A single-stage dual-drive Mach Zehnder modulator was employed for the generation of a 24-GHz-band ultra-wide-band signal. A theoretical model for signal generation was derived based on the modulation technique of a dual-drive Mach Zehnder modulator. By the numerical demonstration, an ultra-wideband signal of 5.8 GHz bandwidth was generated. The signal quality and the bandwidth were thoroughly investigated. The results show that residual local oscillation and low-frequency components can be efficiently suppressed if two modulating electrical signals with proper amplitudes are used. The bandwidth of the signal can be flexibly adjusted by simply controlling the pulse width of the input data signal. The millimeter ultra-wideband signal generator is a good candidate for the applications of automotive short-range radar, intrusion detection sensor and mobile radio services.