Small and large signal S parameters

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Could some electronics guru here help clarify the following.
Small signal S parameter amalysis is based on small signal  
levels and a linearized cirucuit, with a DC operating point(bias) condition.  
Large signal S parameter extends this scheme to high power
operating conditions of non-linear devices, where the  
assumptions of small signal do not hold. Large signal  
S parameter scheme is based on harmonic balance, which  
involves analyzing the signals in the frequency domain.
i.e., Forier transforms.  
Both schemes use a 2 port network, with the signal entering
at the inpit("from") port and coming out at the output("to")
port.
With these in mind, what about oscillators ? These are
one port networks, with a 2 port component (amplifier)
in it. So are large and small signal S parameters  
applicable to oscillators ? Amplifiers are ripe for
large signal S parameters. For that matter, are the S
parameters quoted for older RF|micrwave transistors  
small or karge signal S parameters ?

All hints/suggestions are welcome. Thanks in advance.

Re: Small and large signal S parameters
Am 09.02.19 um 12:36 schrieb snipped-for-privacy@gmail.com:
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Yes. It's currently Gospel that large signal s-parameters are
required for oscillator design. Oscillators are inherently
nonlinear since there must be some limiting / gain control
or the amplitude would collapse or explode otherwise.

I don't see that so extreme. I got the the point where the
crystal phase noise is all that matters without HB.


In the Agilent world, look for x-parameters.

Here are some papers from Rohde; he is a mass publisher
so it will be redundant.
There is more interesting material on the synergy microwave web site.

Older s-parameters should be small signal, esp. when there is
only bias given and no levels.

I'm just trying to determine myself if I could use harmonic
balance to simulate the noise behavior of a chopper amplifier
or if that is too non-linear. I'm still struggling with
importing spice models.

cheers,
Gerhard

<  
https://depositonce.tu-berlin.de/bitstream/11303/1306/1/Dokument_16.pdf

<  
https://www.unibw.de/technische-informatik/mitarbeiter/professoren/large-signal-oszillator-noise-analysis-then-and-today-2.pdf
  >

<   https://synergymwave.com/articles/2013/04/full_article.pdf

<  
https://www.mes.tu-darmstadt.de/media/mikroelektronische_systeme/pdf_3/ewme2010/proceedings/sessionvii/hartnagel_slides.pdf
 >




Re: Small and large signal S parameters
On Saturday, February 9, 2019 at 7:31:54 AM UTC-5, Gerhard Hoffmann wrote:
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It certainly is the Gospel to use large signal S  
parameters, but things are changing rapidly. A new
breed of bi-junction transistors(e.g., HFA3134 -  
Renesas Semiconductor) with a transition frequency  
of 8 GHz(well in the RF/microwave range) DOES NOY
require the use of S parameters at all. The easily
downloadable data sheet does not contain any S parameters. I have used it to SPICE simulate common emitter/base feedback/negative resistance oscillators
upto 2 GHz. No issues at all.

My design scheme is simple.  
1. AS a real-world oscillator cannot be expedted to  
dump all the signal energy at the design frequency, define a set of tolerances (e.g., 5%) on the first
n (3 - 4) harmonics.  
2. Compute passive component values e.g., for a common  
emiiter feedback oscillator, with a simple C program
(to remove silly calculation errors) and then SPICE
simulate it with transientr analysis.
3. Fourier transform transient analysis output, and
compute power spectrun and check if the frequencies
corresponding to the first n(3 - 4) highest peaks fall  
within the predefined tolerances. If not, adjust  
resonator component values and iterate through the  
above steps till tolerances ae satisfied - convergence.
If yes, task is complete.

I do have a copy of Rohde's 2005 book on microwave  
oscillator design, but suffers from the same  
problem as books on this topic by others(Grebennikov,
Ludwig Bretchko, Pozar etc.,) hundreds of pages of
theory.  
    
We do have ADS at work, but most of us think that  
the learning curve is very steep, and the results are
very non-intuitive.

Thank you very much for the URLs _ I will definitely
look through them.

Re: Small and large signal S parameters
On 2/9/19 6:36 AM, snipped-for-privacy@gmail.com wrote:
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The first thing an oscillator has to do is to start up.  It's initially  
in the small signal condition, so the resonator + small signal S params  
have to be unstable.  So you can't ignore them.

