阅读说明：本技术 一种基于可重构全息超表面的毫米波雷达及探测方法 (Millimeter wave radar and detection method based on reconfigurable holographic super surface ) 是由 张浩波 张雨童 邓若琪 于 2021-07-15 设计创作，主要内容包括：本发明涉及一种基于可重构全息超表面的毫米波雷达及探测方法,毫米波雷达包括：控制器和可重构全息超表面；RHS包括平行板波导、N个馈源和M个带有液晶的超材料辐射单元,N个馈源阵列和M个超材料辐射单元均设置在平行板波导上,控制器分别与各液晶和各馈源连接；利用控制器控制液晶的偏置电压调节超材料辐射单元的电磁波幅值；利用超材料辐射单元接收发射信号遇到各目标后返回的回波信号；利用控制器优化并确定雷达探测结果。本发明基于RHS辅助下构建毫米波雷达,使雷达探测性能达到最大化。另外RHS采用电控制的方式能够达到动态多波束控制效果,特别适用于多目标雷达探测,有效降低毫米波雷达的成本。(The invention relates to a millimeter wave radar and a detection method based on a reconfigurable holographic super surface, wherein the millimeter wave radar comprises the following components: a controller and a reconfigurable holographic super surface; the RHS comprises a parallel plate waveguide, N feed sources and M metamaterial radiation units with liquid crystals, wherein the N feed source arrays and the M metamaterial radiation units are arranged on the parallel plate waveguide, and the controller is connected with the liquid crystals and the feed sources respectively; the controller is used for controlling the bias voltage of the liquid crystal to adjust the amplitude of the electromagnetic wave of the metamaterial radiation unit; receiving echo signals returned after the transmitted signals meet all targets by using a metamaterial radiation unit; the controller is used to optimize and determine the radar detection results. The millimeter wave radar is constructed based on the aid of the RHS, so that the detection performance of the radar is maximized. In addition, the RHS can achieve a dynamic multi-beam control effect by adopting an electric control mode, is particularly suitable for multi-target radar detection, and effectively reduces the cost of the millimeter wave radar.)

1. A millimeter-wave radar based on a reconfigurable holographic hypersurface, comprising: a controller and a reconfigurable holographic super surface RHS; the RHS comprises a parallel plate waveguide, N feed sources and M metamaterial radiation units with liquid crystals, wherein the N feed sources are arranged on the parallel plate waveguide, the M metamaterial radiation units are arranged on the parallel plate waveguide, M and N are positive integers larger than 1, and M is larger than N; the controller is respectively connected with the liquid crystals and the feed sources;

the feed source is used for sending electromagnetic waves;

the parallel plate waveguide is used for transmitting the electromagnetic wave in the form of surface wave to the metamaterial radiation unit;

the controller is used for controlling the bias voltage of the liquid crystal so as to adjust the amplitude of the electromagnetic wave of each metamaterial radiation unit; the controller is further used for optimizing and determining a radar detection result;

the metamaterial radiation unit is used for sending emission signals to each target; the transmitting signal is electromagnetic wave with changed amplitude; the metamaterial radiation unit is also used for receiving echo signals returned after the emission signals meet all targets and sending the echo signals to the parallel plate waveguide, so that the parallel plate waveguide sends the returned echo signals to the controller through the feed source.

2. The reconfigurable holographic super surface based millimeter wave radar of claim 1, wherein the controller controls the bias voltage of the liquid crystal in a discrete manner.

3. The reconfigurable holographic hypersurface-based millimeter wave radar of claim 1, wherein the controller comprises:

the optimization module is used for optimizing the electromagnetic waves after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability;

the transmitting signal calculation module is used for calculating transmitting signals sent to all targets based on the electromagnetic waves after each period is optimized and the amplitude vectors of the RHS in the transmitting stage;

the echo signal determining module is used for modeling based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, and constructing echo signals received by all the feed sources of each period;

the prior probability calculation module is used for calculating the prior probability of each assumed establishment in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method;

and the result output module is used for optimizing the assumption that the probability of the false detection is minimum after the set period is set as the result of the radar detection.

