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Re: Small and large signal S parameters
On Tuesday, February 12, 2019 at 10:17:21 AM UTC-5, Phil Hobbs wrote:
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Thanks to all for the clarifications. So, for initial
oscillator start up anaysis, manufacturer supplied
small signal S parameters are required, but for  
teady state analysis, large signal S parameters are  
required. Is that correct ?

Re: Small and large signal S parameters
On 2/15/19 12:21 AM, snipped-for-privacy@gmail.com wrote:
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Well, you can use S parameters or SPICE, but you do have to care about  
both large- and small-signal conditions, yes.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
Am 12.02.19 um 02:11 schrieb Clifford Heath:
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Maybe it ceases conducting ofter 0.6 ns, but the
transition is not, eh, snappy.

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Tunnel diodes, SRDs and the like are pretty much extinct.
You can play with nonlinear transmission lines / small varicaps,
I once have made some half-hearted simulations in Spice,
but that resulted in nothing really usable.

You can get that

<  
https://www.flickr.com/photos/137684711@N07/33305853110/in/album-72157662535945536/
   >

from an Analog Devices ADCMP580, with maybe just a NE555
in front of it.

The hardware that generated this is not very noble, just resurrected
it from the junk bin:

<  
https://www.flickr.com/photos/137684711@N07/46353954234/in/album-72157662535945536/
    >

A home-etched tiny board that has ground plane, decoupling and
input terminations. For the signals that count: run them into semi rigid
coax just at the device pin. The board is 0.5mm Bungard pre-sensitized
FR4. If your laser printer can print it on foil, you can etch it.

And no, the Chinese boards are too thick @ 1.6mm and neither cheap nor
fast if there is anything non-standard. I need just a good hour from
layout in the computer to start soldering.

The pinout of ECL/CML chips or op amps is always the same; a few
stamp types let you hack a pulse generator in no time:

<  
https://www.flickr.com/photos/137684711@N07/32981062014/in/album-72157662535945536/
   >

For TDR, get Picosecod Pulse Labs app note an3045C. Now that PSPL
has been bought by TEk, the app notes are no longer on their web site,
but they are still on the site of PSPL's founder. Maybe they mentioned
HP all too often. Grab all of the app notes, they are worth it.

Cheers, Gerhard

Re: Small and large signal S parameters
On 13/2/19 1:37 pm, Gerhard Hoffmann wrote:
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I ran JL's spice and the turn-off time was 0.6ns, after it decided to  
start turning off.

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...> from an Analog Devices ADCMP580, with maybe just a NE555 in front  
of it.

Or an Arduino, since you need something that can digitise the S&H value.

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I get good results from toner transfer. I've done 0.6mm pin spacing.

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To print on using a laser printer? Or to run controlled transmission  
lines at this speed?

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You made the same comment in December 2017 in eevblog forums.
I mirrored from his site <https://kh6htv.com/pspl-app-notes/ but that  
one isn't there. Did it have a different number?

Clifford Heath.

Re: Small and large signal S parameters
On Wed, 13 Feb 2019 16:02:47 +1100, Clifford Heath

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Lower the 50 ohms and fiddle with the generator and the time step and
it can get a lot faster. A real 1N914 won't do that.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Small and large signal S parameters
Am 13.02.19 um 06:02 schrieb Clifford Heath:
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Never tested toner tranfer.
Here, 6/6 mil is no problem. Large black areas are worse. They take some
discipline during exposure. When I need really high resolution like
for microstrip filters I generate .pdf output and have a local print
shop make me a film for offset printing. With that, 4/4 mil design
rules are easy. That used to cost ?5 for a DIN/ISO A4 oversize page,
( abt. letter size++ , true 2400 dpi). Now that they have seen that
I like it, they have double the price, but it's OK.
My Altium Designer generates too small pads in .pdf when they are
rounded squares. :-(

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On 1.6mm FR-4, a 50 Ohm line is 120 mil or so. No way to attach
that correctly to a chipscale package. Let alone a differential pair.

I had PCPway/China made some boards for me. Price was $5 for PCBway @10,
so each board was just 50 cent. $20 or $25 for DHL, depending on moon
phase. Ah, and $2 for Paypal. The actual work is underpaid.

The boards were excellent, but beware: methinks they make the lines  
wider and the spaces smaller to enhance yield. That's usually OK,
but not for transmission lines. But then, there were no transmission
lines.

Time was 1 day for production(they were allowed a week), 4 days for
DHL for transport via HK to Germany and a good week at the Leipzig
customs office, because they choose not to believe the $5 production
cost for 10 pcbs. Each time. No wonder that I prefer etching it myself
when I get away with 1 Layer + ground, if it's small and just a test.