Gerhard knows more RF than I do, so I'll let him carry on. ;)

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
Phil Hobbs wrote...
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 I'd just like to add that small-signal analysis can be
 very useful in large-signal situations.  For example,
 I'm working on designing high-voltage amplifiers with
 power MOSFETs.  These are capable of fast slewing and
 high power levels, with excursions of hundreds of volts,
 and high currents into capacitive loads.  At first it
 appeared that small-signal measurements and analysis
 would not be so useful.  But then I realized that when
 the circuit was non-linear, slewing, delivering current,
 I'd use the appropriate analysis, i = C dV/dt, etc.,
 but after it was done slewing, it'd be the steady-state
 condition that was most important, and most of my effort
 went into solving the equations for that, and using them
 to make the design rock solid.  I made sure the amplifier
 would then be operating class-A.  This scheme worked well,
 and I created a simple inexpensive design for a 1200-volt
 DC power amplifier that has a -3dB bandwidth of 1 MHz.
 It's gratifying to see the amplifier perform well, fast,
 powerful, yet stable, with low measured phase shifts at
 1MHz and beyond, so that with a transducer, it can work
 well in a wideband servo.  Small-signal analysis rocks!

 BTW, at these frequencies, I wasn't using s-parameters.


--  
 Thanks,
    - Win

Re: Small and large signal S parameters
On 2/9/19 9:29 AM, Winfield Hill wrote:
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Yup.  The math isn't hard, and (when both approaches apply) one formula  
has more information than a week's worth of simulations.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters

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In switch mode power supply design and use, this is known as "slow  
start" of "hard start".  If one punches the start of some  
oscillators too hard the initial swing does not start and the  
oscillator 'latches up' and the circuit start fails. In many cases  
that input needs to be dampened or led or lagged to achieve a "soft  
start" condition that ensures that the oscillator always starts.

Re: Small and large signal S parameters
On Saturday, February 9, 2019 at 7:50:43 AM UTC-5, Phil Hobbs wrote:
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It depends on the type of oscillator one is looking at.  
A differential oscillator, by its very nature, does not need any transistor biasing, and so it does not matter
if the S parameters are used or not.  
In addition, for the new breed of transistors(e/g/.  
HFA3134 from Renessas Semiconductor) the datasheet DOES NOT list ANY S parameters. With a fT of 8 GHz, it  
would work very well in the RF - microwave frequency range.

Re: Small and large signal S parameters
On 2/11/19 6:44 AM, snipped-for-privacy@gmail.com wrote:
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Sure.  It has a super-detailed SPICE model for both the device and the  
package parasitics, which is going to be more useful than S parameters.  
You can generate S parameters from the model, but going the other way is  
a lot more complicated.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
On Mon, 11 Feb 2019 10:30:48 -0500, Phil Hobbs

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Anything really interesting is going to be nonlinear, so may as well
Spice.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Small and large signal S parameters
Am 11.02.19 um 19:06 schrieb John Larkin:
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Unfortunately, nonlinear analysis in Spice is quite meagre.
You just get transient analysis and that's it. OK, add FFT from
the post processor.

For noise and frequency response analysis, the circuit is linearized
around the operating point, so it is small signal only by definition.

No nonlinear noise, no harmonic balance, no large signal frequency response.

I would not get very far determining the noise characteristics of my
chopper amplifiers. How could it linearize the circuit in the presence
of the chopp clock and the continuous switching?

How do I determine the noise level of an amplifier that is near
compression? That is the normal case in the sustaining amplifier
of an oscillator.

How could I see the jitter induced by noise or self heating?
Transient simulation is noise free.

How do I simulate a SRD frequency multiplier? Cannot. There
is no concept of carrier lifetime in Spice. No PIN diodes.
Oh, 1N4007 is a PIN diode. (the others in the series aren't)

cheers,
Gerhard



Re: Small and large signal S parameters
On Mon, 11 Feb 2019 20:16:04 +0100, Gerhard Hoffmann

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I have added time-domain noise sources to LT Spice, but that's hack.
Spice is great for large-signal, time-domain stuff.

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You had me scared for a minute there. A stock 1N914 sure behaves like
an SRD. Probably unrealistically so.


Version 4
SHEET 1 880 680
WIRE 112 128 80 128
WIRE 176 128 112 128
WIRE 304 128 240 128
WIRE 320 128 304 128
WIRE 80 160 80 128
WIRE 320 176 320 128
WIRE 80 288 80 240
WIRE 320 288 320 256
FLAG 80 288 0
FLAG 320 288 0
FLAG 112 128 IN
FLAG 304 128 OUT
SYMBOL diode 176 144 R270
WINDOW 0 -42 34 VTop 2
WINDOW 3 -53 33 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 304 160 R0
WINDOW 0 56 36 Left 2
WINDOW 3 55 69 Left 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 80 144 R0
WINDOW 0 -146 33 Left 2
WINDOW 3 -264 72 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 5 10Meg)
TEXT 552 216 Left 2 !.tran 200n
TEXT 448 128 Left 2 ;1N914 Reverse Recovery
TEXT 512 176 Left 2 ;JL  Feb 11  2019






--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Small and large signal S parameters
On 12/2/19 7:08 am, John Larkin wrote:
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LTSpice says the snap-off time is circa 0.6ns.
What have you measured in real devices?

