Dual-band transmitters using digitally predistorted frequency multipliers for software defined radios

Two methods of implementing dual-band transmitters using re-configurable circuits operating in conjunction with digital predistortion linearizers are investigated. One method utilizes a circuit topology that can be switched between a fundamental-mode in-phase combined amplifier, and a push-push frequency doubler. Measurement results indicated that the circuit was able to amplify IS-95 B CDMA signals in either the 881 MHz, or the 1763 MHz band with an adjacent-channel power ratio (ACPR) of -48 dBc/30 kHz. Another method that was investigated utilizes fundamental-frequency power amplifier followed by a varactor multiplier that can be bypassed. A varactor-diode doubler with a conversion loss of 3.3 dB was built and tested. An ACPR of -53 dBc/30 kHz at 885 kHz offset was achieved for a CDMA signal transmitted at 1892 MHz.