We have already proposed a triple tuned Voltage Controlled Oscillator (VCO) for achieving an ultra-wideband characteristic. The fabricated VCO in C-Ku band has achieved the oscillation bandwidth of 5.6GHz-16.8GHz. In this paper, for achieving the wide oscillation bandwidth in the higher frequency band, we proposes a VCO that consists of a MMIC working as an active circuit and external hyper-abrupt junction varacter diodes connect to the MMIC with Au wires. The fabricated VCO in X-K band achieves the oscillation bandwidth of 9.9GHz-21.9GHz and the phase noise of - 109.4dBc/Hz +/-2.4dB at 1MHz offset from the carrier. In addition, it is shown that the fabricated VCO achieves the widest oscillation bandwidth and the lowest phase noise in X-K band compared with other reported wideband VCOs.