Sigma Delta converter : NTF synthesis

[mickey_melomane]

sigma delta ntf synthesis

Hi...

I used the Schreier Sigma Delta toolbox to design my NTF of order 3...

How do I realize the loop filter in an easily implementable way!!! I mean without using CIFF or CIFB architectures..?

Moreover, I am trying to do the bandpass modulator for GSM as well with order 4...
In which case, my sampling frequency is four times 70M (GSM IF) = 280 MHz.
Can I choose the sampling frequency as merely twice the signal bandwidth (200kHz.)? That relaxes my opamp unity gain bandwidth!!! I find it very tough to obtain a 90dB+ gain with UGB>280MHz...

Need some inputs please...

Sidharth. B

 

[bless_fooling]

ntf converter

the IF seems too large if you use sigma delta modulator .maybe not so fit to use sigma delta modulator you can consider pipeline ADC