An innovative signal distribution system that allows EMI free communications for Navy ships

One of the most significant challenges for the Navy to increase communications capacity is electromagnetic interference (EMI). Increasing the number of antennas boosts the level of both signal adjacent interference and inter-modulation products. Frequency hopping waveforms, used to mitigate jamming by an adversary, produce significant interference in co-located receivers. One method to decrease the interference at its source is to use multi-couplers. These devices allow one antenna to transmit or receive multiple signals. The current device for the 30 to 88 MHz very high frequency (VHF) frequency range can transmit or receive four signals with up to 60 Watts (W) of input power. Only one of the signals can be hopping in frequency. The corresponding device for 225 to 400 MHz ultra high frequency (UHF) can perform a similar function for four 100 W signals, none of which can be hopping in frequency. An innovative device now being fabricated should greatly mitigate EMI and allow up to 75% reduction in the number of antennas used on a large Navy ship. The signal distribution system for the transmit function uses a comb filter architecture to combine the outputs from multiple radios, channel them according to frequency, amplify them, re-combine them, and then couple them to a single transmit antenna. The corresponding system for the receiver feeds multiple signals from an antenna and uses a similar architecture to send them to the appropriate radios. The systems use the frequency dependence of the signal impedance to send them along the appropriate path. The mechanism does not use active control. The transmit sub-system is called comb linear amplifier combiner (CLAC). The receive sub-system is called comb limiter combiner (CLIC). Current tests and simulations indicate that a ten-path system for VHF can handle up to sixteen radio circuits simultaneously, all of which can be frequency hopping. The UHF system increases the number of signals to twenty-four, half of which can be frequency hopping. The existing RF distribution systems on Navy ships can transmit a maximum of three VHF and one UHF frequency hopping without significant EMI. The new RF distribution prototypes fabricated indicate that the Navy can reduce the space and weight allocated for amplifiers and multi-couplers in the radio room and shippsilas power consumed by 50%. The use of CLIC/CLAC on a medium to large-size ship shows promise to increase the number of signals while reducing interference and the number of antennas.