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Agilent PN 89400-5 Measuring Transmitter Transients with the 89400 Series Vector Signal Analyzers Product Note Understanding and controlling the types of analysis can be performed on delay. The IF trigger is the most con- transient behavior of transmitters the same transient event. These include venient for transmitter measurements has become increasingly important calculating the spectrum, instantaneous because it allows the measurement to with the introduction of TDMA and power, phase, amplitude, or frequency be triggered on a change in transmit- spread spectrum systems. In these deviation versus time, to name a few. ter power level. The trigger delay is systems and others, the carrier The time-capture buffer can also be typically set to a negative number so power is continuously changing in stored to disk, allowing the analysis the measurement is pre-triggered. The order to maximize spectrum utiliza- to be performed later, at a more con- use of pre-trigger delay allows events tion and conserve battery power. The venient time and location. leading up to the transient to be transients that occur because of included in the analysis, and provides changes in carrier power and fre- There are three steps to capturing for settling in the overlapped meas- quency can cause interference to data. The first is to select a center urements described later. other stations. Unsettled carriers frequency and span. The span must can also cause high bit-error rates. be wide enough to allow all of the Power Transients transmitter's power to be measured, Instantaneous power measurements The Agilent Technologies 89400 yet narrow enough to prevent inter- are one of the most common meas- Series vector signal analyzers (VSAs) ference from other signals that might urements made today. The measure- can capture a single transient event be present (such as another station). ment is made to find the peak power and repeatedly analyze it in the The VSA's information bandwidth in a digitally modulated signal, to set time, frequency, and modulation (span) can be adjusted with nearly signal levels into the power amplifier, domains. Phase, frequency, and infinite resolution. Setting the span or to test a transmitter pulse against amplitude transients, or transitions, automatically band limits the analysis. an amplitude mask found in a com- can be viewed directly. Also, the munication standard