For example, the measurement bandwidth of the adjacent and first alternate channels is only 30 kHz, not the 1.23 MHz of the transmitting and second alternate channels. Generally, a number of CDMA phones operate simultaneously. This means that peaks will appear in the base station transmitted spectrum caused by the random addition of separate customer s encoded signals. Finally, phase noise must be considered. Summary When choosing a spectrum analyzer, determine what types of measurements the different models support.
Spectrum analyzers are complex instruments.
To ensure spectral purity, several IF stages are used, each contributing to the overall inaccuracy, nonlinearity, and noise. There are time-domain methods available for ACPR measurement, for example, that yield much faster results than a swept spectrum analyzer. Reference 2 describes an approach claimed to yield a 20 speed improvement. It is also said to allow measurement of switching transient effects within the channel, something not possible with swept spectrum analyzers. But, without taking a different approach, you have to believe your spectrum-analyzer measurements.