Need to create a generator that shift in freq. and amplitude over time ranges

Question

Mark 2012-6-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/40877-need-to-create-a-generator-that-shift-in-freq-and-amplitude-over-time-ranges

Hi,

I wanted to create a sin generator that runs say 25 MHz for 30 msec with amplitude of 0.7 volts and then shifts to 78 MHz with 1.4 V amplituded for 150 ms and shifts to 50 MHz with 2.3 volt amplitude for another 100 ms.

I can not find a block that does that. So I went to do this via a matlab function block.

I wrote the following function:

function y = fcn(u1,u2)
%#codegen
Fs = 100;
% a vector of points in thetime ontervai 0<t<T
T = 10;
ts = Simulink.BlockDiagram.getSampleTimes('astor_my_test')
t = 0:1/Fs:T;
if (t  < 25) 
y = u1;
else 
    y= u2;
end

However, when I go to build the code, it says that only scalar is allowed in the if statment. So, I need to bring in sim time as an input. But, I can not find a way to bring in current time or make a comparison.

Is there an easy way to do this so that based on sim time, the output would be generated from a different function? I tried the switch block. but again, I got stuck creating the switch input as it does not undrestand the notion of time.

Thanks for your help