Spectral Energy Requirements and Adjacent-Channel Crosstalk in CAS

Four-frequency channels avoid the prior slot interference that handicaps single-frequency collision avoidance systems of equal message-slot capacity. Crosstalk between adjacent frequency channels is adequately limited If the receiver response to adjacent-channel signals is attenuated at least 52 dB. With 5-MHz channel separation, 48-dB crosstalk rejection was achieved in a test receiver by restricting the RF pulse rise time and decay time to 0.2 μs minimum. Crosstalk resulting from biphase modulation can be effectively attenuated by limiting the minimum envelope transition time to 0.2 μs. The effect of pulse rise time and decay time on the energy density spectrum is discussed.