Optimized Design of Retro-Directive Arrays Based on Self-Oscillating Mixers using Harmonic-Balance and Conversion-Matrix Techniques

In this work, a harmonic-balance technique for the optimized design of retro-directive arrays based on self-oscillating mixers (SOM) is presented. The conversion gain is maximized through the conversion-matrix approach, with the desired gain value as an optimization goal. This requires a harmonic-balance recalculation of the steady-state oscillation at each variation of the circuit-element values. The use of auxiliary generators at the oscillation frequency facilitates the combination of the two analysis techniques and prevents frequency deviations during the optimization process. The two-tone simulation of the SOM array, with an auxiliary-generator per array element, provides the 1dB gain-compression point for different choices of the small-signal gain. The intermodulation distortion of the complete system is analyzed with the envelope-transient method. A 2.9 GHz retro-directive array has been implemented and measured with good results