%按照改的坐標系定義 注意幾何關系
clear all;
close all;
clc;
f=200;               %頻率                  改變頻率是沒有用處的 因為d=bochang/2固定
c=1500;               %聲速
bochang=c/f;          %波長
d=bochang/2;          %陣間距
N=5;                 %陣個數                 陣元個數越多 指向性越尖銳 效果越好 
H=60;                 %基陣到海底的深度
tao=0.1;             %重點：脈寬不能太長
%%%%%%%%%%%%%%%%%%%%%%%根據幾何關系
sita=179*pi/180:pi/180:100*pi/180;%基陣主波束與垂直方向夾角
phi=0*pi/180:pi/180:360*pi/180;  %垂直布放,主波束與垂直方向夾角
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
I0=0.001;                 %發射聲強
Iref=0.67*10.^(-22);  %參考聲強
beam=beam_show(f,N);%顯示波束指向性
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
v=0;
zhixiang=zeros(1,91);
%all=0;
for sita=179*pi/180:-pi/180:100*pi/180%指向性也要改
    v=v+1;
    deta=pi-sita;%注意角的意義
    r=H./cos(deta);
    m=(179*pi/180-sita)/(pi/180)+1;
    all=0;
    for i=1:1:(360-0+1)
        B_T=beam(round(m),round(i));%計算發射波束加權值
        all=all+B_T.^2;
    end
    zhixiang(v)=all;
    Ss=reverse(sita);%計算散射系數
    Ib(v)=I0./(r*r*r*r)*all*Ss*r*c*tao./(2*cos(sita-pi/2));
%%%%%%%%%%%%%%%%%%%%%%%%%
end
RL=10*log(Ib/Iref); 
sita=179*pi/180:-pi/180:100*pi/180;
r=H.*tan(pi-sita);
figure(2);
plot(r,RL);
figure(3);
plot(zhixiang);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%造信號
%for sita=179*pi/180:-pi/180:100*pi/180
sita=100*pi/180;%設角度     主波束角度
    rr=H./cos(pi-sita);
    delay=2*rr/c;%此角度回波時間
    mm=(179*pi/180-sita)/(pi/180)+1;
    P=sqrt(zhixiang(mm));
    fs=10*f;
    Ts=1/fs;
    %n=1:0.01*fs;%要求和后面指向性一致
    n=1:0.1*fs;
    signal_T=sqrt(I0)*cos(2*pi*f*n*Ts);
    %signal_T=cos(2*pi*f*n*1/Ts);
    signal_R=P*cos(2*pi*f*(n*Ts+delay));
figure(4);
plot(signal_T);
figure(5);
plot(signal_R);