CN114252843A - Signal direction finding system and method based on 1-bit programmable metasurface - Google Patents

Abstract

Translated fromChinese

本发明涉及一种基于1‑bit可编程超表面的信号测向系统及方法，属于信号测向技术领域，本发明通过1‑bit可编程超表面上的单元天线接收入射信号，通过控制器对各单元天线施加周期性调制序列，从而对入射信号施加上相移后射向接收天线；根据设计的周期性调制序列，计算出各单元天线的基波分量和一次谐波分量对应的傅里叶系数；计算出接收天线处的基波分量和一次谐波分量；得到一次谐波分量与基波分量的比值与入射信号方向的函数关系；根据实际测得的一次谐波分量与基波分量的比值，计算出入射信号的方向。本发明实现了信号的二维测向，系统结构简洁，数学运算简单，具有低成本、低复杂度的优势。

The invention relates to a signal direction finding system and method based on a 1-bit programmable metasurface, and belongs to the technical field of signal direction finding. Each element antenna applies a periodic modulation sequence, so as to apply an upper phase shift to the incident signal and then send it to the receiving antenna; according to the designed periodic modulation sequence, the Fourier corresponding to the fundamental component and the first harmonic component of each element antenna is calculated. coefficient; calculate the fundamental wave component and the first harmonic component at the receiving antenna; obtain the functional relationship between the ratio of the first harmonic component and the fundamental wave component and the direction of the incident signal; according to the actual measured first harmonic component and the fundamental wave component The ratio calculates the direction of the incident signal. The invention realizes the two-dimensional direction finding of the signal, the system structure is concise, the mathematical operation is simple, and has the advantages of low cost and low complexity.

Description

Translated fromChinese

基于1-bit可编程超表面的信号测向系统及方法Signal direction finding system and method based on 1-bit programmable metasurface

技术领域technical field

本发明属于信号测向技术领域，涉及一种基于1-bit可编程超表面的信号测向系统及方法。The invention belongs to the technical field of signal direction finding, and relates to a signal direction finding system and method based on a 1-bit programmable metasurface.

背景技术Background technique

传统的测向方法可以分为多射频链和单射频链两大类。多射频链类的测向方法多需要获取多个通道的相位差、幅值差或到达时间差等用来估计信号方向，这使得整个系统的结构非常复杂。而现有的单射频链测向方法虽然做到了结构的简化，但大多方法都存在计算复杂度高、稳定性要求高等缺点。近年来诞生了一些基于时间调制阵列的测向方法，该类方法属于单射频链测向，其原理是通过周期性的开关或相移调制使输出的信号包含基波和各次谐波分量，而信号入射方向不同会导致分量之间的相对关系发生变化，故可以通过分析分量之间的数学关系进行角度的计算，它相比传统单射频链测向方法有着更加简单的数学运算需求。然而，时间调制阵列本身也属于天线阵列，其阵元需要根据工作频段定制化设计，且阵元尺寸受到工作波长的限制难以轻量化、小型化。因此，当前在信号测向领域缺少低复杂度、低成本、易部署且能精度也达到一定要求的方法。Traditional direction finding methods can be divided into two categories: multi-RF chains and single-RF chains. The direction finding method of the multi-radio chain type mostly needs to obtain the phase difference, amplitude difference or arrival time difference of multiple channels to estimate the signal direction, which makes the structure of the whole system very complicated. While the existing single-RF chain direction finding methods have achieved the simplification of the structure, most of the methods have the disadvantages of high computational complexity and high stability requirements. In recent years, some direction finding methods based on time-modulated arrays have been born. These methods belong to the direction finding of a single radio frequency chain. The principle is that the output signal contains the fundamental wave and various harmonic components through periodic switching or phase shift modulation. Different signal incident directions will cause the relative relationship between the components to change. Therefore, the angle can be calculated by analyzing the mathematical relationship between the components. Compared with the traditional single-RF chain direction finding method, it has simpler mathematical operation requirements. However, the time-modulated array itself is also an antenna array, and its array elements need to be customized according to the working frequency band, and the size of the array element is limited by the working wavelength, which is difficult to be lightweight and miniaturized. Therefore, there is currently a lack of low-complexity, low-cost, and easy-to-deploy methods in the field of signal direction finding that can meet certain requirements of accuracy.

