Editing Adjacent-channel interference (section)

==Origin==
The adjacent-channel interference which receiver A experiences from a transmitter B is the sum of the power that B emits into A's channel—known as the "unwanted emission", and represented by the ACLR (Adjacent Channel Leakage Ratio)—and the power that A picks up from B's channel, which is represented by the ACS (Adjacent Channel Selectivity). B emitting power into A's channel is called adjacent-channel leakage (unwanted emissions). It occurs for two reasons. First, because RF filters require a [[roll-off]], and do not eliminate a signal completely. Second, due to [[intermodulation]] in B's amplifiers, which cause the transmitted spectrum to spread beyond what was intended. Therefore, B emits some power in the adjacent channel which is picked up by A. A receives some emissions from B's channel due to the roll off of A's selectivity filters. [[Selectivity (radio)|Selectivity]] [[Filter (signal processing)|filters]] are designed to "select" a channel. Similarly, B's signal suffers intermodulation distortion passing through A's RF input amplifiers, leaking more power into adjacent frequencies.