This brief presents a bidirectional nonlinearly coupled quadrature voltage-controlled oscillator (BNC-QVCO) incorporating passive phase interpolation for the generation of multiphase signals. In addition, to generate multiphase signals, the proposed bidirectional nonlinearly coupling network improves the phase noise performance of the QVCO by producing approximate-in-phase injection-coupling currents into the LC tank. Moreover, to balance the amplitude of eight-phase signals, an additional passive amplitude division circuit is implemented with capacitor banks for calibration. For verification, a BNC-QVCO incorporating passive phase interpolation is implemented in a 40-nm CMOS technology with a core area of 0.13 mm2. The measured multiphase signals achieve a phase noise of −116.57 dBc/Hz at 1-MHz offset from 4.32 GHz. The power consumption without buffers is 10.2 mW under 1-V supply voltage and a 20% frequency tuning range from 4 to 4.8 GHz is achieved with the implemented digitally controlled capacitor banks.