Recently, systems operating in the millimeter-wave frequency bands are demonstrated and realized for many applications. A W-band phase-locked loop (PLL) is designed for a 94GHz medical imaging system. Four popular frequency synthesizer architectures are discussed and compared. The PLL using a fundamental voltage-controlled oscillator (VCO) is chosen for the synthesizer architecture and realized in 130nm SiGe BiCMOS process. The employed fundamental Colpitts VCO achieves a tuning range from 92.5 to 102.5GHz, an output power of 6dBm, and a phase noise of -124.5dBc/Hz at 10MHz offset. The locking range of the PLL is from 92.7 to 100.2GHz, the phase noise is -102dBc/Hz at 1MHz offset, and reference spurs are not observable. This work also compares the figure-of-merit for millimeter-wave VCOs and discusses the LO distribution for millimeter-wave applications.