To find Group delay : Error using diff Difference order N must be a positive integer scalar.
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To find Group delay : Error using diff Difference order N must be a positive integer scalar.
I am trying to find the group delay of a modulated signal , which is derivative of phase delay , but while using diff iam getting this error "Error using diff Difference order N must be a positive integer scalar" , can anyone sugget method to do this
this is the code i tried to do
close all;
dt=.0001;
fs=1/dt; %sampling frequency
fn=fs/2;
n=100;
t=dt*(-n/2:n/2); %time base
f0 = 200; %to modulate GP multifly by cos(2ft*pi)
xt = cos(2*pi*t*f0) .* cos(2*pi*fn*t);
y = hilbert(xt);
m = abs(y);
g = angle(y);
ph = -g/(2*pi*f0);
gd = diff (ph,(2*pi*f0));
figure
subplot(3,1,1);
plot(t,xt,'b');
title('signal');
xlabel('Time(s)'); ylabel('Amplitude');
subplot(3,1,2);
plot(t,ph,'b');
title('phase delay');
xlabel('Time(s)'); ylabel('phase');
subplot(3,1,3);
plot(t,gd,'b');
title('group delay');
xlabel('Time(s)'); ylabel('phase');
2 个评论
Walter Roberson
2021-11-29
ph = -g/(2*pi*f0);
gd = diff (ph,(2*pi*f0));
What was your hope that this would accomplish?
Athullia Emmanuel
2021-11-29
group delay is taken as the derivative of phase delay
so i thought taking differential would give me the group delay of the signal envelope.
采纳的回答
KSSV
2021-11-29
Replace the line:
gd = diff (ph,(2*pi*f0));
with
gd = diff([ph (2*pi*f0)]);
2 个评论
Athullia Emmanuel
2021-11-29
Walter Roberson
2021-11-29
I don't think this is right for the circumstances
更多回答（1 个）
Walter Roberson
2021-11-29
1 个投票
MATLAB has two diff() functions. The one that your equation is for, the calculus derivative, is only used for symbolic expressions and symbolic functions.
The other one applies for all numeric types, and is the successive difference operator, x(2:end) - x(1:end-1) . In the case of equidistant points each 1 unit apart it acts as an approximation of numeric derivative.
As you have numeric data, I recommend that you use gradient(), which does more accurate approximation of numeric derivative.
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