Patent ID: 7902930
Filing Date: 2011-03-08
Classification: H03B

Abstract:
1. A colpitts quadrature voltage controlled oscillator comprising: first and second LC resonators connected to a power supply voltage and generating a same resonance frequency, each resonator comprising a coupling capacitor and two inductors respectively having first and second ends, the two inductors being connected to each other at the first ends thereof and connected at the second ends thereof to opposing ends of the coupling capacitor; first and second differential oscillators respectively comprising first and second oscillation transistors that oscillate at the generated same resonance frequency to output an oscillation signal; feedback capacitors and a degeneration capacitor connected between the first and second oscillation transistors; and a negative resistance cell for amplifying amplitudes of orthogonal signals generated from bases of the first and second oscillation transistors so that the amplitudes of the orthogonal signals generated from the bases of the first and second oscillation transistors become the same as amplitudes of orthogonal signals generated from collectors of the first and second oscillation transistors, wherein first and second output nodes of the first LC resonator are respectively connected to the bases of the first and second oscillation transistors, and third and fourth output nodes of the second LC resonator are respectively connected to the collectors of the first and second oscillation transistors, so that quadrature orthogonal signals having a phase difference of 90 degrees are generated from the bases and collectors of the first and second oscillation transistors, wherein the negative resistance cell comprises third and fourth transistors differentially cross-coupled to the first and second output nodes of the first LC resonator.