This work introduces a low phase-noise (PN) wideband voltage-controlled-oscillator (VCO) by proposing five ports transformer in 0.18-μm CMOS technology. The proposed VCO uses five ports transformer and operates in the low band when all the pMOS-nMOS cross-coupled VCO components are activated, whereas this VCO operates in the high band using only part of the transformer, and an nMOS cross-coupled core. The transformer is designed using the top metal layer (M6) and the first inductor is meander line U-shaped center tap inductor, while the second inductor consists of two shunted octagonal loops to increase the quality (Q-) factor compared with using a single-loop inductor. The wideband switched transformer VCO achieves a measured frequency tuning range (FTR) of 16.4-17.1 GHz with a PN of -113.3 dBc/Hz at 1-MHz offset, and from 17 to 17.9 GHz