EP4629437A1

EP4629437A1 - Waveguide device and related product

Info

Publication number: EP4629437A1
Application number: EP22966962.7A
Authority: EP
Inventors: Zhongjie WU; Qiang He; Xiang Gao; Haowei LI
Original assignee: Shenzhen Yinwang Intelligent Technology Co Ltd
Current assignee: Shenzhen Yinwang Intelligent Technology Co Ltd
Priority date: 2022-12-02
Filing date: 2022-12-02
Publication date: 2025-10-08
Also published as: WO2024113376A1; CN120226207A; EP4629437A4

Abstract

This application discloses a waveguide apparatus and a related product, and relates to the field of millimeter-wave radar technologies. The waveguide apparatus includes a cross-structure waveguide, where the cross-structure waveguide includes a first cavity and a second cavity that intersect, and the first cavity and the second cavity intersect at a central point of the cross-structure waveguide; and a filling medium of the cross-structure waveguide is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material. The waveguide apparatus can implement a miniaturized feature of a waveguide and meet a requirement for multi-channel cross-transmission of a millimeter-wave radar.

Description

TECHNICAL FIELD

This application relates to the field of millimeter-wave radar technologies, and in particular, to a waveguide apparatus and a related product.

BACKGROUND

A waveguide (waveguide) is a structure used to directionally guide an electromagnetic wave. The waveguide is mainly used as a microwave-frequency transmission line, to connect a microwave transmitter and a microwave receiver to an antenna of the microwave transmitter and an antenna of the microwave receiver in a microwave radio link device like a radar.
Currently, in a multi-channel transmission scenario of a visible light integrated photoelectronic device, a waveguide manufactured through an insulation silicon process with a high refractive index inside and a low refractive index outside is usually used for feed transmission. However, in a multi-channel cross-transmission scenario of a millimeter-wave radar, the foregoing waveguide is not practical in engineering due to a problem of a large electrical size. Therefore, it is urgent to design a miniaturized waveguide apparatus to meet a multi-channel cross-transmission requirement of the millimeter-wave radar.

SUMMARY

Embodiments of this application provide a waveguide apparatus and a related product, to implement a miniaturized feature of a waveguide, and meet a multi-channel cross-transmission requirement of a millimeter-wave radar.
According to a first aspect, an embodiment of this application provides a waveguide apparatus, and the waveguide apparatus includes:

a cross-structure waveguide, where
the cross-structure waveguide includes a first cavity and a second cavity that intersect, and the first cavity and the second cavity intersect at a central point of the cross-structure waveguide; and
a filling medium of the cross-structure waveguide is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material.

In embodiments of this application, the cross-structure waveguide included in the waveguide apparatus may be centrosymmetric, the first cavity and the second cavity that are included in the cross-structure waveguide are centrosymmetric with respect to the central point of the cross-structure waveguide, the filling medium of the cross-structure waveguide is the first material whose dielectric constant is greater than the first preset threshold, and the outer surface of the cross-structure waveguide is made of the conductive material. According to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, an entire wavelength λ_Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus. According to embodiments of this application, the cross-structure waveguide is filled with a medium of a high dielectric material, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
The high dielectric material in embodiments of this application includes a material with a high dielectric constant. That the dielectric constant is high may mean that the dielectric constant is greater than the first preset threshold. The first preset threshold is not a fixed value, and may be adjusted based on different application scenarios. For example, the dielectric constant of the high dielectric material in embodiments of this application is greater than a dielectric constant of a dielectric material used in a dielectric waveguide implemented by using a silicon on insulator (silicon on insulator, SOI) process with a high refractive index inside and a low refractive index outside.
In a possible implementation, the waveguide apparatus further includes a metal plate, the cross-structure waveguide is located at an upper layer of the metal plate, and the outer surface of the cross-structure waveguide is a metal plating.
In implementations of this application, a possible specific implementation of the waveguide apparatus is provided. Specifically, the waveguide apparatus further includes the metal plate, the cross-structure waveguide is coupled to the metal plate, the cross-structure waveguide is located at the upper layer of the metal plate, and the outer surface of the cross-structure waveguide is the metal plating. According to embodiments of this application, a high dielectric material is deposited on a metal surface and a high dielectric material layer is etched, to form the high dielectric material filled inside the cross-structure waveguide. The metal plating on the outer surface of the cross-structure waveguide is formed through an outer electroplating process. In engineering, the cross-structure waveguide is filled with the medium of the high dielectric material, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
In a possible implementation, the first material includes at least one of the following: silicon, ceramic, and glass.
In an implementation of this application, a possible specific implementation of the first material is provided. Specifically, the first material includes but is not limited to a high dielectric material like silicon, ceramic, and glass. According to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, in a high dielectric material like silicon, ceramic, and glass, an entire wavelength λ _Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus.
In a possible implementation, a body of the waveguide apparatus is a printed circuit board PCB, and the PCB includes a plurality of plated through holes that penetrate an upper surface and a lower surface; and
an area formed by the plurality of plated through holes is the cross-structure waveguide.
In an implementation of this application, a possible specific implementation of the waveguide apparatus is provided. Specifically, the body of the waveguide apparatus is the printed circuit board (printed circuit board, PCB), the PCB is fully distributed with the plurality of plated through holes that penetrate the upper surface and the lower surface, and the area enclosed by the plated through holes is the cross-structure waveguide in the waveguide apparatus. According to embodiments of this application, a cross-structure waveguide in a substrate integration waveguide (substrate integration waveguide, SIW) form is implemented through a PCB processing process. The upper metal layer and the lower metal layer of the PCB are used as an upper electric wall and a lower electric wall of the cross-structure waveguide, and plated through holes on a side of the PCB form a side electric wall of the cross-structure waveguide. A size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. In this way, in engineering, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus is implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar is met.
Optionally, spacings between the plurality of plated through holes are equal.
In a possible implementation, the first material is a board material of the PCB.
In implementations of this application, a possible specific implementation of the first material is provided. Specifically, when the body of the waveguide apparatus is the PCB, the upper metal layer and the lower metal layer of the PCB are used as the upper electric wall and the lower electric wall of the cross-structure waveguide, the plated through holes on the side of the PCB form the side electric wall of the cross-structure waveguide, and the filling medium (namely, the first material) of the cross-structure waveguide is the board material of the PCB. A size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. In this way, in engineering, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus is implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar is met.
In a possible implementation, the first cavity includes a first fundamental mode input waveguide, a first fundamental mode and multimode matching waveguide, and a first multimode interference waveguide;

the first fundamental mode input waveguide and the first multimode interference waveguide are connected through the first fundamental mode and multimode matching waveguide, and a width of the first multimode interference waveguide is greater than a width of the first fundamental mode input waveguide; and
the first fundamental mode input waveguide is configured to input an electromagnetic wave, the electromagnetic wave enters the first multimode interference waveguide through the first fundamental mode and multimode matching waveguide, and the first multimode interference waveguide is configured to perform interference on the electromagnetic wave, to present, at the central point, a fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide.

