what is this error: Unexpected MATLAB expression?? andhow can i fix it???

Dear Sir,

I am looking to make radar system by using the chirp generator (to generate chirp signal as sawtooth signal from low to high frequency). I will use the operational amplifier as part of my research work to make amplification to sawtooth signal so I made search in the internet to learn how I can make operational amplifier by the Matlab. After long time, I found something can help me in how i can make inverting amplifier by Matlab circuit where it is nearest to the operational amplifier that I will use in my research work. After I made run to this program by the matlab that I found there is error " Unexpected MATLAB expression". I would like to know "Where is the error in this program to fix it and making changing in some commands in this program to use it in my research work??"

I would like to help me as soon as possible...

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This is the matlab code:

R1=10e3; % resistance, ohms
R2=20e3; % resistance, ohms
R3=20e3; % resistance, ohms
R4=20e3; % resistance, ohms
R5=20e3; % resistance, ohms
% op amp parameter
vsat=15; % saturation voltage,V
% source parameters
M=3; % amplitude, V
f=1000; % frequency, Hz
w=2*pi*f; % frequency, rad/s
theta=(pi/180)*45; % phase angle, rad
tf=2/f; % final time
N=200; % number of increments
t=0:tf/N:tf; % time, s
vs = M*cos(w*t+theta); % input voltage
for k=1:length(vs)
Y=[ 1/R2, 1/R2 + 1/R3 + 1/R4; % nodal admittance matrix
0, -1/R3];
J=[-vs(k)/R1 0 ]; % input current vector
V=J/Y; % node voltage vector
vo(k)=V(2); % record the output voltage
if (vo(k)>vsat) vo(k)=vsat; % check for saturation
elseif (vo(k)<-vsat) vo(k)=-vsat;
end
end
plot(t, vo, t, vs) % plot the transfer characteristic
axis([0 tf -20 20])
xlabel('time, s')
ylabel('vo(t), V')

Answer 1

[Sean de Wolski]

If you run that, what line does the error occur on? You are likely missing a ')', ']' or '}' or similar.

[Mohamed Elwakdy]

Dear Sean,

Thank you very much on your interesting....

The error is from line 23 to 25:

line 23: vo(k)=V(2); % record the output voltage

line 25: elseif (vo(k)<-vsat) vo(k)=-vsat;

[Sean de Wolski]

Line 25 is not valid. If you would like to have the conditional be vo(k)<-vsat and if this is the case then set vo(k) equal to vsat6 you will need a comma, semicolon, or new line:

elseif (vo(k)<-vsat), vo(k)=-vsat;

Note, you could replace this if statement with

vo(k) = max(vo(k),-vsat)

[Mohamed Elwakdy]

Dear Sir,

Thank you very much on your interesting...

I made the steps that you said but I have the same problem so I would like to make sure that I fix the mistakes such you want:

This is mat. file after changing:

for k=1:length(vs)
Y=[ 1/R2, 1/R2 + 1/R3 + 1/R4; % nodal admittance matrix
0, -1/R3];
J=[-vs(k)/R1 0 ]; % input current vector
V=J/Y; % node voltage vector
vo(k)=v(2); % record the output voltage
if (vo(k)>vsat), vo(k)=vsat; % check for saturation
vo(k) = max(vo(k),-vsat)   
%elseif (vo(k)<-vsat), vo(k)=vsat6;
end
end

Thank you very much

[Sean de Wolski]

No. You would have to remove both components of the if-statement in order to use min/max to perform the saturation.

vo(k) = max(vo(k),-vsat);
vo(k) = min(vo(k),vsat);

Now remove all components of the if-statement.

doc max
doc min

for more information.

[Mohamed Elwakdy]

Dear Sean,

I removed both the if-statment and I am still have the same error:

This is mat. file after changing:

for k=1:length(vs)
Y=[ 1/R2, 1/R2 + 1/R3 + 1/R4; % nodal admittance matrix
0, -1/R3];
J=[-vs(k)/R1 0 ]; % input current vector
V=J/Y; % node voltage vector
vo(k)=v(2); % record the output voltage
%if (vo(k)>vsat), vo(k)=vsat; % check for saturation
vo(k) = min(vo(k),vsat);
vo(k) = max(vo(k),-vsat)   
%elseif (vo(k)<-vsat), vo(k)=vsat6;
end

Thank you very much

[Sean de Wolski]

dbstop if error

Will stop on the line that throws the error. Then run that line piecemeal to find out what part is broken.

[Mohamed Elwakdy]

Dear Sean,

I made such as your told me and I found the error in this line:

vo(k)=V(2);

I do not know "What is the probelm here so i would like to help me to fix this error??"

Thank you very much

[Sean de Wolski]

Does the above expression work?

[Star Strider]

I copy-pasted the posted code to a test file and ran it. It ran without an error.

[Mohamed Elwakdy]

Dear Sean,

Thank you very much on your helping....

With your helping, I can fix the problem...

Thank you very much

Have Great and Fantastic Day

[Greg Heath]

I had no prolems when I cut and pasted your code.

What version of MATLAB do you ave?

[Mohamed Elwakdy]

Thank you very much, Sean...

I have Matlab Version 2008