An oscillator of balanced design in which a resonant impedance network is connected between the control ports of two matched transistors, and a capacitance is connected in parallel, across the two inputs of these transistors. The inputs of the transistors are connected each to a matched current source....http://www.google.de/patents/US4810976?utm_source=gb-gplus-sharePatent US4810976 - Frequency doubling oscillator and mixer circuit
