Passive intermodulation of ICT components

Abstract

Many communication systems today transmit and receive several different closely spaced channels simultaneously through the same antenna path. Any interaction and mixing of these signals by passive devices in the signal path, can result in unwanted mixed signal passive intermodulation (PIM) products. If these PIM products are significant, and occur within the frequency band of the receiver, then the performance of the system in that receiver band will be affected. It is therefore of great importance to ensure that any PIM products which occur within a receiver band, are below the threshold of significance for that band. Communication systems are composed of many interconnecting components between the transmitter and the antenna and the antenna and the receiver. These components may take the form of waveguides, cables, filters, combiners and the antenna itself and its accessories. All of these devices need to be manufactured and connected together in such a manner, that the PIM products generated, are insignificant in the operating bands and at the transmitter power levels which are used. In order to achieve the performance required one must be able to reliably measure the PIM products of the components concerned, both singly and together, under different conditions and for different signal power levels and frequencies. To this end the IEC working group TC46 WG6 are working towards standardising test methods and understanding the processes involved in PIM-emissions, to meet the needs of the rapidly developing telecommunications market.