Presented is an active inductor harmonic filtering technique that improves the phase noise of the wideband LC voltage controlled oscillator (VCO). A Wu folded active inductor structure was chosen to design a wideband filtering device that consists of a single NMOS transistor and a resistor. Using an active inductor can reduce chip area by 37.68% while performing wideband harmonic filtering compared to existing LC filtering techniques. The chip was fabricated in 130 nm CMOS technology. The measured phase noise of the VCO is -119.21 dBc/Hz at a 1 MHz offset frequency at the 4.28 GHz carrier. The VCO is activated by a 3-bit digitally controlled switched capacitor array to achieve a 39% wideband tuning range from 3.8 to 5.6 GHz. A current of 4.2 mA flows continuously for the whole frequency from a 1.2 V supply voltage.