two dimensional chirp z-transform

Hello All,

     would anyone please give me an illustration how to perform 2D czt in matlab? I use the row-column method used in normal fft to perform 2D czt transform on the Gaussian signal. 
amp=exp(-pi*(X.^2+Y.^2)/w0^2);
tmp2=czt(amp,M,wx,ax);
amp_f2=czt(tmp2.',N,wy,ay);
The result doesn't make sense since Gaussian should remain as Gaussian after czt. 
Originally, I think the signal is required to be shift to assure that zero-frequency is located at [0,0]. Thus, I tried tmp2=czt(ifftshift(amp),M,wx,ax). And the result is weird with many segments of original signal.
      Could any expert give me some suggestions how to achieve it? Thanks for your attentions. 


Regards,
Jennifer