Advanced compact butler matrix solutions for MPA applications

Two basic alternatives of advanced Butler matrix implementations are introduced for Multi-port Power Amplifiers (MPA). They are shown to provide different advantages for the design of assigned MPA networks, thus, each of which may be beneficial over the other for particular requirements of a given application. Namely the first solution based on implementations with different hybrids (E- and H-plane types) are suited for broad operational bands (18%), however, the amplitude variations of the different paths over the wide bandwidth varies typically by app. 0.8dB for 8x8 Butler matrix design. Additional filters may be necessary to accommodate the suppression of interfering signals of the amplifiers. The second Butler matrix approach relies on a multi-port of coupled resonators, which inherently provide a bandpass filter characteristic. This solution will be limited to overall bandwidths of app. 5%; however, the amplitude variation of all paths is almost identical. The overall coupled resonator structures will be very compact; selectivity requirements are imposed on the Butler matrix deisgn; i.e. there will be no need of extra bandpass filters. In addition different technologies {waveguide and Surface Integrated Waveguide (SIW)} can be applied for the required input and output Butler matrices of an overall MPA network to facilitate overall low-mass implementations. 8x8 Butler matrices have been designed for both alternatives to validate the feasibility and flexible implementations of the MPA solutions. The analyzed responses of different configurations for both concepts – obtained by full wave Electro-Magnetic (EM) CAD methods – prove the convenient implementations of both solutions while exhibiting their particular properties and advantages.