Salut version 1.0.1 - copyright 2005 Daniel Uppström, upda@eta.chalmers.se
Salut is a small program that performs calculations on networks around two-port devices (like transistors) characterized by s-parameters, at radio frequencies.
The main advantage over many other simple microwave/rf simulation programs is that it has the possibility to model components in series with a two-port block. This is interesting since some reactance to ground will always be present in every application. Salut is also not restricted to the usual common emitter or common source configuration even though many semiconductor manufacturers only provide s-parameters for this case.
With Salut, it is easy to look for negative resistances in oscillator circuits.
The program takes a two-port s-parameter file as input argument and manipulates it with regard to the options specified below.
Please view examples.html for some examples with schematics.
Salut is released under the GNU General Public License. See LICENSE for details.
Misc. command line options:
-h or --help shows the help screen (not very helpful at present) -o specify output file (stdout by default) -Z specify system impedance (50 Ohm by default) -s do stability calculations for a two-port
( A device is unconditionally stable when K>1 and |Delta|<1,
K is known as the Rollett Stability Factor )
Change of common junction. To avoid confusion these arguments can not be given togeher with any other circuit specifications:
--ce2cb common emitter to common base --ce2cc common emitter to common collector --cb2ce common base to common emitter --cb2cc common base to common collector --cc2ce common collector to common emitter --cc2cb common collector to common base
Place elements in series with the common junction:
--cL inductance (H)
--cRL resistance (Ohm) in series with the inductance
--cC capacitance (F)
--cR resistance (Ohm)
--cTs Characteristic impedance (Ohm) of end-shorted transmission line
--cTo Characteristic impedance (Ohm) of open-ended transmission line
--cTl length (degrees)
--cTf frequency at specification (Hz)
(I.e. to insert a transmission line, one of the --cTs/--cTo arguments must be specified together with both --cTl and --cTf)
Place lumped elements in parallell with some port:
--p1parL inductance (H)
--p1parRL resistance (Ohm) in series with the inductance
--p1parC capacitance (F)
--p1parR resistance (Ohm)
p1 stands for port 1 and by replacing p1 with p2, port 2 is equivalently modified.
Terminate a port to form a one-port device:
--p1termL inductance (H)
--p1termRL resistance (Ohm) in series with the inductance
--p1termC capacitance (F)
--p1termR resistance (Ohm)
--p1termTs Characteristic impedance (Ohm) of end-shorted transmission line
--p1termTo Characteristic impedance (Ohm) of open-ended transmission line
--p1termTl length (degrees)
--p1termTf frequency at specification (Hz)
Similar holds for p2.
Note that the unterminated port is always relabeled as port 1, i.e. the result will always be S11. In addition, the equivalent impedances are calculated.
Note also that if several components are connected as port termination or to the common junction, their calculated impedances will be evaluated as a parallell circuit!!
For example, if we have a s2p file for some BJT in common emitter configuration and want to use the device in common base configuration with an inductance of 10 nH that has a stray capacitance of 0.2 pF in series with the base connection, we type
salut bjt.s2p --ce2cb > bjt_cb.s2p
salut bjt_cb.s2p --cL 10e-9 --cC 0.2e-12
and the new s-parameters are written to standard output. These new parameters can then be used by a graphically oriented circuit simulator like Vipec.
If the second line is replaced with
salut bjt_cb.s2p --ce2cb --cL 10e-9 --cC 0.2e-12 --p2termR 50
then port 2 is terminated with 50 Ohm and we get a table of one-port reflection coefficients and the corresponding impedances that port 1 now presents. In this manner negative resistances could be searched for.
Check INSTALL for building instructions.