The inverse of the continous Fractional Fourier Transform (FrFT)

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Foxy Seif Eddine
Foxy Seif Eddine 2013-9-16
评论： zoubir 2023-2-13
Hello,
I'm trying to use this pre-programmed function of the continuous fractional Fourier transform (FrFT) for 1-D arrays available on this website:
http://nalag.cs.kuleuven.be/research/software/FRFT/
Precisely, the one which is the core of the rest of codes (2D,discret ..etc).
http://nalag.cs.kuleuven.be/research/software/FRFT/frft.m
It takes as entry parameters, a 1-D array to transform i.e: X, and the transform fractional order i.e: a, it works fine for the forward transform
F = FrFT(X,a)
But I couldn't get the inverse transform when I tried to obtain the inverse transform to recover the 1D original array X:
Xr = FrFT(F,-a)
Xr obtained values are completely different from the original X values, can anyone tell me what is wrong here, please?
As far as i know, one of the properties of the FrFT, its inverse is obtained by taking the FrFT of the negatif of its order, i.e FrFT with order -a.
Regards,
  2 个评论
Tzila Ajamian
Tzila Ajamian 2017-3-20
Hello Sir, I'm trying to apply the same work that you tried before 4 years. So can you give me some advices from your experience? Did you reach a solution?
Best regards,
Banhi Das
Banhi Das 2023-1-11
Please help me with the Code of inverse fractional fourier transform

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回答（3 个）

Kritika
Kritika 2014-11-5
hello sir,
Even I am trying to do the same thing but with a different frft code and its result are not coming correct. If you can help me with it then let me know so that i can share my program with you.
  1 个评论
zoubir
zoubir 2023-2-13
Hello sir
i have this prb can u help me
Error using .*
Integers can only be combined with integers of the same class, or scalar doubles.
Error in frft (line 31)
fI(m, n) = 1/sqrt(M*N) * sum(sum(I.*exp(-2*pi*1i*((m-1)*U/(M) + (n-1)*V/(N))).*(abs(U/(M))+abs(V/(N)))^alpha));
then i did the double but the same prb
Error using .*
Integers can only be combined with integers of the same class, or scalar doubles.
Error in frft (line 31)
fI(m, n) = 1/sqrt(M*N) * sum(sum(I.*exp(-2*pi*1i*((m-1)*U/(M) + (n-1)*V/(N))).*(double(abs(U/(M))+abs(V/(N))))^alpha));

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Torben Purz
Torben Purz 2018-10-11
Hello, I think I figured out how to fix this without a lot of work. Just add this line:
if (a<0), a = 2+a; end
above the if(a==0) condition. After applying the inverse transform you need to flip your array then. If you think about it, applying first a (FrFT) and then -a (iFrFT) you end up with a "total" a of 2, so you need to flip your end result.
Hope that helps!
  2 个评论
zoubir
zoubir 2023-2-13
Hello sir
i have this prb can u help me
Error using .*
Integers can only be combined with integers of the same class, or scalar doubles.
Error in frft (line 31)
fI(m, n) = 1/sqrt(M*N) * sum(sum(I.*exp(-2*pi*1i*((m-1)*U/(M) + (n-1)*V/(N))).*(abs(U/(M))+abs(V/(N)))^alpha));
then i did the double but the same prb
Error using .*
Integers can only be combined with integers of the same class, or scalar doubles.
Error in frft (line 31)
fI(m, n) = 1/sqrt(M*N) * sum(sum(I.*exp(-2*pi*1i*((m-1)*U/(M) + (n-1)*V/(N))).*(double(abs(U/(M))+abs(V/(N))))^alpha));

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aaru sri
aaru sri 2019-1-21
i m also trying vsame thing but not getting its inverse correct

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