Slot coupling antenna unit, microstrip antenna array and radar system

Abstract

The invention relates to a slot coupling antenna unit, a microstrip antenna array and a radar system, a metal reflecting plate, a first air coupling layer, a metal floor, a first dielectric layer, a microstrip feeder line, a second air coupling layer, a second dielectric layer and a radiation patch are stacked in sequence, and the metal floor is provided with a coupling slot; the coupling gap is used for changing current distribution, so that current in the direction of the microstrip feeder line is cut off by the coupling gap, and part of current in the direction of the microstrip feeder line is reserved in the coupling gap; the microstrip feeder is used for receiving energy, 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 impedance matching between the microstrip feeder and the metal reflecting plate; the second air coupling layer is used for adjusting impedance matching between the radiation patch and the metal floor, the antenna unit adopts a multi-layer structure, compact layout of the antenna unit is achieved, and miniaturization of the antenna array is further achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic antennas, and particularly relates to a slot-coupled antenna unit, a microstrip antenna array and a radar system. BACKGROUND

[0002] In the field of modern wireless communication, radar detection and the like, the requirements for antenna performance are constantly evolving towards high performance, miniaturization, wide frequency band and low cost. With the continuous improvement of the integration of electronic devices, more powerful antenna systems need to be accommodated in limited space, which makes antenna miniaturization a key requirement. At the same time, in order to adapt to the complex and variable signal environment, the antenna must have a wide enough working bandwidth to achieve efficient reception and transmission of multi-band signals, improve the efficiency of electromagnetic energy transmission, and ensure the stability and reliability of communication and detection.

[0003] In a radar system, accurate target detection and tracking functions rely on the excellent beam forming capability of the antenna. The accurate formation of the difference beam is crucial for accurately determining the position, speed and other parameters of the target, and can effectively improve the performance and accuracy of the radar system. Traditional antenna designs gradually reveal many limitations when facing these comprehensive requirements, and it is difficult to meet the constantly developing technical requirements, so innovative design methods are urgently needed to break through the existing bottlenecks. SUMMARY

[0004] Therefore, embodiments of the present application provide a slot-coupled antenna unit, a microstrip antenna array and a radar system, aiming to solve the problem that the radiation array and the feed network of the traditional antenna are difficult to effectively isolate in spatial arrangement, resulting in that the antenna unit cannot be compactly arranged, and limiting the development of the antenna array towards miniaturization.

[0005] To achieve the above-mentioned purpose, the embodiments of the present application provide a slot-coupled antenna unit, comprising: a metal reflector, 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 stacked in sequence, the metal ground plate has a coupling slot, and the microstrip feed line is perpendicular to the coupling slot; wherein the coupling slot is used to change the current distribution, so that the current in the direction of the microstrip feed line is truncated by the coupling slot to retain part of the current in the direction of the microstrip feed line in the coupling slot; the microstrip feed line is used to receive energy, and couple the received energy to the metal ground plate through the first dielectric layer, and transmit the received energy to the radiation 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; and the second air coupling layer is used to adjust the impedance matching between the radiation patch and the metal ground plate.

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

[0007] Optionally, 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.

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

[0009] To achieve the above-mentioned purpose, the application further provides a plurality of the gap coupling antenna units provided in the foregoing embodiment, and a sum-difference device and two groups of 16-way power dividers; each of the two groups of 16-way power dividers has a T-shaped junction, and the two groups of power dividers are cascaded through the T-shaped junctions; the sum-difference device comprises a 3dB bridge and a 90° phase shifter, the 3dB bridge has two input ports and two output ports, wherein the two output ports of the sum-difference device are respectively connected to the T-shaped junctions after the cascading of the two groups of 16-way power dividers, the two input ports respectively perform one-dimensional sum-difference processing on the input beams, and the two groups of 16-way power dividers and the sum-difference device form a feeding network; the microstrip feed lines of the plurality of gap coupling antenna units are respectively connected to the output ports of the 16-way power dividers; wherein the input beams are processed by the sum-difference device to obtain a first sum-difference signal and a second sum-difference signal, and the first sum-difference signal and the second sum-difference signal are respectively sent out by the gap coupling antenna units at the ends of the two groups of 16-way power dividers to emit different radiation signals.

[0010] Optionally, the application further comprises two microstrip-to-coaxial structures connected to the two input ports of the sum-difference device, wherein the microstrip-to-coaxial structure comprises a boss fixed on a metal platform by a screw, a coaxial structure is arranged in the middle of the boss, one end of the coaxial structure is connected to one input port of the sum-difference device, and the other end is connected to an energy transmitting device.

[0011] To achieve the above-mentioned purpose, the application further provides a radar system provided with the gap coupling microstrip antenna array with one-dimensional sum-difference function provided in the foregoing embodiment.

[0012] To achieve the above-mentioned purpose, the application further provides a gap coupling antenna unit.

