A communications device capable of simultaneously operating in a dual-band
CDMA communications system having a cellular and a PCS CDMA
communications systems and a dual-band GSM communications system having a
GSM 900 and a GSM 1800 communications systems includes a radio signal
transceiver module, a CDMA module, a GSM module, a first CDMA filtering
unit, a second CDMA filtering unit, a first GSM filtering unit, and a
second GSM filtering unit. The first CDMA filtering unit, the second CDMA
filtering unit, the first GSM filtering unit, and the second GSM
filtering unit are utilized for discarding signals in an overlapping
frequency band between the dual-band CDMA and the dual-band GSM
communications systems.