In implementations of this application, a possible specific implementation of the first cavity is provided. Specifically, the first fundamental mode input waveguide and the first multimode interference waveguide in the first cavity are connected through the first fundamental mode and multimode matching waveguide. Because the cross-structure waveguide is centrosymmetric, and the first cavity and the second cavity that are included in the cross-structure waveguide intersect at the central point of the cross-structure waveguide, the first cavity includes two first fundamental mode input waveguides, two first fundamental mode and multimode matching waveguides, and one first multimode interference waveguide. In addition, the central point of the cross-structure waveguide is a central point of the first multimode interference waveguide in the first cavity, that is, a connection sequence of the waveguides included in the first cavity is successively "the first fundamental mode input waveguide, the first fundamental mode and multimode matching waveguide, the first multimode interference waveguide, the first fundamental mode and multimode matching waveguide, and the first fundamental mode input waveguide". The width of the first multimode interference waveguide is greater than the width of the first fundamental mode input waveguide. The width of the waveguide is designed, to implement five-order higher-order mode expansion of each waveguide included in the first cavity. According to embodiments of this application, the first fundamental mode input waveguide inputs the electromagnetic wave, and the electromagnetic wave enters the first multimode interference waveguide through the first fundamental mode and multimode matching waveguide, to present, at the central point after interference, the fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide, so that crosstalk can be better suppressed, and a transmission loss of the electromagnetic wave can be reduced.
It may be understood that a composition structure of the second cavity is the same as a composition structure of the first cavity.
In a possible implementation, a joint between the first fundamental mode and multimode matching waveguide and the first fundamental mode input waveguide is of a tapered structure, and a joint between the first fundamental mode and multimode matching waveguide and the first multimode interference waveguide is of a tapered structure.
In an implementation of this application, a possible specific implementation of a waveguide connection is provided. Specifically, a joint between the first fundamental mode and multimode matching waveguide and the first fundamental mode input waveguide is of a tapered structure, and a joint between the first fundamental mode and multimode matching waveguide and the first multimode interference waveguide is of a tapered structure. According to embodiments of this application, a gradually changing tapered structure at a joint between different waveguides is designed, so that mode matching at the joint between the first multimode interference waveguide and the first fundamental mode input waveguide can be improved, to optimize an echo.
In a possible implementation, a cross-sectional size of the first multimode interference waveguide meets the following condition: 0.53λ≤a≤0.72λ, where
a is a first side of a cross section of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the cross-sectional size of the first multimode interference waveguide is provided. Specifically, the waveguide apparatus includes the cross-structure waveguide and the metal plate, the cross-structure waveguide is coupled to the metal plate, the cross-structure waveguide is located at the upper layer of the metal plate, and the outer surface of the cross-structure waveguide is the metal plating. When the waveguide apparatus is implemented, the first side (which may be understood as a width of the cross section of the first multimode interference waveguide) of the first multimode interference waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a cross-sectional size of the first multimode interference waveguide meets the following condition: 1.2λ≤a≤1.5λ, where
a is a first side of a cross section of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the cross-sectional size of the first multimode interference waveguide is provided. Specifically, the body of the waveguide apparatus is the PCB, the upper metal layer and the lower metal layer of the PCB are used as the upper electric wall and the lower electric wall of the cross-structure waveguide, and the plated through holes on the side of the PCB form the side electric wall of the cross-structure waveguide. A size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. When the waveguide apparatus is implemented, the size of the first side (which may be understood as a width of the cross section of the first multimode interference waveguide) of the cross section of the first multimode interference waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a length of the first multimode interference waveguide meets the following condition: 1.9λ≤L3≤2.1λ, where
L3 is the length of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the length of the first multimode interference waveguide is provided. Specifically, the waveguide apparatus includes the cross-structure waveguide and the metal plate, the cross-structure waveguide is coupled to the metal plate, the cross-structure waveguide is located at the upper layer of the metal plate, and the outer surface of the cross-structure waveguide is the metal plating. When the waveguide apparatus is implemented, the length of the first multimode interference waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a length of the first multimode interference waveguide meets the following condition: 4.8λ≤L3≤5.3λ, where
L3 is the length of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the length of the first multimode interference waveguide is provided. Specifically, the body of the waveguide apparatus is the PCB, the upper metal layer and the lower metal layer of the PCB are used as the upper electric wall and the lower electric wall of the cross-structure waveguide, and the plated through holes on the side of the PCB form the side electric wall of the cross-structure waveguide. A size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. When the waveguide apparatus is implemented, the length of the first multimode interference waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a length of the first fundamental mode and multimode matching waveguide meets the following condition: 0.13λ≤L2≤0.18λ, where
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the length of the first fundamental mode and multimode matching waveguide is provided. Specifically, the waveguide apparatus includes the cross-structure waveguide and the metal plate, the cross-structure waveguide is coupled to the metal plate, the cross-structure waveguide is located at the upper layer of the metal plate, and the outer surface of the cross-structure waveguide is the metal plating. When the waveguide apparatus is implemented, the length of the first fundamental mode and multimode matching waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a length of the first fundamental mode and multimode matching waveguide meets the following condition: 0.3λ≤L2≤0.45λ, where
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
In implementations of this application, a possible specific implementation of the length of the first fundamental mode and multimode matching waveguide is provided. Specifically, the body of the waveguide apparatus is the PCB, the upper metal layer and the lower metal layer of the PCB are used as the upper electric wall and the lower electric wall of the cross-structure waveguide, and the plated through holes on the side of the PCB form the side electric wall of the cross-structure waveguide. A size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. When the waveguide apparatus is implemented, the length of the first fundamental mode and multimode matching waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, a thickness of the cross-structure waveguide meets the following condition: 0.35W1≤h≤0.6W1, where
h is the thickness of the cross-structure waveguide, and W1 is the width of the first fundamental mode input waveguide.
In implementations of this application, a possible specific implementation of the length of the first fundamental mode and multimode matching waveguide is provided. Specifically, the waveguide apparatus includes the cross-structure waveguide and the metal plate, the cross-structure waveguide is coupled to the metal plate, the cross-structure waveguide is located at the upper layer of the metal plate, and the outer surface of the cross-structure waveguide is the metal plating. Alternatively, the body of the waveguide apparatus is the PCB, the upper metal layer and the lower metal layer of the PCB are used as the upper electric wall and the lower electric wall of the cross-structure waveguide, and the plated through holes on the side of the PCB form the side electric wall of the cross-structure waveguide. The size of the device (the cross-structure waveguide) is compressed thanks to an internal medium of the PCB. In any one of the implementations of the foregoing waveguide apparatus, the thickness of the cross-structure waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible implementation, when an electromagnetic current is formed through feeding in the first cavity, density of a magnetic current in the second cavity is less than a second preset threshold.
In implementations of this application, a possible specific implementation of electromagnetic wave transmission is provided. Specifically, when the electromagnetic current is formed through feeding in the first cavity, the density of the magnetic current in the second cavity is less than the second preset threshold, so that the electromagnetic current is ensured to be transmitted in the first cavity, crosstalk can be better suppressed, an electromagnetic wave transmission loss can be reduced, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met in engineering while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change.
Optionally, when an electromagnetic current is formed through feeding in the second cavity, density of a magnetic current in the first cavity is less than a third preset threshold.
In a possible implementation, a plurality of cross-structure waveguides in the waveguide apparatus are arranged in a cascade manner.
In implementations of this application, a possible specific implementation of the waveguide apparatus is provided. Specifically, the waveguide apparatus may include a plurality of cross-structure waveguides, and the plurality of cross-structure waveguides are arranged in the cascade manner. In embodiments of this application, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
According to a second aspect, an embodiment of this application provides a radar or a radar system, where the radar or the radar system includes the waveguide apparatus according to the first aspect or any possible implementation of the first aspect. It should be noted that there may be a plurality of smart sensors integrated with sensors. When the smart sensor includes a millimeter-wave detection function, the smart sensor may also be referred to as a millimeter-wave radar or a millimeter-wave radar system.
According to a third aspect, an embodiment of this application provides a terminal device, where the terminal device includes the waveguide apparatus according to the first aspect or any possible implementation of the first aspect, or includes the radar or the radar system according to the second aspect.
According to a fourth aspect, an embodiment of this application provides a vehicle, where the vehicle includes the waveguide apparatus according to the first aspect or any possible implementation of the first aspect, or includes the radar or the radar system according to the second aspect, or includes the terminal device according to the third aspect.
According to embodiments of this application, the cross-structure waveguide is filled with a medium of a high dielectric material, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in embodiments of this application more clearly, the following briefly describes the accompanying drawings for describing embodiments of this application. It is clear that the accompanying drawings in the following description show merely some embodiments of this application, and a person of ordinary skill in the art may derive other drawings from these accompanying drawings without creative efforts.