可编程超表面是一种新兴的人工电磁材料，其结构是一种具有若干个人工单元的薄板，每个人工单元可以对入射的信号施加设计好的相移后使其出射，因为造价低、单元尺寸比传统阵元小、易于部署，被认为是具有潜力的新型相控阵的解决方案。Programmable metasurface is an emerging artificial electromagnetic material. Its structure is a thin plate with several artificial units. Each artificial unit can apply a designed phase shift to the incident signal and then make it out. The element size is smaller than traditional array elements and easy to deploy, and it is considered as a potential new phased array solution.

发明内容SUMMARY OF THE INVENTION

有鉴于此，本发明的目的在于提供一种基于1-bit可编程超表面的信号测向系统及方法。In view of this, the purpose of the present invention is to provide a signal direction finding system and method based on a 1-bit programmable metasurface.

为达到上述目的，一方面，本发明提供如下技术方案：In order to achieve the above object, on the one hand, the present invention provides the following technical solutions:

一种基于1-bit可编程超表面的信号测向系统，包括1-bit可编程超表面，若所述可编程超表面为反射型，则其接收信号的一面分布有M×N个单元天线，若为透射型，则两面对称分布有M×N个单元天线，其中M为单元天线的行数，N为单元天线的列数；所述可编程超表面还连接有用于对单元天线施加周期性调制序列的控制器；在距离所述可编程超表面几何中心一定距离处设有接收天线，所述接收天线连接接收机，所述接收机内设有信号处理模块和角度计算模块；所述信号处理模块用于通过快速傅里叶变换FFT或离散傅里叶变换DFT处理接收信号；所述角度计算模块用于根据各单元天线的周期性调制序列和接收信号处理模块的结果，计算出入射信号的方向。A signal direction finding system based on a 1-bit programmable metasurface, comprising a 1-bit programmable metasurface. If the programmable metasurface is a reflective type, M×N unit antennas are distributed on the side that receives the signal. , if it is a transmission type, there are M×N unit antennas symmetrically distributed on both sides, where M is the number of rows of the unit antennas, and N is the number of columns of the unit antennas; the programmable metasurface is also connected to the unit antenna. A controller of a linear modulation sequence; a receiving antenna is arranged at a certain distance from the geometric center of the programmable metasurface, the receiving antenna is connected to a receiver, and a signal processing module and an angle calculation module are arranged in the receiver; the The signal processing module is used to process the received signal through fast Fourier transform FFT or discrete Fourier transform DFT; the angle calculation module is used to calculate the incident signal according to the periodic modulation sequence of each element antenna and the result of the received signal processing module direction of the signal.

另一方面，本发明提供一种基于1-bit可编程超表面的信号测向方法，包括以下步骤：In another aspect, the present invention provides a signal direction finding method based on a 1-bit programmable metasurface, comprising the following steps:

S1：通过1-bit可编程超表面上的各单元天线接收入射信号；S1: Receive the incident signal through each element antenna on the 1-bit programmable metasurface;

S2：对各单元天线施加周期性调制序列；S2: apply a periodic modulation sequence to each element antenna;

S3：各单元天线对入射信号施加上相移后射出，被接收天线接收；S3: Each element antenna applies an upper phase shift to the incident signal and then emits it, and is received by the receiving antenna;

S4：根据周期性调制序列计算出各单元天线的基波分量和一次谐波分量对应的傅里叶系数；S4: Calculate the Fourier coefficients corresponding to the fundamental wave component and the first harmonic component of each element antenna according to the periodic modulation sequence;

S5：计算出接收天线处的基波分量和一次谐波分量；S5: Calculate the fundamental wave component and the first harmonic component at the receiving antenna;

S6：得到一次谐波分量与基波分量的比值与入射信号方向的函数关系；S6: Obtain the functional relationship between the ratio of the first harmonic component and the fundamental component and the direction of the incident signal;

S7：根据实际测得的一次谐波分量与基波分量的比值，计算出入射信号的方向。S7: Calculate the direction of the incident signal according to the ratio of the first harmonic component to the fundamental component actually measured.

