Evaluation of a lossless combiner in a LINC transmitter

Two combiners are compared for use in a LINC transmitter. Most LINC transmitters use matched hybrid combiners as they provide high isolation between input ports to provide undistorted signal combining. A tee combiner has also been explored for use in a LINC transmitter but was evaluated under the assumption of high input port isolation and perfectly matched amplifier outputs. This paper evaluates the use of a lossless tee combiner with input port coupling and unmatched amplifier outputs and their effects on the LINC transmitter´s linearity and efficiency. It is shown that efficiency may be improved at the expense of overall transmitter distortion when a lossless tee combiner is used.