POWER SPLITTING AND COMBINING TECHNIQUES ON MMICS

This article reviews several power splitting and combining techniques that are commonly used on, oi could be applied to, monolithic microwav e integrated circuits (MMICs). Several techniques for splitting and co mbining power off-chip using alumina hybrid structures are included bu t only where the technique has the potential for monolithic implementa tion in the future. The text considers the characteristics of the acti ve devices that limit their power-handling ability and explains the re quirement for power splitting and combining structures. Only passive s plitters and combiners al e covered, as active structures are ineffici ent and suitable only for small-signal application. In general, the sa me structures are used for splitters oi combiners, so the two componen ts are considered separately only where appropriate. The types of comb iner addressed al e as follows: parallel devices; impedance transformi ng networks; Wilkinson combiners; bus-bar combiners; Lange couplers; t ravelling-wave combiners; and Dolph-Chebychev tapered-line combiners. The most important attributes of all these types of combiner are their insertion loss, physical size, frequency bandwidth, bias compatibilit y, and effect on odd-mode stability The performance advantages offered by each type of combiner to each of these areas are compared, and tra de-offs between the combiner types are analysed.