Can anyone suggest the best way to implement "low-pass filter modulation" which removes high frequencies in square (or compound) waves at the specified rate per second?
In addition to hardware, is there a DSP software application that can perform this function?
Not totally sure what you mean. A lowpass with controllable cutoff? That would be called a tracking filter and is customary on ultrasound machines and radar. Tracking means that the cutoff is scooted so you reduce bandwidth for echoes originating farther away from the transducer/antenna, IOW trading off signal bandwidth versus SNR.
I'll have to leave that question to others but you haven't mentioned frequency ranges.
1) DSP IIR filter with coefficents moved in real time based on this sine wave
2) switched cap filter where the clock frequency is moved based on this sine wave
3) tracking filter using variable transconductance amplifiers with the sine wave altering the transconductance.
4) fixed LPF and some sort of mixer scheme where the baseband is mixed up then down with an offset. The only reason this would work is the source is noise, so the frequency offset shouldn't be an issue. There is a dual of this using DSP.
Hey if that's what he wants, this looks like the perfect place to use the Voltage coefficient of the ZU5 (YU7 whatever the 'crappy' ones are.) tantalum caps. Except I'm not sure how to make it work at DC for his low pass filter.
Haven't found out how (yet). I am using Thunderbird. It does have a white-listing method for email but when trying to use that for a news account the feature is grayed out :-(
Yeah, but I am not going through the hassle just because of one provider with sub-par ethics. Interestingly, it seems that (very few) of your posts get chopped by my new news provider. Like the one with the topic "IE crap". Maybe their filter took offense with the wording :-)
Also, in foreign NGs it seems hardly anyone uses the gmail domain anymore because there are never gaps in threads like here on s.e.d.
Anyhow, why would people have to use gmail when there are so many better option including free ones?
No worries Joerg, I've been thinking of signing up at 'eternal- september.org' they give free access to Usenet. And then I can have access to all the sages at SED.
George H.
PS. would someone please respond so Joerg can 'see it' Thanks Geo
I think the term "low pass modulate" is extremely misleading, if not just plain self-contradictory.
You want to apply the signal to a low-pass filter with a modulated corner frequency (maybe).
I'm with 'miso' -- there are a lot of ways to do this, choose the one that's best. Think about what's important to you, and make sure you understand the issues -- some filter topologies will 'pump' the signal at the modulation frequency, some won't, some (if not all) may not pump some classes of signals but will pump others.
Maybe so but it's the same company and it was spewing spam like crazy. Until I deep-sixed it, after that it became nice and quiet in all the groups I follow. I wrote to them, didn't even get a response and nothing was done about it, so ...
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