微带原理.doc

天线阵的方向系数书中给出的概念我还是可以理解的，现在想了解下这个公式是怎么得来的，
公式中分母中的全空间积分表示什么？是整个此天线的整个空间功率能量？分母除以4π（r的平方）表示单位面积的平均功率能量？，分子除以（r的平方）表示什么？

记得西电教材的天线原理有讲，公式推导比较全面。

请做天线阵的专业人士来解答一下吧

这个公式就是天线方向性的公式，天线阵方向性与天线方向性的定义没有区别，就是某方向辐射电磁波的能力与全方向辐射电磁波的总能力之比。

R平方是在分母上被约掉了，跟分子没关系吧。

请做天线阵的专业人士来解答一下吧

楼主应该先了解方向性系数的概念，是天线在某点的的辐射强度与相同辐射功率的全向性天线在同一点的辐射强度的比值。然后楼主再想想辐射功率如何求的，不是在整个空间对辐射强度进行积分吗，然后再利用全向性天线辐射强度和辐射功率的关系。
这样是不是可以理解那个式子了？

6.3  N-ELEMENT LINEAR ARRAY: UNIFORM AMPLITUDE
AND SPACING
Now that the arraying of elements has been introduced and it was illustrated by the
two-element array, let us generalize the method to include N elements. Referring to the
geometry of Figure 6.5(a), let us assume that all the elements have identical amplitudes
but each succeeding element has a月progressive phase lead current excitation relative
to the preceding one( beta represents the phase by which the current in each element leads
the current of the preceding element). An array of identical elements all of identical
magnitude and each with a progressive phase is referred to as a uniform array. The
array factor can be obtained by considering the elements to be point sources. If the
actual elements are not isotropic sources, the total field can be formed by multiplying
the array factor of the isotropic sources by the field of a single element. This is the
pattern multiplication rule of (6-5), and it applies only for arrays of identical elements.






  Since the total array factor for the uniform array is a summation of exponentials,
it can be represented by the vector sum of N phasors each of unit amplitude and
progressive phase业relative to the previous one. Graphically this is illustrated by the
phasor diagram in Figure 6.5(b). It is apparent from the phasor diagram that the ampli-
tude and phase of the AF can be controlled in uniform arrays by properly selecting
the relative phase    between the elements; in nonuniform arrays, the amplitude as
well as the phase can be used to control the formation and distribution of the total
array factor.
  The array factor of (6-7) can also be expressed in an alternate, compact and closed
form whose functions and their distributions are more recognizable. This is accom-
plished as follows.
Multiplying both sides of (6-7) by  , it can be written as



If the reference point is the physical center of the array, the array factor of (6-10)
reduces to




For n=N, 2N, 3N,.…(6-l0c) attains its maximum values because it reduces to a
sin(0)/0 form. The values of n determine the order of the nulls (first, second, etc.). For
a zero to exist, the argument of the arccosine cannot exceed unity. Thus the number
of nulls that can exist will be a function of the element separation d and the phase
excitation difference月.   The maximum values of (6-lOc) occur when











Figure 6.16   Linear array of N isotropic elements positioned along the x-axis.

   N-ELEMENT LINEAR ARRAY: UNIFORM AMPLITUDE
AND SPACING

最基本的概念啦，可以看看书，比在论坛上搞得清楚啦

非常感谢，各位的指导，受教了，{:soso_e100:}

shoucnagla!

你的理解是对的

找本经典的 天线教程 看看就明白了

方向系数和增益的定义是根据辐射强度得出，辐射强度是建立在立体角的概念上的。所以就没有R。
全空间积分代表的就是天线的辐射能量。

方向系数和增益的定义是根据辐射强度得出，辐射强度是建立在立体角的概念上的。所以就没有R。
全空间积分代表的就是天线的辐射能量。