进一步，所述步骤S1中，1-bit可编程超表面的单元天线间距D为半波长，接收天线位于超表面中心正前方，距离为F；1-bit可编程超表面上有M×N个单元天线，其中M为单元天线的行数，N为单元天线的列；在笛卡尔坐标系中，第(m,n)单元天线的坐标为[(m-(M+1)/2)D,(n-(N+1)/2)D,0]，其中m表示该单元天线所在行数，n表示该单元天线所在列数，接收天线坐标为[0,0,F]，则第(m,n)单元天线与接收天线的距离l_m,n为：Further, in the step S1, the unit antenna spacing D of the 1-bit programmable metasurface is half a wavelength, the receiving antenna is located directly in front of the center of the metasurface, and the distance is F; there are M×N on the 1-bit programmable metasurface Element antenna, where M is the row number of the element antenna, and N is the column of the element antenna; in the Cartesian coordinate system, the coordinates of the (m, n)th element antenna are [(m-(M+1)/2)D ,(n-(N+1)/2)D,0], where m represents the row number of the unit antenna, n represents the column number of the unit antenna, and the coordinates of the receiving antenna are [0,0,F], then the first (m,n) The distance lm_,n between the unit antenna and the receiving antenna is:

进一步，步骤S2中所述周期性调制序列包括：Further, the periodic modulation sequence in step S2 includes:

引入第(m,n)单元的周期性切换函数U_m,n(t)，其值域为{1,-1}，代表0和π两种相移；在一个时间调制周期T_p内，所述周期性切换函数U_m,n(t)表示为The periodic switching function U_m,n (t) of the (m,n)th unit is introduced, and its value range is {1,-1}, representing two phase shifts of 0 and π; in a time modulation period T_p , The periodic switching function U_m,n (t) is expressed as

进一步，所述步骤S3中，一个频点为F_c的正弦信号从

方向入射，θ为俯仰角，

为方位角，θ∈(-π/2,π/2)，

各单元天线的方向图为

l_m,n导致的路径损耗为a(l_m,n)，引入周期性调制序列后，超表面和接收天线组成的接收系统的瞬时方向图函数为：Further, in the step S3, a sinusoidal signal whose frequency point is F_c is from

direction incident, θ is the pitch angle,

is the azimuth, θ∈(-π/2,π/2),

The pattern of each element antenna is

The path loss caused by l_m,n is a(l_m,n ). After introducing the periodic modulation sequence, the instantaneous pattern function of the receiving system composed of the metasurface and the receiving antenna is:

其中，

表示信号从各单元天线出射到接收天线方向的增益，d_m,n表示信号到达各单元天线的波程差，j表示虚数符号，λ表示入射信号的波长。in,

Represents the gain of the signal from each element antenna to the direction of the receiving antenna, d_m,n represents the wave path difference of the signal reaching each element antenna, j represents the imaginary number symbol, and λ represents the wavelength of the incident signal.

进一步，在所述步骤S4中，U_m,n(t)满足U_m,n(t)＝U_m,n(t+nT_p)，τ_m,n,on和τ_m,n,off分别表示第(m,n)单元归一化的相移π的开启时间和关闭时间；作为周期性函数，U_m,n(t)以傅里叶级数的形式展开为：Further, in the step S4, U_m,n (t) satisfies U_m,n (t)=U_m,n (t+nT_p ), τ_m,n,on and τ_m,n,off are respectively represents the on-time and off-time of the normalized phase shift π of the (m,n)th element; as a periodic function, U_m,n (t) is expanded in the form of a Fourier series as:

其中，α_m,n,k是第k次谐波的傅里叶系数，通过下式计算：where α_m,n,k are the Fourier coefficients of the kth harmonic, calculated by the following formula:

进一步，步骤S5中所述接收天线处的基波分量和一次谐波分量为：Further, the fundamental wave component and the first harmonic component at the receiving antenna described in step S5 are:

进一步，步骤S6中所述一次谐波分量和基波分量的比值与入射信号方向的函数关系为：Further, the functional relationship between the ratio of the first harmonic component and the fundamental wave component and the direction of the incident signal in step S6 is:

进一步，令实际测得的一次谐波与基波的比值为p+qj，当根据m、n的奇偶将所有单元天线划分为4个子阵，则向各单元天线施加的周期性调制序列U_m,n(t)表示为：Further, let the ratio of the first harmonic actually measured to the fundamental wave be p+qj, when all the element antennas are divided into 4 sub-arrays according to the parity of m and n, the periodic modulation sequence U_m applied to each element antenna_,n (t) is expressed as:

则入射信号的方向估计值

由下式计算：Then the estimated value of the direction of the incident signal

Calculated by:

