In this paper, a concept for a super-harmonic injection locked oscillator with very precise quadrature outputs is proposed and studied. The circuit has a frequency range from 57 GHz to 64.5 GHz. It features an integrated push-push frequency doubler operating at the second harmonic and a robust Marchand balun. The circuit can maintain a very low quadrature phase and amplitude error in the locking range. The maximum measured quadrature phase and amplitude errors are 0.8° and 0.6 dB, while the minimum can be as low as 0.083° and 0.11 dB.