A number of test signal injectors are used when evaluating the performance of power supplies and other low-frequency components with a network analyzer.
Network analyzers are invaluable instruments in the laboratory, used for a variety of tasks that include stability analysis, component characterization, and frequency response measurements. Many commercial models are available, with different frequency ranges and features, but all rely on the proper injection of a test signal to accurately perform tests.
The quality of the test signal injector (or test adapter) and the injection method can directly impact test results. Too often, low-quality transformers are used to inject signals into the loops of power supplies during a measurement, and the results can be distorted due to the poor frequency response and impedance matching of the transformer.
When selecting a test adapter, its bandwidth limitations and impedance should be well understood. In addition, the injection signal magnitude can have tremendous impact on the accuracy of network analyzer measurements. In order to avoid problems, several types of signal injectors should be used, each for a different type of test. These include injection transformers, solid state signal injectors (current and voltage), line injectors, and other coupling elements.