Large-range, close-range and millimeter-level stepping target time delay method and large-range, close-range and millimeter-level stepping target time delay equipment

Abstract

The invention discloses a large-range, close-range and millimeter-level stepping target delay method and equipment, which are mainly different from the prior art in that a complete delay line is formed by adopting a combination mode that three analog delay line technologies are connected in series and in parallel, and small stepping and short delay are realized by adopting a PCB delay module. Large-distance-range simulation is achieved through the optical fiber delay module, meanwhile, the optical fiber delay module can be short-circuited by a parallel branch, and the coaxial cable delay module is mainly used for achieving distance connection between the maximum delay of the PCB delay module and the minimum delay of the optical fiber delay module.

Description

Technical Field

[0001] This patent involves a radar target simulator that simulates a delay line system, which belongs to the field of radar testing. The delay device can solve technical indicators such as short distance, large range, and small step. Background Art

[0002] With the rapid development of automobile autonomous driving technology around the world, the safety, accuracy and reliability of autonomous driving vehicles have become the focus of attention in the industry. Among them, automotive millimeter-wave radar is an indispensable key sensor in the autonomous driving system, and its technological innovation and application expansion are particularly important. With the continuous advancement of radar technology and the increasing requirements of autonomous driving systems for environmental perception, the demand for automotive millimeter-wave radar measurement equipment, that is, radar target simulators, has also shown a rapid growth trend. The maximum bandwidth of existing automotive radars has reached 4GHz, the corresponding distance resolution is 0.0375m, and the distance measurement accuracy can reach 3mm. Therefore, the simulator is required to have a smaller distance step, such as 1mm step and accuracy. In addition, automotive radars can generally detect about 1m, but the internal delay of existing simulators is generally between 2m and 3m, so it cannot meet the use requirements well.

[0003] In the automotive field, the true delay of digital simulators is relatively large, and targets within tens of meters cannot be simulated. Therefore, most manufacturers use optical fiber delay line technology to make simulators. However, the distance stepping and close-range simulation performance of some international manufacturers cannot meet the level required by radar. For example, the latest product of Rohde & Schwarz AREG800A has a distance step of 0.25m and a minimum simulation distance of 4m. Keysight's latest product E8718A has a distance step of 0.1m and a minimum simulation distance of 3m. Since foreign products are basically based on optical fiber technology, there are inherent technical defects, and the shortest distance and distance step are limited.

[0004] The system composition of the target simulator is generally an RF module plus an intermediate frequency delay device. The closest distance and minimum step that can be simulated are mainly limited by the delay device. In order to simulate a large range, such as 300m, the number of fiber cascades will be required to be relatively high. The minimum delay step of the optical fiber is generally limited by the manufacturing process, and can generally be achieved at the level of 1mm to 5mm. When a larger simulation range and a smaller step are required, the number of fiber switch cascades will inevitably be higher. At this time, it is difficult to make the shortest delay very small.

[0005] Therefore, developing a delay simulator that meets the requirements of large range, small step, and close distance is crucial for automotive radar testing. Summary of the invention

[0006] The present invention adopts a series-parallel combination of multiple simulation delay technologies to realize target simulation of close-range radar, which can achieve the following beneficial effects:

[0007] 1) Improving the short-distance simulation capability: The present invention significantly improves the minimum simulation distance level of the delay device, so that the minimum simulation distance of the delay device reaches 130 mm.

[0008] 2) Maintaining long-distance simulation capability: The present invention not only significantly improves the short-distance simulation capability of the delay device, but also ensures that the maximum simulation distance of the delay device is above 1000m.

[0009] 3) Achieve small step distance: While ensuring that the delay device has both short-distance simulation capabilities and long-distance simulation capabilities, the minimum distance step of the delay device can reach 1mm.

[0010] 4) Increase the working bandwidth: The delay device of the present invention can operate at a working bandwidth of 5 GHz.

