DDS 1 as a Signal Generator
Build Level Requirement: Any
Mode of Operation: Any
Primary Function: Disabled
DDS 1 can be commanded to any fixed frequency between 0 Hz and 32 MHz
(or one half the Master Clock frequency). This is useful if only
the Basic MSA is constructed and there is no MSA Tracking
Generator. The spare output of DDS 1 can be
used as a CW Signal Generator. The power level is about -8
dBm. The frequency output is extremely stable, with very low
phase noise. However, the harmonics and alias frequencies will
extend well into the GHz range. They too, are extremely stable
and can be used for a variety or laboratory experiments.
Click
the menu item, Setup, and select Special
Tests. The "Special Tests Window" will open.
The
data that is displayed in the "Command
DDS
1" box is the present output frequency
of
DDS 1.
To command the frequency of DDS 1,
enter a new value
into the "Command DDS
1" box, in MHz. Then click the "Command
DDS
1" button. To maintain frequency
accuracy, do not change the value in the "with DDS Clock at" box unless you know it is
incorrect. DDS 1 will immediately
command to the frequency value. You may use as many decimal
places as wanted, but the DDS output frequency will be rounded off to
14.9 millihertz. The value must be between
"0"
and "32" (MHz), one half
the value of the DDS clock. If the
entered data is outside these limits, and when the "Command DDS 1" button is clicked,
an error
will occur, and the program will halt. The DDS 1 output frequency
will remain at the new fixed frequency until the "Restart" button is
clicked, even if the Special Tests Window is closed. Therefore, if the sweep is
resumed by using the "Continue" or "One Step" button, the DDS 1
output frequency will remain at the fixed frequency and the sweep plot
may be meaningless, or not even there.
When finished with this special test, close the
Special Tests Window and click "Restart" to revert to normal operation.
DDS 3 as a Signal Generator
Build Level Requirement:
MSA/TG or VNA
Mode of Operation: Spectrum Analyzer
Primary Function: Enabled
DDS 3
can be commanded to any fixed frequency between 0 Hz and 32 MHz (or one
half the Master Clock frequency). Using DDS 3 as an independent
Signal Generator does not impact the operation of the Spectrum
Analyzer. The spare output power level is about -8
dBm. The frequency output is extremely
stable, with very low phase noise. However, the harmonics and
alias
frequencies will extend well into the GHz range. They too, are
extremely stable and can be used for a variety or laboratory
experiments.
Click
the menu item, Setup, and select Special
Tests. The "Special Tests Window" will open.
The
data that is displayed in the "Command
DDS 3" box is the present output frequency
of
DDS 3. To command the frequency of DDS 3,
enter a new value
into the box, in MHz. Then click the "Command DDS 3" button. To maintain frequency
accuracy, do not change the value in the "with DDS Clock at" box unless you know it is
incorrect. DDS 3 will immediately
command to the frequency value. You may use as many decimal
places as wanted, but the DDS output frequency will be rounded off to
14.9 millihertz. The value must be between
"0"
and "32" (MHz), one half
the value of the DDS clock. If the
entered data is outside these limits, and when the "Command DDS 1" button is clicked,
an error
will occur, and the program will halt. The DDS 3 output frequency
will remain at the new fixed frequency until the "Restart" button is
clicked, even if the Special Tests Window is closed. Therefore, if the sweep is
resumed by using the "Continue" or "One Step" button, the DDS 3
output frequency will remain at the fixed frequency and the sweep plot
will be unaffected.
When finished with this special test, close the Special Tests Window
and click "Restart" to revert to normal operation. DDS 3 as the Tracking
Generator for the Spectrum Analyzer
Build
Level Requirement: MSA/TG or VNA
Mode of Operation: Spectrum Analyzer
Primary Function: Enabled
Of course, if
DDS 3 is installed in the MSA, you already have a Tracking Generator
capability. Sometimes it is prudent to use the DDS 3 in lieu of
the normal TG and that is why this Function was included in the
software. By clicking the "DDS
3 Track"
button, the
DDS 3 will
become a Tracking Generator and the DDS 3 output frequency will
track the Command
frequency of the MSA. It is limited to 0 MHz to 1/2 the Master Clock frequency,
nominally 0-32 MHz. The normal Tracking Generator
output becomes non-functional when the DDS 3 is tracking. The DDS
3 output is accessed on the DDS
3 Module, J3.
Follow
these steps for proper
operation:
Open the Sweep
Parameters Window, enter the wanted Center
Frequency, anywhere between 0-32 (MHz). This will be not only the
MSA command frequency but also the DDS 3 output frequency. Enter
Sweep Width,
but make sure the sweep will not go below 0, nor above 1/2 the
frequency of the Master Clock. If either value is outside these
limits, this special test will crash. Click OK, Restart, and then
Halt
the
sweep. Open the Special Tests Window.
