谁记得这个公式 gain=10log10((（PI*D*D/r）^2)*N)

公式不对吧，r是什么东西?哪里体现频率?

Please clarify the quesion. It is difficult to guess the meaning of the parameters in the formula.

我软件上用积分法计算增益的代码
'************************************
'*计算增益
'************************************
Public Function gine(jihua As Integer, start_point As Integer) As Currency   '计算增益
    'jihua 为极化方式,0--E面,1--H面,2--H面交叉极化,3--临时测试,start_point起始点
    Dim i, j As Integer
    Dim v(2), jifen, jiaodu As Currency 'v(1)为两点电平,jifen为积分值,jiaodu为角度
    
    '移动的点数< 0
    Do While start_point < 0
        start_point = start_point + point_num(jihua)
    Loop
    
    '移动的点数超过总数
    If start_point > point_num(jihua) Then
        start_point = start_point Mod point_num(jihua)
    End If
    
    jifen = 0
    i = start_point
    v(0) = test_data(jihua, i)
    v(0) = 10 ^ ((v(0) - P_max(jihua)) / 20)
    For j = 1 To point_num(jihua)   'E_plane(i)
        i = i + 1
        If i >= point_num(jihua) Then '忽略最后一个点
            i = 0
        End If
        v(1) = test_data(jihua, i)
        v(1) = 10 ^ ((v(1) - P_max(jihua)) / 20)
        v(2) = ((v(0) + v(1)) / 2) ^ 2 '(v(0) ^ 2 + v(1) ^ 2) / 2
        jiaodu = 2 * j * Pi / point_num(jihua)
        jifen = jifen + v(2) * Abs(Sin(jiaodu)) * 2 * Pi / point_num(jihua)
        v(0) = v(1)
    Next
    gine = 10 * Log(4 / jifen) / Log(10)
End Function

公式应该是这样导出的：
gain＝10×log10[4×pi×Ae/lambda^2]
        =10×log10[(pi×D/lambda)^2×Eta]
Eta为效率

多谢楼上几位 几位说的很正确啊 小弟谢过 呵呵

看看，学习一下