Cable test instrument having interchangeable performance modules

摘要

A test instrument (50) for testing a cable (52), the test instrument having a main unit (54) and an interchangeable performance module (56). The main unit of the test instrument contains signal generators for generating AC and DC test signals. The AC test signals are generated as single-ended signals and applied to a pair selection switching array (76). The pair selection switching array switches the single-ended test signals to a plurality of lines (84a-84d) that couple to the performance module. The performance module is an interchangeable module having a plurality of balancing networks (baluns) (102a-102d) that are connected to the plurality of lines. Single-ended test signals applied to the baluns are converted into balanced signals and applied to a cable being tested. The performance module may be interchanged to allow the main unit to be connected to cables having various impedances and connectors. The conversion to a balanced signal after the switching array improves the test instrument accuracy and allows the switching array to be constructed of transistors.