4. The reconfigurable holographic super surface based millimeter wave radar according to claim 3, wherein the electromagnetic wave optimized in each period, the amplitude vector of RHS in the transmitting stage and the amplitude vector of RHS in the receiving stage are optimized based on the minimum error detection probability, and the specific formula is as follows:

w_j＝p^c(U_j)

wherein, W^cRepresents the electromagnetic wave after the c-th period is optimized, w_jA weight indicating that the jth hypothesis is satisfied, J indicates the total number of hypotheses,represents an electromagnetic waveform of W^cRHS has a magnitude vector s in the transmission phase^t,cRHS has a magnitude vector s in the receiving stage^r,cThen, the probability of misinterpreting the jth hypothesis as the jth hypothesis, p^c(U_j) Watch (A)Let c-th cycle assume U_jPrior probability of being true, w_jThe weight indicating that the jth hypothesis holds.

5. The reconfigurable holographic super surface based millimeter wave radar according to claim 3, wherein the transmission signal sent to each target is calculated based on the electromagnetic wave after each period is optimized and the amplitude vector of the RHS in the transmission phase, and the specific formula is as follows:

Y^t,c＝A×R(s^t,c)×H×W^c

wherein, Y^t,cDenotes a transmission signal transmitted in the c-th period in each target direction, a denotes a steering vector, and a ═ a₁,…,a_K)^TK represents the total number of targets, and the directions of the K targets are respectivelya_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, R(s)^t,c) Indicating the radiation matrix of the c-th period RHS during the emission phase, i.e. the first radiation matrix, s^t,cRepresenting the amplitude vector constituting the first radiation matrix, H representing the surface wave propagation matrix, W^cShowing the electromagnetic wave after the c-th period optimization.

6. The reconfigurable holographic super surface based millimeter wave radar according to claim 3, wherein the echo signals received by all the feed sources in each period are constructed by modeling based on the electromagnetic waves optimized in each period, the amplitude vector of RHS in the transmitting stage and the amplitude vector of RHS in the receiving stage, and the specific formula is as follows:

wherein, Y^cRepresenting the echo signals received by all the feeds in the c-th period, gamma_kDenotes the reflectivity of the K-th target direction, K denotes the total number of targets, J_kRepresenting a time delay matrix, H representing a surface wave propagation matrix, R(s)^r,c) Amplitude matrix representing the c-th period RHS in the receiving phase, i.e. the second amplitude matrix, s^r,cRepresenting the magnitude vectors, R(s), constituting a second magnitude matrix^t,c) Amplitude matrix, s, representing the c-th period RHS during the transmit phase^t,cRepresenting the magnitude vectors constituting the first radiation matrix, a_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, W^cRepresents the electromagnetic wave with the optimized c period, V^cRepresenting the noise and interference matrix.

7. The reconfigurable holographic super surface based millimeter wave radar of claim 3, wherein the prior probability calculation module specifically comprises:

the estimation matrix calculation unit is used for estimating the distance and the reflectivity according to each echo signal by adopting a maximum likelihood method under the condition that each hypothesis is established to obtain a distance estimation matrix and a reflectivity estimation matrix;

and the prior probability calculation unit is used for determining the prior probability of the establishment of each hypothesis in each period according to the received echo signals in each period, the distance estimation matrix and the reflectivity estimation matrix under the condition of the establishment of each hypothesis.

8. The reconfigurable holographic super surface-based millimeter wave radar according to claim 7, wherein when each hypothesis is satisfied, the prior probability that each hypothesis is satisfied in each period is determined according to each echo signal received in each period, the distance estimation matrix and the reflectivity estimation matrix, and the specific formula is as follows:

wherein p is^(c)(Y^(c)|U_j) Representing a hypothesis U_jOn the premise of being true, the probability of receiving each echo signal,representing a hypothesis U_jIs established by a distance estimation matrix ofThe reflectivity estimation matrix isOn the premise that the echo signal Y is received in the c-th periodⁱProbability of (U)_jIndicates that the jth hypothesis is true, YⁱRepresenting the echo signal received in the i-th cycle, Y^(c)Representing all echo signals received in periods 1 to c, p^c+1(U_j) Denotes the c +1 th cycle hypothesis U_jPrior probability of being established, p¹(U_j) Indicates that period 1 assumes U_jPrior probability of being true, w_jThe weight indicating that the jth hypothesis holds, and (c) the 1 st to the c-th periods.

