LTSpice: Complex numbers?

[Joerg]

Folks,

Is there a way to coax LTSpice to display complex numbers in the form of
x+jY (or x-jy if leading phase)?

--
Regards, Joerg

http://www.analogconsultants.com/

[Jim Thompson]

On Thu, 06 Jun 2013 18:11:29 -0700, Joerg <inv...@invalid.invalid>
wrote:

>Folks,
>
>Is there a way to coax LTSpice to display complex numbers in the form of
>x+jY (or x-jy if leading phase)?

You probably can't get an Algebraic display like that, but you should
be able to display, for example...

Real(V(1))

and

Imag(V(1))

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85140 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Joerg]

Joerg wrote:
> Folks,
>
> Is there a way to coax LTSpice to display complex numbers in the form of
> x+jY (or x-jy if leading phase)?
>

So I asked this question on the Yahoo group (after finally getting past
this dreaded captcha stuff), and the LTSpice-guru Helmut Sennewald had
the answer:

<quote>

Make the waveform window active.
Left click on any number of the left vertical axis.
Then select Cartesian instead of Bode or Nyquist.
Representation: "Cartesian"
When you now select a signal, LTspice will show the numbers
for the real and imaginary part.

<unquote>

I had found that on the web yesterday but gave up because it did not
work. Turns out it does not work in a transient analysis but it does in
an AC analysis.

[Jim Thompson]

On Fri, 07 Jun 2013 12:39:36 -0700, Joerg <inv...@invalid.invalid>
wrote:

But doesn't that show them as separate numbers, not as A + jB ??

[Joerg]

Jim Thompson wrote:
> On Fri, 07 Jun 2013 12:39:36 -0700, Joerg <inv...@invalid.invalid>
> wrote:
>
>> Joerg wrote:
>>> Folks,
>>>
>>> Is there a way to coax LTSpice to display complex numbers in the form of
>>> x+jY (or x-jy if leading phase)?
>>>
>> So I asked this question on the Yahoo group (after finally getting past
>> this dreaded captcha stuff), and the LTSpice-guru Helmut Sennewald had
>> the answer:
>>
>> <quote>
>>
>> Make the waveform window active.
>> Left click on any number of the left vertical axis.
>> Then select Cartesian instead of Bode or Nyquist.
>> Representation: "Cartesian"
>> When you now select a signal, LTspice will show the numbers
>> for the real and imaginary part.
>>
>> <unquote>
>>
>> I had found that on the web yesterday but gave up because it did not
>> work. Turns out it does not work in a transient analysis but it does in
>> an AC analysis.
>
> But doesn't that show them as separate numbers, not as A + jB ??
>

It shows them as:

2.3V,-3.9iV

A bit unorthodox but good enough for me. The nice thing is you can make
them visible just by hovering over the spot of interest in the waveform
window. I need this to corroborate the numbers my software will calculate.

Full confession: This stuff has been so long ago that I needed to brush
up. And right now I am getting a complex impedance where there should
only be a capacitance (sans real component). Hurumph!

[Jim Thompson]

On Fri, 07 Jun 2013 13:10:26 -0700, Joerg <inv...@invalid.invalid>
wrote:

I do a lot of impedance analysis, creating subcircuits to match
wirebonds from DC up into the GHz range, so my AC skills are still
quite well-honed ;-)

[Joerg]

Same here, but you know how it goes. Wet finger in the air, black cat
crosses street, "Oh, need another 3nH here and 4pf over yonder", throw
onto SPICE, find it's really 4nH and 5pF, put that in the design, done.

I have to extract the capacitance from a ref/sense ratio measurement and
through a lossy LC network. No fun. One of our guys had a billiant idea:
Give it to a college kid, let him/her solve it and pay $50 or whatever
is fair for it. But that feels like cheating :-)