Why Analog continuous time filters are important ?

I want to know why analog filters are important and why still researchers are working on continuous time filters when every thing is almost digital? Where continuous time analog filter be used in what application? If a filter is designed for 10MHz then where it can be used?

They do not alias so are kind of important in front of ADCs (And are a vital part of correctly reconstructing DAC outputs)....

Up in the RF they are more then somewhat important for building radio systems, everything from cell phones to TVs needs both RF and IF filters and of course transmitters need filters to comply with the out of band emissions regulations.

The art of designing high performance radio systems is all about filtering out everything you dont need as early as possible, by the time you digitize signal bandwidths should be a fraction of those at the antenna input.

There are plenty of places where SAW, Crystal and even simple LC network filters are still the best way to solve a problem, and microwave filters designed as PCB geometry can of course have a really attractive BOM cost.

Then we have the fact that a filter can be designed to transform impedances, which can be a huge thing, and indeed you often see LC networks used primarily for this effect (They filter as well, but that is incidental).

Then of course we have unintentional filters, long power grid lines for example can have significant phase shift, and I well remember when grid stability was mostly rule of thumb....

73 Dan.

Hi,

and
* filtering ESD pulses
* Filters to improve EMI and EMC
* crossover in speaker
* bulk capacitors in power supplies
* decoupling capacitors for power supply
* and, and, and..

Klaus

simplsoft said:

I want to know why analog filters are important and why still researchers are working on continuous time filters when every thing is almost digital?

Click to expand...

Because the real world is still analog and nothing seems to change in this matter…

Look at the "overhead" involved in creating a simple 1-pole
filter using digital methods. You need a clock source, a power
supply (or N of them) unrelated to the signal and its source,
ADC, mass memory and a processor and a DAC, and in the
end probably still a dumb ol' analog reconstruction filter at
the DAC output.

Versus a couple or so dirt-cheap passives. And a small fraction
of the board space.

Now more complex filters might make this trade less absurd,
to some extent. And volume pricing can make you think that
a million-gate DSP is the same BOM-cost-wise as a high
quality op amp. But just because you -can- still doesn't
mean you -should-. And there's value remaining in figuring
out the simple elegant approach, rather than letting brute
force, high transistor count have its way.