Passive IM Measurements On Power Combiner/Dividers

Power combiners and power dividers present unique challenges for IM measurement. Improperly measured, these devices can appear to generate acceptable levels of passive IM distortion while, when installed, they are capable of degrading communications quality and system capacity in a base station.

Each IM source contributes to the overall IM distortion produced by the device. The generated IM appears at all three ports (although not necessarily with the same amplitude).

Measuring The IM Of A Power Combiner Using Individual CW Tones

Using this technique, a high power CW carrier is injected into each input port of the combiner. The frequencies of each carrier are selected to produce the an IM frequency within the desired measurement band. The power divider serves a dual-role in this example: It is the device which combines the two CW tones to a single coaxial path and it is also the device under test. IM generated within the power divider appears at the duplexer and the receive-band IM signal is measured by the spectrum analyzer.

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