Defines and controls the source power and attenuation for the
active channel.
Note: External
sources can be controlled from this dialog. Learn
more.
Power On
(All Channels) Check to enable source power for all
channels (same function as RF
Power). Only turns power ON if channel power setting is
ON or Auto.
Port
Powers Coupled
Coupled
(checked) The power levels are the same at each test
port. Set power at any test port and all test ports change
to the same power level. Uncoupled
(cleared) The power levels are set independently for
each test port. Uncouple power, for example, if you want to
measure the gain and reverse-isolation
of a high-gain amplifier. The power required for the input
port of the amplifier is much lower than the power required
for the output port. A power sweep can also be performed with
uncoupled power. Learn more about Setting
Independent Port Power
Name
Lists the analyzer test ports.
State
Port Power
Sets the power level at the output of the source.
Start
/ Stop Power Available
ONLY when sweep type is set to Power Sweep. Set the start and
stop power values of a power sweep. Learn
how to set Power Sweep.
You
can specify whether to maintain source power at either the
start power or stop power level at the end of a power sweep.
Learn more. A
power sweep can be performed with uncoupled
power. Different power ranges can be swept in the forward
and reverse directions.
Auto
Range Check to allow the analyzer to select the optimum attenuation value to
achieve the specified test port power.
Clear to
manually set the attenuation for each port. Type or select the
attenuation value in the adjacent Attenuator Control box.
When using
manual attenuation (Auto Range cleared), Port Power can be set
within a 60 dB range. For example:
With 0 dB of manual attenuation, Port
Power can be set from -30 dBm to +30 dBm. With 10 dB of manual attenuation,
Port Power can be set from -40 dBm to +20 dBm, and so forth.
Important Note: The available
power range can also be adjusted AUTOMATICALLY by a Source Power
Calibration, Guided Power Cal, or Power Compensation. If you are
NOT seeing the range that you expect, or the correct power level
at your DUT, view the Power Offset column in the Power Limits
and Offsets dialog.
Source Attenuator
When Port Powers are Uncoupled, manual attenuator control
allows you to set a wide range of power levels by setting the
attenuation. See
Setting Independent Port Power. Also
use manual attenuation control when a measurement requires a very
good impedance match with the source, such as with oscillators
or conditionally unstable amplifiers. Choose an attenuation level
of 10 dB or more to ensure the best source match.
Attenuators or other mechanical switches
are NOT allowed to switch continuously. Learn more. When Port
Powers are Coupled, changing one port Attenuation Control
value changes all port values.
Default Source Attenuation
Based on Measurement Class
The table below lists the default
source attenuation values (dB) for each port, based on the selected
measurement class. These are the initial source attenuation values
that appear when you open the Power and Attenuators dialog box.
Meas.
Class |
Port
1 |
Port
2 |
Src2
Out1 |
Src2
Out2 |
Port
1
Src2 |
Std. |
0 |
0 |
0 |
0 |
0 |
AHP |
0 |
0 |
0 |
0 |
0 |
GCA |
0 |
0 |
0 |
0 |
0 |
DIQ |
0 |
0 |
0 |
0 |
0 |
IMS |
0 |
10 |
0 |
0 |
0 |
IMD |
0 |
10 |
0 |
0 |
0 |
MOD |
0 |
0 |
0 |
0 |
0 |
NF |
20 |
10 |
0 |
0 |
20 |
PN |
0 |
0 |
0 |
0 |
0 |
SA |
0 |
0 |
0 |
0 |
0 |
TDR |
NA |
NA |
NA |
NA |
NA |
GCX |
0 |
0 |
0 |
0 |
0 |
IMSX |
0 |
10 |
0 |
0 |
0 |
IMDX |
0 |
10 |
0 |
0 |
0 |
MODX |
0 |
0 |
0 |
0 |
0 |
NFX |
20 |
10 |
0 |
0 |
20 |
SMC |
5 |
5 |
0 |
0 |
5 |
VMC |
5 |
5 |
0 |
0 |
5 |
Note: Because
the reference receiver is not in the attenuation path,
there is more power at the reference receiver than at
the test port by the amount of source attenuation.
