The modern network analyzer system sweeps very large frequency bandwidths and measures the incident power, P i , and the reflected power, P r . Because of the considerable computing power in the network analyzer, the return loss is calculated from the equation given previously, and displayed in real time. Optionally, the VSWR can also be calculated from the return loss and displayed real time. If a filter is needed on the output of a jammer, it is desirable to place it approximately half way between the jammer and antenna. This may allow the use of a less expensive filter, or a reflective filter vs an absorptive filter.
Special cases exist when comparing open and shorted circuits.
These two conditions are used to calibrate a network analyzer.