EMC analysis of collocated UHF frequency hopping systems employing active noise cancellation

Active noise (interference) cancellation, which involves sampling the outputs of each on-site in-band transmitter, applying the appropriate delays and gain, and inverting the phases, can allow UHF receivers to operate with adequate sensitivity during the simultaneous operation of high power UHF transmitters with minimal antenna spacing. Active noise (interference) cancellation can be used in both the standard, fixed frequency mode of operation, or in a frequency hopping mode. Active interference cancellation is being used with much success on land, air, and sea based communication systems to solve collocation problems. This paper shows the benefits gained by active noise cancellation and reviews the details of the several items that must be considered and analyzed when designing a UHF communication system for a dense cosite installation where active noise (interference) cancellation must be used