9. A millimeter wave radar detection method, the method comprising:

optimizing the electromagnetic wave after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability;

calculating a transmission signal sent to each target based on the electromagnetic wave after each period is optimized and the amplitude vector of the RHS in the transmission stage;

establishing a model based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, and constructing echo signals received by all the feed sources of each period;

calculating the prior probability of each assumed establishment in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method;

and after the optimization setting period, taking the assumption of the minimum false detection probability as the radar detection result.

10. The millimeter wave radar detection method according to claim 9, wherein the calculating, by using a maximum likelihood method, a prior probability that each hypothesis of each period is true according to the echo signals received by all the feed sources of each period specifically includes:

under the condition that all the assumptions are established, estimating the distance and the reflectivity according to all the echo signals by adopting a maximum likelihood method to obtain a distance estimation matrix and a reflectivity estimation matrix;

and determining the prior probability of the establishment of each hypothesis in each period according to the received echo signals in each period, the distance estimation matrix and the reflectivity estimation matrix under the condition that each hypothesis is established.

Technical Field

The invention relates to the field of millimeter wave radar design, in particular to a millimeter wave radar based on a reconfigurable holographic super surface and a detection method.

Background

Under the promotion of the requirements of applications such as virtual reality and unmanned driving, positioning and perception become important functions of future wireless networks. Millimeter wave radar is an emerging location and sensing technology. Due to the advantages of precision and robustness, millimeter wave radar is increasingly widely applied to the applications such as virtual reality and unmanned driving, and is gradually becoming an essential key technology of a wireless network in the future.

The existing millimeter wave radar generally has two implementation modes. One is to transmit and receive radar signals by using a reflector antenna, and the other is to transmit and receive radar signals by using a phased array antenna. The difference between the two is that the reflector antenna utilizes the reflector to converge the beam to realize higher antenna gain, and has simple structure and lower cost. However, the antenna has a large volume due to the space feeding mode. In addition, in order to detect radar targets in different directions, the reflector antenna needs to be mechanically rotated, and the detection rate is limited. The phased array antenna realizes higher antenna gain by adjusting the phase difference of different antenna units, and does not need to rotate mechanically when detecting targets in different directions. However, the phase control circuit has a very complicated structure, high cost and large power consumption.

In order to realize a millimeter wave radar with a small volume, low power consumption, and low cost at the same time, a more economical and efficient antenna technology is required. Among the existing antenna technologies, the holographic antenna is a small-sized, low-power-consumption planar antenna, and is receiving increasing attention due to its multi-beam control capability with low manufacturing cost and low hardware cost. Specifically, the holographic antenna uses a metal patch to construct a holographic pattern on the surface, and records the interference between a reference wave and a target wave according to the interference principle, and the radiation characteristic of the reference wave can be changed through the holographic pattern to generate a required radiation direction. However, the conventional hologram antenna has a drawback in that radiation characteristics are fixed. In order to detect targets in different directions, the holographic antenna needs to be mechanically rotated, which increases the cost of the radar.

The emerging RHS technology shows great potential, and the RHS is an ultra-light thin planar antenna, and a plurality of metamaterial radiation units are embedded on the surface of the antenna. In particular, the RHS is excited by the reference wave generated by the antenna feed in the form of a surface wave, making it possible to manufacture an RHS based on Printed Circuit Board (PCB) technology with a compact structure. According to the hologram pattern, each radiation element can generate a desired radiation direction by electrically controlling the radiation amplitude of the reference wave. Compared with the traditional reflector antenna and the traditional phased array antenna, the RHS can realize dynamic beam forming without a heavy mechanical movement device and a complex phase-shifting circuit, can greatly save the manufacturing cost and the power loss of the antenna, and is very convenient to install due to a light and thin structure. But the research work of the existing RHS has been largely focused on RHS hardware component design and radiation direction control. However, most researches only prove the feasibility of realizing dynamic beam control by the RHS, and no technical scheme for constructing a millimeter wave radar based on the assistance of the RHS so as to maximize the detection performance of the radar exists in the current researches.

