A 200MHz IF BiCMOS chip for linear LINC transmitters

The LINC transmitter is an architecture that provides linear amplification using nonlinear high efficiency amplifiers. The signal component separator (SCS) is a crucial signal processing function in this scheme. In this paper a new SCS architecture based on analog integrated circuit techniques is presented. A 200MHz IF SCS chip using the proposed architecture has been designed and fabricated in a 0.8µm BiCMOS process. An experimental LINC transmitter setup was built with the SCS chip, nonlinear amplifiers and a power combiner. Test results showed that spurious levels around -50dBc could be obtained with a π/4-shifted DQPSK modulated North American Digital Cellular (NADC) signal. This implies a high degree of linearity in the implemented LINC transmitter system.