Electronics > Projects, Designs, and Technical Stuff
Analog Filters: a Compilation of Standard Transfer Functions (UPDATED 2)
RoGeorge:
--- Quote from: Dunckx on March 28, 2021, 10:28:14 pm ---I have just discovered that Zverev's "Filter Synthesis" book is out of copyright and may be downloaded from the Internet Archive for free!
https://ia803101.us.archive.org/20/items/HandbookOfFilterSynthesis/Handbook%20of%20Filter%20Synthesis.pdf
HTH
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Great handbook I didn't know before, thank you! :)
It even shows the "N-Path mixer"/"PolyPhase Mixer" at page 35/586, "Fig.1.33 The Digital Filter", recently discussed in
https://www.eevblog.com/forum/rf-microwave/polyphase-or-n-path-mixer/
--- Quote from: Zverev's "Filter Synthesis" ---A method having the dimensions of a genuine breakthrough is shown in Fig. 1.33. Here the mech-anical commutators, shown schematically, would be replaced in practice by transistor diode analog-gates driven by conventional logic circuits at an angular velocity, co0. The identical RC circuits have a lowpass response which is so modified by the sampling action that VJV2 exhibits a related bandpass response centered at a>0. This method shows promise of yielding figures for Q and stability which have pre-viously been obtainable only with crystal filters. Definite results on the performance of this device will be available soon, but it is too new to be evaluated at present.
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mawyatt:
Yes, even Zverev referred to this commutating filter, which even predates Zverev's classic reference book by a few years!! However, these Discrete Time Continuous Amplitude (DTCA) filter concepts for other uses evaded general discovery until the Tayloe's Detector in the late 90s and then the PolyPhase, or N-Path Mixers ~2008. We did employ the DTCA commutating filter (as well as DTCA Chirp-Z techniques for Real Time SA) techniques in the early 80s for a narrow band tunable RF filter, but it took another 20~30 years for "other" uses of this very powerful technique to emerge!
Best,
teletypeguy:
For just getting to work on a filter without all the synthesis, Analog Devices has an awesome tool:
https://tools.analog.com/en/filterwizard/
Define low/high/bandpass and passband/stopband needs, and boom you get a schematic. Not only can you view mag/phase... you can specify cap and resistor tolerances and see the sensitivity envelope. The recommended opamps are ADI, of course, but you can look up the gain-bandwidth and such to determine substitutions for each stage. Plug it all into ltspice and fine tune. ADI make great components, though I am more partial to ti opamps as they are usually cheaper than adi for the same performance, and cmos opamps (eg: opa2376) are finally getting into the realm of really low noise for low-power/low-volt applications.
KRISTOFFER:
I had a play with this a year back for use in my guitar amplifier. Without getting into the maths, if you want an active steep slopped high pass, low pass or bandpass filter you will get to a point where there is an unwanted peak just before the slope. In audio, the peak looks bad on paper but to the human ear it is pretty much undetected. In my case it was to attenuate everything below 120 hz before any distortion. But, a bit like any classic guitar amplifier with trebble middle and bass controls, you will be on for ever tweaking it then listening to it and chasing your tail.
precaud:
--- Quote from: mawyatt on February 02, 2021, 06:39:39 pm ---For specific filter types, like Butterworth, Bessel, Chebyshev, Cauer and so on, Zverev's Handbook of Filter Synthesis is a great resource.
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Confession: That is the only book I have ever stolen from a library and never returned (40 years ago).
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