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简易点目的的雷达相差方程,基于MATLAB的雷达时

2019-08-27 08:51

举个例子,考虑一个峰值发射功率为1千瓦的X波段雷达和波束宽度为1°的笔形波束天线,假设在10公里距离接收到一个雷达散射截面为100平米的巨型喷气式飞机的回波。

2.2.2.分布式目标的距离方程

As an example, consider an X-band radar with a peak transmitted power of 1 kW and a pencil beam antenna with a 1°beamwidth, and suppose an echo is received from a jumbo jet aircraft with anRCS of 100 m2at arange of 10 km.

2.2.2. Distributed TargetForms of the Range Equation

接收的雷达回波功率可用式确定。

并不是所有的散射现象都能被模拟为来自单点散射源的反射。

The received power can be determined usingEq. .

Not all scattering phenomena can be modeledas a reflection from a single point scatterer.

天线增益可由式估算为G = 26000/= 26000 = 44dB。

例如,地杂波最好建模为来自表面的分布式散射,而天气现象则建模为来自三维体的分布式散射。

The antenna gain can be estimated from Eq. to be G = 26,000/ = 26,000 = 44 dB.

Ground clutter, for example, is bestmodeled as distributed scattering from a surface, while meteorologicalphenomena such as rain or hail are modeled as distributed scattering from athree-dimensional volume.

图片 1

雷达距离方程可以用一种通用的方法重新推导,这种方法适用于所有三种情况。

虽然这个例子是一个近程大型目标,但接收的回波功率只有3.07nw,比发射功率小近12个数量级!

The radar range equation can be rederivedin a generalized way that accommodates all three cases.

Even though this example is a large targetat short range, the received power is only 3.07 nW, nearly 12 orders ofmagnitude less than the transmitted power!

式仍然可用作推导的起点。

尽管如此,在许多情况下,这种信号水平足以进行可靠的检测。

Equation is still applicable as astarting point.

Nonetheless, this signal level is adequatefor reliable detection in many cases.

考虑分布式散射问题,由于天线增益随方位角和俯仰角变化,式必须替换为另一个方程,从而考虑天线功率方向图P(θ, ϕ)在特定方向(θ, ϕ)上辐射的功率密度,即:

这个例子说明了雷达在发射和接收信号功率之间观察到的巨大动态范围。

To consider distributed scatterers, andbecause the gain of the antenna varies with azimuth and elevation angle, Eq. must be replaced with an equation that accounts for the effect of theantenna power pattern P(θ, ϕ) on the power density radiated in a particulardirection (θ, ϕ):

This example illustrates the huge dynamicranges observed in radar between transmitted and received signal powers.

图片 2

式的一个重要结果是,对于点目标,回波接收功率随着从雷达到目标距离的四次方减小。

假设天线视距方向对应于θ =ϕ = 0。

An important consequence of Eq. isthat for a point target, the received power decreases as the fourth power ofrange from the radar to the target.

Assume that the antenna boresightcorresponds to θ = ϕ = 0.

因此,探测给定雷达横截面目标的能力随着距离的增加而迅速降低。

天线视距通常是最大增益的轴方向,因此P = G。

Thus, the ability to detect a target of agiven radar cross section decreases rapidly with range.

The antenna boresight is normally the axisof maximum gain so that P = G.

雷达探测距离可以通过增大发射功率来提高,但是由于R4的依赖性,功率必须增大16倍,才能使探测范围扩大一倍。

现在考虑距离和角度坐标(R,θ, ϕ)上增量体积为dV的散射情况。

Range can be increased by increasingtransmitted power, but because of the R4dependence, the power mustbe raised by a factor of 16 just to double the detection range.

Now consider the scattering from anincremental volume dV located at range and angle coordinates (R, θ, ϕ).

或者,天线增益增加4倍,意味着天线面积增加了4倍。

假设体积单元的增量RCS为dσ平方米,dσ一般随空间位置变化。

Alternatively, the antenna gain can beincreased by a factor of 4 , implying an increase in antenna area by afactor of 4.

Suppose the incremental RCS of the volumeelement is dσ square meters, and that dσ in general varies with position inspace.

另一方面,“隐形”飞机和其它目标车辆的设计者必须将RCS降低16倍,才能将给定雷达系统检测目标的距离减半。

dV的后向散射功率增量为

On the other hand, designers of"stealth" aircraft and other target vehicles must reduce the RCS σ bya factor of 16 inorder to halve the range at which they can be detected by a given radar system.

The incremental backscattered power from dVis

距离方程是雷达系统设计和分析的基础工具。

图片 3

The range equation is a fundamental radarsystem design and analysis tool.

如前所述,dσ的定义是假设该散射功率是各向同性的,然后由天线有效孔径接收,并根据到达角进行调整变化。

该方程的更详细或更专业版本可以被表述为显示其它变量的影响,例如脉冲长度、中频带宽或信号处理增益。

As before, dσ is defined such that it isassumed this power is reradiated isotropically, and then collected by theantenna effective aperture, adjusted for the angle of arrival.

More elaborate or specialized versions ofthe equation can be formulated to show the effect of other variables, such aspulse length, intermediate frequency bandwidth, or signal processinggains.

在替换有效孔径并考虑损耗后,这会导致接收到的增量功率

在Richards等人的书中给出了几种不同的变化形式。

After substituting for effective apertureand accounting for losses, this results in an incremental received power of

Several such variations are given inRichards et al. .

图片 4

距离方程也为雷达系统的标定提供了依据。

同样,该功率是在电磁波传输2R/c秒后接收到的。

The range equation also provides the basisfor calibrating a radar system.

Again, this power is received 2R/c secondsafter transmission.

如果对系统功率、增益和损耗进行了仔细的描述,则可以计算出已知RCS测试目标的预期接收回波功率。

通过对空间所有的电磁波进行积分得到总接收功率,从而获得一个通用的雷达距离方程。

If the system power, gain, and losses arecarefully characterized, then the expected received power of echoes from testtargets of known RCS can be computed.

The total received power is obtained byintegrating over all space to obtain a generalized radar range equation.

根据这些信号处理技术,可以增加有效接收功率,从而增加可探测的距离范围;校准表格数据由观察到的接收机电压组成。

图片 5

Calibration tables equating receivervoltage observed due to those signal processing techniques can increase theeffective received power, and therefore increase the obtainable range.

式中,被积分的体积V包括整个三维空间。

每种技术对回波接收功率的影响将在后面的章节中介绍。

In Eq. , the volume of integration Vis all of three-dimensional space.

The effect of each technique on receivedpower is discussed as they are introduced in later chapters.

然而,来自所有距离的后向散射能量并不能同时到达雷达。

——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing(Second edition)》

However, the backscattered energy from allranges does not arrive simultaneously at the radar.

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如第1.4.2节所述,只有在距离分辨率单元ΔR内的散射体对任何给定时刻的雷达接收机输出有显著贡献。

As discussed in Sec. 1.4.2,only scatterers within a single range resolution cell of extent ΔR contributesignificantly to the radar receiver output at any given instant.

因此,更合适的通用雷达距离方程形式给出了接收回波功率随时间变化的函数为:

Thus, a more appropriate form of thegeneralized radar range equation gives the received power as a function of time

图片 7

其中,ΔR是以距离R0为中心的分辨率单元,Ω表示角坐标上的积分。

where ΔR is the range interval of the resolutioncell centered at range R0and Ω represents integration over theangular coordinates.

——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing(Second edition)》

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