Normalized tables for filter design must annoy you. w_c=1, R=1, L and C are near 1.
Similarly, many (most) modern synthesis tools use the LP Proto method (parameters normalized about "1") in the background. The tool user simply doesn't see it.
Right, most filter books, like Williams, normalize filters to w=1 and
1 ohm, so the simplest double-terminated Butterworth has C=1.414 and L=1.424.Must annoy the hell out of him.
We have the NuHertz passive filter design software. It will make all sorts of filter forms at a specified impedance and frequency using all standard values; I can't imagine how he manages that.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Summing two filters together doesn't do anything sacred.
vo/vi* = ((s/(s^2 + bs + c)) + (s/(s^2 + ds +e))
Cross multiply and you get a 4th order denom and third order numerator. It is just a filter. Factor out an s in the numerator and you can see it is still a bandpass. No surprise there.
But if you need a 4th order filter, well, just design a 4th order ladder. The bandpass filter summation simply isn't interesting to anyone skilled in filter design.
Yeah, this design could actually generate some zero crossings. I'm still shaking my head at this farce.
Miso, you're being a bit dense, you know. The design requirement was unusual but not unreasonable, despite needing a narrow region of negative group delay. Can you do that with a ladder filter?
Unusual requirements leading to unusual solutions makes it interesting to folks who like to learn stuff.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
"Any" dispersion can theoretically do that, and there is always dispersion unless all transmission is pure TEM. The better the bandpass filtering, th e lower the probability.
Put a rectangular wave (vary the duty cycle) through it and see if you can manage to get such a hitch. I'd like to see it.
To even contemplate a hitch, the harmonic content has to be very high, and the band pass filtering very poor.
Of course, any slope reduction at the zero crossing can increase phase nois e. That is one of the trade-offs in deciding whether to filter or not in t he first place, because a properly maintained rectangular wave has a very h igh gradient through the "zero crossing." (More than a sine wave.)
Miso is just saying that there exists an ordinary 4th-order filter that behaves in the same fashion as the "summation" architecture... I'm sure his math proves that.
I've determined a whole series of Q and separation pairs that satisfy a spot of flat-phase... parameterization is a wonderful simulation tool.
I suspect there's a flat-amplitude version also with a flat-phase "spot", but I haven't gotten back to this particular problem... busy writing up IP descriptions for yet more patents in my dossier ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
It was to me. Develop the ladder equivalent.
Taking off on your last circuit post, I experimented with a ladder approach . Prima facie (meaning with reservation), I would say "yes." Network anal ysis is unique. Network synthesis is not unique. Admittedly, I have not t aken the transfer function from your (or John's) circuit, obtained a drivin g point function, and then performed a strict synthesis into a ladder netwo rk.
folks who like to learn stuff.
Exactly. This was interesting, which is perhaps surprising, since in one s ense it seemed so elementary.
Cool. He should post one. Or since it's so easy, you could do it.
I'm glad you are getting into the idea, instead of just trashing it.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Sure. It was the "simply isn't interesting to anyone skilled in filter design" bit that I was pinging him for. His comment from a day or two ago that he was "always 100% on-target" might have been gentle self-mockery, but the two taken together makes it seem unlikely somehow.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
This from the guy who accused me of violating the laws of thermodynamics because I wanted a bandpass filter with a region of no phase shift.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
I didn't say it couldn't be done. I just fail to see the practical usefulness of a narrow region of flat phase. That's why I asked you for a demo illustrating the benefits. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I generally don't see miso posts unless someone, as you did, replies to his posts >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
You didn't exactly say it couldn't be done, but you did zing John for allegedly not reading or understanding my (completely erroneous) nonexistence proof, so you fell into the "causality implies no negative group delay" trap the same way I did, and others did. C'mon in, the water's fine. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I have a use for it, but that's not the point. I thought it was kind of cool to have the flat spot, or an upward hickey and negative group delay.
Don't be such a grouch.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Is it warm ?:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I'm not. If you can show a beneficial response I'll steal the idea
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I guarantee that the Second Law of Thermodynamics is observed at all times, at least in my vicinity. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
-Lasse
. . .
-- http://www.youtube.com/watch?v=-m6PEKX4SIw
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