[0013] The embodiment of the application provides a slot coupling antenna unit, a microstrip antenna array and a radar system, the slot coupling antenna unit is stacked by 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 in sequence, the metal ground plate is provided with a coupling slot, and the microstrip feed line is perpendicular to the coupling slot; wherein 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, so that part of the current in the direction of the microstrip feed line is reserved in the coupling slot; the microstrip feed line is used for receiving energy, and coupling the received energy to the metal ground plate through the first dielectric layer, and transmitting the received energy to the radiation patch through the second air coupling layer and the second dielectric layer; the second air coupling layer is used for adjusting the impedance matching between the radiation patch and the metal ground plate; the first air coupling layer is used for adjusting the impedance matching between the microstrip feed line and the metal reflecting plate, the application adopts a multilayer structure, effectively realizes effective isolation of the radiation array and the spatial arrangement of the feed network, realizes compact layout of the antenna unit, and further realizes miniaturization of the antenna array; secondly, by adding the air coupling layer, the resonance point is increased, the bandwidth of the array antenna is widened, the electromagnetic energy transmission efficiency is improved, the microstrip antenna array realizes excellent sum and difference beam forming performance while maintaining a compact structure through the sum and difference device design, the application realizes a low-profile small-size wideband array antenna, and provides a high-performance and low-cost solution for a radar antenna system. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a slot coupling antenna unit stacking structure provided by the embodiment of the application;

[0015] Figure 2 It is a slot coupling antenna unit structure top view provided by the embodiment of the application;

[0016] Figure 3 It is a reflection coefficient and corresponding frequency point peak gain curve diagram of the antenna unit provided by the embodiment of the application;

[0017] Figure 4 It is an antenna unit standing wave ratio simulation result diagram provided by the embodiment of the application;

[0018] Figure 5 It is a 5.3GHz polar coordinate system directional diagram of the antenna unit provided by the embodiment of the application;

[0019] Figure 6 It is a sum and difference device structure diagram provided by the embodiment of the application;

[0020] Figure 7 It is an optimized sum and difference device S parameter amplitude simulation result diagram provided by the embodiment of the application;

[0021] Figure 8is a simulation result chart of the phase of the S parameter of the difference after optimization provided by the embodiment of the present application;

[0022] Figure 9 is a structure chart of the power division network provided by the embodiment of the present application;

[0023] Figure 10 is a simulation result chart of the reflection coefficient of the power division network after optimization provided by the embodiment of the present application;

[0024] Figure 11 is a result chart of the coupling degree of the power division network after optimization provided by the embodiment of the present application;

[0025] Figure 12 is an arrangement chart of the slot coupling microstrip antenna array provided by the embodiment of the present application;

[0026] Figure 13 is a simulation result of the E plane and the directional diagram of the antenna array provided by the embodiment of the present application;

[0027] Figure 14 is a simulation result of the H plane and the directional diagram of the antenna array provided by the embodiment of the present application;

[0028] Figure 15 is a simulation result of the difference directional diagram of the antenna array provided by the embodiment of the present application;

[0029] Figure 16 is a simulation result chart of the S parameter of the antenna array provided by the embodiment of the present application;

[0030] Figure 17 is a structure chart of the microstrip to coaxial structure at the antenna outlet provided by the embodiment of the present application;

[0031] Figure 18 is a simulation result chart of the microstrip to coaxial structure at the antenna outlet provided by the embodiment of the present application;

[0032] Figure 19 is a real object chart of the antenna printed board provided by the embodiment of the present application;

[0033] Figure 20 is a real measurement result chart of the S parameter of the antenna provided by the embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are proposed in order to make the readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed by the present application can be implemented. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation modes of the present application, and the embodiments can be combined and quoted with each other without contradiction.

[0035] In the field of electromagnetic field radome, the prior art has many shortcomings in the design and implementation of slot-coupled microstrip antenna array. These shortcomings limit the further application and development of the antenna in the field of modern communication and radar system, and the present application proposes an innovative solution to these pain points, which include:

[0036] 1. The prior art has great difficulty in the miniaturization of the antenna array. The traditional design cannot effectively isolate the spatial arrangement of the radiation array and the feed network, resulting in loose layout of the antenna units and inability to be placed compactly. This not only occupies too much space, but also increases the difficulty and cost of system integration, seriously hindering the development of antenna array towards miniaturization and light weight, and making it difficult to meet the stringent requirements of modern electronic devices for compact structure.

[0037] 2. Bandwidth and electromagnetic energy transmission efficiency are also shortcomings of the prior art. The bandwidth of the antenna array under ordinary design is narrow, which cannot adapt to the signal transmission demand of multi-band and wide-band. At the same time, the electromagnetic energy is greatly lost in the transmission process, and the transmission efficiency is low, which limits the performance of the antenna in receiving and transmitting signals, and cannot guarantee the stability and efficiency of communication and detection, and is prone to signal distortion, interruption and other problems in complex electromagnetic environment.