FIG. 1 is a diagram of radar distribution according to an embodiment of this application;
FIG. 2 is a diagram of an architecture of a radar according to an embodiment of this application;
FIG. 3 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application;
FIG. 4 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application;
FIG. 5 is a diagram of a three-dimensional structure of a waveguide apparatus according to an embodiment of this application;
FIG. 6 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application;
FIG. 7 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application;
FIG. 8 is a diagram of a three-dimensional structure of a waveguide apparatus according to an embodiment of this application;
FIG. 9A is a diagram of an effect of waveguide transmission according to an embodiment of this application;
FIG. 9B is a diagram of an effect of waveguide transmission according to an embodiment of this application;
FIG. 10 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application;
FIG. 11 is a diagram of a return loss according to an embodiment of this application;
FIG. 12 is a diagram of a transmission insertion loss according to an embodiment of this application; and
FIG. 13 is a diagram of a transmission isolation according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

To make objectives, technical solutions, and advantages of this application clearer, the following describes embodiments of this application with reference to accompanying drawings in embodiments of this application.
The terms "first", "second", and the like in the specification, claims, and accompanying drawings of this application are used to distinguish between different objects, but are not used to describe a specific sequence. In addition, terms such as "include" and "have" and any other variants thereof are intended to cover a non-exclusive inclusion. For example, processes, methods, systems, products, or devices that include a series of steps or units are not limited to listed steps or units, but instead, optionally further include steps or units that are not listed, or optionally further include other steps or units inherent to these processes, methods, products, or devices.
"Embodiments" mentioned herein mean that specific features, structures, or characteristics described in combination with the embodiments may be included in at least one embodiment of this application. The phrase shown in various positions in the specification may not necessarily refer to a same embodiment, and is not an independent or optional embodiment exclusive from another embodiment. It may be understood explicitly and implicitly by a person skilled in the art that embodiments described herein may be combined with other embodiments.
It should be understood that in this application, "at least one (item)" means one or more, "a plurality of" means two or more than two, "at least two (items)" means two, three, or more than three, and "and/or" is used to describe an association relationship between associated objects, and represents that there may be three relationships. For example, "A and/or B" may represent that only A exists, only B exists, and both A and B exist, where A and B may be singular or plural. The character "/" generally indicates an "or" relationship between the associated objects. "At least one of the following items (pieces)" or a similar expression thereof means any combination of these items, including any combination of singular items (pieces) or plural items (pieces). For example, at least one of a, b, or c may indicate a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c may be singular or plural.
As described in the background, how to design a miniaturized waveguide apparatus needs to be studied, to meet a multi-channel cross-transmission requirement of a millimeter-wave radar. This application provides a waveguide apparatus and a related product, and relates to the field of millimeter-wave radar technologies, to implement a miniaturized feature of a waveguide, and meet a multi-channel cross-transmission requirement of a millimeter-wave radar.
To describe the solutions of this application more clearly, the following first describes some knowledge related to a radar.
The radar is a transliterated name of the radar in English, and is short for radio detection and ranging, that is, radio detection and ranging. The radar is configured to discover a target and determine a spatial position of the target by using a radio method.
A detection medium of the radar is an electromagnetic wave, and the radar implements detection of a target, for example, ranging, speed measurement, or azimuth measurement, through transmission and reception of the electromagnetic wave. The radar can implement ranging on the target based on a time of flight of the electromagnetic wave. The time of flight is a time difference between receiving and transmitting of the electromagnetic wave. The radar transmits an electromagnetic wave signal, receives an echo signal of the electromagnetic wave signal, and may range the target based on a time difference between the received echo signal and the transmitted electromagnetic wave signal and a propagation speed of the electromagnetic wave. A distance between the radar and the target may be determined based on the following formula: s=c×t/2, where s is the distance of the target, t is the time of flight, namely, a time period from transmitting of the electromagnetic wave signal from the radar to receiving of the echo signal, and c is the speed of light.
The radar implements speed measurement on the target based on a Doppler effect (Doppler effect). A principle of the Doppler effect is as follows: When a vibration source like a sound, light, and a radio wave moves relative to an observer at a relative speed, frequency of vibration received by the observer is different from frequency generated by the vibration source. When there is relative movement between the electromagnetic wave transmitted by the radar and a detected object, frequency of the echo signal is different from frequency of the transmitted electromagnetic wave signal. When the target approaches an antenna of the radar, the frequency of the echo signal is higher than the frequency of the transmitted electromagnetic wave signal. When the target moves away from the antenna of the radar, the frequency of the echo signal is lower than the frequency of the transmitted electromagnetic wave signal. A frequency change caused by the Doppler effect is referred to as a Doppler frequency shift, which is proportional to the relative speed and inversely proportional to the vibration frequency. Therefore, by detecting a frequency difference between the transmitted electromagnetic wave signal and the echo signal, a moving speed of the target relative to the radar, namely, the relative speed between the target and the radar, can be measured.
The radar may measure an azimuth in an amplitude method, a phase method, or the like. The amplitude method is used to measure an angle by using an amplitude value of an echo signal received by an antenna, and a change rule of the amplitude value depends on an antenna directivity pattern and a scanning manner of the antenna. The phase method is used to measure an angle by using a phase difference between echo signals received by a plurality of antenna elements. For example, the radar receives echo signals reflected by a same target through an antenna array, and calculates the azimuth of the target based on a phase difference of the echo signals.
A detection medium of a millimeter-wave radar is an electromagnetic wave within a specific wavelength range, for example, a microwave. Currently, a millimeter wave (millimeter wave) and a centimeter wave (for example, a centimeter wave in a 24 GHz frequency band) adjacent to the millimeter wave in wave bands are commonly used. The millimeter wave is an electromagnetic wave with a wavelength of 1 to 10 millimeters (mm), and a wavelength of an electromagnetic wave in the 24 GHz frequency band is slightly greater than 10 mm. A wavelength of the detection medium of the millimeter-wave radar is in an overlapped wavelength range of the microwave and a far infrared wave. Therefore, the detection medium of the millimeter-wave radar has characteristics of two spectrums. According to a wave propagation theory, higher frequency indicates a shorter wavelength, higher resolution, and a stronger penetration capability, while in this case, a loss in a propagation process is larger, and a transmission distance is shorter. On the contrary, lower frequency indicates a longer wavelength, a stronger diffraction capability, and a longer transmission distance. Therefore, compared with the microwave, the detection medium of the millimeter-wave radar has high resolution, good directivity, a strong anti-interference capability, and good detection performance. Compared with infrared, the detection medium of the millimeter-wave radar has lower atmospheric attenuation and better penetration to smoke and dust, and is less affected by weather. Therefore, the millimeter-wave radar is increasingly widely used in a plurality of fields such as intelligent vehicles, drones, intelligent transportation, and industrial automation.
Based on a detection distance, the radar can be classified into a long range radar (long range radar, LRR), a medium range radar (mid/medium range radar, MRR), and a short range radar (short range radar, SRR). The LRR has a high requirement on a detection distance, and has a low requirement on a width of a detection angular domain. The SRR has a low requirement on a detection distance, and has a high requirement on a width of a detection angular domain. A requirement of the MRR on a detection distance and a width of an angular domain may be understood as being between that of the LRR and that of the SRR. For example, the detection distance of the LRR may be more than 200 meters, and the width of the angular domain may be ± 15°; the detection distance of the MRR may be within 100 meters, and the width of the angular domain may be ±45°; and the detection distance of the SRR may be within 60 meters, and the width of the angular domain may be ±80°. During use, different types of radars may be installed at different positions of a vehicle body based on a function requirement of autonomous driving and a use status of another sensor. A quantity and types of the radars may be selected based on a requirement.
FIG. 1 is a diagram of radar distribution according to an embodiment of this application.
FIG. 1 shows possible installation positions of several types of radars. The installation positions are merely examples, and during actual use, more or fewer radars may be selected, and the types may also be adjusted.
As shown in FIG. 1, the LRR may be installed on the front of the vehicle body and serve as a forward radar; the MRR may be installed on the front or the rear of the vehicle body and serve as a forward radar or a backward radar; and the SRR may be installed on a side of the vehicle body or four corners of the vehicle body and serve as a side radar or an angle radar. In addition, the MRR may alternatively be installed on a side of the vehicle body or the four corners of the vehicle body, and the SRR may alternatively be installed on the front or the rear of the vehicle body.
The radar may be classified based on a modulation manner (or a radiation manner) of an electromagnetic wave of the radar. The modulation manner of the electromagnetic wave of the radar includes a pulse manner and a continuous wave manner. Therefore, the radar may be classified into a pulse radar and a continuous wave radar. The continuous wave manner may be further classified into frequency shift keying (frequency shift keying, FSK), phase shift keying (phase shift keying, PSK), a constant-frequency/single-frequency continuous wave (continuous wave CW), a frequency modulated continuous wave (frequency modulated continuous wave, FMCW), multiple frequency shift keying (multiple frequency shift keying, MFSK), a phase modulated continuous wave (phase modulated continuous wave, PMCW), and another manner. Featuring in multiple target detection, high resolution, and low costs, the FMCW manner has become a mainstream radar modulation manner.
FIG. 2 is a diagram of an architecture of a radar according to an embodiment of this application.
As shown in FIG. 2, the radar includes an MMIC, a microcontroller unit (microcontroller unit, MCU), and a power management integrated circuit (power management integrated circuit, PMIC). The MMIC may integrate a function of a radio frequency part. The MCU may integrate a function of a baseband part, for example, integrate a function of a signal processor. In addition, the MCU may further provide a communication interface for communicating with another in-vehicle device. The PMIC is a chip that supplies power to a hardware system of the radar.
A waveguide (waveguide) is a structure used to directionally guide an electromagnetic wave. In electromagnetics and communication engineering, the waveguide may be any linear structure in which an electromagnetic wave is transmitted between endpoints of the linear structure. The waveguide is mainly used as a microwave-frequency transmission line, to connect a microwave transmitter and a microwave receiver to an antenna of the microwave transmitter and an antenna of the microwave receiver in a radar, a communication satellite, and a microwave radio link device.
At present, with improvement of a system function, an antenna of an in-vehicle millimeter wave radar is developing towards a lower loss and a multi-channel large array. Compared with a conventional PCB printed antenna, a waveguide antenna has obvious advantages in terms of low loss and broadband characteristics, but has bigger difficulty in wiring of a plurality of waveguide feeders in limited system space due to a multi-channel transmission requirement. Therefore, designing a same-layer cross-structure waveguide with a low insertion loss and a small size is key to implementing a multi-channel waveguide antenna. However, in a process of transmitting an electromagnetic wave through a conventional cross-structure waveguide, a large part of energy is severely lost at an intersection of the waveguide due to mode coupling, resulting in poor transmission performance.
For problems that the foregoing waveguide has a large electrical size and is not practical in engineering, in embodiments of this application, a cross-structure waveguide that can be used in a feed network of a radar waveguide antenna of 76 to 77 GHz is designed based on a cross multimode interference (multimode interference, MMI) principle in a method combining theoretical calculation and simulation optimization, so that good transmission performance with a lower single-time transmission loss (as low as 0.2 dB) and a higher isolation (as high as 37 dB) can be implemented. In addition, a cross-structure waveguide in an SIW form that is implemented based on a board material of the PCB and a PCB processing process is further designed, so that a design requirement for the feed network of the radar waveguide antenna in a millimeter wave frequency band of 76 to 77 GHz can also be met.
The following describes a waveguide apparatus in embodiments of this application with reference to the accompanying drawings in embodiments of this application.

