Range to Fault Technology

Passive intermodulation (PIM) has been recognized as a problem in communications systems for nearly 50 years. The phenomenon occurs when two or more signals encounter a non-linear junction and “child” frequencies are generated that are mathematically related to the “parent” signals. With the advent of cellular communications, PIM began to rise in prominence as a concern due to the quality of service impact these unintended signals can have by interfering or blocking the uplink (receive) channels of the base station.

Occasionally PIM faults will occur that do not produce large spikes in magnitude when dynamically tested. Determining the location of these “non-responsive” or “static” PIM sources becomes more challenging and can often be time consuming. To address this problem Kaelus has developed Range to Fault (RTF) technology similar to that used in VSWR testing to help identify the location of these static PIM sources. This paper discusses the capability and limitations of this new technology as well a recommended test method for deploying RTF analysis in the field.