Millimeter-wave radar time-domain reflectometer's picosecond edge pulse generator

To meet the requirements of a millimeter-wave radar time-domain reflectometer (TDR) for a pulse generator that outputs pulses with short edge times, adjustable pulse widths, adjustable pulse amplitudes, and flat pulse signal levels, a pulse signal generator is designed that outputs pulses with an edge time of 30 ps, adjustable pulse width and amplitude, and flat pulse tops and bottoms. Based on the measurement principles of TDR, the design objectives of the pulse signal generator are established. A high-speed XOR (exclusive OR) gate with adjustable output pulse amplitude is used to achieve pulse edge acceleration and amplitude adjustment. A programmable delay circuit is employed to realize pulse width adjustment in 10 ps steps. The pulse signal output transmission line is designed based on transmission line theory, and its transmission characteristics are measured, with an impedance of 51.7 ohms and a bandwidth of 19 GHz. Test results show that the output pulse rise time of the pulse signal generator can reach 30 ps, the pulse width is adjustable in 10 ps steps, the differential pulse amplitude is adjustable from 600 mv to 1200 mv, the single-ended amplitude is adjustable from 300 mv to 600 mv, and the top overshoot is 20 mV.