An approach to generate high-quality broadband frequency swept millimeter-wave (mm-wave) pulses based on photonics-assisted direct frequency up conversion of a low-frequency chirped microwave drive signal has been proposed and demonstrated. This is made possible by using an unbalanced temporal pulse shaping system involving two cascaded Mach-Zehnder modulators both biased at the minimum transmission points. The proposed approach is verified by simulations. A frequency swept mm-wave pulse with instantaneous frequency spanning from 40 to 100 GHz is generated thanks to 40 times frequency up conversion. Two-fold improvement on the time-bandwidth product of the generated waveform is also achieved thanks to cascaded modulation.