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Yes. Copy & paste error of mine.  Application Note AN-5c
"10 ps Risetime Network TDT and TDR Measurements using the PSPL 15 ps  
Pulse Generator and HP 50 GHz Oscilloscope"
The interesting thing was the junction of generator, scope and DUT.
That is normally hidden in one plug in. The app note removed some
doubts.

regards,
Gerhard

Re: Small and large signal S parameters
On Wed, 13 Feb 2019 13:55:48 +0100, Gerhard Hoffmann

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Have you seen my pics of the SD24 internals? I could post again.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Small and large signal S parameters
On 13/2/19 11:55 pm, Gerhard Hoffmann wrote:
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I haven't tried your method, but other folk have, and found that most  
laser printers have problems fusing toner to a copper sheet - not enough  
heat. But you find it works ok? Perhaps the photoresist has reduced  
thermal conductivity.

I also like to be able to quickly make single-sided boards with solid  
copper backside.

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Right. I haven't used those tiny packages, but generally SMD pads have  
some extra capacitance so I don't mind necking down the trace to meet  
it. A friend simulated this in the past and found that the impedance  
discontinuities acted like a LPF at 10GHz or so, above my max 6GHz  
expectations. But I must try to get some thin double-copper blanks.

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OSHPark is meant to be a very good middle ground between the super cheap  
producers and those of better capabilities.

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No worries, thanks. I must read them again.

Clifford Heath.

Re: Small and large signal S parameters
onsdag den 13. februar 2019 kl. 23.09.15 UTC+1 skrev Clifford Heath:
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I'm assuming the laser printed on overhead film used to expose the pre-sensitized pcb ...  






Re: Small and large signal S parameters
On 14/2/19 9:34 am, Lasse Langwadt Christensen wrote:
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That wasn't clear to me from Gerhard's description:

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"Printing on foil" sounded like printing directly on 0.5mm, but you're  
probably right, and it wasn't.

Re: Small and large signal S parameters
On 2/13/2019 10:06 PM, Clifford Heath wrote:
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I never tried printing on copper because it's really hard on the  
sensitized drum.

I have printed on paper and transferred that to copper with an iron.
The trick is getting the toner to come off the paper onto the copper.
It's VERY sensitive to the type of paper used.  I found certain types
of photo paper worked best...but the next batch of the same paper
brand/type/SKU behaved differently.
The other issue is that you need very thin copper so it etches
before the toner resist comes off.
Not exactly a production process, but I've been able to make
boards for stuff I wouldn't have been able to hook up with wires.

I also tried removing the fuser heater and transferring from paper to  
copper.
Was never able to get the paper to the copper without smudging it.
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Re: Small and large signal S parameters
On 14/2/19 5:42 pm, Mike wrote:
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I have too. It works badly or not at all, smudging some bits and not  
adhering others.

I use a (high temperature) modified laminator, properly warmed up.

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I have paper which was sold for the purpose. It's consistent and has the  
right characteristics.

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I've had no issues with the toner coming off during etch. You might need  
to clean your copper better so it adheres, or use more heat.

The toner can have pin-holes. For best results, laminate the special  
foil after removing the paper layer. The foil covers the pinholes  
without covering features elsewhere.

Clifford Heath.

Re: Small and large signal S parameters
Am 11.02.19 um 21:08 schrieb John Larkin:

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<  
https://www.flickr.com/photos/137684711@N07/47014667932/in/album-72157662535945536/
   >


This is a dirty power supply. With it, you can check in a LTspice noise  
simulation how much dirt you can tolerate on a supply voltage until it  
starts to impair the performance of your amplifier.

The 60 Ohms resistor provides 1 nV / rt Hz. The VCVS amplifies
it to the required level and adds it to clean Vcc.
The 100 nV dc source is only there to avoid a simulator crash.

regards,
Gerhard

Re: Small and large signal S parameters
On Tue, 12 Feb 2019 02:36:03 +0100, Gerhard Hoffmann

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That works in frequency domain analysis, but I don't think that
Johnson and other noise sources can appear in a transient analysis.

I actually built some time-domain voltage noise sources using random
functions. I don't remember why I did that, to make jitter maybe.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Small and large signal S parameters
Am 12.02.19 um 16:30 schrieb John Larkin:
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Yes, I wrote that in my  complaints list, what Spice cannot do.

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regards, Gerhard


Re: Small and large signal S parameters
On 2/12/19 11:24 AM, Gerhard Hoffmann wrote:
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You can make a .wav file of band-limited white Gaussian noise pretty  
easily in Octave--use the Box-Mueller method and the wavwrite()  
function.  <https://p5r.uk/blog/2009/audio-with-gnu-octave.html

LTspice reads and writes them pretty well, I believe.  (I haven't done  
it myself.)