[0038] 3. The design of the sum-difference device also has significant defects in the prior art. The amplitude balance and phase consistency of the sum-difference device are poor, there is a large phase deviation and amplitude fluctuation of the signal at the output port, the return loss is high, and accurate sum-difference signal output cannot be achieved. This greatly affects the accuracy and reliability of target detection and tracking for radar systems that rely on accurate beam forming.

[0039] In summary, due to the inability to effectively realize miniaturization, have sufficient bandwidth and high energy transmission efficiency, and achieve ideal sum-difference device performance, it is difficult to design a low-profile, small-size and wide-band high-performance antenna array. Designing a high-performance, low-cost antenna array to meet the practical application needs of radar antenna systems and other fields has become a key problem to be solved.

[0040] In the prior art, there are various implementation schemes in the design of gap-coupled microstrip antennas. In the design of antenna units, the common structure is also composed of multiple layers of media, including basic parts such as radiation patches, medium substrates, and feed lines. However, these designs often cannot effectively solve the isolation problem of the spatial arrangement of the radiation array and the feed network. The radiation array and the feed network interfere with each other, making it difficult to achieve a compact layout of the antenna unit, thereby hindering the development of antenna arrays towards miniaturization. At the same time, due to the lack of effective bandwidth expansion means, the working bandwidth is relatively narrow, and the electromagnetic energy transmission efficiency needs to be improved.

[0041] In the design of hybrid combiners, it is difficult for previous schemes to achieve ideal hybrid beamforming performance while maintaining a compact structure. Some hybrid combiners can achieve signal sum-difference functions, but perform poorly in key indicators such as amplitude balance, phase consistency, and return loss. For example, some hybrid combiners based on traditional circuit structure design have high input port return loss in the working frequency band, cannot achieve good impedance matching, and result in serious energy loss during signal transmission. Moreover, the energy distribution at the output port is uneven, the coupling degree is unstable, the phase deviation between the two output ports is large, and the amplitude fluctuation also exceeds the acceptable range, making it difficult to meet the high-precision sum-difference beamforming requirements.

[0042] In the design of power division feed networks, existing schemes have difficulty in balancing high-precision power division characteristics and good impedance matching performance when implementing power division. Some power division networks can achieve power division in a certain proportion, but their input port return loss is high in the entire working frequency band, which cannot guarantee stable impedance matching. At the same time, the power division characteristics of each output port are not ideal, the coupling coefficient fluctuates greatly, the amplitude balance and phase consistency are poor, which affects the stability and reliability of the overall performance of the antenna array.

[0043] In the prior art, antenna arrays face challenges in miniaturization. The spatial arrangement of the radiation array and the feed network of traditional antennas cannot be effectively isolated, which makes it difficult to achieve a compact layout of the antenna unit, limiting the development of antenna arrays towards miniaturization. The present invention uses a multi-layer structure to successfully achieve effective isolation of the spatial arrangement of the radiation array and the feed network, creating conditions for the compact layout of the antenna unit, and thereby promoting the miniaturization process of the antenna array, meeting the needs of modern electronic devices for miniaturized antennas.

[0044] The bandwidth and electromagnetic energy transmission efficiency of the antenna are also key issues. In the prior art, the bandwidth of the antenna is narrow, and the electromagnetic energy transmission efficiency is low, which affects the performance. The present application adds an air coupling layer, increases the resonance point, effectively expands the bandwidth of the array antenna, and improves the electromagnetic energy transmission efficiency, so that the antenna can work stably in a wider frequency range, and the energy transmission is more efficient, laying a foundation for improving the performance of the whole system.

[0045] The performance of the sum-difference device cannot be ignored. In the past, it is difficult to achieve excellent sum-difference beam forming performance while maintaining a compact structure. The present application has made a breakthrough in the design of the sum-difference device, and has achieved excellent sum-difference beam forming performance under the premise of maintaining a compact structure, providing strong support for the accurate detection and tracking of the target by the radar antenna system.

[0046] In addition, the antenna designed in the prior art is difficult to balance the low profile and small size with the wideband characteristics, and cannot meet the high performance requirements of the radar antenna system. The present application realizes a low profile, small size and wideband array antenna through a series of optimization designs, and the effectiveness of the design scheme is verified by the actual measurement results, providing a high-performance and low-cost solution for the radar antenna system, effectively solving the problem of balancing the size, bandwidth and performance of the antenna in the prior art, and promoting the technical progress in the field of electromagnetic antenna covers.

[0047] The prior art has different degrees of defects in the design of each key component of the slot-coupled microstrip antenna array, which is difficult to meet the comprehensive requirements of modern technology for high performance, miniaturization and wideband of the antenna, which highlights the necessity and urgency of the innovative design method proposed in the present application.