[0011] A method for delaying a target over a large range, at a short distance, and at a millimeter level, characterized in that: a complete delay line is formed by combining three types of analog delay line technologies in series and parallel, namely, a PCB delay module, a coaxial cable delay module, and an optical fiber delay module. The PCB delay module realizes small steps and short delays, the optical fiber delay module realizes large-range simulation using multiple stages, and the coaxial cable delay module is mainly used to realize the distance connection between the maximum delay of the PCB delay module and the minimum delay of the optical fiber delay module.

[0012] Preferably, the optical fiber delay module can be short-circuited in the PCB, and an attenuator is designed in the short-circuited link to achieve power adjustment.

[0013] The present invention also proposes a large-range, short-distance, millimeter-level step target delay device, wherein the device implements the target delay method as described above.

[0014] In summary, the present invention provides a new type of analog delay line radar target delay device, which successfully realizes the target simulation capability of large range, close distance and millimeter-level stepping through unique series and parallel structure design and combination of multiple delay technologies, and provides effective technical support for the research and development and production testing of radar systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a principle block diagram of the optical fiber delay line part of the prior art;

[0016] Figure 2 It is a principle block diagram of the method of the present invention; DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Figure 1 It is a principle block diagram of the optical fiber delay line part of the prior art. Figure 2 This is a system block diagram of the delay device corresponding to the present invention. The system is divided into three parts: a PCB delay module, a coaxial cable delay module and an optical fiber delay module.

[0019] 1.PCB delay module

[0020] In the present invention, the PCB delay module can use high-performance Rogers RO3003 plate as the substrate, and realize the control of long delay by cascading multiple 1-to-N or N-to-1 electronic switches. A binary or quaternary cascade relationship is used, and the combination meets the demand for uniform distance growth. Since the PCB microstrip line or strip line has very precise control over the length, the minimum step of mm level can be achieved. The maximum length of this part is designed to be 0.25m to 0.512m. If it is too long, it is difficult to ensure excellent performance of the amplitude and phase flatness of the PCB.

[0021] 2. Coaxial cable delay module

[0022] Coaxial cable has better performance than PCB and can complete the delay function of a longer distance than PCB. The coaxial cable delay module realizes the delay function by connecting multiple coaxial cable delay units in series. Each coaxial cable delay unit contains two SPDT switches. SPDT has two paths, one of which is connected by PCB strip line and an attenuator is connected in series. The purpose is to ensure the power stability of the system when switching the SPDT switch. The other path needs to be connected by coaxial cable. Specifically, the connection ports of the other path of the two SPDTs are connected to the surface-mount SNP connector using PCB strip line.

[0023] 3. Fiber optic delay module

[0024] The fiber delay module is specifically composed of two SPDT switches, a PCB stripline and a fiber delay line. The SPDT switch is connected in parallel to the fiber delay line and a section of PCB stripline, and the PCB stripline is connected in series with an attenuator to ensure the power stability of the system when the SPDT switch switches to different states. The other path of the SPDT switch is the fiber delay line. Users can choose to achieve long distance through the fiber delay line, or to achieve short distance by short-circuiting the fiber delay line through the circuit board routing.

[0025] 4. Module connection and balance

[0026] To ensure the stability of the entire delay device, the PCB delay module, coaxial cable delay module and optical fiber delay module are connected through optimized PCB strip lines. At the same time, amplifiers and equalizers are connected in series at key locations to compensate for system losses and improve signal flatness.

[0027] The feasibility of the method of the present invention is analyzed below.

[0028] Traditional technologies such as Figure 1 As shown, four 2×2 magneto-optical switches SW1 to SW4 are used to form a cascade of three lengths. The first stage selects 1 from L1 and L1+τ, the second stage selects 1 from L2 and L2+2τ, and the third stage selects 1 from L3 and L3+4τ. In this way, the shortest simulated distance can be L1+L2+L3, plus the device delay length. At the same time, the longest simulated distance is L1+L2+L3+7τ, plus the device delay length, with a step of τ.