其中：in:

本发明的有益效果在于：本发明将1-bit可编程超表面与时间调制技术相结合，实现了信号的二维测向。本发明所提出的测向系统结构简洁，成本低，易于部署，仅需要FFT或DFT对信号进行处理，数学运算简单，具有低成本、低复杂度的优势。The beneficial effect of the present invention is that: the present invention combines the 1-bit programmable metasurface and the time modulation technology to realize the two-dimensional direction finding of the signal. The direction finding system proposed by the invention has the advantages of simple structure, low cost, easy deployment, only needs FFT or DFT to process the signal, simple mathematical operation, low cost and low complexity.

本发明的其他优点、目标和特征在某种程度上将在随后的说明书中进行阐述，并且在某种程度上，基于对下文的考察研究对本领域技术人员而言将是显而易见的，或者可以从本发明的实践中得到教导。本发明的目标和其他优点可以通过下面的说明书来实现和获得。Other advantages, objects and features of the present invention will be set forth in the description which follows, to the extent that will be apparent to those skilled in the art based on a study of the following, or may be learned from is taught in the practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the following description.

附图说明Description of drawings

图1为本发明所述基于1-bit可编程超表面的信号测向系统结构示意图；1 is a schematic structural diagram of a signal direction finding system based on a 1-bit programmable metasurface according to the present invention;

图2为本发明所述可编程超表面与喇叭天线位置示意图；2 is a schematic diagram of the positions of the programmable metasurface and the horn antenna according to the present invention;

图3为本实施例中施加的周期性调制序列示意图；3 is a schematic diagram of a periodic modulation sequence applied in this embodiment;

图4为本实施例中对接收信号进行FFT得到的结果图；FIG. 4 is a result diagram obtained by performing FFT on the received signal in the present embodiment;

图5为通过1000次蒙特卡洛得到的SNR在0至20时的均方误差曲线。Figure 5 is the mean square error curve of SNR from 0 to 20 obtained by 1000 times of Monte Carlo.

具体实施方式Detailed ways

可编程超表面本身为无源器件，作为接收状态使用时，入射信号被施加改变后会出射然后被天线接收。可编程超表面一般配有实时控制器(通常为FPGA或DSP)，其单元可以达到极快的相移响应切换速度，因此可以将时间调制技术引入到超表面的实时控制中以实现测向功能。1-bit可编程超表面是结构最简单、成本最低廉的可编程超表面，其单元能够对入射的电磁波施加0或π的相移。The programmable metasurface itself is a passive device. When used as a receiving state, the incident signal will be emitted after being changed and then received by the antenna. Programmable metasurfaces are generally equipped with real-time controllers (usually FPGAs or DSPs), whose units can achieve extremely fast phase-shift response switching speeds, so time modulation techniques can be introduced into the real-time control of metasurfaces to achieve direction finding functions . 1-bit programmable metasurfaces are the simplest and cheapest programmable metasurfaces, and their units can apply a phase shift of 0 or π to incident electromagnetic waves.

本发明提供了一种基于1-bit可编程超表面时间调制的低复杂度、低成本的信号测向系统。The invention provides a low-complexity and low-cost signal direction finding system based on 1-bit programmable metasurface time modulation.

1-bitM×N可编程超表面可以为透射型或反射型，超表面相邻单元间距一般为半波长λ2，根据超表面的类型，将接收天线置于超表面几何中心正前方(对应反射型超表面)或正后方(对应透射型超表面)，通过馈线与接收机相连。采用控制器施加周期性调制序列，通过快速傅里叶变换(FFT)或离散傅里叶变换(DFT)处理接收信号，解析信号入射方向。在本实施例中，单元天线为贴片天线，接收天线为喇叭天线。The 1-bitM×N programmable metasurface can be either transmissive or reflective, and the spacing between adjacent units of the metasurface is generally half-wavelength λ2. metasurface) or directly behind (corresponding to the transmissive metasurface), which is connected to the receiver through a feeder. A controller is used to apply a periodic modulation sequence, and the received signal is processed through Fast Fourier Transform (FFT) or Discrete Fourier Transform (DFT) to resolve the direction of incidence of the signal. In this embodiment, the unit antenna is a patch antenna, and the receiving antenna is a horn antenna.