Disclosure of Invention

The invention aims to provide a millimeter wave radar based on a reconfigurable holographic super surface and a detection method, so that the millimeter wave radar is constructed based on the aid of RHS, and the detection performance of the radar is maximized.

In order to achieve the above object, the present invention provides a millimeter wave radar based on a reconfigurable holographic super surface, comprising: a controller and a reconfigurable holographic super surface RHS; the RHS comprises a parallel plate waveguide, N feed sources and M metamaterial radiation units with liquid crystals, wherein the N feed sources are arranged on the parallel plate waveguide, the M metamaterial radiation units are arranged on the parallel plate waveguide, M and N are positive integers larger than 1, and M is larger than N; the controller is respectively connected with the liquid crystals and the feed sources;

the feed source is used for sending electromagnetic waves;

the parallel plate waveguide is used for transmitting the electromagnetic wave in the form of surface wave to the metamaterial radiation unit;

the controller is used for controlling the bias voltage of the liquid crystal so as to adjust the amplitude of the electromagnetic wave of each metamaterial radiation unit; the controller is further used for optimizing and determining a radar detection result;

the metamaterial radiation unit is used for sending emission signals to each target; the transmitting signal is electromagnetic wave with changed amplitude; the metamaterial radiation unit is also used for receiving echo signals returned after the emission signals meet all targets and sending the echo signals to the parallel plate waveguide, so that the parallel plate waveguide sends the returned echo signals to the controller through the feed source.

Optionally, the controller controls the bias voltage of the liquid crystal in a discrete manner.

Optionally, the controller comprises:

the optimization module is used for optimizing the electromagnetic waves after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability;

the transmitting signal calculation module is used for calculating transmitting signals sent to all targets based on the electromagnetic waves after each period is optimized and the amplitude vectors of the RHS in the transmitting stage;

the echo signal determining module is used for modeling based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, and constructing echo signals received by all the feed sources of each period;

the prior probability calculation module is used for calculating the prior probability of each assumed establishment in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method;

and the result output module is used for optimizing the assumption that the probability of the false detection is minimum after the set period is set as the result of the radar detection.

Optionally, the electromagnetic wave optimized in each period, the amplitude vector of the RHS in the transmission phase, and the amplitude vector of the RHS in the reception phase are optimized based on the minimum error detection probability, and the specific formula is as follows:

w_j＝p^c(U_j)

wherein, W^cRepresents the electromagnetic wave after the c-th period is optimized, w_jA weight indicating that the jth hypothesis is satisfied, J indicates the total number of hypotheses,represents an electromagnetic waveform of W^cRHS has a magnitude vector s in the transmission phase^t,cRHS has a magnitude vector s in the receiving stage^r,cThen, the probability of misinterpreting the jth hypothesis as the jth hypothesis, p^c(U_j) Denotes the c-th period hypothesis U_jPrior probability of being true, w_jThe weight indicating that the jth hypothesis holds.

Optionally, the transmitting signal sent to each target is calculated based on the electromagnetic wave after each period is optimized and the amplitude vector of the RHS at the transmitting stage, and the specific formula is as follows:

Y^t,c＝A×R(s^t,c)×H×W^c

wherein, Y^t,cDenotes a transmission signal transmitted in the c-th period in each target direction, a denotes a steering vector, and a ═ a₁,…,a_K)^TK represents the total number of targets, and the directions of the K targets are respectivelya_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, R(s)^t,c) Indicating the radiation matrix of the c-th period RHS during the emission phase, i.e. the first radiation matrix, s^t,cRepresenting the amplitude vectors constituting the first radiation matrix, H representing the propagation moments of the surface wavesArray, W^cShowing the electromagnetic wave after the c-th period optimization.

