Co-Site Analysis

When mutiple transmitters and receivers are co-located on the same platform, there are opportunities for the transmitting systems to interfere with the receiving systems. The interference can be in-band or out-of-band interference. Additionally, effects such as intermodulation products created in the mixers of receivers can cause interference that is not obvious when one performs a frequency spectrum analysis.

Analyzing co-site problems is a non-trivial problem. One must model the antennas performance when installed on the platform (both in-band and out-of-band performance), characterize the receiver front end (e.g. filters, RF amplifiers, mixers, receiver sensitivity, etc.), characterize the transmitter emissions (e.g. fundamental, harmonics and spurious emissions power levels) and then look for interferring frequencies. Care must be taken to use accurate installed antenna patterns or simulations can easily be inaccurate by tens of dB. Additionally, care must be taken when modeling receiver front ends. Simplistic receiver front end models will often not accurately model intermodulation products generated by mixers. These inaccuracies can lead to predicting no interference when an interference problem exists or you are operating dangerously close to an interference problem.

Delcross Technologies has performed co-site analyses for both commercial and defense applications. Further, we have developed the EMIT software for predicting cosite interference.