minimization of side-lobe levels, interference canceling and multiple beam operation without changing the physical architecture of the phased array antenna. Every mode of operation of the digital beam former is created and controlled by means of code written on a programmable device of the digital beam former.
The advances in digital circuitry technology made possible and feasible the idea of implementing the beam forming networks through digital signal processing. Digital Beam forming (DBF) offers advantages in terms of power consumption, flexibility, and accuracy. In general, digital systems tend to consume less power. Phased array antenna designs based on DBF implementation are currently being devised for radar applications [3]. Finally, phased array antennas have been used largely in communication systems [4]. Their capability to change radiation pattern electronically, multi-beam capacity and high spatial.
ARRAY
An array of sensors can be organized in any form in space, where the position of each sensor can be described by a coordinate p = ( px, py,
pz ). If a plane wave signal f (t,p) is arriving at a particular point in space, and the position each sensor in space is different, the signal received by each sensor will be the same original signal with a time-delay, depending on the position of the sensor. The following vector can be used to describe the signal received by each sensor
=
(1)
Where M is the number of elements in the array and τ is a time-delay associated with the position of the element. If the signal f(t,p) generated in space is a far-field planar wave, the equation to describe each signal in the sensor array reduces to
(2)
Where N represents the wave number, w is the frequency of the plane wave; t is a variable representing the time. If the Fourier Transform is applied to the incoming signal in each sensor, the signal in the spectral domain can be represented as:
f(w)v(k)
(3)
The resulting vector v (k) is array manifold vector [5] and it gives
a representation of the position of each sensor with respect to the incidence angle of an incoming plane wave. The incoming signal can be acquired if each sensor is considered a discrete sample in space. The resulting signal can be considered a superposition of all the sensor signal
B(k)=
(4)
If a series of weight are applied to the output of each sensor and superposition is applied to acquire the incoming
plane wave coming from the far-field, the equation for y(t) then reduces to:
y
W=
(5)
SPATIAL FILTDESIGN:
The process of obtaining a geometrical distribution and the coefficients for the weight vector for a beam pattern response is called beam pattern synthesis. In Antenna Theory, the radiation pattern response is constructed based on a realization of an analytical or desired model by an antenna model [6]. The classification of beam synthesis technology is the formation of rule three: optimal beam based on the maximum signal to noise ratio, the minimum mean square error, and linear constrained minimum variance. The three criterion is determined by the algorithm and the most fundamental is the coefficient of determination of weight vector. A popular null placement synthesis technique is the Schelkunoff
polynomial method . The last category of beam pattern synthesis based on spatial response design constraints is the beamwidth-sidelobe behavior. In these techniques, the weight vector coefficients are determined based on the desired behavior of the MRA’s beam width and side lobe level. A common synthesis technique used in the spectral analysis of time series in signal processing is the Spectral weighting technique.
外文资料译文
相控阵天线和相控阵雷达波束形成系统
Dr A. Jhansi rani Lakshmi
摘要
相控阵雷达对于许多未来的任务，如可重复使用运载器（RLV），人类的太空任务，并跟踪空间碎片是必不可少的。相控阵雷达可以实现如多个目标的范围皮肤模式跟踪，机械误差和瞬时光束定位能力的消除等功能。本文呈现了一种基于传感器阵列上的远场的平面波入射的数学模型的发射/接收数字波束形成（DBF）设计。模拟一个DBF发射器和接收器进行控制的4元件的线性阵列的功率模式。对于传感器阵列，两个空间滤波器被构造具有不同的图案要求说明操作的数字波束形成。
关键词：数字波束形成，空间滤波器，Schelkunoff多项式零配置方法，相控阵列天线。
绪论
相控阵天线知名于它对于波束方向图的高效处理能力、设法得到最小的silobe水平和窄波束宽度。实现了从20世纪50年代在很大程度上取决于微波的电路元件如移相器，可变放大器。为了达到如窄波束宽度或相当的扫描范围内具有高的角度分辨率的性能要求，我们需要大量的天线来构建阵列。然而大量微波元件使用对于良好性能也造成了大量障碍以及使相控阵天线的维护过程变得复杂。
相控阵天线设计的另一种方法是使用数字波束形成。数字波束形成包括相移，
数字波束形成
