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.