Separation of sub-bands of communications signals to reduce interference in distributed antenna systems (DASs) is disclosed. A sub-band separation circuit coupled to a plurality of antennas is configured to distribute and receive and transmit a pair of downlink and uplink sub-band signals. The sub-band separation circuit is coupled to a duplexed port of a remote unit that distributes uplink communications signals to the DAS and receives downlink communications signals from the DAS. In order to isolate the downlink communications signals from the uplink communications path in the remote unit, the isolation circuit includes a plurality of sub-band isolation circuits. Each sub-band isolation circuit is configured to isolate at least one sub-band of the downlink communications signal to generate a downlink sub-band signal that has a desired frequency separation or gap with uplink communication signals received at the duplexed port.