page 10 of 16 File: SG1024_r1eng - April 2017 - Technical note: SG 1024
PM 250
SG 1024 S
olid
S
tate
M
icrowave
G
enerator
- ratio R/F greater than 10%
- ratio at point “B” smaller than 2% if compared to the maxi-
mum R/F ratio. If larger than 2% the algorithm may decide to
“converge” and stabilize the frequency around this point.
The first frequency from which the autotuning starts is the
last frequency, set manually and at which the generator was
running before entering into autotune mode.
The time it takes by the algorithm to find the best frequency,
with the lowest R/F figure, depends on the distance between
the current and the final frequency, as well as the complexity
of the R/F shape.
In the worst case it should not exceed 500 msec, but it may
take as little as a 50 msec or less.
To shorten the tuning time you may have to select manually a
frequency closer to the expected final frequency (e.g. running
the autotune a first time with the purpose to get this info for
the next trial).
[10]PARAM Threshold
R/F: moving the front
panel knob, you can set
the threshold of the ratio
Rev Power/Forw Power
which has an effect on
the Automatic Frequency
Tuning, when this is enabled.
If the current R/F value is below the above “Threshold R/F”
the autotuning has no effect.
The actual R/F figure is computed every 200 mseconds. We
suggest to set a number higher than 10%. With smaller figure,
and a cavity with low Q factor, the system may not be able to
reach a fixed frequency.
[11]PARAM Reverse Power Max: moving the front panel
knob, you can set the limit of the reverse power before the
alarm. The unit can bear
a total reflection condi
-
tion for a certain time,
but be careful: in case
of heavy standing wave,
the generator may be
overloaded with the sum
of both forward and reverse power, and parts of the circuit on
the final power combiner, as well as the coaxial socket may be
damaged.
[6] INFO: this page shows
the last alarm that occured,
the software version the
generator is running, the
total working hours of
the unit in MW ON and
READY states.
[7] MODE: with the knob
you may select to run
the unit in MANUAL
or EXTERNAL or
REMOTE. In Manual
mode the output power
is adjusted using the
rotating knob on the panel, in EXTERNAL the power is con-
trolled only by reference signal 0-10V (to be supplied on the
signal connector) and in REMOTE the reference value is set
through the fieldbus module. Confirm the selection with Enter.
[8] PARAM Frequency:
on this page you can set
the operating frequency if
the manual tuning is set.
If automatic tuning is set
you will only be able to
visualize the frequency
value. You can also see a moving bar which refers to the ratio
between Reverse/Forward power (R/F xx%).
[9] PARAM Frequency
Tuning: moving the
front panel knob, you
can choose between the
Manual tuning mode and
the Automatic tuning
mode.
The term “Tuning” in this context is used on the searching
for a working frequency, within the permissible band from
2400 MHz to 2500 MHz, exhibiting the lowest ratio between
Reverse and Forward Power figures (Rev/Forw or simply
indicated as R/F).
Selecting Manual Tuning you will have the possibility to
change the frequency from the previous menu PARAM Fre-
quency [8].
With Automatic Tuning the algorithm implemented will find
the best frequency out of the broad range of frequencies for
that cavity.
As an example see the next drawing, where a hypothetical R/F
curve is plotted: the algorithm is able to find frequency point
“A” a where the lowest R/F ratio is. It will stay there even if
point “B” also represents an optimal frequency, but not the
lowest, regardless of the starting frequency, which could be
anywhere on the spectrum.
The unique given conditions to reach point “A” are
A
B
0
max
% R/F
10%
<2%
2.4 GHz
2.5 GHz
f
