Minimizing RF interference is one of the toughest challenges for wireless communications network designers. In the case of microwave radio link networks— whether used for communications backbones, branch links or other forms of distribution— the overall density of the network depends largely on how well the interference between links is controlled.

One of the main causes of interference between point-to-point microwave links is ‘side lobes’—spurious reflections that radiate in directions other than the main beam (Figure 1). Side lobes up to 30 degrees away from the main beam tend to have sufficient energy to interact and interfere with physically adjacent links, causing reduction in signal quality and increases in bit error rate. By minimizing side lobes through sophisticated microwave antenna design, a greater number of point-to-point links may be deployed within a given area without being affected by interference.

In order to quantify the impact of side lobes on microwave radio link interference, the Swiss Federal Office of Communications (OFCOM) recently conducted a study involving a Radio Frequency Systems ultra high-performance CompactLine antenna, along with a similar antenna from another leading supplier (Antenna B). Since Switzerland has possibly one of the highest radio link densities in Europe, the OFCOM has established a reputation as a leader in radio link interference calculation.