Quadrature generation and phase adjustment architecture for Cartesian loop transmitter

Linearization is used in cellular radio portable transmitters to improve transmitted signal Adjacent Channel Coupled Power Ratio ( ACCPR) while keeping high RF power amplifier (RFPA) efficiency. Cartesian feedback loop based linearizer are commonly used in linear digital cellular portable transmitters ( TETRA, iDENtrade, etc. ). Cartesian feedback linearizers enable improved adjacent and alternative channels ACP while still allowing the RFPA to operate close to its saturation point, which maintains good RFPA efficiency. Phase training is used in a Cartesian feedback loop to correctly adjust loop phase to facilitate negative feedback (stability). This paper discuss architectures for quadrature generation and phase adjustments in Cartesian loop transmitters.