Ruthroff Transformer Doherty Combiner for Compact Power Amplifiers

The patent combines the functions of impedance matching and power combining into a single Ruthroff transformer structure. The Ruthroff transformer integrates the impedance transformation function (typically requiring separate matching networks) and the power combining function (requiring separate combiner circuits) into one compact component, thereby reducing the overall physical area while maintaining linearity and efficiency performance

The Ruthroff transformer serves multiple functions simultaneously: it acts as an impedance matching transformer, a power combiner, and provides a DC path for the drains of all transistors. This multi-functionality eliminates the need for separate dedicated components for each function, significantly reducing the combiner's physical footprint while preserving the required performance characteristics

The patent replaces the traditional quarter wavelength transmission line structure (which occupies large physical space and is difficult to integrate) with a Ruthroff transformer implemented using planar transmission line techniques. This substitution maintains the electrical performance for linearity while enabling compact fabrication using standard IC/IM/MMIC manufacturing processes

The Ruthroff transformer changes the electrical parameters (impedance transformation ratio, phase relationships) through its winding configuration and turns ratio, achieving the same linearity performance as quarter wavelength lines but with significantly reduced physical dimensions that are compatible with integrated circuit fabrication