Click the "DDS 3 Track" button.
DDS3 will immediately command to
the frequency that the MSA sweep halted at.
You may resume
sweeping the
Spectrum Analyzer by clicking [One Step] or
[Continue].
If [Restart] is clicked, the MSA will
revert to it's normal operation, that is, DDS 3 will return to its
normal operation condition.
If
[Restart] was clicked, and you wish to return to this
special test for DDS 3 as
a Tracking Generator, the "DDS 3 Track" button must be
re-clicked
Then use only the [Continue] or [One Step] buttons.
When
finished with this special test, close the Special Tests Window
and click "Restart" to revert to normal operation.
DDS 1 as a Sweep
Generator
Build
Level Requirement: Any
Mode of Operation: Any
Primary Function: Disabled DDS
1 can be used as an independent sweep generator between 0 Hz and 32 MHz
(or one
half the Master Clock frequency). This is useful if only the
Basic MSA
is constructed and there is no MSA Tracking Generator. The spare output of DDS 1 power level is about -8 dBm.
If the normal MSA Tracking Generator is installed the TG output will
remain functional during this special test. Normal operation of
the Spectrum Analyzer will become altered, although some attributes are
still functional. The Log Detector and A to D
converters
remain functional.
Follow these steps for proper
operation:
Open the Sweep Parameters Window, enter the wanted Center
Frequency, anywhere
between 0-32 (MHz). This will become the command to the DDS
1. Enter Sweep Width, but make sure the
sweep will
not go below 0, nor above 1/2 the frequency of the Master Clock. If either value is outside
these limits, this special test will crash. Click OK, Restart, and
then Halt
the sweep.
Open the Special
Tests Window.
Click the "DDS 1 Sweep" button.
DDS1 will immediately command to
the frequency that the MSA sweep is halted at. The MSA will resume
sweeping when
[One Step] or [Continue] is pressed. DDS 1 will sweep, coinsiding
with the frequencies that are displayed. If [Restart] is clicked,
the
MSA
will revert to it's normal Spectrum Analyzer operation.
Therefore, to maintain DDS
1 as
a Sweeping Generator, the "DDS 1 Sweep" button must be re-clicked, and then use only the [Continue] or [One Step] buttons.
When finished with this special test, close the Special Tests Window
and click "Restart" to revert to normal operation.
DDS 1 as a Tracking
Generator or Scalar Network Analyzer
Build
Level Requirement: Any
Mode of Operation: Any
Primary Function: Disabled (This
section is under construction)
DDS
1 can be used as a Tracking Generator in combination with the Log
Detector Module. It has a frequency limitation of about 1 MHz to 32
MHz. The "front end" of the MSA is not used and the Log Detector
is disconnected from the Final Crystal Filter. The spare output
connection (J3) of DDS 1 is used as a sweeping signal source and the
Log Detector is used as the receiving detector. Although the Log
Detector has an input dynamic range from +10 dBm to -100 dBm, the DDS 1
spare output has only an output power of about -8 dBm. Therefore
the total dynamic range of the DDS 1 and Log Detector combination is
only 92 dB. However, a low gain amplifier could be placed on the
DDS 1 spare output to increase its output power, and thusly, increase
the total dynamic range to over 100 dB.
The following Graph is a Monolithic Crystal Filter
response using the DDS 1 and Log Detector combination. The DDS 1
spare output (J3) is connected to the MCF. The output of the MCF is
connected to the Log Detector input (J1). I have modified the
Path 4 Calibration File to indicate power into the Log Detector rather
than power into the input to the MSA. This gives the Magnitude scale a
good indication of real power levels.
Operation is the same as the previous paragraph, "DDS 1 as a Sweep
Generator".
Open
the Sweep
Parameters Window, enter the wanted Center
Frequency, anywhere
between 0-32 (MHz). This will become the center frequency command
for DDS
1. Enter Sweep Width, but make sure the
sweep will
not go below 0, nor above 1/2 the frequency of the Master Clock. If either value is outside
these limits, this special test will crash. Click OK, Restart, and
then Halt
the sweep. Any indication in the Graph is meaningless.
Open the Special
Tests Window.
Click the "DDS 1 Sweep" button.
DDS1 will immediately command to
the frequency that the MSA sweep is halted at. The MSA will resume
sweeping when
[One Step] or [Continue] is pressed. DDS 1 will sweep, coinsiding
with the frequencies that are displayed. If [Restart] is clicked,
the
MSA
will revert to it's normal Spectrum Analyzer operation.
Therefore, to maintain DDS
1 as
a Tracking Generator, the "DDS 1 Sweep" button must be re-clicked, and then use only the [Continue] or [One Step] buttons.
When finished with this special test, close the Special Tests Window
and click "Restart" to revert to normal operation.