Optionally, the modeling is performed based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmission phase and the amplitude vector of the RHS in the reception phase, and the echo signals received by all the feed sources of each period are constructed, where the specific formula is as follows:

wherein, Y^cRepresenting the echo signals received by all the feeds in the c-th period, gamma_kDenotes the reflectivity of the K-th target direction, K denotes the total number of targets, J_kRepresenting a time delay matrix, H representing a surface wave propagation matrix, R(s)^r,c) Amplitude matrix representing the c-th period RHS in the receiving phase, i.e. the second amplitude matrix, s^r,cRepresenting the magnitude vectors, R(s), constituting a second magnitude matrix^t,c) Amplitude matrix, s, representing the c-th period RHS during the transmit phase^t,cRepresenting the magnitude vectors constituting the first radiation matrix, a_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, W^cRepresents the electromagnetic wave with the optimized c period, V^cRepresenting the noise and interference matrix.

Optionally, the prior probability calculation module specifically includes:

the estimation matrix calculation unit is used for estimating the distance and the reflectivity according to each echo signal by adopting a maximum likelihood method under the condition that each hypothesis is established to obtain a distance estimation matrix and a reflectivity estimation matrix;

and the prior probability calculation unit is used for determining the prior probability of the establishment of each hypothesis in each period according to the received echo signals in each period, the distance estimation matrix and the reflectivity estimation matrix under the condition of the establishment of each hypothesis.

Optionally, in the case that each hypothesis is satisfied, the prior probability that each hypothesis is satisfied for each period is determined according to each received echo signal for each period, the distance estimation matrix, and the reflectivity estimation matrix, and a specific formula is as follows:

wherein p is^(c)(Y^(c)|U_j) Representing a hypothesis U_jOn the premise of being true, the probability of receiving each echo signal,representing a hypothesis U_jIs established by a distance estimation matrix ofThe reflectivity estimation matrix isOn the premise that the echo signal Y is received in the c-th periodⁱProbability of (U)_jIndicates that the jth hypothesis is true, YⁱRepresenting the echo signal received in the i-th cycle, Y^(c)Representing all echo signals received in periods 1 to c, p^c+1(U_j) Denotes the c +1 th cycle hypothesis U_jPrior probability of being established, p¹(U_j) Indicates that period 1 assumes U_jPrior probability of being true, w_jThe weight indicating that the jth hypothesis holds, and (c) the 1 st to the c-th periods.

The invention also provides a millimeter wave radar detection method, which comprises the following steps:

optimizing the electromagnetic wave after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability;

calculating a transmission signal sent to each target based on the electromagnetic wave after each period is optimized and the amplitude vector of the RHS in the transmission stage;

establishing a model based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, and constructing echo signals received by all the feed sources of each period;

calculating the prior probability of each assumed establishment in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method;

and after the optimization setting period, taking the assumption of the minimum false detection probability as the radar detection result.

Optionally, the calculating, by using a maximum likelihood method, a prior probability that each hypothesis of each period is true according to the echo signals received by all the feed sources of each period specifically includes:

under the condition that all the assumptions are established, estimating the distance and the reflectivity according to all the echo signals by adopting a maximum likelihood method to obtain a distance estimation matrix and a reflectivity estimation matrix;

and determining the prior probability of the establishment of each hypothesis in each period according to the received echo signals in each period, the distance estimation matrix and the reflectivity estimation matrix under the condition that each hypothesis is established.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention constructs the millimeter wave radar based on the RHS assistance, so as to maximize the detection performance of the radar, compared with the traditional reflecting surface radar which uses a heavy mechanical device to control the rotation of the antenna so as to realize the beam control, the invention has the advantages of small size, compact structure, lightness, thinness, low manufacturing cost and the like, in addition, the RHS adopts an electric control mode to achieve good dynamic multi-beam control effect, is particularly suitable for multi-target radar detection, and can effectively reduce the cost of the millimeter wave radar.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a diagram illustrating the operation of a millimeter wave radar according to the present invention;

FIG. 2 is a schematic diagram of the operation of a reconfigurable holographic super surface of the present invention;

FIG. 3 is a flow chart of a millimeter wave radar control method of the present invention;

description of the symbols:

