134Measuring Digital Communications SignalsSpurious Emissions MeasurementsTroubleshooting hintsSpurious emissions measurements can reveal the presence of degraded or defectiveparts in the transmitter section of the UUT. The following are examples of problemswhich, once indicated by testing, may require further attention:• Faulty DC power supply control of the transmitter power amplifier• RF power controller of the pre-power amplifier stage• I/Q control of the baseband stage• Reduction in the gain and output power level of the amplifier due to a degradedgain control and/or increased distortion• Degradation of amplifier linearity and other performance characteristicsPower amplifiers are one of the final stage elements of a base transmitter and play acritical part in meeting the important power and spectral efficiency specifications.Measuring the spectral response of these amplifiers to complex wideband signals iscrucial to linking amplifier linearity and other performance characteristics to thestringent system specifications.