Embodiment 1

FIG. 3 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application.
As shown in FIG. 3, the waveguide apparatus includes a cross-structure waveguide.
The cross-structure waveguide may be centrosymmetric.
The cross-structure waveguide includes a first cavity A and a second cavity B that intersect at a same layer, and the first cavity A and the second cavity B intersect at a central point of the cross-structure waveguide.
A filling medium of the cross-structure waveguide is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material.
It may be understood that the cross-structure waveguide included in the waveguide apparatus in this embodiment of this application may be centrosymmetric, and the first cavity A and the second cavity B that are included in the cross-structure waveguide are centrosymmetric with respect to the central point of the cross-structure waveguide. The filling medium of the cross-structure waveguide is the first material whose dielectric constant is greater than the first preset threshold, that is, filling media of the first cavity A and the second cavity B are the first materials whose dielectric constants are greater than the first preset threshold. The outer surface of the cross-structure waveguide is made of the conductive material, that is, outer surfaces of the first cavity A and the second cavity B are made of conductive materials.
It may be understood that the first preset threshold in this embodiment of this application is not a fixed value, and may be adjusted based on different application scenarios, so that the first material is a high dielectric filling medium that meets a requirement of the cross-structure waveguide.
According to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, an entire wavelength λ_Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus.
According to this embodiment of this application, the cross-structure waveguide is filled with a medium of a high dielectric material and an outer surface of the cross-structure waveguide is electroplated, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
In a possible embodiment, the waveguide apparatus further includes a metal plate, the cross-structure waveguide is located at an upper layer of the metal plate, and the outer surface of the cross-structure waveguide is a metal plating.
Specifically, refer to FIG. 4. FIG. 4 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application. It may be understood that the waveguide apparatus shown in FIG. 4 may be implemented as an independent embodiment. Alternatively, the waveguide apparatus shown in FIG. 4 may be understood as a deformation or a supplement of the waveguide apparatus in FIG. 3. In this case, FIG. 4 is a main view of the waveguide apparatus, and FIG. 3 is a top view of the waveguide apparatus.
As shown in FIG. 4, the waveguide apparatus further includes a metal plate 102, a cross-structure waveguide 101 is located at an upper layer of the metal plate 102, and an outer surface of the cross-structure waveguide 101 is a metal plating 103.
It may be understood that the waveguide apparatus in this embodiment of this application includes the cross-structure waveguide 101 and the metal plate 102. The cross-structure waveguide 101 is coupled to the metal plate 102, and is located at the upper layer of the metal plate 102, and the outer surface of the cross-structure waveguide 101 is the metal plating 103.
According to this embodiment of this application, a high dielectric material is deposited on a metal surface and a high dielectric material layer is etched, to form the high dielectric material filled inside the cross-structure waveguide. The metal plating on the outer surface of the cross-structure waveguide is formed through an outer electroplating process. In engineering, the cross-structure waveguide is filled with the medium of the high dielectric material, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
Based on the diagrams of the structures of the waveguide apparatuses shown in FIG. 3 and FIG. 4, a diagram of a possible three-dimensional structure of the waveguide apparatus may be obtained.
For example, FIG. 5 is a diagram of a three-dimensional structure of a waveguide apparatus according to an embodiment of this application.
As shown in FIG. 5, the waveguide apparatus in this embodiment of this application includes the metal plate 102, the cross-structure waveguide 101, and the metal plating 103. A structural relationship and functional features of the metal plate 102, the cross-structure waveguide 101, and the metal plating 103 are consistent with those described in FIG. 3 and FIG. 4. Details are not described herein again.
It may be understood that the diagram of the structure of the waveguide apparatus shown in FIG. 3 is a top view of the waveguide apparatus in this embodiment of this application, and the diagram of the structure of the waveguide apparatus shown in FIG. 4 is a main view of the waveguide apparatus in this embodiment of this application.
Optionally, a filling medium (namely, the first material) of the cross-structure waveguide shown in FIG. 3 and/or FIG. 4 and/or FIG. 5 includes but is not limited to a high dielectric material like silicon, ceramic, or glass.
It should be understood that, according to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, in the high dielectric material like silicon, ceramic, or glass, an entire wavelength λ_Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus.
In a possible embodiment, the first cavity A includes a first fundamental mode input waveguide a1, a first fundamental mode and multimode matching waveguide a2, and a first multimode interference waveguide a3.
The first fundamental mode input waveguide a is connected to the first multimode interference waveguide a3 through the first fundamental mode and multimode matching waveguide a2, and a width (a) of the first multimode interference waveguide a3 is greater than a width (W1) of the first fundamental mode input waveguide a1.
The first fundamental mode input waveguide a1 is configured to input an electromagnetic wave, the electromagnetic wave enters the first multimode interference waveguide a3 through the first fundamental mode and multimode matching waveguide a2, and the first multimode interference waveguide a3 is configured to perform interference on the electromagnetic wave, to present, at the central point, a fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide a3.
It may be understood that the first fundamental mode input waveguide a1 and the first multimode interference waveguide a3 that are in the first cavity A are connected through the first fundamental mode and multimode matching waveguide a2. Because the cross-structure waveguide is centrosymmetric, and the first cavity A and the second cavity B that are included in the cross-structure waveguide intersect at the central point of the cross-structure waveguide, the first cavity A includes two first fundamental mode input waveguides, two first fundamental mode and multimode matching waveguides, and one first multimode interference waveguide. In addition, the central point of the cross-structure waveguide is a central point of the first multimode interference waveguide in the first cavity A, that is, a connection sequence of the waveguides included in the first cavity is successively "the first fundamental mode input waveguide a1, the first fundamental mode and multimode matching waveguide a2, the first multimode interference waveguide a3, a first fundamental mode and multimode matching waveguide a4, and a first fundamental mode input waveguide a5". Optionally, the first cavity A may alternatively include two first fundamental mode input waveguides, two first fundamental mode and multimode matching waveguides, and two first multimode interference waveguides, and the central point of the cross-structure waveguide is a connection point of the two first multimode interference waveguides in the first cavity A, that is, a connection sequence of the waveguides included in the first cavity is successively "the first fundamental mode input waveguide a1, the first fundamental mode and multimode matching waveguide a2, the first multimode interference waveguide a3, the first multimode interference waveguide a3, a first fundamental mode and multimode matching waveguide a4, and a first fundamental mode input waveguide a5". The two first multimode interference waveguides a3 may alternatively be a multimode interference waveguide that is integrally formed. This is not limited in embodiments of this application.
It should be understood that, if one of the first fundamental mode input waveguide a1 and the first fundamental mode input waveguide a5 is an input waveguide, the other fundamental mode waveguide is an output waveguide. A width of the first multimode interference waveguide is greater than a width of the first fundamental mode input waveguide. The width of the waveguide is designed, to implement five-order higher-order mode expansion of each waveguide included in the first cavity.
According to this embodiment of this application, the first fundamental mode input waveguide inputs the electromagnetic wave, and the electromagnetic wave enters the first multimode interference waveguide through the first fundamental mode and multimode matching waveguide, to present, at the central point after interference, the fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide, so that crosstalk can be better suppressed, and a transmission loss of the electromagnetic wave can be reduced.
It may be understood that a composition structure of the second cavity B is the same as a composition structure of the first cavity A. Details are not described herein again.
In a possible embodiment, a joint between the first fundamental mode and multimode matching waveguide a2 and the first fundamental mode input waveguide a1 is of a tapered structure, and a joint between the first fundamental mode and multimode matching waveguide a2 and the first multimode interference waveguide a3 is of a tapered structure.
According to this embodiment of this application, a gradually changing tapered structure at a joint between different waveguides is designed, so that mode matching at the joint between the first multimode interference waveguide and the first fundamental mode input waveguide can be improved to optimize an echo.
In a possible embodiment, a cross-sectional size of the first multimode interference waveguide a3 meets the following condition: $0.53 λ \leq a \leq 0.72 λ,$ where
a is a first side of a cross section of the first multimode interference waveguide a3, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, a size of the first side (which may be understood as a width a of the cross section of the first multimode interference waveguide) of the cross section of the first multimode interference waveguide a3 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a length L3 of the first multimode interference waveguide a3 meets the following condition: $1.9 λ \leq L 3 \leq 2.1 λ,$ where
L3 is the length of the first multimode interference waveguide a3, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, the length L3 of the first multimode interference waveguide a3 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a length of the first fundamental mode and multimode matching waveguide a2 meets the following condition: $0.13 λ \leq L 2 \leq 0.18 λ,$ where
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, the length L2 of the first fundamental mode and multimode matching waveguide a2 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a thickness h of the cross-structure waveguide meets the following condition: $0.35 W 1 \leq h \leq 0.6 W 1,$ where
h is the thickness of the cross-structure waveguide, and W1 is a width of the first fundamental mode input waveguide a1.
According to this embodiment of this application, the thickness h of the cross-structure waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, when an electromagnetic current is formed through feeding in the first cavity A, density of a magnetic current in the second cavity B is less than a second preset threshold, so that the electromagnetic current is ensured to be transmitted in the first cavity, crosstalk can be better suppressed, an electromagnetic wave transmission loss can be reduced, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met in engineering while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change.
Optionally, when an electromagnetic current is formed through feeding in the second cavity B, density of a magnetic current in the first cavity A is less than a third preset threshold.
Specifically, refer to FIG. 9A and FIG. 9B. FIG. 9A and 9B are diagrams of effects of waveguide transmission according to an embodiment of this application.
As shown in FIG. 9A and FIG. 9B, when an electromagnetic current is formed through feeding in one of the first cavity A and the second cavity B (the electromagnetic current is transmitted in an arrow direction in FIG. 9A and FIG. 9B), density of a magnetic current in the other cavity is far less than density of a magnetic current in the cavity in which the electromagnetic current is transmitted, and may be specifically less than a preset threshold.
According to this embodiment of this application, mode expansion and interference of the electromagnetic current are implemented during transmission of the electromagnetic current, so that the electromagnetic current is ensured to be transmitted in a cavity in the cross-structure waveguide, crosstalk is better suppressed, an electromagnetic wave transmission loss is reduced, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met in engineering while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change.
In a possible embodiment, the waveguide apparatus may include a plurality of cross-structure waveguides, and the plurality of cross-structure waveguides are arranged in a cascade manner.
Specifically, refer to FIG. 10. FIG. 10 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application.
As shown in FIG. 10, the waveguide apparatus includes four cross-structure waveguides, and the four cross-structure waveguides are arranged in a cascade manner.
It may be understood that a quantity of cross-structure waveguides arranged in the cascade manner is not limited, and lengths of fundamental modes of the cross-structure waveguides arranged in the cascade manner are not limited.
It may be understood that, in addition to the manner shown in FIG. 10, the four cross-structure waveguides may be arranged in a column of serial cross-structure waveguides. This is not limited in embodiments of this application.
According to the cascade arrangement manner shown in this embodiment of this application, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.

