A Technology To Generate Fast-Edge Pulses

Ultra-wide-band rectangular pulse generation technology has a widerange of applications in ultra-wide-band radar, nuclear physics,high-speed photography and ultra-fast signal compensation.Ultra-wide-band radar requires a pulse source which could generate pulseswith high amplitude, fast rising and falling edge. Pulse amplitude couldachieve to hundreds of volts using avalanche transistor with transmissionline technology, but its band width maybe just2G because of restrictionson devices. Therefore, ultra-wide-band rectangular pulse has greatsignificance in developing ultra-wide-band radar.A rectangular pulse with ultra-fast rising edge and falling edge hasbeen developed by using step recovery diodes (SRD) and avalanchetransistors. I have studied on avalanche effect in transistors and steprecovery effect in step recovery diodes、discussed parameters of thesedevices、offered the principle in device choosing and researched on theprinciple and method to shape the pulse by regular the capacitor andinductance in the circuit. I have developed a primary rectangular pulsewith rising edge and falling edge all about400ps by charging the cablewhen the transistor is cutoff and discharging quickly when the transistoris avalanche. Then I shaped the rising edge with two step recovery diodesand falling edge with one step recovery diode. With this method we cansteepen the edge of the pulse as well as increasing the stability of thepulse and the flatness of the pulse. The circuit was mainly designed byusing micro strip line.The circuit can generate rectangular pulses with rising edge about160ps, falling edge about300ps, amplitude about8v and pulse width about 5ns, and in50Ω load. The trig jitter is less than5ps(RMS) and theflatness of top is better than4%.