<http://electrostud.wikia.com/wiki/Using_WAVE_files_as_input/output_in_LTSpice

I expect that's how Robert Macy does his .tranoise simulations that he  
posted about in 2014 or thereabouts.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
On Tue, 12 Feb 2019 13:08:10 -0500, Phil Hobbs

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This is a basic noise gen

Version 4
SHEET 1 880 680
WIRE 320 64 128 64
WIRE 368 64 320 64
WIRE 400 64 368 64
WIRE 128 96 128 64
WIRE 320 112 320 64
WIRE 128 208 128 176
WIRE 320 208 320 192
FLAG 128 208 0
FLAG 320 208 0
FLAG 368 64 NOISE
SYMBOL bv 128 80 R0
WINDOW 0 -198 53 Left 2
WINDOW 3 -336 104 Left 2
SYMATTR InstName B1
SYMATTR Value V=random(100*time) - 0.5
SYMBOL res 304 96 R0
WINDOW 0 -59 37 Left 2
WINDOW 3 -56 73 Left 2
SYMATTR InstName R1
SYMATTR Value 1
TEXT -96 64 Left 2 !.tran 5



and this one is more gaussian, fun but kinda overkill.


Version 4
SHEET 1 1484 680
WIRE 208 64 128 64
WIRE 256 64 208 64
WIRE 416 64 336 64
WIRE 480 64 416 64
WIRE 528 64 480 64
WIRE 128 96 128 64
WIRE 416 112 416 64
WIRE 128 208 128 176
WIRE 416 208 416 176
FLAG 128 208 0
FLAG 208 64 RAW
FLAG 416 208 0
FLAG 480 64 OUT
SYMBOL bv 128 80 R0
WINDOW 0 34 107 Left 2
WINDOW 3 -79 203 Left 2
SYMATTR InstName B1
SYMATTR Value V= VS * (  rand(K1*time) + rand(K2*time) + rand(K3*time)
+ rand(K4*time) + rand(K5*time)  + rand(K6*time)   - 3 )
SYMBOL res 352 48 R90
WINDOW 0 63 52 VBottom 2
WINDOW 3 68 54 VTop 2
SYMATTR InstName R1
SYMATTR Value 1
SYMBOL cap 400 112 R0
WINDOW 0 85 22 Left 2
WINDOW 3 63 55 Left 2
SYMATTR InstName C1
SYMATTR Value 1.6e-4
TEXT 736 216 Left 2 !.tran 0 50 0 5u
TEXT 88 -64 Left 2 ;1 volt RMS  1 KHz  Time-domain Noise Generator
TEXT 240 -16 Left 2 ;J Larkin  August 1, 2014
TEXT 704 -64 Left 2 !.PARAM K2 =
TEXT 704 -104 Left 2 !.PARAM K1 =
TEXT 704 -24 Left 2 !.PARAM K3 =
TEXT 704 16 Left 2 !.PARAM K4 =
TEXT 704 152 Left 2 !.PARAM VS =
TEXT 704 56 Left 2 !.PARAM K5 =
TEXT 704 96 Left 2 !.PARAM K6 =


(fix the usenet line wraps)








--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Small and large signal S parameters
On Sat, 9 Feb 2019 03:36:06 -0800 (PST), snipped-for-privacy@gmail.com wrote:

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Think about the Barkhausen criterion, the  total loop gain must be
larger than 1 and the total phase around the loop must be correct.

At oscillator startup, there is always some amplifier  input related
white thermal noise. The amplifier amplifies the noise G times. This
noise is them coupled back to the input via the frequency selective
network with quality Q with correct phase, thus a narrow band noise
with bandwidth f/Q is connected back to amplifier input. The noise is




This continues, until the signal amplitude is limited by the available
voltage swing.

The small signal s-parameters are initially critical, since the
Barkhausen criterions must be satisfied from thermal noise levels up
to limiting.


Re: Small and large signal S parameters
On Sat, 09 Feb 2019 17:52:12 +0200, snipped-for-privacy@downunder.com wrote:

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If the amp's transfer function has the right (ie, wrong) shape you can
make an oscillator that will run but not start.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Small and large signal S parameters
On Sat, 09 Feb 2019 09:22:56 -0800, John Larkin

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Biasing the amplifier into class-C and the oscillator will not
automatically start. Once started the amplification in class C will
kick the resonator once each cycle.  

In practice, such oscillators may start by quickly applying the
operating voltage, which allows some collector current to flow
momentarily. You may end up with an oscillator, which starts nicely
when battery powered but not when mains powered through linear power
supply with big electrolytes :-). With such power supply, the voltage
may start too slowly to initiate the initial cycle.
  

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