1. the device comprises a controller, 2, a reconfigurable holographic super surface, 3, a parallel plate waveguide, 4, a feed source, 5 and a metamaterial radiation unit.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a millimeter wave radar based on a reconfigurable holographic super surface and a detection method, so that the millimeter wave radar is constructed based on the aid of RHS, and the detection performance of the radar is maximized.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in fig. 1-2, the present invention discloses a millimeter wave radar based on reconfigurable holographic super surface, which includes: a controller 1 and a Reconfigurable Holographic super Surface 2 (RHS); the RHS comprises a parallel plate waveguide 3, N feed sources 4 and M metamaterial radiating units 5 with liquid crystal, wherein the N feed sources 4 are arranged on the parallel plate waveguide 3, the M metamaterial radiating units 5 are arranged on the parallel plate waveguide 3, M and N are positive integers larger than 1, and M is far larger than N; the controller 1 is connected to each of the liquid crystals and each of the feed sources 4. Preferably, the N feed sources 4 and the M metamaterial radiation units 5 are arranged on the parallel plate waveguide 3 in an array mode.

The feed source 4 is used for sending electromagnetic waves; the parallel plate waveguide 3 is used to propagate the electromagnetic wave in the form of a surface wave; the controller 1 is used for controlling the bias voltage of the liquid crystal so as to adjust the amplitude of the electromagnetic wave transmitted to each metamaterial radiation unit 5; the controller 1 is used for determining radar detection results according to the received echo signals; the metamaterial radiation unit 5 is used for sending a transmission signal to each target; the transmitting signal is electromagnetic wave with changed amplitude; the metamaterial radiation unit 5 is further configured to receive echo signals returned after the transmission signals meet the targets, and send the echo signals to the parallel plate waveguide 3, so that the parallel plate waveguide 3 sends the returned echo signals to the controller 1 through the feed source 4.

In this embodiment, the controller 1 includes: the device comprises an optimization module, a transmitting signal calculation module, an echo signal determination module, a prior probability calculation module and a result output module. The optimization module is used for optimizing the electromagnetic waves after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability; the transmitting signal calculating module is used for calculating transmitting signals sent to all targets based on the electromagnetic waves after each period is optimized and the amplitude vectors of the RHS in the transmitting stage; the echo signal determining module is used for modeling based on the optimized electromagnetic waves of each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, and constructing echo signals received by all the feed sources of each period; the prior probability calculation module is used for calculating the prior probability of each assumed establishment in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method; and the result output module is used for taking the hypothesis with the minimum false detection probability as the radar detection result after the optimal setting period. In this embodiment, the result of radar detection is output after C cycles are optimized.

The modules are analyzed in detail below:

preferably, in the transmission process, the metamaterial radiation unit is covered with a layer of liquid crystal, and the dielectric constant of the liquid crystal can be changed by adjusting the bias voltage of the liquid crystal, so that the amplitude adjustment of the electromagnetic wave transmitted to the metamaterial radiation unit is realized. Considering that the circuit implementation of the continuous variable voltage is relatively complex, the bias voltage of the liquid crystal is adjusted in a discrete mode by using the controller, so that the amplitude (namely the amplitude) of the metamaterial radiation unit is discretely adjustable.

In this embodiment, the amplitude of each metamaterial radiation unit has N_sThe seed values are {0, 1/(N)_s-1),…,(N_s-2)/(N_s-1),1}. The number of the radar targets to be detected is K, the specific value of K is unknown, but K is known<K^MWherein, K is^MRepresenting the number of maximum objects that the system can identify. The amplitude values must be satisfied in subsequent optimization calculations.

The RHS has two modes of operation, a transmit mode and a receive mode. In the transmitting mode, the controller controls the amplitude of the RHS, so that the transmitting signal with the changed amplitude is transmitted. The RHS will then transition to the receive mode. The transmitted signal is reflected by the target and then received by the RHS in the receiving mode, the received echo signal is processed by the controller so as to detect the target, and finally, a radar detection result is obtained, namely, the number and the direction of the target are judged.

