More on retina and vision

Exactly. AM produces sidebands alongside the carrier, not harmonics. The more agressive the modulation waveform, the wider the sideband spread.

A perfect laser beam is a perfect sine wave with infinite autocorrelation distance. Modulate it with a fast gaussian pulse, and you get a soft tone burst with sidebands and a short correlation distance. Which is why radars don't use sine waves to measure distance; too many ambiguities.

There are attosecond lasers that make just a few cycles of optical sine wave. An incoherent LED is a cheap option.

One of the great revelations in my life was a 1-semister EE course at Tulane, Signals and Systems. I should write an essay or maybe a book about S+S. It's very important.

This is OK,

One has to wonder why. The process of gating it down to a finite width is multiplying by a narrow pulse which has all frequencies up to with width of the pulse. You certainly don't get just two sidebands - that is what you get when you multiply two pure sine waves.

I wonder what John means by "aggressive"?

The side-bands are spread by the modulation frequency, The higher the frequency of the modulating sine wave, the the further the two sidebands are above and below the carrier frequency

Lots of sidebands, because a fast guassian pulse has a very wide fourier transform - lots of frequencies, up to the limit set by the width of the pulse, and down to the limit set by its repetition rate,

Somebody who knew how to spell semester might be a better candidate, as would somebody who knew something about the subject.

It clearly didn't tell John as much as he needed to learn.

On a sunny day (Tue, 01 Nov 2022 05:34:45 -0700) it happened John Larkin snipped-for-privacy@highlandSNIPMEtechnology.com wrote in snipped-for-privacy@4ax.com:

Jeroen already gave the correct answer, modulate with a gaussian. bit different from your 'femtosecond monochromatic pulse'

EEEH Python snake language BAD Radio and teefee is all about spectra, even the old US NTSC color system is a very interesting thing.

I have heard of maaz but am just a neural net,

I think someone else may have suggested that too.

Maybe not.

Some do - almost. Chirp radars use a frequency swept sinewave.

John

Sure, but the autocorrelation function of that chirp is a narrow spike, which is what you need to get good range resolution.

Jeroen Belleman

Then there is FMCW, originally for radar altimeters in airplanes.

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Joe Gwinn

I knew a guy who patented an HF navigation system sort of like Loran, but the transmitters sent pseudo-random modulated RF, the idea being that a cross-correlating receiver could distinguish the ground wave and ignore ionosphere paths. Same idea, really.

Sadly, he invented that just as GPS was ramping up.

Am 05.11.22 um 01:04 schrieb John Larkin:

Looks like he re-invented GPS, only at frequencies that do not work well for BW reasons.

Gerhard

The ranging modulation on the Apollo program operated below 1Mbaud, yet was still capable of ranging accuracy getting down to 1 metre - which meant they could achieve phase locking within 2-3 degrees after correlation. So it's not clear to me that HF is out of the question for accurate positioning.

Clifford Heath.

BTDT. I have done PN generation, modulation, demodulation, ranging by cross correlation + sweeping for some TV and phone sats.

Gerhard