By default, ALL VNA
models mathematically offset the reported power at the
reference receivers by the amount of source attenuation.
See
Block diagram.
A preference can be set to NOT mathematically offset
the reported power of the reference receiver by the amount
of source attenuation.
Learn how to set the preference. |
Leveling Mode
(ALC
Hardware
Softkey)- Refer to the following diagram:
Internal
- ALC leveling. Power level within an attenuator setting is
limited to the ALC Range. See Source Unleveled. Open
Loop - No ALC and NO Receiver Leveling. (Used during
pulse conditions with the internal source modulators). NOT
available on N523x models. No leveling is used in setting
the source power. The lowest settable power, without attenuation,
is limited to -30dBm. The source power level accuracy is very
compromised. Use a source power calibration to make the source
power somewhat more accurate. Receiver
Rx - Receiver Leveling.
Select a receiver to use for leveling the source. Learn more. Note:
Receiver Leveling can be used with EITHER Internal ALC or
Open Loop. See Enable ALC Hardware
on the Receiver Leveling dialog.
Channel
Power Slope
Helps compensate for cable and test fixture
power losses at increased frequency. With power slope enabled,
the port output power increases (enter positive value) or decreases
(enter negative value) as the sweep frequency increases.
Slope Select
to set the power slope. Clear to set power slope OFF.
Power slope is computed and applied from
0 GHz – not from the measurement start frequency.
For example, with the following measurement
settings:
The power into the DUT from 10 GHz
to 20 GHz is 10 dBm sloping to 20 dBm
Offset and Limits Launches
the Power
Offset and Limits dialog.
Receiver Leveling Launches
the Receiver Leveling dialog.
Receiver Attenuator
Launches the Receiver Attenuator
dialog.
Path
Configurator Launches the Path Configurator
dialog.
Source Unleveled
When the power level that is required at a test port is
higher than can
be supplied, a Source Unleveled error
message appears on the screen and the letters LVL appear on
the status
bar.
To perform a power sweep, the
range of power is usually limited to the range of the Automatic
Leveling Control (ALC) loop. (The PNA-X allows a very wide power
range using Open Loop).
Specifications guarantee the
ALC power range over which power can be supplied without an unleveled
indication. However, the actual achievable power range on your
analyzer is probably greater than the specified range.
How to calculate the specified
achievable power range
From the specifications for
a frequency span from 15 GHz to 20 GHz:
For this frequency range the
specified power range is calculated as:
When using Source Attenuators:
with 10dB of attenuation, this becomes -18 dBm to -35
dBm with 20dB of attenuation, this becomes -28 dBm to -45
dBm, and so forth.
To resolve an unleveled condition, change either the Test Port
Power or Attenuator setting.
Important Note:
The available power range can also be adjusted AUTOMATICALLY by
a Source Power Calibration, Guided Power Cal, or Power Compensation.
If you are NOT seeing the range that you expect, or the correct
power level at your DUT, view the Power Offset column in the Power Limits
and Offsets dialog.
Setting
Independent Port Power
You can uncouple port power and
specify different power levels at each test port. There are a
few things to consider when setting independent port powers.
Does your required high and low power levels
fall within the specified Min and Max power range of the analyzer?
See Unleveled Indicator. If
they do not, you may need to use the internal Source Attenuators. Does
the analyzer have source attenuators? If so, how many source
attenuators? Some VNA models have one attenuator for each
port. In most multiport VNA systems, the attenuators are shared
by at least two test ports. See VNA
Options to see the availability and range
of source attenuation on your VNA.
Note:
To prevent premature wear, attenuators or other mechanical
switches are NOT allowed to switch continuously.
These mechanical devices are set for the
entire channel. When more than one channel is used, and
a mechanical device setting is NOT the same for all channels,
only the ACTIVE channel is allowed to sweep. All other
channels are NOT allowed to sweep (Blocked).
