Radio designers need to perform intermodulation-distortion (IMD) testing on their gear. During such tests, a two-tone signal is typically presented to the device under test and a measurement taken of the device's IMD. IMD tests are performed on both receivers and transmitters. As performance requirements increase, it becomes more difficult to generate two-tone signals having the required spectral purity.

To generate a test signal during two-tone IMD testing, it is generally desirable to combine the outputs of two standard signal generators. However, insufficient isolation between the combiner ports produces IMD products in the output stages of the generators themselves that mask the performance of the device under test. 

Port isolation of around 30 dB is the best possible value for a simple hybrid combiner. That has made it difficult to make IMD measurements on newer equipment that must be tested to high input-signal levels. Usually, special (read expensive) test fixtures are needed to achieve clean, high-level test signals.

Ten-Tec's two-port IsoLine combiner/splitter achieves a typical port-to-port isolation of >50 dB over any 30-MHz of bandwidth within most of its range of 2-300 MHz.  The IsoLine typically achieves greater than 60 dB of isolation over narrower frequency ranges.  That is the best in the industry and is fully three orders of magnitude better than anything else we are aware of.  A built-in adjustment control allows users to optimize isolation for their particular frequencies of interest.