掃描/線性調頻脈衝信號不正確的頻率

Question

我創建使用MATLAB /倍頻掃描/線性調頻信號結束，我的結束信號，似乎在錯誤的頻率接近尾聲。我該如何修復它，以便信號以正確的頻率結束。

PS：因爲我創建使用特定的方程式線性調頻/掃頻信號，我不能在八度使用啁啾命令。

實施例的代碼與簡單的等式。而問題的情節

%test sweep/chirp 

clear all,clc 
freq1=20; %start freq 
freq2=200; %end freq 
fs=44100; 
dur=1; %duration of signal in seconds 

t = linspace(0,2*pi,fs*dur); 

f=freq1:(freq2-freq1)/length(t):freq2-(freq2-freq1)/length(t); 
%20:(200-20)/lenght(t) :200-(200-20)/length(t) 

data=sin(f.*t); %build signal 
data=(data/max(abs(data))*.8); %normalize signal 
wavwrite([data'] ,fs,32,strcat('/tmp/del.wav')); %export file 
plot(t,data) 

PS：我使用的是八度3.8.1

Answer 1

下面的代碼說明如何生成可變頻率正弦波。

freq1=20; %start freq 
freq2=200; %end freq 
dur=1; %duration of signal in seconds 


freq=@(t)freq1+(freq2-freq1)/dur*t; 
%another example, may help to understand the code 
%dur=2 
%freq=@(t)heaviside(t-1)*10+heaviside(t-1.5)*-9; 
%Integerate over the time-local frequency, gives the average frequency until t which later on gives the sin with the right phase 
%In case you don't have symbolic toolbox, integrate manually. For the given numbers Ifreq=@(x)x.*(x.*9.0+2.0) 
Ifreq=matlabFunction(int(freq(sym('x')))); 
%Defining wave function based on `Ifreq` 
wave=@(t)(sin(Ifreq(t)*2*pi)); 
t=0:.00001:dur; 
plot(t,wave(t));