[0048] In view of the above shortcomings of the prior art, the present application aims to comprehensively make up for the shortcomings of the prior art. By adopting a multi-layer structure, the radiation array and the feed network are effectively isolated in space, creating conditions for the compact layout of the antenna unit, and then realizing the miniaturization of the antenna array, significantly reducing the system space occupation and integration cost. The air coupling layer is introduced to increase the resonance point, widen the bandwidth of the array antenna, and improve the electromagnetic energy transmission efficiency, ensuring stable and efficient transmission of signals in a wide frequency band. A breakthrough is made in the design of the sum-difference device, and excellent sum-difference beam forming performance is achieved under a compact structure, ensuring high precision of the sum-difference signal output. Finally, through a series of innovative designs, a low profile, small size and wideband array antenna is realized, and the effectiveness of the scheme is verified by actual measurement, providing a high-performance and low-cost solution for the radar antenna system, and effectively promoting the technical progress and practical application expansion in the field of electromagnetic antenna covers.

[0049] The gap coupling antenna unit provided in the embodiment comprises, in sequence, a metal reflector 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, the metal ground plate is provided with a coupling gap, and the microstrip feed line is perpendicular to the coupling gap; wherein the coupling gap is used to change the current distribution, so that the current in the direction of the microstrip feed line is truncated by the coupling gap to reserve part of the current in the direction of the microstrip feed line in the coupling gap; the microstrip feed line is used to receive energy and couple the received energy to the metal ground plate through the first dielectric layer, and transmit the received energy to the radiation 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 plate; and the second air coupling layer is used to adjust the impedance matching between the radiation patch and the metal ground plate.

[0050] Specifically, the gap coupling microstrip antenna structure comprises a multi-layer structure, wherein the uppermost layer is a radiation patch, the lower layer of the radiation patch is a second dielectric layer and a second air coupling layer, the next layer is a microstrip feed line and a first dielectric layer, the lower layer of the first dielectric layer is a metal ground plate, the metal ground plate is provided with a coupling gap, and the coupling gap is located at the center position of the projection of the radiation patch on the metal plate. By loading the gap on the metal ground plate, the current distribution can be changed so that the current in the direction of the feed line is truncated by the gap, thereby only a small amount of current in the direction of the feed line is reserved in the rectangular gap. The regions between the upper radiation patch and the metal ground plate, and between the microstrip feed line and the reflector plate are used to adjust the air layers for matching. Energy is coupled from the microstrip feed line to the ground plate through the air layer, and then the energy is finally transmitted to the upper radiation patch through the second dielectric layer and the second air layer.

[0051] Next, based on the equivalent circuit model of the gap coupling microstrip antenna, the gap coupling microstrip antenna is theoretically analyzed, Z in The input impedance of the unit structure, the impedance of the open stub, the ground plate gap and the radiation patch are input. The calculation formula is as follows:

[0052]

[0053] Wherein, n1 is the coupling coefficient of the gap and the patch, Y p and Y a are the admittance of the patch and the gap, n2 is the coupling coefficient of the gap and the feed line; Z om is the characteristic impedance, β m is the wave number, and S is the equivalent radiation aperture of the antenna. The admittance Y a of the gap can be expressed as:

[0054] Y a = -j2Y os ctg(β s L a / 2)

[0055] where Y os is the characteristic admittance, β s is the wave number, L a is the length of the antenna element, the equivalent circuit model shown, the admittance Y p is calculated as follows:

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

[0057]

[0058] where β open is the wave number in open circuit state, and x represents the relative position of the slot.

[0059] The microstrip antenna with a coupled feed structure has its radiation part and feed part usually located in different planes, and this layered design can significantly reduce the interference of the feed network on the radiation pattern.

[0060] It should be noted that before designing the antenna element, the material and size of the dielectric plate need to be determined first.

[0061] wherein the slot-coupled antenna element structure is composed of 2 layers of PCB materials, the PCB materials are composed of Taconic-TMS-DS, the dielectric constant is 2.95, and the loss tangent is 0.0028. When designing, the dielectric material with the existing standard plate thickness needs to be selected.

[0062] Figure 1 、 Figure 2 The slot-coupled antenna element structure is shown, and there are 2 layers of PCB materials designed. Among them, the thickness h1 of the dielectric layer 1 is 4.572 mm, which is used for antenna radiation. The air coupling layer with a middle interval d1 of 3.3 mm forms a gradual change region of electromagnetic field, and the coupling effect is controlled by adjusting the cavity height. The thickness h2 of the dielectric layer 2 is 1.524 mm, wherein the upper dielectric layer is a microstrip feed line, and the lower dielectric layer is a metal bottom plate with a coupling slot, which also serves as the metal ground of the microstrip feed line. The air coupling layer with a middle interval d2 of 3.2 mm, and the lowermost layer is a metal reflector plate. The air cavity combined with the metal reflector plate constitutes a resonant cavity.

[0063] According to the calculation formula and the known antenna index, the approximate size of the radiation patch and the slot of each element can be calculated. The initial model of the element is established by using the known parameters.

