GHz operating bandwidth, the array's sum and difference port return losses and port isolation are both better than -15 dB, exhibiting excellent impedance matching. When operating at a center frequency of 5.3 GHz, the peak gain in the main beam direction reaches 19.25 dBi, while the maximum sidelobe levels in the E-plane and H-plane are suppressed to below -13.1 dB and -11.05 dB, respectively, effectively achieving sidelobe suppression. The difference beam gain reaches 16.9 dBi at the same center frequency, and a null depth of -31 dB is formed in the E-plane with a zero level of -14.1 dB, fully demonstrating the array's excellent difference beamforming capability and fully meeting the stringent technical requirements of modern radar systems for target detection and tracking. In comparison, existing technologies struggle to achieve such comprehensive and superior performance within such a small size.

[0109] 5. Furthermore, in designing a 50Ω microstrip line outlet, this invention incorporates a microstrip-to-coaxial outlet structure at the feed port to address the connection requirements with RF components. After HFSS simulation optimization, this structure achieves a return loss better than -18dB within the application frequency band, realizing near-ideal transmission efficiency and ensuring efficient energy transfer. This design is of significant practical importance, as existing technologies may not have fully considered or effectively addressed such interface design and performance optimization issues.

[0110] In summary, this invention demonstrates significant advantages over existing best technologies in several key aspects, including antenna miniaturization, bandwidth expansion, improved electromagnetic energy transmission efficiency, differential performance optimization, and overall antenna array performance realization. It brings innovative breakthroughs to the field of electromagnetic field radomes and has extremely high application value and market competitiveness.

[0111] Based on the above embodiments, this application also provides a radar system, which is equipped with a slot-coupled microstrip antenna array with one-dimensional sum and difference functions provided in the foregoing embodiments.

[0112] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A slot-coupled antenna element, characterized in that, include: The metal reflector, the first air coupling layer, the metal ground plane, the first dielectric layer, the microstrip feed line, the second air coupling layer, the second dielectric layer, and the radiating patch are stacked in sequence. The metal ground plane has coupling gaps, and the microstrip feed line is perpendicular to the coupling gaps. The coupling gap is used to change the current distribution so that the current in the direction of the microstrip feed line is cut off by the coupling gap, so as to retain a part of the current in the direction of the microstrip feed line within the coupling gap. The microstrip feeder is used to receive energy and couple the received energy to the metal ground plane through the first dielectric layer, and to transfer the received energy to the radiating patch through the second air coupling layer and the second dielectric layer. The first air coupling layer is used to adjust the impedance matching between the microstrip feed line and the metal reflector. The second air coupling layer is used to adjust the impedance matching between the radiating patch and the metal ground plane; The thickness of the second air coupling layer is 3.3mm ± 0.1mm, the thickness of the first air coupling layer is 3.2mm ± 0.1mm, the thickness of the first dielectric layer is 1.524mm ± 0.01mm, and the thickness of the second dielectric layer is 4.572mm ± 0.01mm.

2. The slot-coupled antenna element according to claim 1, characterized in that, The coupling gap is a rectangular gap.

3. The slot-coupled antenna element according to claim 1, characterized in that, Both the first dielectric layer and the second dielectric layer are PCB boards, wherein the PCB board is composed of Taconic-TMS-DS, the dielectric constant of the PCB board is 2.95, and the loss tangent of the PCB board is 0.0028.

4. A slot-coupled microstrip antenna array with one-dimensional sum-difference functionality, characterized in that, include: Multiple slot-coupled antenna elements as described in any one of claims 1-3, a sum and difference unit, and two sets of 16 equal power dividers; Each of the two sets of 16-equal-division power dividers has a T-junction, and the two sets of power dividers are cascaded through the T-junction; The sum and difference device includes a 3dB bridge and a 90° phase shifter. The 3dB bridge has two input terminals and two output terminals. The two output terminals of the sum and difference device are respectively connected to the T-junctions of the cascaded 16-equal power dividers. The two input ports of the sum and difference device perform one-dimensional sum and difference processing on the input beam. The two 16-equal power dividers and the sum and difference device form a feeding network. Each of the multiple slot-coupled antenna elements has its microstrip feed line connected to the output terminal of the 16-equal power divider. The input beam is processed by a sum and difference device to obtain a first sum and difference signal and a second sum and difference signal. The first sum and difference signal and the second sum and difference signal are respectively transmitted outward as different radiation signals through the slot-coupled antenna elements at the ends of two sets of 16 equal power dividers.

5. The slot-coupled microstrip antenna array with one-dimensional sum-difference function as described in claim 4, characterized in that, Also includes: Two microstrip-to-coaxial structures are respectively connected to the two input terminals of the sum and difference device. Each microstrip-to-coaxial structure includes a boss fixed to a metal platform by screws. A coaxial structure is provided in the middle of the boss. One end of the coaxial structure is connected to one input terminal of the sum and difference device, and the other end is connected to the energy transmitting device.

6. A radar system, characterized in that, The array is equipped with a slot-coupled microstrip antenna array having one-dimensional sum and difference functionality as described in claim 4.

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