The dialog form shown below allows you to select an event delay time interval that applies to Event 1, Event 2, and Event 3, set a pulse modulation alignment time to adjust the pulse modulation signal with the I/Q waveform, and set a coarse modulation alignment time to adjust the pulse modulation alignment for the internal Arbs.
This menu item allows you to specify a time delay within ±50 ns for the user-defined Events 1, 2, and 3 configured in the Pattern Details Advanced section. The time delay resolution is related to sampling rate: time delay resolution = 1/sampling rate. For a 100 MHz sampling rate the resolution is 10 ns. With no delay the event markers are synchronized with the RF output. Setting an event delay allows you to fine tune the timing of the event marker as a trigger for other devices. When the ALC Hold Line is enabled, Event Delay (ns) is not applied to Event 3. Changing this value requires you to Download and Play the signal to view results.
This parameter is for configurations using the N603xA/M933xA, N824xA, or internal Arbs only. Pulses are generated using both the I/Q waveform as well as the signal generator pulse modulator. The pulse modulator is driven by the marker 4 signal provided by the Arb. The N7620B software has delay times built into its signal calculations to insure that the I/Q pulse reaches the pulse modulator at the same time as the marker signal. This insures that the pulse has the best on/off ratio possible. The I/Q waveform provides a pulse on off ratio of approximately 65 dBc by itself. When combined with the pulse modulator the pulse on/off ratio is better than 80 dBc.
However, it may be necessary to fine-tune the pulse marker delay to insure the I/Q data and the marker data reach the pulse modulator at the same time.
The delay range for the internal Arb is
Range –10 ns to 10 ns
Resolution 0.01 ns.
The range for the N603xA/M933xA or N824xA Arb is
Range: –6.4 ns to 25.6 ns
Resolution: 1.6 ns
Default: 0 ns
The delay times are based on the I/Q signal path and the marker signal path. For External I/Q and Wideband I/Q it is assumed that the external signal paths are equal. If the external signal paths are equal the Pulse Modulation Alignment should be left at 0 ns. If this is not the case see the Pulse Modulation Alignment procedure.
The pulse modulation alignment resolution for
the N603xA/M933xA or N824xA is 1.6 ns, however, the waveform 
marker resolution
is 6.4 ns (8 / Sampling Rate). This results in a stepped pulse shape.
The application builds a marker signal that is greater than or equal to
the pulse on time as discussed in Pulse
Modulation Alignment. Click here
to see an exaggerated misalignment to illustrate the step.
This menu item is a coarse alignment adjustment for a low RF signal frequency, with a limit of ±50 ns. It moves the pulse modulation signal an integer number of sample points relative to the I/Q data. This modulation alignment adjustment is for an internal Arb where you cannot physically adjust cable lengths. This can be used with an external Arb, but may not have sufficient range. When adjusting the pulse modulation alignment for an external Arb, adjusting the cable lengths is the preferred method. See below for the frequency range.
This menu item is a coarse alignment adjustment for a high RF signal frequency, with a limit of ±50 ns. It moves the pulse modulation signal an integer number of sample points relative to the I/Q data. This modulation alignment adjustment is for an internal Arb where you cannot physically adjust cable lengths. This can be used with an external Arb, but may not have sufficient range. When adjusting the pulse modulation alignment for an external Arb, adjusting the cable lengths is the preferred method. See below for the frequency range.
|
|
Low |
High |
|---|---|---|
|
PSG |
<3.2 GHz |
>3.2 GHz |
|
ESG |
<4.0 GHz |
>4.0 GHz |