[0064] The parameters of the structure are optimized and simulated in the HFSS simulation software. Figure 3 、 Figure 4 、 Figure 5For the simulation result of the antenna unit, the antenna has a port 1 reflection coefficient better than -15 dB, a standing wave ratio less than 1.5, and a gain corresponding to each frequency point greater than 8 dBi in the application frequency band of 5.1 GHz-5.5 GHz, and has good in-band gain flatness.

[0065] In an embodiment of the present application, the coupling slot is a rectangular slot.

[0066] In an embodiment of the present 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, the first dielectric layer and the second dielectric layer are both PCB board materials, wherein the PCB board material is composed of Taconic-TMS-DS, the dielectric constant of the PCB board material is 2.95, and the loss tangent of the PCB board material is 0.0028.

[0069] On the basis of the above-mentioned embodiment, the present application further provides a slot-coupled microstrip antenna array with one-dimensional and difference functions, comprising:

[0070] The slot-coupled antenna unit, the adder and the two groups of 16 equal power dividers mentioned above;

[0071] The two groups of power dividers in each of the 16 equal power dividers have a T-junction, and the two groups of power dividers are cascaded through the T-junctions; and the difference device includes a 3dB bridge and a 90° phase shifter, the 3dB bridge has two input ends and two output ends, the two output ends are connected to the cascaded T-junctions of the two groups of 16 equal power dividers respectively, and the two input ends are connected to two input signals respectively, the difference device is used for one-dimensional sum and difference processing of the input beam, and the two groups of 16 equal power dividers and the difference device form a feeding network; the microstrip feed lines of the plurality of slot coupling antenna units are connected to the output ends of the 16 equal power dividers respectively; wherein, after the input signal is processed by the difference device, a first sum and difference signal and a second sum and difference signal are obtained, and the first sum and difference signal and the second sum and difference signal are respectively sent out by the slot coupling antenna units at the ends of the two groups of 16 equal power dividers to send out different radiation signals.

[0072] Next, the design of the difference device needs to be carried out. The 3dB bridge is a four-port network that can divide the input signal into two output signals and introduce a 90° phase difference. Based on the principle of the 3dB bridge, the microstrip line is used to realize the sum and difference of the signals.

[0073] Suppose the input signal is V in , then in the ideal case, the signals at the two output ports of the 3dB bridge are: where the 90° phase shifter delays the phase of the input signal by 90°. In a microwave circuit, the phase shifter can be realized in many ways, such as by changing the length of the transmission line or using a special circuit structure. Suppose 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 the difference device is to combine two input signals into a sum signal and a difference signal. Suppose the two input signals are V1 and V2, then the sum signal V sum and the difference signal V diff can be represented as:

[0076] V sum = V1 + V2

[0077] V diff = V1 - V2

[0078] When the 3dB bridge is combined with the 90° phase shifter, suppose the input signal is V in , after passing through the 3dB bridge, two signals V out1 and V out2 are obtained, where V out2 passes through the 90° phase shifter again. Then the final sum and difference signals can be represented as:

[0079]

[0080] The combination of 3dB bridge and 90° phase shifter can realize the sum-difference synthesis of signals, and through reasonable circuit design, the accurate sum-difference signal output can be realized.

[0081] Based on the above principle, the microstrip sum-difference device is simulated and analyzed by using HFSS, Figure 6 The structure diagram of sum-difference device is shown in FIG. 4, Figure 7 , Figure 8 The simulation results of the sum-difference device are shown in FIG. 5. In the working frequency band of 5.1-5.5GHz, the return loss of the two input ports is better than-20dB, which indicates that the coupler has good impedance matching characteristics. The output port energy is uniformly distributed to ports 3 and 4, and the coupling degree is stable at about-3dB. The sum-difference device meets the amplitude balance and phase consistency. The phase deviation between the two output ports is not more than ±5°, and the amplitude fluctuation is controlled within ±0.5dB. The sum-difference device realizes good sum-difference performance in the application frequency band.

[0082] The design process of the power division feeding network includes the following steps:

[0083] Figure 9 The structure diagram of the power division network is shown in FIG. 6. The antenna adopts a 4×8 unit layout, and a 32-dividing power divider is used for the corresponding feeding network. The sum-difference device is used to realize one-dimensional sum-difference of the beam, i.e. only the E-plane pattern is designed by using the sum-difference device. The two output ports of the sum-difference device are connected with the symmetrically distributed 1:16 power distribution network, forming a complete feeding network.

[0084] The power division network adopts T-shaped junction as the basic construction unit, and realizes the power distribution ratio of 1:16 through cascading.

