Filter design for power supply
Have you added decoupling capacitors to all the ICs? add 0.1uF on each supply pin of the ICs, sometimes the datasheet of the component specifies the capacitor that you need and make sure the decoupling capacitors are close to the component.

Also a decoupling capacitor of 22uF or 47uF should be added on the output of the power supply, as noted in the datasheet of the NET-35B using 47uF with 0.1uF will make ripple if you are working on a 20Mhz frequency, a decoupling capacitor would filter noises with high frequency, there is really no rule in the capacitance needed most people add 0.1uF or 0.01uF sometimes they go with what is recommended in the component datasheet, if an IC pulls a very big amount of current such as a mosfet driver you would need to use a 10uF Bulk capacitor in parallel with the 0.1uF the reason for this is that a capacitor has a small resistance which is called ESR increasing the current would increase the voltage for a resistor and this isn't good for our goal, adding a capacitor in parallel is like adding also a resistor in parallel 2 resistors in parallel would decrease the resistance and that means will decrease the voltage, also adding a capacitor with a big capacitance would reduce current swing in and it's good for eliminating low frequency ripples.

If the ripples still occurs you would need a ferrite bead to add on the supply line, the ferrite bead eliminates chosen frequency by varying it's resistance according to the frequency, i can't help you much on this one as you would need to know the frequency you're working with and the frequency you need to eliminate. you can see this link from TI for making DC filter and this link for Choosing and Using Ferrite Beads this link also have previous articles about bypass capacitors.