What other non-SRD device would you choose for a fast step-recovery  
pulse generator, e.g. in a hobby TDR? (aside from fast logic e.g. CML,  
TinyLogic, that I'm already aware of)

Clifford Heath.

Re: Small and large signal S parameters
On Tue, 12 Feb 2019 12:11:23 +1100, Clifford Heath

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Well, a CML gate or comparator is about perfect. The TEK SD24 used a
set of current-steering diodes. There's a patent somewhere.


One can build a fast but ratty TDR and use a fairly simple
deconvolution program to make it pretty.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Small and large signal S parameters
On 2/11/19 8:11 PM, Clifford Heath wrote:
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ChesterW and I built a 100-ps-class single-diode TDR with a BOM of about  
$2, using a pHEMT driven by a line receiver and a very small Schottky  
diode, all done dead-bug style.  'Tweren't as clean as an SD-24, of  
course, but it was surprisingly good for what it was.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
On 13/2/19 2:17 am, Phil Hobbs wrote:
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I've been paying close attention to JL's fast ramp generators, CML  
drivers and discussions on LVDS receivers to know where to start  
tinkering, but I would be stumbling around, not engineering it. I'm very  
envious of you having enough sekrit sauce and the right test gear to do  
it, especially so cheaply, because I'd love to put something like that  
out into the maker community. But I didn't ask for details because it's  
your livelihood. I reckon I could stumble to 500ps without much more  
than what I have, and any result beyond that would be randumb luck.

So (beggar holds out his bowl), any further tips are welcome.

Clifford Heath.

Re: Small and large signal S parameters
On Wed, 13 Feb 2019 08:09:37 +1100, Clifford Heath

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I have a circuit, and a built board, for a TDR that might be in the 40
ps range. The step generator is a CML comparator, and the sampler is a
fast ecl D-flop, working in slideback/single-bit mode. I never got
around to making it work.

The parts are a tad expensive, but 100 ps is do-able cheap, as Phil
notes. 100 ps is about as slow as you'd want to go for PCB work.

There was also a TDR student project at SF State, which I sponsored.
It used an SRD for the step and a classic 2-diode sampler. One of my
guys was on the team, as a student, and he may have the paper still.
I'll see. After he did that, I hired him.

I also have a PowerBasic program that does targeted deconvolution,
namely designs a software FIR filter that makes an ugly TDR step into
a pretty one.

https://www.dropbox.com/s/iqpldbkq2awdeml/TDR_Decon_demo.jpg?dl=0


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Small and large signal S parameters
On 2/12/19 4:09 PM, Clifford Heath wrote:
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I can't post the full schematic because it belongs to the customer, and  
because Chester designed the delay generator part, but the speedy bits  
of a slightly earlier version are at

<
https://electrooptical.net/www/sed/DiodeSamplerSchematic.png


   It was the first TDR I ever built, so it's not like there's that much  
at stake. ;)

Here's a mildly redacted version of the simulation, without the  
customer's device attached to the sampling line at top right.

<
https://electrooptical.net/www/sed/DiodeSampler.png


and the measured TDR response
<https://electrooptical.net/www/sed/PulseResponseOfSamplerProto.pdf

It works a lot better with a pHEMT like an ATF55143 at Q4.  Probably one  
of the Mini-Circuits SAV series would be a drop-in substitute, but I  
haven't had the opportunity to check.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Small and large signal S parameters
On 13/2/19 10:32 am, Phil Hobbs wrote:
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Many thanks, Phil. Quite a bit more complexity in the receive amp than  
I'd expected. Looks like the voltages written at Q4 might be wrong -  
1.66 right but 1.9V should be 1.66-Vbe or about 1V? I see why you were  
complaining about fast PNPs becoming EOL! You have a lot of fast stages  
before the T&H - not easily reducible?

Clifford Heath.

Re: Small and large signal S parameters
On 2/12/19 11:29 PM, Clifford Heath wrote:
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A fast op amp such as an ADA4817 would have worked fine for the back  
end, but would never have been as cheap as the discrete version. ;)

The BFT92 was replaced by a bootstrapped pair of MMBT3906es, which  
worked just as well in this instance.  For the given application, it  
turned out that making the transducer cleaner was cheaper than using  
70-cent pHEMTs anyway, so fortuitously they wound up with some fast NPN  
in place of the EOL ATF55143.  IIRC the eventual performance was closer  
to 250 ps and the jitter was around 10 ps.

For super low cost, all-discrete designs are still often a win.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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