1-bitM×N反射型可编程超表面的单元间距为D＝λ2，即半波长，接收天线位于超表面中心正前方，距离为F。如图2所示，在笛卡尔坐标系中，第(m,n)单元的坐标为[(m-(M+1)/2)D,(n-(N+1)/2)D,0]，接收天线坐标为[0,0,F]，则第(m,n)单元与接收天线的距离为The unit spacing of the 1-bitM×N reflective programmable metasurface is D=λ2, which is half a wavelength. The receiving antenna is located directly in front of the center of the metasurface, and the distance is F. As shown in Figure 2, in the Cartesian coordinate system, the coordinates of the (m, n)th unit are [(m-(M+1)/2)D, (n-(N+1)/2)D, 0], the coordinates of the receiving antenna are [0,0,F], then the distance between the (m,n)th unit and the receiving antenna is

入射信号被各单元接收，被1比特单元施加上相移后出射，最后被接收天线接收。假设各单元的方向图为

由于l_m,n导致的路径损耗为a(l_m,n)，则可以求出该超表面和接收天线组成的接收系统的瞬时方向图函数The incident signal is received by each unit, is phase-shifted by a 1-bit unit, and then exits, and is finally received by the receiving antenna. Assume that the direction map of each unit is

Since the path loss caused by lm_,n is a(lm_,n ), the instantaneous pattern function of the receiving system composed of the metasurface and the receiving antenna can be obtained

其中，w_m,n是(m,n)^th单元上移相器的权值，有0和1两种取值，分别对应0和π两种相移。Among them, w_m,n is the weight of the phase shifter on the (m,n)^th unit, and there are two values of 0 and 1, corresponding to the two phase shifts of 0 and π respectively.

一个频点为F_c的正弦信号从

方向入射，θ为俯仰角，

为方位角，θ∈(-π/2,π/2)，

A sinusoidal signal with frequency_Fc from

direction incident, θ is the pitch angle,

is the azimuth, θ∈(-π/2,π/2),

通过FPGA或DSP设备对各单元施加周期性调制序列，在此引入第(m,n)单元的周期性切换函数U_m,n(t)，其值域为{1,-1}，代表0和π两种相移，则公式(2)引入时间维度后，可以得到新的方向图函数A periodic modulation sequence is applied to each unit through FPGA or DSP equipment, and the periodic switching function U_m,n (t) of the (m,n)th unit is introduced here, and its value range is {1,-1}, representing 0 and π two phase shifts, then formula (2) can get a new pattern function after introducing the time dimension

在一个时间调制周期T_p内，函数U_m,n(t)可以表示为In a time modulation period T_p , the function U_m,n (t) can be expressed as

U_m,n(t)满足U_m,n(t)＝U_m,n(t+nT_p)，τ_m,n,on和τ_m,n,off分别表示第(m,n)单元归一化的相移π的开启时间和关闭时间。作为周期性函数，U_m,n(t)可以以傅里叶级数的形式展开为U_m,n (t) satisfies U_m,n (t)=U_m,n (t+nT_p ), τ_m,n,on and τ_m,n,off represent the (m,n)th unit normalization respectively Normalized phase shift π on time and off time. As a periodic function, U_m,n (t) can be expanded in the form of a Fourier series as

α_m,n,k是第k次谐波的傅里叶系数，可以通过下式计算：α_m,n,k are the Fourier coefficients of the kth harmonic, which can be calculated by:

此时分别将基波和一次谐波分量的傅里叶系数代入公式(4)可以表示出接收天线处的基波和一次谐波：At this time, the Fourier coefficients of the fundamental wave and the first harmonic component are respectively substituted into formula (4) to express the fundamental wave and the first harmonic at the receiving antenna:

则可以计算一次谐波和基波分量的比值Then the ratio of the first harmonic to the fundamental component can be calculated

若实际测得的一次谐波与基波的比值为p+qj，我们可以得到等式If the ratio of the first harmonic actually measured to the fundamental is p+qj, we can get the equation

设计各单元的调制函数U_m,n(t)，可以通过求解(11)估计出入射信号的方向

By designing the modulation function U_m,n (t) of each unit, the direction of the incident signal can be estimated by solving (11)

实施例1：Example 1:

