The types of filters used to prevent aliasing in ADC's in theory are called Nyquist filters, which define the stop bandwidth fSTOP must be <= 1/2 of the sampling rate.
The implementation however is a tradeoff between distortion from noise above fSTOP , group delay distortion in the passband, amplitude ripple in the passband and degree of complexity with higher order filters.
The names for different filters have existed for many decades such as
Cauer, Gaussian, Chebychev etc. Each is optimized for one of these tradeoffs.
First you define , the signal and then the noise to determine what is critical for the filter properties, such as ;
- limits of
bandwidth, normally the 3dB fBW,
- the
ripple in the passband, which increases in cycles according to higher order filters but the amount of ripple is traded off with steepness of the skirts of the filter
- one measure is the ratio of fstop to fBW or in other words the slope in dB/Hz.
-
non-linear phase shift in the passband and its derivative time delay if unequal which produces jitter on the data edges,
- linear phase filters are often used for data filters.
- A special class of these have ringing with zero jitter at the time interval boundary where all data pattern zero crossings coexist called
Raised Cosine filters.
For analog data, where voltage accuracy is desired, then the lowest ripple in the passband is traded off with the order of filter like 5,6 or 7th order filters for telephony to get 3.5kHZ bandwidth in an 8KHz sample rate. Ripple of 0.5dB, 1dB 2 dB 3 dB are examples in the passband.
The bandstop depth is determined by the desired accuracy, SNR, ADC resolution etc so fSTOp may be specified for example as 60,80, 100dB or something in between.
SAW filters are useful for creating very high order order filters with one of these characteristics due to tight process control unattainable with 5% passive components or even 1% parts.
This is what your specification show look like, which is the first step to define with upper and lower tolerances on each value.
1. Passband Ripple [dB]
2. fBW [f, -3dB]
3. fSTOP [f, dB]