% 畫圖看看sinc函數
figure;
plot(0:0.01:5,sinc(0:0.01:5));grid on;
% 下面用數值方法計算主瓣
A_main_lobe = 0.01*abs(sum(sinc(0:0.01:1)));
% 下面用數值方法計算第壹旁瓣
A_side_lobe = 0.01*abs(sum(sinc(1:0.01:2)));
% 下面用計算主瓣面積/第壹旁瓣面積
ratio = A_main_lobe/A_side_lobe