Assuming that each target may be atOne of the I directions, where theta is the azimuth angle,refers to the pitch angle. The K targets and the I directions are arranged and combined to obtainThe results of (1). And because the value range of K is [0,1, …, K^M]Therefore, all are commonPossible combined results. Each result corresponds to a target number and direction. It is determined which result is correct, meaning that radar detection is complete.

In order to judge which result is correct, the invention adopts a hypothesis testing method to establish J hypotheses, wherein the jth hypothesis U_jCorresponding to the above-mentioned j-th target number and direction combination result. Initially, the probability of the jth hypothesis is p⁰(U_j). The probability of each hypothesis is then continuously updated by analyzing the radar reception signals, and the hypothesis with the highest final probability is considered as the result of radar detection.

The working flow of the invention comprises C periods, and each period respectively carries out four steps of optimization, transmission, reception and detection. When all periods are over, the assumption that the final probability is the highest (i.e. the probability of false detection is the lowest) is considered as the result of radar detection.

Optimizing: optimizing the electromagnetic wave after each period is optimized, the amplitude vector of RHS in the transmitting stage and the amplitude vector of RHS in the receiving stage based on the minimum error detection probability, wherein the specific formula is as follows:

w_j＝p^c(U_j)

wherein, W^cRepresents the electromagnetic wave after the c-th period is optimized, w_jA weight indicating that the jth hypothesis is satisfied, J indicates the total number of hypotheses,represents an electromagnetic waveform of W^cRHS has a magnitude vector s in the transmission phase^t,cRHS has a magnitude vector s in the receiving stage^r,cWhen it is going toProbability of j hypotheses being misinterpreted as the jth hypothesis, p^c(U_j) Denotes the c-th period hypothesis U_jPrior probability of being true, w_jThe weight indicating that the jth hypothesis holds.

Emission: determining a transmitting signal sent to each target based on the electromagnetic wave after each period is optimized and the amplitude vector of the RHS in the transmitting stage, wherein the calculation formula is as follows:

Y^t,c＝A×R(s^t,c)×H×W^c

wherein, Y^t,cIndicating the transmitted signal transmitted in the c-th cycle in each target direction, and the k-th line indicating the directionA denotes a steering vector, a ═ a₁,…,a_K)^TK represents the total number of targets, and the directions of the K targets are respectivelya_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, R(s)^t,c) Indicating the radiation matrix of the c-th period RHS during the emission phase, i.e. the first radiation matrix, s^t,cRepresenting the amplitude vector forming the first radiation matrix, which is a diagonal matrix, H represents a surface wave propagation matrix, M is multiplied by N, the mth row and the nth column represent the amplitude and phase change in the process of propagating from the nth feed source to the mth metamaterial radiation unit, and W is^cShowing the electromagnetic wave after the c-th period optimization.

Receiving: establishing echo signals received by all feed sources in each period based on the electromagnetic waves optimized in each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage, wherein the specific formula is as follows:

wherein, Y^cRepresenting the echo signals received by all the feeds in the c-th period, the n-th row representing the signal received by the feed n, gamma_kDenotes the reflectivity of the K-th target direction, K denotes the total number of targets, J_kA time delay matrix is shown for describing the time delay caused by the reflection path of the signal through the kth target, H represents the surface wave propagation matrix, R(s)^r,c) Amplitude matrix representing the c-th period RHS in the receiving phase, i.e. the second amplitude matrix, s^r,cRepresenting the magnitude vectors constituting the second magnitude matrix, as a diagonal matrix, R(s)^t,c) Amplitude matrix representing the c-th period RHS during the transmit phase, i.e. the first radiation matrix, s^t,cRepresenting the magnitude vectors constituting the first radiation matrix, as diagonal matrix, a_kIndicating directionCorresponding guide vector, θ_kIndicating the azimuth angle in the k-th direction,denotes the pitch angle in the k-th direction, W^cRepresents the electromagnetic wave with the optimized c period, V^cRepresenting the noise and interference matrix.