[0029] For the three lengths L1 to L3, due to the problem of manufacturing process, the corresponding length of the short delay part below in the figure can reach about 15cm. The more cascades there are, the greater the minimum distance delay. When long-distance simulation reaches 1000m, while taking into account the small step of 1mm, a 20-level cascade is required, corresponding to 21 magneto-optical switches. The length of each magneto-optical switch is about 10cm, and the total length is 10cm×21+15cm×20, corresponding to 5.1 meters, which cannot meet the requirements of short distance. In addition, it is very difficult to achieve a 1mm step using optical fiber technology, and the production level requirements are too high, making it difficult to achieve mass production. The general mass production level can only achieve 5mm~10mm.

[0030] On the basis of the conventional technology, the fiber delay module of the present invention is composed of a structure in which a fiber delay line and a PCB attenuator are connected in parallel. When the short distance is realized, the fiber simulator can be short-circuited, and the length after the short-circuit is about 1 to 3 cm, so that the shortest distance is not limited by the internal series of the fiber. At this time, the shortest distance can be simulated by other methods.

[0031] Since the delay of the delay device will change suddenly when the parallel structure of the optical fiber delay module is switched, but the PCB delay module is limited by factors such as loss flatness and cannot simulate a large range of distances, a coaxial cable delay module is required to connect the shortest distance corresponding to the PCB delay module and the optical fiber delay module.

[0032] In summary, the present invention takes into account both large range and small stepping, and can also meet the performance of close-range simulation. In order to obtain the best performance, we can also adopt the following optimization measures.

[0033] Close-range simulation optimization: In order to improve the accuracy of close-range simulation, the present invention introduces the switch parallel fiber delay line and attenuator technology. By controlling the on and off state of the switch, the delay device can be flexibly switched under different working conditions, effectively avoiding the problems that may exist in the fiber delay line during close-range simulation. At the same time, the other delay lines of the delay device are selected from strip lines and coaxial cables, both of which have very small inherent delays and will not affect the close-range simulation capability of the delay device.

[0034] Small step distance realization: In order to realize the small step distance of the delay device, the present invention uses a stripline delay line. At the same time, it can provide accurate and controllable delay in a shorter physical length, meeting the demand for small step distance in radar target simulation.

[0035] Large-range delay simulation: In order to achieve large-range delay simulation, the present invention uses an optical fiber delay line as one of the delay elements. The optical fiber delay line, with its large delay and good flatness, can provide stable and accurate delay control in radar target simulation, thus meeting the needs of large-range delay simulation.

[0036] Working bandwidth expansion: In order to expand the working bandwidth of the delay device, the present invention uses an optical fiber delay line with a large working bandwidth and good flatness. The flatness performance of the stripline is not good, so the delay of the stripline delay line cannot be too large. The coaxial cable delay line can provide additional delay to ensure that the overall working bandwidth of the delay device is large enough and the flatness performance is good enough, while also ensuring the stability of the delay device when switching between different working states.

[0037] Device embodiment of the present invention: automobile radar target simulator delay device.

[0038] For automotive radar, the technical indicators of the closest distance simulation of 1.2m, the farthest distance of 1km, and the stepping of 1mm are planned to be completed. Among them, the PCB delay module realizes small steps and short delays, and the simulation range of the PCB delay module is 0.001-0.255m. The coaxial cable delay module realizes the connection and short delay of the PCB delay module and the optical fiber delay module, and the simulation range is 0.256-1.023m. The optical fiber delay module realizes a large range, and the simulation range of the optical fiber delay module is 1.024-1000m.

[0039] The specific implementation is as follows:

[0040] 1.PCB delay module

[0041] In the present invention, the PCB delay module uses high-performance Rogers RO3003 board as the substrate, and is combined with the PCB strip line through the SP4T switch to achieve delay control. The internal design of each PCB delay unit includes four paths, one of which is a reference path, and its PCB strip line length is optimized to the shortest, about 0.5mm, to reduce the inherent delay. The PCB strip line lengths of the remaining three paths are increased by the corresponding radar distances relative to the reference path to achieve different levels of delay.

[0042] For example, the PCB stripline lengths of the three paths of the first PCB delay unit increase the radar distance by 1 mm, 2 mm, and 3 mm, respectively, relative to the reference path.

[0043] The PCB stripline lengths of the three paths of the second PCB delay unit increase the radar distance by 4 mm, 8 mm, and 12 mm respectively relative to the reference path.

