Discrete Load-Modulated Single-RF MIMO Transmitters

Some recent progresses in Load-Modulated Single- RF (LMSRF) multiple-antenna transmitters are presented including the circuit analysis in the case of closely spaced antennas. Mutual coupling effect is considered and it is shown that there is no need for any decoupling network since the mutual coupling effect can be considered in digital baseband domain. Furthermore, discrete LMSRF is introduced and an implementation method for it using PIN diodes and microstrip lines is presented. Some simulation results for Orthogonal Frequency Division Multiplexing (OFDM) signals with Quadrature Amplitude Modulation (QAM) and Quadrature Phase Shift Keying (QPSK) inputs are presented, e.g., it is shown that using 8 switches in every load modulator results in a signal to distortion ratio of 17.8dB at the transmitter.