[0085] Figure 10 , Figure 11 The simulation results of the power division network are shown in FIG. 7. The feeding network exhibits excellent transmission characteristics in the working frequency band of 5.1-5.5GHz. The return loss of the input port is better than-20dB, showing good impedance matching performance. At the same time, the power distribution characteristics of the 16-way output port are outstanding, and the coupling coefficients of each channel are stable at about-12.5dB, and the amplitude fluctuation is controlled within ±0.25dB, realizing high-precision power distribution.

[0086] The power division network design meets the amplitude and phase consistency requirements, and has good impedance matching characteristics in the whole working frequency band.

[0087] Figure 12For the slot-coupled microstrip antenna array layout, the antenna array adopts a 4x8 unit layout, and by optimizing the slot-coupled structure, the feed network design and the array element spacing, the beam can ensure high gain characteristics while achieving a lower sidelobe level; the difference beam has good null depth. The slot-coupled microstrip antenna array is simulated and designed by using HFSS:

[0088] The array exhibits excellent impedance characteristics within the operating bandwidth of 5.1-5.5 GHz, with the return loss of the sum and difference ports and the port isolation both better than -15 dB, showing good impedance matching effect.

[0089] Figure 13 , Figure 14 The radiation characteristics of the multi-layer antenna array are shown. When operating at a center frequency of 5.3 GHz, the main beam direction obtains a peak gain of 19.25dBi. At the same time, the maximum sidelobe levels in the E-plane and H-plane are suppressed to below -13.1dB and -11.05dB respectively, indicating that the design realizes effective sidelobe suppression while ensuring high directivity.

[0090] As shown in Figure 15 and 16 , the simulation results of the 4x8 LTCC slot-coupled microstrip antenna array difference beam are shown in Figure 15 and 16 . At the same center frequency, the difference beam gain reaches 16.9dBi, and a null of -31dB is formed in the E-plane, with a null level of -14.1dB. These parameters fully demonstrate the excellent difference beam forming capability of the array, fully meeting the technical index requirements of modern radar systems for target detection and tracking.

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

[0092] Figure 17 The microstrip to coaxial structure diagram of the antenna outlet is shown, and the S parameter simulation results obtained by HFSS are shown in Figure 18 . The return loss is better than -18dB within the application frequency band, and the transmission efficiency close to the ideal value is realized. The simulation data show that the optimized adapter structure has good impedance matching characteristics and transmission characteristics in the entire operating frequency band, ensuring efficient energy transmission.

[0093] In this embodiment, the final processed 4x8 scale slot-coupled microstrip antenna array has a physical size of 122mmx242mmx1mm. Figure 19 The photos of the antenna physical sample radiation patch layer and the feed network layer for testing are shown. ​

[0094] The antenna after processing is assembled, and a high-performance vector network analyzer is used to test the S parameters of the antenna. Figure 20 The port S parameter test results are shown, and the measured and simulated S parameter curves have good consistency, but due to the errors caused by antenna manufacturing tolerances and assembly, the measured reflection coefficient is slightly higher than the simulated value; due to the shell structure, the measured port isolation is lower than the simulated value, and the isolation effect is better.

[0095] The application adopts a multi-layer structure for design. The multi-layer structure effectively isolates the radiation array and the feed network in space, which realizes the compact layout of the antenna unit and is a key innovative point for achieving the miniaturization of the antenna array. This structure design not only solves the problem of spatial layout in traditional design, but also lays a foundation for subsequent performance optimization, and should be protected as a core point to prevent others from imitating similar structures to achieve the same function.

[0096] The application uses an air coupling layer to expand the working bandwidth. By adding an air coupling layer, the bandwidth of the array antenna is successfully expanded by increasing the resonance points, and the electromagnetic energy transmission efficiency is significantly improved. This unique design method changes the limitations of traditional antennas in bandwidth and energy transmission, which is a key breakthrough in improving the performance of the antenna, and needs to be protected to ensure the uniqueness and innovation of the application.

[0097] The application realizes high-performance and difference design. Under the premise of maintaining a compact structure, excellent sum and difference beamforming performance is realized. By using a microstrip line based on the 3dB bridge principle and combining a 90° phase shifter for reasonable circuit design, the sum and difference device meets the amplitude balance and phase consistency requirements in the application frequency band, the input return loss is low, and the output port energy distribution is uniform and stable. This unique sum and difference device design scheme is an important feature that distinguishes the application from the prior art, and should be protected as a key technology point.

[0098] The application realizes a high-performance antenna array through overall optimization design. Through overall optimization of the slot coupling structure, feed network design and array element spacing, the antenna array exhibits excellent impedance characteristics within the 5.1-5.5GHz operating bandwidth, the sum beam has high gain and low sidelobe level, and the difference beam has good null depth, meeting the technical index requirements of modern radar systems for target detection and tracking. This design concept and method of optimizing each part to achieve overall high performance is the core value of the application and should be highlighted in patent protection.

