A method suppresses transmission noise comprised in a plurality of downlink signals received by one of a first radio module or a second radio module comprised in a communications apparatus. The method receives a plurality of first signals and a plurality of second signals, wherein the first signals and the second signals are the downlink signals respectively received via different antennas of the one of the first radio module or the second radio module, or the first signals are the downlink signals received by the one of the first radio module or the second radio module and the second signals are a portion of the uplink signals provided by the other one of the first radio module and the second radio module, and processes the plurality of first signals and the plurality of second signals to cancel transmission noise comprised in the plurality of downlink signals.