Detecting: adopting a maximum likelihood method, calculating prior probability of each assumed establishment in each period according to echo signals received by all feed sources in each period, specifically:

based on the fact that each hypothesis is established, the maximum likelihood method is adopted to obtain the echo signals (Y)¹,…,Y^c) Estimating the distance and the reflectivity to obtain a distance estimation matrixAnd a reflectivity estimation matrixSpecifically, aWill determine the delay matrix J_k). Distance estimation matrixInRepresenting the estimated distance to the radar for all targets (this term determines the delay matrix J)_k) The reflectivity estimation matrixInRepresenting the reflectivity in all k directions.

Based on the condition that each hypothesis is established, determining the prior probability of each hypothesis establishment of each period according to each received echo signal, the distance estimation matrix and the reflectivity estimation matrix of each period, wherein the specific formula is as follows:

wherein p is^(c)(Y^(c)|U_j) Representing a hypothesis U_jOn the premise of being true, an echo signal (Y) is received¹,…,Y^c) The probability of (a) of (b) being,representing a hypothesis U_jIs established by a distance estimation matrix ofReflectivity estimationThe matrix isOn the premise that the echo signal Y is received in the c-th periodⁱProbability of (U)_jIndicates that the jth hypothesis is true, YⁱRepresenting the echo signal received in the i-th cycle, Y^(c)Representing all echo signals received in periods 1 to c, i.e. (Y)¹,…,Y^c)，p^c+1(U_j) Denotes the c +1 th cycle hypothesis U_jPrior probability of being established, p¹(U_j) Indicates that period 1 assumes U_jA priori probability of being true, this value being a constant, w_jThe weight indicating that the jth hypothesis holds, and (c) the 1 st to the c-th periods.

1. The invention constructs the millimeter wave radar based on the RHS assistance, so as to maximize the detection performance of the radar, compared with the traditional reflecting surface radar which uses a heavy mechanical device to control the rotation of the antenna so as to realize the beam control, the invention has the advantages of small size, compact structure, lightness, thinness, low manufacturing cost and the like, in addition, the RHS adopts an electric control mode to achieve good dynamic multi-beam control effect, is particularly suitable for multi-target radar detection, and can effectively reduce the cost of the millimeter wave radar.

2. The RHS disclosed by the invention has low power consumption and low hardware cost: although the phased array antenna radar also utilizes electric control of the beam direction, the phased array relies on a large number of phase shifters to control the phase of electromagnetic waves in each antenna, and a large number of power amplifiers are also needed, so that the phased array antenna needs a complex phase shifting circuit, and has large power loss and high hardware cost. Compared with the prior art, the RHS does not need a phase shifter and a complex phase shifting circuit, the difference of the electromagnetic wave energy radiated by each radiating unit can be controlled by utilizing the dielectric property of the voltage-regulated liquid crystal, namely, the wave beam control can be completed in an amplitude modulation mode, so that the RHS-assisted radar has low power consumption and low hardware cost, and has great advantages compared with a phased array antenna.

Example 2

As shown in fig. 3, the present invention further provides a millimeter wave radar detection method, including:

step S301: and optimizing the electromagnetic wave after each period is optimized, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage based on the minimum error detection probability.

Step S302: and calculating the transmitting signals sent to each target based on the electromagnetic waves after each period is optimized and the amplitude vectors of the RHS in the transmitting stage.

Step S303: and constructing echo signals received by all the feed sources in each period based on the electromagnetic waves optimized in each period, the amplitude vector of the RHS in the transmitting stage and the amplitude vector of the RHS in the receiving stage.

Step S304: and calculating the prior probability of each hypothesis in each period according to the echo signals received by all the feed sources in each period by adopting a maximum likelihood method.

Step S305: and after the optimization setting period, taking the assumption of the minimum false detection probability as the radar detection result.

As an optional implementation manner, step S305 of the present invention specifically includes:

under the condition that all the assumptions are established, estimating the distance and the reflectivity according to all the echo signals by adopting a maximum likelihood method to obtain a distance estimation matrix and a reflectivity estimation matrix;

and determining the prior probability of the establishment of each hypothesis in each period according to the received echo signals in each period, the distance estimation matrix and the reflectivity estimation matrix under the condition that each hypothesis is established.

The above formula is the same as that of embodiment 1, and is not described in detail here.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to assist in understanding the core concepts of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.