32SCPI Programming FundamentalsTechniques for Improving Measurement Performance• When doing bottom/middle/top measurements on Base Stations, you can reduce transactions by making a time slotactive at each of the B,M,T frequencies. Then, issue three measurements at once in the programming code andretrieve three data sets with just one bus transaction pair (write, read).For example, send READ:PFER? ; PFER? ; PFER? . This singletransaction initiates three different phase and frequency error measurements at each of the three different frequenciesprovided and returns three sets of data.Use USB or LAN Connection instead of GPIBUSB and LAN networks allow faster data input and output, relative to GPIB. This is especially important if you are movinglarge blocks of data.Note that LAN transfer speeds are affected by the volume of LAN traffic, and may be degraded if, for example, theinstrument is connected to a busy enterprise LAN. Thus you may want to use a private LAN that is dedicated for the testsystem.Minimize DUT/instrument Setup changes• Some instrument setup parameters are common to multiple measurements, making it possible to organize the testprocess in such a way as to minimize setup changes. If the process involves nested loops, make sure that theinnermost loop is the fastest. Also, check whether the loops could be nested in a different order to reduce the numberof parameter changes as you step through the test.• If you must switch between measurements, remember that if you have already set your Meas Setup parameters for ameasurement, and you want to make another one of these measurements later, you should use the queryREAD:?.The MEASure:?. command resets all the settings to the defaults, while READ changes back to thatmeasurement without changing the setup parameters from the previous use.• If you must switch between measurements, remember that Mode Setup parameters remain constant across all themeasurements in a given mode (for example, Center/Channel Frequency, Amplitude, Radio Standard, Input Selection,Trigger Setup). You do not need to re-initialize these parameters each time you change to a different measurement.Avoid Unnecessary Use of *RSTRemember that while *RST does not change the current Mode, it presets all the measurements and settings to theirfactory defaults. This forces you to reset the instrument’s measurement settings even if they use similar mode setup ormeasurement settings. See “Minimize DUT/instrument Setup changes” on page 32.Note also that *RST may put the instrument in Single measurement/sweep for some modes.Avoid Automatic Attenuator SettingMany of the one-button measurements use an internal process for automatically setting the value of the attenuator. Itrequires measuring an initial burst to identify the proper attenuator setting before the next burst can be measuredproperly. 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 such as:Output RF Spectrum, Transmit Spurs, Adjacent Channel Power, Spectrum Emission Mask). These types of measurementsstart by tuning to the signal, then they tune away from it and must be able to reset the attenuation value as needed.Avoid using RFBurst trigger for Single Burst SignalsRFBurst triggering works best when measuring signals with repetitive bursts. For a non-repetitive or single burst signals,use the IF (video) trigger or external trigger, depending on what you have available.
