DonR
Major Contributor
Is that something he does with the homeless?
Is that something he does with the homeless?
You might not use 1 million sine waves, but the frequency content must be there to look "square'ish".
Sure but digital data rates are up to 100Hz now!I could only find about 1,100 discrete frequencies in the 10Hz square I measured, of course I was bandlimited...
Theres a dozen ways to modulate a digital signal for transmission, voltage swings is one.Yeah, digital audio is transferred by voltage swings if you use a coaxial connection. USB probably works differently (but in the end its still based voltage changes). Optical has no voltage swing of course.
I'm pretty sure Darko understands this, but he is just peddling nonsense because that can make him more money.
Again, I would respectfully disagree. I do not need the “squareish” look only, I need rise time and fall time of the square wave shorter than 10ns. 10ns rise time is 35MHz corner frequency, 1ns means 350MHz. Why? Because square is to investigate stability. And you may get into troubles even at frequencies between 10 MHz (power amp) to 300MHz (preamp with diamond buffer). Again, I speak based on real circuits, real experience, not just to debate. And for the same reason I am not much interested in a school type lecturing debate.You might not use 1 million sine waves, but the frequency content must be there to look "square'ish"
Yes but I want rise time 10ns and shorter. 35MHz BW at least. Squares generated by any audio DAC are good for fun only. They are useless for stability investigation. This is the key, you guys only think in low frequency perspective, thus talking about synthesis of a square from sines and created by audio DAC. You need fast impulse generator, not the DAC.I could only find about 1,100 discrete frequencies in the 10Hz square I measured, of course I was bandlimited...
I guess I got my kick in the nuts afterall. What I was trying to explain was PCM but its hard when I started out with a stupid asumption which fucked it all up. I will shut my mouth and go back to school about this.I am not sure what this means. A "digital" signal is a sequence of bits (bitstream) that could in general be any pattern, e.g. 10101... or 100011011111000111... or whatever. Most high-speed serial interfaces recover the clock from the data stream, obviating the need for a separate clock line and attendant need to synchronize clock and data lines. Many standards (SAS, SATA, PCIe, etc.) encode the bitstream to prevent long runs of 1's or 0's that can cause the clock recovery circuit to lose lock (get out of synch with the signal) -- a PLL needs frequent transitions (edges) to phase-lock to the signal. There is not a carrier in the sense of an RF modulated signal that mixes LO (carrier) and IF/baseband signals to produce an RF output (or vice versa in the receiver).
How to make a square wave: https://www.audiosciencereview.com/.../composition-of-a-square-wave-important.1921/
AES or S/PDIF, as well as the aforementioned protocols, send a bitstream using a reference clock for Tx and the receiver recovers the clock from the signal. I2C and I2S are example of protocols that have an explicit, separate clock line.
FWIWFM - Don
That is not in disagreement with the composition of a square wave, e.g. the frequency bandwidth (content) needed to provide the desired risetime. And my data (measured, not just theoretical) showed signal content commensurate with the risetime as one might expect. Limiting the bandwidth leads to things like the Gibbs Effect, which is a real-world, measurable, observable phenomenon. I do in fact have real-world experience with real circuits, including the square-wave generator I built and mentioned that had ps edges, but this is going nowhere and is off-topic so I'll drop it.Again, I would respectfully disagree. I do not need the “squareish” look only, I need rise time and fall time of the square wave shorter than 10ns. 10ns rise time is 35MHz corner frequency, 1ns means 350MHz. Why? Because square is to investigate stability. And you may get into troubles even at frequencies between 10 MHz (power amp) to 300MHz (preamp with diamond buffer). Again, I speak based on real circuits, real experience, not just to debate. And for the same reason I am not much interested in a school type lecturing debate.
Ah, I suspected as much after rereading your post. Carry on. I've already been accused of being a schoolboy lecturer without real-world experience so I think I'd best stay out of this thread. I'm busy testing some 32 Gb/s devices and trying to explain to a customer why adding a couple feet of cable thoroughly mucks up a 22.5 Gb/s signal that is supposed to be measured at the pins of the device. Sometimes I wish I was back in school.I guess I got my kick in the nuts afterall. What I was trying to explain was PCM but its hard when I started out with a stupid asumption which fucked it all up. I will shut my mouth and go back to school about this.
