Keysight N9038A, Service Manual

Page: 395 / 745

Keysight N9038A MXE Service Guide 395
Optional Assemblies
A26 Wideband Digital IF Assembly Description
Pulse Stretcher
The pulse stretcher is used to get information about when an asynchronous
trigger arrives relative to an ADC sample. This is needed since such triggers
usually arrive between two samples rather that coincident with one, and the
instrument needs to know when they arrive with more precision.
A pulse sent to the pulse stretcher from the FPGA is extended in time and sent
back to the FPGA where its new stretched length can be counted using the
ADC Sample clock. Typical stretch ratios are approximately seven hundred to
one
Prior to interpolating the arrival of triggers, the pulse stretcher must be
calibrated so that the slope and offset of its stretching abilities are known.
There is an instrument internal alignment for this calibration.
A26 Wideband Digital IF Assembly Connections
The connections to and from the A26 Wideband Digital IF assembly are as
listed in Table 14-2 and as illustrated in Figure 14-6 .
Figure 14-6 A26 Wideband Digital IF Connections
Table 14-2 A25 Wideband Analog IF Assembly Connections
Port Description To/From Cable Frequency
J501 Bias & Control A8 Motherboard J51 n/a n/a
J502 PCI Bus A8 Motherboard J52 n/a n/a
J778 Digital Signal Input A25 Wideband Analog IF J2 W10 Digital
J9000 PCIe/LVDS n/a n/a n/a