A W-band 2.5 GHz bandwidth pulse generator comprising a voltage-controlled oscillator (VCO) and a novel pulse former in a 65 nm CMOS technology is presented. The proposed sub-harmonic pumped pulse former, which plays roles as both a frequency doubler and a pulse former, is designed to obtain high efficiency using a transformer-based current reuse circuit. The VCO is implemented with a parallel combining transformer, which makes it insensitive to load variations due to pulse formation. Measurements show that the pulse generator achieves -1 dBm peak output power at 79 GHz. It can generate 800 ps pulse signals with an RF carrier of 76.1-79.6 GHz, achieving the energy cost rate of 50 pJ/pulse with a 1.25 GHz pulse repetition period.