Embodiment 2

FIG. 6 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application. It may be understood that the waveguide apparatus shown in FIG. 6 may be implemented as an independent embodiment. Alternatively, the waveguide apparatus shown in FIG. 6 may be understood as a deformation or a supplement of the waveguide apparatus in FIG. 3.
As shown in FIG. 6, the waveguide apparatus includes a cross-structure waveguide.
The cross-structure waveguide may be centrosymmetric.
The cross-structure waveguide includes a first cavity A and a second cavity B that intersect at a same layer, and the first cavity A and the second cavity B intersect at a central point of the cross-structure waveguide.
A filling medium of the cross-structure waveguide is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material.
It may be understood that the cross-structure waveguide included in the waveguide apparatus in this embodiment of this application may be centrosymmetric, and the first cavity A and the second cavity B that are included in the cross-structure waveguide are centrosymmetric with respect to the central point of the cross-structure waveguide. The filling medium of the cross-structure waveguide is the first material whose dielectric constant is greater than the first preset threshold, that is, filling media of the first cavity A and the second cavity B are the first materials whose dielectric constants are greater than the first preset threshold. The outer surface of the cross-structure waveguide is made of the conductive material, that is, outer surfaces of the first cavity A and the second cavity B are made of conductive materials.
It may be understood that the first preset threshold in this embodiment of this application is not a fixed value, and may be adjusted based on different application scenarios, so that the first material is a high dielectric filling medium that meets a requirement of the cross-structure waveguide.
According to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, an entire wavelength λ_Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus.
According to this embodiment of this application, the cross-structure waveguide is filled with a medium of a high dielectric material and an outer surface of the cross-structure waveguide is electroplated, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
In a possible embodiment, a body of the waveguide apparatus is a printed circuit board PCB, and the PCB includes a plurality of plated through holes that penetrate an upper surface and a lower surface.
An area formed by the plurality of plated through holes is the cross-structure waveguide.
Further, an envelope of the plated through hole forms a cross area, and a cavity that can be used to transmit an electromagnetic wave is formed inside the cross area. It may be understood that the formed cavity that is used to transmit an electromagnetic wave is also of a cross structure.
Specifically, refer to FIG. 7. FIG. 7 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application. It may be understood that the waveguide apparatus shown in FIG. 7 may be implemented as an independent embodiment. Alternatively, the waveguide apparatus shown in FIG. 7 may be understood as a deformation or a supplement of the waveguide apparatus in FIG. 6. In this case, FIG. 7 is a main view of the waveguide apparatus, and FIG. 6 is a top view of the waveguide apparatus.
As shown in FIG. 7, a body of the waveguide apparatus is a printed circuit board PCB, and the PCB includes a plurality of plated through holes 201 that penetrate an upper surface and a lower surface, a lower metal layer 202 of the PCB, and an upper metal layer 203 of the PCB.
An area formed by the plurality of plated through holes 201 is a cross-structure waveguide.
It may be understood that the body of the waveguide apparatus in this embodiment of this application is the printed circuit board PCB, the PCB is fully distributed with a plurality of plated through holes 201 that penetrate the upper surface and the lower surface, and the area enclosed by the plated through holes 201 is the cross-structure waveguide in the waveguide apparatus.
According to this embodiment of this application, a cross-structure waveguide in an SIW form is implemented by using a PCB processing process. The upper metal layer and the lower metal layer (202 and 203) of the PCB are used as an upper electric wall and a lower electric wall of the cross-structure waveguide, and plated through holes 201 on a side of the PCB form a side electric wall of the cross-structure waveguide. A size of the device (the cross-structure waveguide) is compressed due to a medium in the PCB, so that in engineering, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus is implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar is met.
Optionally, spacings among the plurality of plated through holes 201 are equal.
Based on the diagrams of the structures of the waveguide apparatus shown in FIG. 6 and FIG. 7, a diagram of a possible three-dimensional structure of the waveguide apparatus may be obtained.
For example, FIG. 8 is a diagram of a three-dimensional structure of a waveguide apparatus according to an embodiment of this application.
As shown in FIG. 8, a body of the waveguide apparatus in this embodiment of this application is a printed circuit board PCB, and the PCB includes a plurality of plated through holes 201 that penetrate an upper surface and a lower surface, a lower metal layer 202 of the PCB, and an upper metal layer 203 of the PCB. Structure relationships and functional features of the plurality of plated through holes 201, the lower metal layer 202 of the PCB, and the upper metal layer 203 of the PCB are consistent with those described in FIG. 6 and FIG. 7. Details are not described herein again.
It may be understood that the diagram of the structure of the waveguide apparatus shown in FIG. 6 is a top view of the waveguide apparatus in this embodiment of this application, and the diagram of the structure of the waveguide apparatus shown in FIG. 7 is a main view of the waveguide apparatus in this embodiment of this application.
Optionally, the filling medium (namely, the first material) of the cross-structure waveguide shown in FIG. 6 and/or FIG. 7 and/or FIG. 8 is a board material of the PCB.
It should be understood that, according to a formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, in a high dielectric material like the board material of the PCB, an entire wavelength λ_Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension of the waveguide can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the waveguide apparatus.
In a possible embodiment, the first cavity A includes a first fundamental mode input waveguide a1, a first fundamental mode and multimode matching waveguide a2, and a first multimode interference waveguide a3.
The first fundamental mode input waveguide a1 is connected to the first multimode interference waveguide a3 through the first fundamental mode and multimode matching waveguide a2, and a width (a) of the first multimode interference waveguide a3 is greater than a width (W1) of the first fundamental mode input waveguide a1.
The first fundamental mode input waveguide a1 is configured to input an electromagnetic wave, the electromagnetic wave enters the first multimode interference waveguide a3 through the first fundamental mode and multimode matching waveguide a2, and the first multimode interference waveguide a3 is configured to perform interference on the electromagnetic wave, to present, at the central point, a fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide a3.