本实施例中，测向系统结构如图1到图2所示，接收信号为频点是29GHz的单音信号，1比特20×20反射型可编程超表面的单元间距D等于该频点下的半波长λ/2，接收天线位于超表面中心正前方，距离为5λ。将可编程超表面的人工单元按照行列序号(m,n)编号，根据m、n的奇偶将众多单元划分为4个子阵，如图3所示，控制器向1比特20×20反射型可编程超表面各单元施加的周期性调制序列U_m,n(t)表示为In this embodiment, the structure of the direction finding system is shown in Figures 1 to 2. The received signal is a single-tone signal with a frequency of 29 GHz, and the unit spacing D of a 1-bit 20×20 reflective programmable metasurface is equal to the frequency at this frequency. The half-wavelength λ/2 of , the receiving antenna is located right in front of the center of the metasurface with a distance of 5λ. The artificial units of the programmable metasurface are numbered according to the row and column serial numbers (m, n), and many units are divided into 4 sub-arrays according to the parity of m and n. The periodic modulation sequence U_m,n (t) applied by each unit of the programmed metasurface is expressed as

根据公式(6)可计算出各单元的基波分量和一次谐波分量对应的傅里叶系数According to formula (6), the Fourier coefficient corresponding to the fundamental wave component and the first harmonic component of each unit can be calculated

代入公式(9)就可以计算出一次谐波分量与基波分量的比值Substituting into formula (9), the ratio of the first harmonic component to the fundamental component can be calculated

令make

有Have

若实际测得的一次谐波与基波的比值为p+qj，根据公式(11)可以得到If the ratio of the first harmonic to the fundamental wave actually measured is p+qj, it can be obtained according to formula (11)

由(15)和(17)可以求解出x和y的值，则来波方向的估计值

可由下式计算The values of x and y can be solved by (15) and (17), then the estimated value of the incoming wave direction

can be calculated by the following formula

本实施例基于MATLAB仿真验证了本发明的效果。令信号从(30°，-40°)方向入射，时间调制频率设置为T_p＝1MHz，按信噪比为SNR＝10添加加性高斯白噪声(AWGN)，对接收信号进行FFT得到的结果如图4所示，通过FFT结果中一次谐波和基波的比值，根据公式(16)(17)计算出

表1展示了此参数场景下10次独立测向的结果。This embodiment verifies the effect of the present invention based on MATLAB simulation. The signal is incident from the (30°, -40°) direction, the time modulation frequency is set to T_p = 1MHz, the SNR = 10 is added with additive white Gaussian noise (AWGN) according to the signal-to-noise ratio, and the result obtained by performing FFT on the received signal As shown in Figure 4, through the ratio of the first harmonic to the fundamental wave in the FFT result, it can be calculated according to formulas (16) and (17)

Table 1 shows the results of 10 independent direction finding times under this parameter scenario.

表1Table 1

图5为SNR从0变化至20时，通过1000次蒙特卡洛得到的信噪比(SNR)在0至20时的均方误差(MSE)曲线，可以看出随SNR提高，θ和

估计的均方误差趋近于0，估计精度提高。Figure 5 shows the mean square error (MSE) curve of the signal-to-noise ratio (SNR) obtained by 1000 times of Monte Carlo from 0 to 20 when the SNR changes from 0 to 20. It can be seen that with the increase of SNR, θ and

The estimated mean square error approaches 0, and the estimation accuracy is improved.

本实施例验证了本发明提供的一种基于1-bit可编程超表面的信号测向系统及方法的有效性。This embodiment verifies the effectiveness of a signal direction finding system and method based on a 1-bit programmable metasurface provided by the present invention.

最后说明的是，以上实施例仅用以说明本发明的技术方案而非限制，尽管参照较佳实施例对本发明进行了详细说明，本领域的普通技术人员应当理解，可以对本发明的技术方案进行修改或者等同替换，而不脱离本技术方案的宗旨和范围，其均应涵盖在本发明的权利要求范围当中。Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should all be included in the scope of the claims of the present invention.

Claims (9)

1. A signal direction finding system based on 1-bit programmable super surface is characterized in that: the antenna comprises a 1-bit programmable super surface, wherein M multiplied by N unit antennas are distributed on one surface of the programmable super surface for receiving signals if the programmable super surface is a reflection type, and M multiplied by N unit antennas are symmetrically distributed on two surfaces if the programmable super surface is a transmission type, wherein M is the number of rows of the unit antennas, and N is the number of columns of the unit antennas; the programmable super surface is also connected with a controller used for applying a periodic modulation sequence to the unit antenna; a receiving antenna is arranged at a certain distance from the geometric center of the programmable super surface and is connected with a receiver, and a signal processing module and an angle calculation module are arranged in the receiver; the signal processing module is used for processing a received signal through Fast Fourier Transform (FFT) or Discrete Fourier Transform (DFT); the angle calculation module is used for calculating the direction of the incident signal according to the periodic modulation sequence of each unit antenna and the result of the received signal processing module.