[0099] Continuing to refer to Figure 17The application carries out microstrip-to-coaxial outlet design. Exemplarily, two microstrip-to-coaxial structures are connected to two inputs of a hybrid, and the microstrip-to-coaxial structure comprises a boss fixed on a metal platform by a screw, and a coaxial structure is arranged in the middle of the boss, one end of the coaxial structure is connected to one input of the hybrid, and the other end is connected to an energy transmitting device.

[0100] The array antenna is designed to have a 50Ω microstrip line outlet, and a microstrip-to-coaxial outlet structure is designed at the feeding port. The structure is optimized through HFSS simulation, has low return loss in the application frequency band, and has transmission efficiency close to the ideal value, thereby ensuring efficient transmission of energy and good impedance matching and transmission characteristics in the entire working frequency band. The innovative interface design for actual application requirements is also included in the protection range to ensure the integrity and uniqueness of the application in actual production and application.

[0101] In another embodiment of the application, under the premise of maintaining the overall function of the antenna array, the 4x8 unit layout can be replaced by other forms, such as an 8x8 unit layout or a circular array layout. Different layout methods will affect the radiation characteristics of the antenna. For example, the 8x8 unit layout can change the width and directivity of the beam in some directions, and the circular array layout can exhibit unique advantages in omnidirectional radiation characteristics. By reasonably adjusting the unit layout and correspondingly optimizing the feed network and element spacing, it is also possible to achieve the purpose of the application of high gain, low sidelobe level, and good null depth of the beam. In addition, the application realizes one-dimensional sum and difference functions, and through adjustment of the hybrid, the same way can realize similar two-dimensional sum and difference beam performance, and complete the purpose of the application.

[0102] In another embodiment of the application, different feeding methods can be used. In addition to the 32-section power divider combined with the feed network design of the hybrid in the application, a Wilkinson power divider can be used to construct the feed network. The Wilkinson power divider has good isolation and power distribution characteristics, and can effectively reduce the mutual interference between the ports in some application scenarios. By reasonably designing the number of stages and parameters of the Wilkinson power divider, it can be matched with the hybrid to realize the feeding of the antenna array, which can simplify the structure of the feed network while meeting the performance requirements of the antenna. In addition, the use of distributed feed network can also be explored. This feeding method can more flexibly allocate power according to the position and characteristics of the antenna elements, which can further optimize the radiation performance of the antenna array and achieve the purpose of the application.

[0103] In another embodiment of the present application, the rectangular patch array elements in the present application can be replaced by circular patch array elements. Circular patch array elements have different current distribution and radiation characteristics, which may exhibit better bandwidth characteristics or lower cross-polarization in certain frequency ranges. By optimizing the size, position and coupling mode of the circular patch array elements with the feed network, combined with the adjustment of the slot coupling structure and the array element spacing, it is expected to achieve similar and different beam performance and complete the purpose of the application. Similarly, due to its unique structure, the annular patch array element may have different advantages when generating sum and difference beams, and can also be used as an alternative solution for further research and exploration.

[0104] Compared with the prior art, the present application has the following advantages:

[0105] 1. In terms of antenna miniaturization, the prior art is often limited by the difficulty of effectively isolating the radiation array and the feed network in space arrangement, resulting in loose antenna unit layout and difficulty in achieving compactness. However, the present application successfully achieves compact layout of antenna units by adopting a multi-layer structure, effectively separating the radiation array and the feed network in space, and achieving miniaturization of the antenna array. For example, the actual size of the 4x8 scale slot-coupled microstrip antenna array after final processing is only 122mmx242mmx1mm, which is extremely competitive in similar products, providing an ideal solution for the demand of modern electronic equipment for small-sized antennas, and effectively reducing the overall space occupation and integration difficulty of the equipment.

[0106] 2. Bandwidth and electromagnetic energy transmission efficiency are key indicators for measuring antenna performance. The antenna arrays in the prior art generally have narrow bandwidth and low electromagnetic energy transmission efficiency. The present application innovatively adds an air coupling layer, increasing the resonance point and effectively expanding the bandwidth of the array antenna. In the application frequency band of 5.1GHz-5.5GHz, the antenna of the present application exhibits good performance, meeting the demand of multi-frequency signal transmission. At the same time, the electromagnetic energy transmission efficiency is also significantly improved, ensuring the stability and efficiency of the signal in the transmission process, reducing signal distortion and loss, and effectively guaranteeing the quality of communication and detection.

[0107] 3、The design of a sum-difference wave beam former is difficult to achieve excellent performance while maintaining a compact structure in the prior art. Based on the 3dB bridge principle, the present invention uses microstrip lines and combines 90° phase shifters to achieve high-precision sum-difference wave beam forming in a compact structure. Within the 5.1-5.5GHz operating frequency band, HFSS simulation analysis shows that the return loss of the two input ends of the microstrip sum-difference wave former is better than -20dB, showing good impedance matching characteristics. The output port energy is evenly distributed to ports 3 and 4, with a coupling degree of about -3dB, and the sum-difference wave former meets the amplitude balance and phase consistency, with a phase deviation between the two output ports of no more than ±5° and an amplitude fluctuation within ±0.5dB. This precise sum-difference signal output capability provides strong support for the accurate detection and tracking of targets by radar systems, greatly improving the performance and accuracy of radar systems.