It may be understood that the first fundamental mode input waveguide a1 and the first multimode interference waveguide a3 that are in the first cavity A are connected through the first fundamental mode and multimode matching waveguide a2. Because the cross-structure waveguide is centrosymmetric, and the first cavity A and the second cavity B that are included in the cross-structure waveguide intersect at the central point of the cross-structure waveguide, the first cavity A includes two first fundamental mode input waveguides, two first fundamental mode and multimode matching waveguides, and one first multimode interference waveguide. In addition, the central point of the cross-structure waveguide is a central point of the first multimode interference waveguide in the first cavity A, that is, a connection sequence of the waveguides included in the first cavity is successively "the first fundamental mode input waveguide a1, the first fundamental mode and multimode matching waveguide a2, the first multimode interference waveguide a3, a first fundamental mode and multimode matching waveguide a4, and a first fundamental mode input waveguide a5". Optionally, the first cavity A may alternatively include two first fundamental mode input waveguides, two first fundamental mode and multimode matching waveguides, and two first multimode interference waveguides, and the central point of the cross-structure waveguide is a connection point of the two first multimode interference waveguides in the first cavity A, that is, a connection sequence of the waveguides included in the first cavity is successively "the first fundamental mode input waveguide a1, the first fundamental mode and multimode matching waveguide a2, the first multimode interference waveguide a3, the first multimode interference waveguide a3, a first fundamental mode and multimode matching waveguide a4, and a first fundamental mode input waveguide a5". The two first multimode interference waveguides a3 may alternatively be a multimode interference waveguide that is integrally formed. This is not limited in embodiments of this application.
It should be understood that, if one of the first fundamental mode input waveguide a1 and the first fundamental mode input waveguide a5 is an input waveguide, the other fundamental mode waveguide is an output waveguide. A width of the first multimode interference waveguide is greater than a width of the first fundamental mode input waveguide. The width of the waveguide is designed, to implement five-order higher-order mode expansion of each waveguide included in the first cavity.
According to this embodiment of this application, the first fundamental mode input waveguide inputs the electromagnetic wave, and the electromagnetic wave enters the first multimode interference waveguide through the first fundamental mode and multimode matching waveguide, to present, at the central point after interference, the fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide, so that crosstalk can be better suppressed, and a transmission loss of the electromagnetic wave can be reduced.
It may be understood that a composition structure of the second cavity B is the same as a composition structure of the first cavity A. Details are not described herein again.
In a possible embodiment, a joint between the first fundamental mode and multimode matching waveguide a2 and the first fundamental mode input waveguide a1 is of a tapered structure, and a joint between the first fundamental mode and multimode matching waveguide a2 and the first multimode interference waveguide a3 is of a tapered structure.
According to this embodiment of this application, a gradually changing tapered structure at a joint between different waveguides is designed, so that mode matching at the joint between the first multimode interference waveguide and the first fundamental mode input waveguide can be improved, to optimize an echo.
In a possible embodiment, a cross-sectional size of the first multimode interference waveguide a3 meets the following condition: $1.2 λ \leq a \leq 1.5 λ,$ where
a is a first side of a cross section of the first multimode interference waveguide a3, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, a size of the first side (which may be understood as a width a of the cross section of the first multimode interference waveguide) of the cross section of the first multimode interference waveguide a3 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a length L3 of the first multimode interference waveguide a3 meets the following condition: $4.8 λ \leq L 3 \leq 5.3 λ,$ where
L3 is the length of the first multimode interference waveguide a3, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, the length L3 of the first multimode interference waveguide a3 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a length of the first fundamental mode and multimode matching waveguide a2 meets the following condition: $0.3 λ \leq L 2 \leq 0.4 λ,$ where
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
According to this embodiment of this application, the length L2 of the first fundamental mode and multimode matching waveguide a2 in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, a thickness h of the cross-structure waveguide meets the following condition: $0.35 W 1 \leq h \leq 0.6 W 1,$ where
h is the thickness of the cross-structure waveguide, and W1 is a width of the first fundamental mode input waveguide a1.
According to this embodiment of this application, the thickness h of the cross-structure waveguide in the waveguide apparatus is greatly reduced, thereby implementing a miniaturized design of the waveguide apparatus.
In a possible embodiment, when an electromagnetic current is formed through feeding in the first cavity A, density of a magnetic current in the second cavity B is less than a second preset threshold, so that the electromagnetic current is ensured to be transmitted in the first cavity, crosstalk can be better suppressed, an electromagnetic wave transmission loss can be reduced, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met in engineering while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change.
Optionally, when an electromagnetic current is formed through feeding in the second cavity B, density of a magnetic current in the first cavity A is less than a third preset threshold.
Specifically, refer to FIG. 9A and FIG. 9B. FIG. 9A and 9B are diagrams of effects of waveguide transmission according to an embodiment of this application.
As shown in FIG. 9A and FIG. 9B, when an electromagnetic current is formed through feeding in one of the first cavity A and the second cavity B (the electromagnetic current is transmitted in an arrow direction in FIG. 9A and FIG. 9B), density of a magnetic current in the other cavity is far less than density of a magnetic current in the cavity in which the electromagnetic current is transmitted, and may be specifically less than a preset threshold.
According to this embodiment of this application, mode expansion and interference of the electromagnetic current are implemented during transmission of the electromagnetic current, so that the electromagnetic current is ensured to be transmitted in a cavity in the cross-structure waveguide, crosstalk is better suppressed, an electromagnetic wave transmission loss is reduced, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met in engineering while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change.
In a possible embodiment, the waveguide apparatus may include a plurality of cross-structure waveguides, and the plurality of cross-structure waveguides are arranged in a cascade manner.
Specifically, refer to FIG. 10. FIG. 10 is a diagram of a structure of a waveguide apparatus according to an embodiment of this application.
As shown in FIG. 10, the waveguide apparatus includes four cross-structure waveguides, and the four cross-structure waveguides are arranged in a cascade manner.
It may be understood that a quantity of cross-structure waveguides arranged in the cascade manner is not limited, and lengths of fundamental modes of the cross-structure waveguides arranged in the cascade manner are not limited.
It may be understood that, in addition to the manner shown in FIG. 10, the four cross-structure waveguides may be arranged in a column of serial cross-structure waveguides. This is not limited in embodiments of this application.
According to the cascade arrangement manner shown in this embodiment of this application, while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.
It may be understood that, in both of the foregoing Embodiment 1 and Embodiment 2, the cross-structure waveguide is filled with a medium of a high dielectric material, so that while electromagnetic wave transmission performance of the waveguide apparatus is ensured to not change, a miniaturized design of the waveguide apparatus can be implemented, and a multi-channel cross-transmission requirement of a millimeter-wave radar can be met.

