Agilent Technologies N8201A Service Manual download pdf (Page 591)

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Programming Fundamentals 28

Agilent N8201A Performance Downconverter Synthetic Instrument Module, 250 kHz to 26.5 GHz 591

Using an Option Mode: Avoid automatic attenuator setting

The internal process for automatically setting the value of the attenuator requires

measuring an initial burst to identify the proper attenuator setting before the next burst can

be measured properly. If you know the amount of attenuation or the signal level needed for

your measurement, just set it.

Note that spurious types of measurements must be done with the attenuator set to

automatic (for measurements like: output RF spectrum, transmit spurs, adjacent channel

power, spectrum emission mask). These types of measurements start by tuning to the

signal, then they tune away from it and must be able to reset the attenuation value as

needed.

Using an Option Mode: Optimize your GSM output RF spectrum switching

measurement

For ORFS (switching), setting the break frequency to zero (0) puts the N8201A in a

measurement setup where it can use a direct time measurement algorithm, instead of an

FFT-based algorithm. This non-FFT approach is faster. (However, remember that your break

frequency for ORFS (modulation) measurements must be >400 kHz for valid measurements,

so you will need to change the break frequency if you are making both types of

measurements.)

Using an Option Mode: Avoid using RFBurst trigger for single burst signals

RFBurst triggering works best when measuring signals with repetitive bursts. For a

nonrepetitive or single burst signals, use the IF (video) trigger or external trigger, depending

on what you have available.

RFBurst triggering depends on its establishment of a valid triggering reference level, based

on previous bursts. If you only have a single burst, the peak detection nature of this

triggering function, may result in the trigger being done at the wrong level/point generating

incorrect data, or it may not trigger at all.

Are you making a single burst measurement?

To get consistent triggering and good data for this type of measurement application, you

need to synchronize the triggering of the DUT with the N8201A. You should use the

N8201A’s internal status system for this.

The first step in this process is to initialize the status register mask to look for the “waiting

for trigger” condition (bit 5). Use :STATus:OPERation:ENABle 32

Then, in the measurement loop:

1 :STATus:OPERation:EVENt? This query of the operation event register is to

clear the current register contents.

2 :READ:PVT? initiates a measurement (in this example, for GSM power versus time)

using the previous setup. The measurement will then be waiting for the trigger.

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Agilent Technologies N8201A Service Manual Page 591

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