Learn
how to view
the settings of all mechanical devices. |
Setting Port Power On/Off for the
Second source and Multi Module/Unit configuration
When the unit has the second source
capability or multi module/unit configuration in PXI/USB VNA,
Source power ALWAYS ON can be applied for each source group.
The following dialog shows an example
of three module configuration of six, four and two port
PXI VNAs. In this case, there are three independent source group,
port 1to 6, 7 to 10 and 11 to 12. You can set one port in each
group at ON state.
Optimum
Attenuation Value
The attenuator has different
positions, allowing a wide range of power levels. The number of
power ranges available is determined by the source attenuation
installed in your VNA. See VNA
Options to see the availability and range of
source attenuation on your VNA.
Each range has a total specified span (50
dB in the following Attenuation Values graphic ). The optimum setting is the middle of the range.
This range provides the best accuracy and performance of the
source leveling system. The optimum ranges are the blue regions
in the following graphic. An attenuator setting can be selected manually
or automatically. If automatic is selected, the blue optimum
ranges (shown in the following graphic) are used.
Note:
Error correction is fully accurate only for the power level at
which a measurement calibration was performed. However, when changing
power within the same attenuator range at which the measurement
calibration was performed, ratioed measurements can be made with
nearly full accuracy (non-ratioed measurements with less accuracy).
Receiver
Attenuators dialog box help |
|
Receiver Attenuators
are offered as an option. Learn more.
Type or select independent
attenuation values for each receiver.
Receiver A is at Test Port 1 Receiver B is at Test Port 2 Receiver C is at Test Port 3 Receiver D is at Test Port 4
Receiver Attenuation is used to protect the VNA
test port receivers from damage or compression.
Receiver attenuation
causes the reported power at the receiver to be less than
the power at the test port by the specified amount of
attenuation.
When an external
test set is connected, Receiver Attenuation control
is only available for the physical receivers in the VNA.
Switching receiver attenuation using logical
receiver notation is NOT allowed.
CAUTION! You
can damage the analyzer receivers if the power levels
exceed the maximum values.
|
Power
ON and OFF during Save / Recall, User Preset, and Preset
To protect your DUT from being inadvertently powered ON, the
following RF Power ON/OFF settings occur:
If power is OFF when an instrument state is saved, then power
will always be OFF after the instrument state is recalled.
If power is ON when an instrument state is saved, and the current
power setting is OFF, then power will be OFF after the instrument
state is recalled.
If power is OFF when a User
Preset is saved, then power will always be OFF after a User Preset.
If power is ON when a User
Preset is saved, and the current power setting is OFF, then power
will be OFF after a User Preset.
Instrument Preset sets power ON by default.
This can be changed with a Preference
setting so that, if the current power setting is OFF, then
power will be OFF after Preset.
Power
ON and OFF during Sweep and Retrace
The frequency range of the
VNA covers several internal frequency bands. The higher the frequency
range of the VNA, the larger the number of bands. For example,
a 9 GHz VNA has 6 frequency bands, a 50 GHz VNA has 25 frequency
bands. See the frequency
band crossings.
Power to the DUT is turned
OFF during band changes to avoid causing power spikes to the DUT.
Retrace occurs when the source
gets to the end of your selected frequency span and moves back
to the start frequency. Power to the DUT is again turned OFF when
retracing across frequency
bands.
The following power ON/OFF
states occur for various stimulus settings:
Single band sweep - The
power ON/OFF state to the DUT during retrace is determined
by a preference setting. Multi-band
sweep - The power to the DUT is turned OFF while sweeping
across a band crossing. It is turned OFF again during retrace. Power sweep - Power sweep
is always done at a single frequency, Therefore, like
item 1, the power ON/OFF state to the DUT during retrace is
determined by a preference setting Single sweep:
Manual
trigger mode - At the end of a multiband sweep, power
is turned OFF during retrace, and then power is turned
back ON before arming for the next trigger. Hold
mode - Power can be ON or OFF depending on when and how
Hold mode is entered. However, power can be immediately
turned OFF manually or remotely.
Caution:
Avoid expensive repairs to your analyzer. Read Electrostatic
Discharge Protection.
|
