RF Design Of The GSM/CDMA 1X Simultaneous Dual-mode Mobile Terminal

The goal of this paper is to deeply research on the RF design of GSM/CDMA1X simultaneous dual-mode mobile terminal that embedded GSM radio unit and CDMA1X radio unit can work simultaneously. The total research work includes not only independently implementation of the GSM and CDMA radio units, but also the study on effective methods eliminating and alleviating the interference between the two radio units with aim to ensure the overall RF wireless performance of the mobile terminal, compliant to certain standard requirements when working at multi-frequency bands.The interference issue of transmitters to receivers between GSM RF and CDMA RF units is emphasized in this paper, which is consisted of 4 cases of interference patterns as followed. Case 1, interference of GSM transmitting signals to CDMA receiver, which is especially strong within the overlapping and adjacent frequencies of GSM tramsmitter and the CDMA receiver; Case 2, interference of GSM transmitting spurious emissions to CDMA receiver; Case 3, interference of CDMA transmitting signals to GSM receiver; Case 4, Interference of CDMA transmitting spurious emissions to GSM receiver.In the paper, the principle and implementation methods of eliminating and alleviating RF interference claimed above are introduced. The essential guideline is to effectively increase and maximize the RF isolation between GSM RF and CDMA RF units, of detailed methods such as: respectively designing GSM and CDMA antennas to enhance spatial radiated isolation; separating the GSM and CDMA radio units to enhance board level conducted isolation. With all these methods adopted in the real product design, the GSM/CDMA1X simultaneous dual-mode mobile terminal was successfully developed finally.