Forums

half-sine

Started by John Larkin April 26, 2016

I need to Spice a pretty good Gaussian pulse. So I'm thinking square
pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait,
will Spice make somethig better as the starting point? Duh, it will
generate a half-sine.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg

That should be a lot easier to filter than a pulse.

Any other ideas for making a nice Gaussian pulse?

I'm simulating the reflection off a particle zipping through a laser
beam, to test the sort-of-constant-fraction discriminator.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

On 04/26/2016 03:30 PM, John Larkin wrote:
> > > I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg > > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse? > > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator.
Well, the FT of a Gaussian is another Gaussian, so you don't need too many sinusoids to do a good job. Depends on the rep rate you want, of course, but you can always cut one pulse out with switches. Another approach would be to use the LTspice switch with negative hysteresis, which makes a nice smooth differentiable curve. Apply a constant voltage across the switch, stick a triangular pulse into the control input, and subtract off a little of the triangle to cancel the cusp in the output. It won't be perfect, of course, but then neither will the laser beam (especially if it's from a diode). 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
On Tue, 26 Apr 2016 12:30:09 -0700, John Larkin wrote:

> I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/
Half_Sine.jpg
> > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse? > > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator.
Uh -- use the equation for a Gaussian in a behavioral source? Or do you need to launch the pulses at arbitrary times? Version 4 SHEET 1 880 680 WIRE 160 160 160 96 WIRE 160 272 160 240 FLAG 160 272 0 FLAG 160 96 Vpulse SYMBOL bv 160 144 R0 SYMATTR InstName B1 SYMATTR Value V=exp(-((200 * (time - 0.02))**2)) TEXT 126 296 Left 2 !.tran 0 50m 0 10u -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On 26.4.16 22:30, John Larkin wrote:
> > > I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg > > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse? > > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator.
Sine squared, or better, cosine squared might be a better starting point. -- -TV
On Tuesday, April 26, 2016 at 3:30:15 PM UTC-4, John Larkin wrote:
> I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg > > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse?
You mean a pulse that looks like a Gaussian distribution... the bell curve. Or something with Gaussian filter. Hmm I guess the two are the same... https://en.wikipedia.org/wiki/Gaussian_filter Well if the pulse response of a Gaussian filter is the Gaussian distribution, Then hit your filter with a (narrow) pulse and not a 1/2 sine. George H.
> > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator. > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
On Tue, 26 Apr 2016 14:46:29 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:

>On Tue, 26 Apr 2016 12:30:09 -0700, John Larkin wrote: > >> I need to Spice a pretty good Gaussian pulse. So I'm thinking square >> pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, >> will Spice make somethig better as the starting point? Duh, it will >> generate a half-sine. >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/ >Half_Sine.jpg >> >> That should be a lot easier to filter than a pulse. >> >> Any other ideas for making a nice Gaussian pulse? >> >> I'm simulating the reflection off a particle zipping through a laser >> beam, to test the sort-of-constant-fraction discriminator. > >Uh -- use the equation for a Gaussian in a behavioral source? Or do you >need to launch the pulses at arbitrary times? > >Version 4 >SHEET 1 880 680 >WIRE 160 160 160 96 >WIRE 160 272 160 240 >FLAG 160 272 0 >FLAG 160 96 Vpulse >SYMBOL bv 160 144 R0 >SYMATTR InstName B1 >SYMATTR Value V=exp(-((200 * (time - 0.02))**2)) >TEXT 126 296 Left 2 !.tran 0 50m 0 10u
Well, that's approximately perfect. Thanks. I don't use Spice enough to use all the tricks. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 26.04.2016 21:30, John Larkin wrote:
> > > I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg > > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse? > > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator.
Better yet: instead of a half sine, use a full sine. Offset the sine by +1, start it from -90 degrees and run it to 270 degrees phase, that will likely need less filtering. Dimitrij
On Wed, 27 Apr 2016 22:07:45 +0200, Dimitrij Klingbeil
<nospam@no-address.com> wrote:

>On 26.04.2016 21:30, John Larkin wrote: >> >> >> I need to Spice a pretty good Gaussian pulse. So I'm thinking square >> pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, >> will Spice make somethig better as the starting point? Duh, it will >> generate a half-sine. >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg >> >> That should be a lot easier to filter than a pulse. >> >> Any other ideas for making a nice Gaussian pulse? >> >> I'm simulating the reflection off a particle zipping through a laser >> beam, to test the sort-of-constant-fraction discriminator. > >Better yet: instead of a half sine, use a full sine. > >Offset the sine by +1, start it from -90 degrees and run it to 270 >degrees phase, that will likely need less filtering. > >Dimitrij
See... <http://www.analog-innovations.com/SED/MyRealPulse.png> and "RealPulse.pdf" on the Simulation Tools & Macros Page of my website. ...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 | The touchstone of liberalism is intolerance
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
> > > I need to Spice a pretty good Gaussian pulse. So I'm thinking square > pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, > will Spice make somethig better as the starting point? Duh, it will > generate a half-sine. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg > > That should be a lot easier to filter than a pulse. > > Any other ideas for making a nice Gaussian pulse? > > I'm simulating the reflection off a particle zipping through a laser > beam, to test the sort-of-constant-fraction discriminator. > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com > >
You could use Python or Matlab to generate the Gaussian and write it to a .wav file and use that as input... -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
On Sat, 30 Apr 2016 08:34:04 -0400 (EDT), bitrex
<bitrex@de.lete.earthlink.net> wrote:

>John Larkin <jjlarkin@highlandtechnology.com> Wrote in message: >> >> >> I need to Spice a pretty good Gaussian pulse. So I'm thinking square >> pulse and a biggish, like 6 pole, Bessel lowpass filter. But wait, >> will Spice make somethig better as the starting point? Duh, it will >> generate a half-sine. >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Spice/Half_Sine.jpg >> >> That should be a lot easier to filter than a pulse. >> >> Any other ideas for making a nice Gaussian pulse? >> >> I'm simulating the reflection off a particle zipping through a laser >> beam, to test the sort-of-constant-fraction discriminator. >> >> >> -- >> >> John Larkin Highland Technology, Inc >> picosecond timing precision measurement >> >> jlarkin att highlandtechnology dott com >> http://www.highlandtechnology.com >> >> > >You could use Python or Matlab to generate the Gaussian and write > it to a .wav file and use that as input...
Tim's B source that depends on the TIME variable is perfect for the simple Gaussian. The .wav thing would be good for something more complex. -- John Larkin Highland Technology, Inc lunatic fringe electronics