2. A signal direction finding method based on a 1-bit programmable super surface is characterized in that: the method comprises the following steps:

s1: receiving incident signals through each unit antenna on the 1-bit programmable super surface;

s2: applying a periodic modulation sequence to each unit antenna;

s3: each unit antenna applies phase shift to the incident signal and then emits the incident signal to be received by a receiving antenna;

s4: calculating Fourier coefficients corresponding to fundamental wave components and first harmonic components of each unit antenna according to the periodic modulation sequence;

s5: calculating fundamental wave components and first harmonic wave components at a receiving antenna;

s6: obtaining a functional relation between the ratio of the first harmonic component to the fundamental component and the direction of the incident signal;

s7: and calculating the direction of the incident signal according to the ratio of the actually measured first harmonic component to the fundamental component.

3. The signal direction finding method based on the 1-bit programmable super surface of claim 2, characterized in that: in the step S1, the distance D between the unit antennas of the 1-bit programmable super surface is half wavelength, the receiving antenna is positioned right in front of the center of the super surface, and the distance is F; the 1-bit programmable super surface is provided with M multiplied by N unit antennas, wherein M is the number of rows of the unit antennas, and N is the columns of the unit antennas; in the Cartesian coordinate system, the (M, N) th unit antenna has the coordinates of [ (M- (M +1)/2) D, (N- (N +1)/2) D,0]Wherein m represents the number of rows where the unit antenna is located, n represents the number of columns where the unit antenna is located, and the coordinates of the receiving antenna are [0,0, F]The distance l between the (m, n) th unit antenna and the receiving antenna_m,nComprises the following steps:

4. the method of claim 3, wherein the method comprises the following steps: the periodic modulation sequence in step S2 includes:

periodic switching function U incorporating an (m, n) -th unit_m,n(t) having a value range of {1, -1}, representing both phase shifts of 0 and π; modulating the period T at a time_pIn, the periodic switching function U_m,n(t) is represented by

5. The method of claim 4, wherein the method comprises the following steps: in step S3, one frequency point is F_cOf a sinusoidal signal from

The direction is incident, theta is a pitch angle,

theta epsilon (-pi/2, pi/2) as the azimuth angle,

the directional pattern of each unit antenna is

l_m,nThe resulting path loss is a (l)_m,n) After introducing the periodic modulation sequence, the instantaneous directional diagram function of the receiving system formed by the super-surface and the receiving antenna is as follows:

wherein,

representing the gain in the direction of the signal emerging from the respective element antenna into the receiving antenna, d_m,nRepresents the difference in the path lengths of the signals arriving at the respective element antennas, j represents the imaginary sign, and λ represents the wavelength of the incident signal.

6. The method of claim 5, wherein the method comprises the following steps: in the step S4, U_m,n(t) satisfies U_m,n(t)＝U_m,n(t+nT_p)，τ_m,n,onAnd τ_m,n,offRespectively representing the turn-on time and the turn-off time of the normalized phase shift pi of the (m, n) -th unit; as a periodic function, U_m,n(t) is developed as a Fourier series:

wherein alpha is_m,n,kIs the fourier coefficient of the kth harmonic, calculated by:

7. the method of claim 6, wherein the method comprises the following steps: the fundamental component and the first harmonic component at the receiving antenna in step S5 are:

8. the method for signal direction finding based on 1-bit programmable super surface of claim 7, wherein: in step S6, the functional relationship between the ratio of the first harmonic component to the fundamental component and the direction of the incident signal is:

9. the method for signal direction finding based on 1-bit programmable super surface of claim 8, wherein: let the ratio of the actually measured first harmonic to the fundamental wave be p + qj, when dividing all the unit antennas into 4 sub-arrays according to the parity of m, n, the periodic modulation sequence U applied to each unit antenna_m,n(t) is expressed as:

the direction estimate of the incident signal

Calculated from the following formula:

wherein:

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