[0044] The PCB stripline lengths of the three paths of the third PCB delay unit increase the radar distance by 16 mm, 32 mm, and 48 mm, respectively, relative to the reference path.

[0045] The PCB stripline lengths of the three paths of the fourth PCB delay unit increase the radar distance by 64 mm, 128 mm, and 192 mm, respectively, relative to the reference path.

[0046] By connecting multiple PCB delay units in series, a PCB delay module with a larger delay range can be constructed. For example, four PCB delay units of the present invention connected in series can achieve 1 mm stepping and a maximum range simulation of 255 mm.

[0047] 2. Coaxial cable delay module

[0048] The coaxial cable delay module realizes the delay function by connecting two coaxial cable delay units in series. Each coaxial cable delay unit contains two SPDT switches. SPDT has two paths, one of which is connected by PCB strip lines and an attenuator is connected in series to ensure the power stability of the system when switching the SPDT switch. The other path needs to be connected by coaxial cable. Specifically, the connection ports of the other paths of the two SPDTs are connected to the surface-mount SNP connectors by PCB strip lines.

[0049] In the present invention, the coaxial cable lengths of the coaxial cable delay unit are 256 mm and 512 mm respectively. By selecting different channel combinations and coordinating with the PCB delay module, a 1 mm step and a maximum range simulation of 1023 mm can be achieved.

[0050] 3. Fiber optic delay module

[0051] The fiber delay module is specifically composed of two SPDT switches, a PCB stripline and a fiber delay line. The SPDT switch is connected in parallel to the fiber delay line and a section of PCB stripline, and the PCB stripline is connected in series with an attenuator to ensure the power stability of the system when the SPDT switch switches to different states. The other path of the SPDT switch is the fiber delay line.

[0052] Figure 1 The specific structure of the optical fiber delay line. The optical fiber delay line consists of two 5-bit optical switches in series, and each 5-bit optical switch has 6 channels. The first channel is a straight-through channel. When this channel is selected, the optical signal passes directly through the optical switch. The optical fiber radar distance of the second channel of the first optical switch is 1.024m longer than that of the first channel. The optical fiber radar distance of the third channel is 2.048m longer than that of the first channel. Similarly, the radar distances of the subsequent channels are 4.096m, 8.192m, and 16.384m longer than those of the first channel. The last five channels of the second optical switch are 32.768m, 65.536m, 131.072m, 262.144m, and 524.288m longer than those of the first set of channels.

[0053] 4. Module connection and balance

[0054] In order to ensure the stable performance of the entire delay device, the PCB delay module, the coaxial cable delay module and the optical fiber delay module are connected by an optimized PCB stripline. The length of the PCB stripline at the connection is selected according to the index requirements of the delay device, and the shortest solution is selected to reduce the inherent delay of the system. In the present invention, the length of the PCB stripline at the connection is about 1mm.

[0055] At the same time, amplifiers and equalizers are connected in series at key locations to compensate for system losses and improve signal flatness.

[0056] According to the above analysis, the longest distance can reach more than 1km, the minimum distance step is the 1mm step provided by the PCB, the closest distance is the shortest distance corresponding to all cascade modules, plus the external RF delay, the overall distance can easily reach within 1.2 meters.

[0057] In summary, the present invention provides a method and device for target delay in a large range, close distance, and millimeter-level step. The above are only some embodiments of the present invention and are not intended to limit the protection scope of the present invention. In fact, the present invention has no restrictions on the frequency band and bandwidth of the radar. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A target delay method with large range, short distance and millimeter-level stepping, characterized by: The complete delay line is composed of three analog delay line technologies in series and parallel, namely, PCB delay module, coaxial cable delay module and optical fiber delay module. The PCB delay module realizes small steps and short delays, the optical fiber delay module uses multiple stages to realize large-scale simulation, and the coaxial cable delay module is mainly used to realize the distance connection between the maximum delay of the PCB delay module and the minimum delay of the optical fiber delay module.

2. The optical fiber delay module according to claim 1 can be short-circuited in the PCB, and an attenuator is designed in the short-circuit link to achieve power adjustment.

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