Nonlinear-optimization techniques for quadruple-push oscillators

A systematic procedure for the design of quadruple-push oscillators is presented. The 4th-harmonic output power is maximized through load-pull optimization of the sub-oscillator circuit. Two variants of the technique are considered: the use of ideal harmonic terminations, defined by their reflection coefficients, and the use of a substitution generator at the output frequency. The latter enables a direct control of the output amplitude at the 4th-harmonic component. A further global optimization of the entire quadruple-push configuration is performed, connecting one auxiliary generator to each sub-oscillator to impose the required 90deg phase shift and preventing undesired oscillation modes. A statistical analysis of the design sensitivity to discrepancies between the four sub-oscillator elements is also presented. The proposed techniques have been applied to the design of a quadruple-push oscillator operating at 20 GHz.