Specifically, performance indicators of the foregoing Embodiment 1 and Embodiment 2 may be shown in the following table.

Performance indicator	SOI process	Embodiment 1	Embodiment 2
MMI length (L3)	8.4λ	(1.9λ to 2.1λ)	(4.8λ to 5.3λ)
MMI width (a)	1.1λ	(0.53λ, to 0.72λ)	(1.2λ to 1.5λ)
Matching area length (L2)	2.8λ	(0.13λ to 0.18λ)	(0.3λ, to 0.45λ)
Fundamental mode width (W1)	0.3λ	(0.2λ to 0.4λ)	(0.3λ to 0.7λ)
Thickness (h)	/	(0.35 to 0.6)W1	(0.35 to 0.6)W1
Operating frequency band	Optical wave band (λ=1.55 mm)	Millimeter wave 76 to 77 GHz (λ=3.9 mm)	Millimeter wave 76 to 77 GHz (λ=3.9 mm)
Return loss (dB)	/	S11≤-30	S11≤-15
Insertion loss (dB)	<0.8	<0.2	<1.8 (including a medium loss of 1.5)
Isolation (dB)	≥35	≥37	≥23
Waveguide form	Dielectric waveguide with a low refractive index outside and a high refractive index inside	Metal waveguide filled with a medium with a high dielectric constant like silicon	SIW waveguide filled with a PCB medium

It can be learned from the foregoing table that both miniaturization performance and waveguide transmission performance of the waveguide apparatus are improved.
Further, a miniaturization process of the waveguide apparatus based on an MMI principle may be shown as follows.

Step 1: Determine a width a of a multimode interferometer.

1. In a vacuum condition, the following conditions need to be met for an electromagnetic wave to be transmitted in a rectangular waveguide: $λ \leq λ_{c} = \frac{2}{\sqrt{{(\frac{m}{a})}^{2} + {(\frac{n}{b})}^{2}}}$

In the formula, λ represents a vacuum wavelength of a wave of a minimum frequency (76 GHz) that needs to be transmitted, λ _c represents a maximum wavelength (a cut-off wavelength) of a wave that can be transmitted by the waveguide of the dimension, m and n each represents a quantity of modes of a TE mode, and a and b represent sizes of a long side and a narrow side of a cross section of the rectangular waveguide. After λ is determined, for a TE50 mode, m=5, and n=0, and it can be calculated by using the foregoing formula that a cross section a of the waveguide needs to meet: a ≥ 2.5λ.

Step 2: Determine a length x of the multimode interferometer.

1. The electromagnetic wave in the waveguide meets constraints of a dispersion equation. The dispersion equation is as follows: $β_{m}^{2} + k_{ym}^{2} = n_{r}^{2} k_{0}^{2}$ $k_{0} = \frac{2 π}{λ_{0}}$ $k_{ym} = \frac{(m + 1) π}{a}$

In the formula, β_m is a propagation constant of an m-order mode, k_ym is a quantity of vacuum waves of the m-order mode, a is an MMI width, k ₀ is a quantity of vacuum waves of a fundamental mode, and n_r is a refractive index of a medium in the waveguide.
A Taylor expansion of β_m obtained from the foregoing three formulas is as follows: $β_{m} = n_{r} k_{0} - \frac{{(m + 1)}^{2} {πλ}_{0}}{4 a^{2} n_{r}}$

2. Define a beat length L_π , which is calculated based on propagation constants of the fundamental mode and a first-order higher-order mode as follows: $L_{π} = \frac{π}{β_{0} - β_{1}} = \frac{4 a^{2} n_{r}}{3 λ_{0}}$
3. Substitute the beat length L_π into an expression of a propagation constant β_m, and after simplification, establish a relationship expression of β_m, β ₀, order quantity m, and L_π as follows: $β_{m} = β_{0} - \frac{m (m + 2) π}{3 L_{π}}$
4. Perform mode expansion in the waveguide, where only the mode quantity m, the beat length L_π, and a transmission length x are reserved in the expression after calculation.

MMI entry field function: φ(y,0) = Σ_m c_mφ_m(y)
Field function after transmission of a distance x in the MMI: $\begin{array}{l} φ (y, x) = \sum_{m} c_{m} φ_{m} (y) \times \exp (iωt - {iβ}_{m} x) \\ = \sum_{m} c_{m} φ_{m} (y) \times \exp (i \frac{m (m + 2) π}{3 L_{π}} x) \end{array}$
When the transmission length x in the foregoing formula meets the following formula, $\exp (i \frac{m (m + 2) π}{3 L_{π}} x) = \pm 1$ φ(y,0)=φ(y,x), and interfere is self-imaged.

Step 3: Implement a miniaturization principle by using a silicon dielectric.

