In certain aspects, a voltage controlled oscillator (VCO), a system circuit, and a control method thereof are disclosed. The VCO includes a first oscillator circuit and a second oscillator circuit. The first oscillator circuit includes a first inductor. The second oscillator circuit includes a second inductor. The first inductor is embedded inside the second inductor so that a total mutual inductance between the first and second inductors is smaller than or equal to a predetermined threshold.