Design ultralow power, narrow band ADC

Hi,
I want to design an ADC with these specifications:
Fin = 20MHz
BW= 20MHz
ENOB > 4
Power consumption P < 1mW
Could anyone suggest me some ADC for this kind? I have searched a lot in
IEEE but there are only two ADC with SAR ADC and time-interleaved ADC.
The ultralow power consumption makes it hard for me to find a
architecture. I have little experience about this. Kindly help me.

20Mhz is not very narrow band. Nyquist theorem tells you that you need to sample at at leat 40M samples per second, which I doubt will consume less than 1mW.
What exactly do you need to convert? The whole signal, or just amplitude?

kubeek said:

20Mhz is not very narrow band. Nyquist theorem tells you that you need to sample at at leat 40M samples per second..

Click to expand...

And that is just the theory. I would say that you need to sample at least 100M samples per second to get somewhat decent representation of 20Mhz signal.

An relatively easy way to convert high frequencies at low resolution is to use a Flash Converter. But I doubt you can keep the power below a mW with even the best of today's IC processes.

Thanks all for help. Regarding to power consumption, how much power consumption do you think possible, not too difficult to design?
I have found two papers that seem appropriate for the project. Could you take a look and advise?
https://www.mediafire.com/download/bl6bvl3ieesueaa/ADC+papers(2).rar