S-Band Second Harmonic VCO with Auxiliary Fundamental Frequency Output for PLL Stabilization

A second harmonic push-push VCO with auxiliary fundamental frequency output is presented. The fundamental frequency is extracted directly from the base of the transistor using only a small coupling capacitor. By this method a simple means is provided to extend the upper frequency limit of standard PLL stabilization based on ECL dividers (fmax = 1.5 - 1.8 GHz) by a factor of two. The operating principle of the oscillator, its practical realization in thin film lumped element technique and its electrical performance are described.