[0108] 4、From the overall antenna array performance, the present invention achieves a low-profile small-size wideband array antenna through comprehensive optimization of the slot coupling structure, feed network design and element spacing. Within the 5.1-5.5GHz operating bandwidth, the sum-difference port return loss and port isolation of the array are both better than -15dB, showing excellent impedance matching effect. When operating at a center frequency of 5.3GHz, the main beam direction peak gain reaches 19.25dBi, while the maximum side lobe levels in the E-plane and H-plane are suppressed to below -13.1dB and -11.05dB respectively, effectively realizing side lobe suppression. The difference beam has a gain of 16.9dBi at the same center frequency, and forms a zero in the E-plane with a depth of -31dB and a zero value level of -14.1dB, fully demonstrating the excellent difference beam forming capability of the array, fully meeting the stringent technical index requirements of modern radar systems for target detection and tracking. In comparison, the prior art is difficult to achieve such comprehensive and excellent performance in such a small size.

[0109] 5、In addition, in the case of designing an outlet of 50Ω microstrip line, the present invention designs a microstrip to coaxial outlet structure at the feed port to meet the connection requirements with radio frequency components. After HFSS simulation optimization, the return loss within the application frequency band is better than -18dB, achieving a transmission efficiency close to the ideal value and ensuring efficient energy transmission. This design is of great significance in practical applications, while the prior art may not have fully considered or effectively solved such interface design and performance optimization problems.

[0110] In summary, the present invention has obvious advantages compared to the best prior art in terms of antenna miniaturization, bandwidth expansion, electromagnetic energy transmission efficiency improvement, sum-difference wave former performance optimization, and overall antenna array performance realization. It brings an innovative breakthrough to the field of electromagnetic antenna covers and has very high application value and market competitiveness.

[0111] On the basis of the above-mentioned embodiments, the application further provides a radar system, which is provided with the slot-coupled microstrip antenna array with one-dimensional and difference functions provided in the above-mentioned embodiments.

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

Claims

1. A slot-coupled antenna unit, characterized in that: include: A metal reflector, a first air coupling layer, a metal floor, a first dielectric layer, a microstrip feed line, a second air coupling layer, a second dielectric layer, and a radiation patch are stacked in sequence, wherein the metal floor has a coupling slot, and the microstrip feed line and the coupling slot are perpendicular to each other; 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 that part of the current along the direction of the microstrip feed line is retained in the coupling slot; The microstrip feed line is used to receive energy and couple the received energy to the metal floor through the first dielectric layer, and to transfer the received energy to the radiation 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.

2. The slot-coupled antenna unit according to claim 1, wherein: The coupling gap is a rectangular gap.

3. The slot-coupled antenna unit according to claim 1, wherein: 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.

4. The slot-coupled antenna unit according to claim 1, wherein: The first dielectric layer and the second dielectric layer are both PCB materials, wherein the PCB material is made of Taconic-TMS-DS, the dielectric constant of the PCB material is 2.95, and the loss tangent of the PCB material is 0.0028.

5. A slot-coupled microstrip antenna array with one-dimensional sum and difference functions, characterized in that: include: A plurality of slot-coupled antenna units according to any one of claims 1 to 4, and a sum-differential device and two groups of 16-equal power dividers; Each of the two groups of 16 equally divided power has a T-junction, and the two groups of power dividers are cascaded through the T-junction; The summator and the differencer include 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 summator and the differencer are respectively connected to the T-junctions of two groups of 16-equal-division power dividers, each of which is cascaded. The two input ports of the summator and the differencer respectively perform one-dimensional sum and difference processing on the input beams. The two groups of 16-equal-division power dividers and the summator and the differencer form a feeding network. The microstrip feed lines of the plurality of slot-coupled antenna units are respectively connected to the output ends of the 16-equal power dividers; Among them, after the input beam is processed by the summator, a first sum-difference signal and a second sum-difference signal are obtained. The first sum-difference signal and the second sum-difference signal respectively send different radiation signals outward through the slot-coupled antenna units at the end of two groups of 16-equal power dividers.

6. The slot-coupled microstrip antenna array with one-dimensional sum and difference functions according to claim 5, characterized in that: Also includes: Two microstrip-to-coaxial structures are respectively connected to the two input ends of the summator and the differential device. The microstrip-to-coaxial structure includes a boss fixed on a metal platform by screws, and a coaxial structure is provided in the middle of the boss. One end of the coaxial structure is connected to an input end of the summator and the other end is connected to the energy sending device.

7. A radar system, characterized in that: A slot-coupled microstrip antenna array with one-dimensional sum and difference functions as claimed in claim 5 is provided.

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