According to the formula $λ_{Medium} = λ / \sqrt{DK}$ (where DK is a dielectric constant of a material) for calculating a medium wavelength of an electromagnetic wave, an entire wavelength λ _Medium of a same frequency may be $1 / \sqrt{DK}$ times of a vacuum wavelength λ. In this way, a dimension can be ensured to be greatly compressed in a case of a same quantity of distributed field modes in the device. A dielectric constant of pure silicon is 11.9. In engineering, the rectangular cross waveguide may be filled with a silicon medium through a procedure of metal surface silicon deposition, silicon layer etching for filling the waveguide, and an outer electroplating process. In this way, a miniaturized design of the device can be implemented while transmission performance is ensured to not change.
Further, for waveguide transmission performance of the waveguide apparatus based on the MMI principle (for example, the waveguide apparatus shown in FIG. 3 to FIG. 5), refer to FIG. 11, FIG. 12, and FIG. 13.
FIG. 11 is a diagram of a return loss according to an embodiment of this application.
As shown in FIG. 11, it can be learned that a return loss S11 of a port whose operating frequency band is a millimeter-wave frequency band of 76 to 77 GHz (λ=3.9 mm) is less than or equal to -30 dB.
FIG. 12 is a diagram of a transmission insertion loss according to an embodiment of this application.
As shown in FIG. 12, it can be learned that a transmission insertion loss of a port whose operating band is the millimeter-wave frequency band of 76 to 77 GHz (λ=3.9 mm) is less than 0.2 dB.
FIG. 13 is a diagram of a transmission isolation according to an embodiment of this application.
As shown in FIG. 13, it can be learned that an isolation of a port whose operating frequency band is the millimeter-wave frequency band of 76 to 77 GHz (λ=3.9 mm) is greater than or equal to 37 dB.
It can be learned from the diagrams of the performance indicators of the waveguide transmission performance of the waveguide apparatus shown in FIG. 11, FIG. 12, and FIG. 13 that the waveguide apparatus provided in this embodiment of this application can implement high transmission performance of a radio frequency signal at 76 to 77 GHz.
In a possible embodiment, a waveguide apparatus preparation method is further provided. A specific procedure of the preparation method is as follows:
Deposition/etching of a high dielectric material (a first material) on a metal surface is performed on a first metal layer, to form a cross-structure waveguide, where the cross-structure waveguide includes a first cavity and a second cavity that intersect at a same layer, and the first cavity and the second cavity intersect at a central point of the cross-structure waveguide.
Then, a metal plating is formed on an outer surface of the cross-structure waveguide through an outer electroplating process.
It can be learned from the foregoing preparation method that a filling medium of the obtained waveguide apparatus is a first material whose dielectric constant is greater than a first preset threshold, and the outer surface of the cross-structure waveguide is made of a conductive material. It may be understood that the first preset threshold is not a fixed value, and may be adjusted based on different application scenarios, so that the first material is a high dielectric filling medium that meets a requirement of the cross-structure waveguide.
For example, the waveguide apparatus shown in any one of FIG. 3 to FIG. 5 may be obtained by using the foregoing waveguide apparatus preparation method. For a structure feature and a functional feature of the waveguide apparatus, refer to the foregoing descriptions in FIG. 3 to FIG. 5. Details are not described herein again.
In a possible embodiment, another waveguide apparatus preparation method is further provided. A specific procedure of the preparation method is as follows.
APCB processing process is used to make a PCB be fully distributed with a plurality of plated through holes that penetrate an upper surface and a lower surface, and an area enclosed by the plated through holes forms a side electric wall of a cross-structure waveguide, where the cross-structure waveguide includes a first cavity and a second cavity that intersect at a same layer, and the first cavity and the second cavity intersect at a central point of the cross-structure waveguide.
An upper metal layer and a lower metal layer of the PCB are used as an upper electric wall and a lower electric wall of the cross-structure waveguide.
It can be learned from the foregoing preparation method that a filling medium of the obtained waveguide apparatus is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material. It may be understood that the first preset threshold is not a fixed value, and may be adjusted based on different application scenarios, so that the first material is a high dielectric filling medium that meets a requirement of the cross-structure waveguide.
For example, the waveguide apparatus shown in any one of FIG. 6 to FIG. 8 may be obtained by using the foregoing waveguide apparatus preparation method. For a structure feature and a functional feature of the waveguide apparatus, refer to the foregoing descriptions in FIG. 6 to FIG. 8. Details are not described herein again.
This application provides a radar or a radar system. The radar or the radar system includes the waveguide apparatus provided in this application. It should be noted that there may be a smart sensor integrated with a plurality of sensors. When the smart sensor includes a millimeter-wave detection function, the smart sensor may also be referred to as a millimeter-wave radar or a millimeter-wave radar system.
This application provides a terminal device. The terminal device includes the waveguide apparatus provided in this application. For example, the terminal device may be a transportation means, for example, a vehicle, a truck, an aircraft, an uncrewed aerial vehicle, a slow transport vehicle, a spacecraft, or a ship, or any other means of transportation used in any possible scenario, or may be any device that can carry a millimeter-wave detection apparatus, for example, a surveying and mapping device. One or more waveguide apparatuses provided in this application are deployed on the terminal device.
The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

A waveguide apparatus, comprising:
a cross-structure waveguide, wherein

the cross-structure waveguide comprises a first cavity and a second cavity that intersect, and the first cavity and the second cavity intersect at a central point of the cross-structure waveguide; and

a filling medium of the cross-structure waveguide is a first material whose dielectric constant is greater than a first preset threshold, and an outer surface of the cross-structure waveguide is made of a conductive material.
The waveguide apparatus according to claim 1, wherein the waveguide apparatus further comprises a metal plate, the cross-structure waveguide is located at an upper layer of the metal plate, and the outer surface of the cross-structure waveguide is a metal plating.
The waveguide apparatus according to claim 1 or 2, wherein the first material comprises at least one of the following: silicon, ceramic, and glass.
The waveguide apparatus according to claim 1, wherein a body of the waveguide apparatus is a printed circuit board PCB, and the PCB comprises a plurality of plated through holes that penetrate an upper surface and a lower surface; and
an area formed by the plurality of plated through holes is the cross-structure waveguide.
The waveguide apparatus according to claim 4, wherein the first material is a board material of the PCB.
The waveguide apparatus according to any one of claims 1 to 5, wherein the first cavity comprises a first fundamental mode input waveguide, a first fundamental mode and multimode matching waveguide, and a first multimode interference waveguide;
the first fundamental mode input waveguide and the first multimode interference waveguide are connected through the first fundamental mode and multimode matching waveguide, and a width of the first multimode interference waveguide is greater than a width of the first fundamental mode input waveguide; and

the first fundamental mode input waveguide is configured to input an electromagnetic wave, the electromagnetic wave enters the first multimode interference waveguide through the first fundamental mode and multimode matching waveguide, and the first multimode interference waveguide is configured to perform interference on the electromagnetic wave, to present, at the central point, a fundamental mode field pattern of the electromagnetic wave entering the first multimode interference waveguide.
The waveguide apparatus according to claim 6, wherein a joint between the first fundamental mode and multimode matching waveguide and the first fundamental mode input waveguide is of a tapered structure, and a joint between the first fundamental mode and multimode matching waveguide and the first multimode interference waveguide is of a tapered structure.
The waveguide apparatus according to claim 2 or 3, wherein a cross-sectional size of the first multimode interference waveguide meets the following condition: 0.53λ≤a≤0.72λ, wherein
a is a first side of a cross section of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to claim 4 or 5, wherein a cross-sectional size of the first multimode interference waveguide meets the following condition: 1.2λ≤a≤1.5λ, wherein
a is a first side of a cross section of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to claim 2 or 3, wherein a length of the first multimode interference waveguide meets the following condition: 1.9λ≤L3≤2.1λ, wherein
L3 is the length of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to claim 4 or 5, wherein a length of the first multimode interference waveguide meets the following condition: 4.8λ≤L3≤5.3λ, wherein
L3 is the length of the first multimode interference waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to claim 2 or 3, wherein a length of the first fundamental mode and multimode matching waveguide meets the following condition: 0.13λ≤L2≤0.18λ, wherein
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to claim 4 or 5, wherein a length of the first fundamental mode and multimode matching waveguide meets the following condition: 0.37t≤L2≤0.457t, wherein
L2 is the length of the first fundamental mode and multimode matching waveguide, and λ is a vacuum wavelength of a transmitted electromagnetic wave.
The waveguide apparatus according to any one of claims 1 to 13, wherein a thickness of the cross-structure waveguide meets the following condition: 0.35W1≤h≤0.6W1, wherein
h is the thickness of the cross-structure waveguide, and W1 is the width of the first fundamental mode input waveguide.
The waveguide apparatus according to any one of claims 1 to 14, wherein when an electromagnetic current is formed through feeding in the first cavity, a density of a magnetic current in the second cavity is less than a second preset threshold.
The waveguide apparatus according to any one of claims 1 to 12, wherein a plurality of cross-structure waveguides in the waveguide apparatus are arranged in a cascade manner.
A radar, wherein the radar comprises the waveguide apparatus according to any one of claims 1 to 16.
A terminal device, wherein the terminal device comprises the waveguide apparatus according to any one of claims 1 to 16, or the radar according to claim 17.
A vehicle, wherein the vehicle comprises the waveguide apparatus according to any one of claims 1 to 16, or the radar according to claim 17, or the terminal device according to claim 18.