A Nonlinear Transmission Approach to Compressing Rise and Fall Time in Picosecond Pulse Generation

This article presents the generation scheme of picosecond (ps) pulses based on both step recovery diode (SRD) topology and nonlinear transmission line (NLTL) scheme with a focus on simultaneous rise and fall time compression. First, the SRD topology is suggested and investigated for manifesting the capability of pulse compression. The SRD solution is then integrated with different NLTL schemes for alienating and achieving rise or fall time compression in the ps regime. It is observed that single NLTL integration only sharpens the rising or falling edge at the same time. To overcome this challenge, two NLTLs having different diode polarities are then integrated with SRD topology-based ps pulse generator to compress rise and fall time simultaneously. The theory of NLTL is developed in each case, and based on it, the shortest rise and fall time is selected for the final design. Several parameters that are responsible for waveform distortion are also investigated in detail as well. Finally, we have fabricated four different pulse generators in which the first three only compress the rise time whereas the fourth one is responsible for both rise and fall time compressions. The overall pulse duration for the first three generators falls within 80-95 ps having different ringing levels and they are based on rise time compression only. The pulse duration for the fourth pulse generator is almost 25 ps having a detailed ringing level of -14.24 dB and full-width at half-maximum (FWHM) of 10.1 ps based on both rise and fall time compressions. Finally, all these pulse generators are compared with the state of the arts in the literature where they utilize different techniques for sharpening and the superiority of our proposed designs is provided. These generators will find their key role and will be the best candidates for ultra-wide band (UWB) radars for electromagnetic imaging and sensing applications, ultrafast electronic techniques including edge sharpening, future oscilloscopes, comb, or pulse generators, and geophysical exploration.