A 3-5 GHz 4-channel UWB beamforming transmitter with 1° scanning resolution and 135° scanning range is presented in this paper. The fine resolution is attained through Vernier delay lines capable of fine resolution down to 10 ps. Accurate path delay across channels as well as UWB pulse center frequency are achieved through the proposed ΔΣ DLL calibration technique, which speeds up the calibration by 48 times compared with a counter-based approach. A novel power spectral density calibration circuit is included to adjust the UWB pulse shape for meeting the FCC mask. Fabricated in 0.13-μm CMOS, the proposed transmitter occupies only 7.2 mm². The power consumption is 9.6 mW while transmitting at 80 Mbps, with each transmitter achieving 10 pJ/bit and transmitter efficiency of 7.5%. This is about ten times better than those existing UWB beamforming transmitters.