A LINC transmitter using a new signal component separator architecture

The LINC (LInear amplification with Nonlinear Components) transmitter is an architecture that provides linear amplification using nonlinear but power efficient amplifiers. The signal component separator (SCS) is a crucial signal processing function of LINC. DSP implementation of the SCS at baseband has so far been assumed to be the best choice although it suffers from matching and power consumption problems. A new SCS architecture based on analog integrated circuit (IC) techniques is presented to avoid the problems faced by a DSP-based realization. The proposed scheme is studied at system level by both analysis and simulation. Experimental results are also obtained from a 200 MHz experimental LINC transmitter built around a full-custom analog IC that implements the SCS using this new architecture. Test results showed that spurious levels around -50 dBc could be obtained with a /spl pi//4-shifted DQPSK modulated North American Digital Cellular (NADC) signal. This implies a high degree of linearity.