Lol. Good luck with that! IT pays good I bet, you have to comfort yourself with that when they make you do stuff. Dream about the hifi stuff u could buyAh, I suspected as much after rereading your post. Carry on. I've already been accused of being a schoolboy lecturer without real-world experience so I think I'd best stay out of this thread. I'm busy testing some 32 Gb/s devices and trying to explain to a customer why adding a couple feet of cable thoroughly mucks up a 22.5 Gb/s signal that is supposed to be measured at the pins of the device. Sometimes I wish I was back in school.
Not in IT, analog circuit design and test, don't get me started on our IT department's imaginative means of blocking productivity ("takes a computer")...Lol. Good luck with that! IT pays good I bet, you have to comfort yourself with that when they make you do stuff. Dream about the hifi stuff u could buy
Of course, I am not as knowledgeable, but isn't Fourier analysis just a mathematical dissection of a square wave into virtual sine waves of odd harmonics?The link was specifically about the "Composition of a Square Wave". If you have a better explanation of square wave composition than the sum of odd harmonics, I'm all ears
Exactly! For the testing purposes that needed shortest impulse edges, we used avalanche transistors to switch (short) DC via a resistor and got a sub-nanosecond edge. For testing high current shunts, mercury wet realy was used to do a similar job.if one wants to imagine a square wave as an infinite number of sine waves, as a means or aid of calculations, they may do so, but a square wave is composed of nothing but DC getting switched off and on FAST!
Of course, I am not as knowledgeable, but isn't Fourier analysis just a mathematical dissection of a square wave into virtual sine waves of odd harmonics?
A square wave is a square wave, as he correctly states:
View attachment 247279
A square wave is not composed of anything but DC that switches on or off, of course one can create a facsimile of a square wave using sine waves, but just because a piece of glass can be shattered into millions of smaller triangular or otherwise pieces, the reverse is not true!
i.e. , claiming the glass was originally compromised of those smaller pieces.
The act of shattering the glass creates the smaller pieces, just a filtering a square wave, creates the sine waves!
I state that @pma is spot-on about square waves, if one wants to imagine a square wave as an infinite number of sine waves, as a means or aid of calculations, they may do so, but a square wave is composed of nothing but DC getting switched off and on FAST!
Isn't it a question of Horses for courses ?I ran an engineering and compliance certification team at a major telecom company, which included EMI, RFI and Signal Integrity engineering for very high speed core and peripheral equipment.
In that role, there’s no such thing as a digital signal…it’s high speed analogue.
In fact, one of the most significant and frequently analyzed changes we would make to emerging designs was to add limiting resistors onto data lines with excessively fast risetime, so that the unnecessary highest order harmonics of the “digital” signal don’t bounce back and forth such that a zero or one cannot be reliably detected.
So in my space, it is just analogue.
Aha!Mathematics is like that: if you have two equivalent representations of the same signal, these representations are both valid and can be used interchangeably. Neither one is "the one correct" representation. Just because DC switching is easier to understand and use in practice, doesn't make the Fourier representation any less valid.
It depends on speed, and the basic principle is that where possible you should limit the bandwidth of the signal you send so that the ability of the far end receiver to detect a valid one or zero is maximized. That essentially means you don’t want to send a mathematically perfect square wave, because that would degrade that ability of the far end to detectIsn't it a question of Horses for courses ?
Under certain applications (i.e. long cabling, Telecom, very high data rates etc. ..) it is practical to think of everything as analogue as anything that can cause a problem in an analogue domain, can and will have an impact on digital transmission too.
But narrowing it down to a short USB or SPDIF cable, or anything that maybe used in a Hifi environment, then those analogue problems become insignificant, and one can treat the transmission as Digital.
Of course, if the cable being used happens to be so bad and substandard that the problems become noticeable, it should not be an excuse to say transmission was analogue.
Well, here is a question that might help.Aha!
But isn't Fourier analysis an approximation? After all, sine wave components approximate a square wave, but never actually make it.
Staying with mathematics, a perfect square wave does exist, but a composition of sine waves keeps getting closer and closer to a perfect square wave, and indeed one needs an infinite number of them.
Using switches (transistor, relays or even a push button) to create a square wave, one starts with DC , where are the sine wave components?
There aren't any!
Now if you filter that, you create the sine waves, just like my glass example.