A compact ultra-wideband sub-nanosecond pulse generator with step recovery diodes

This article presents a compact ultra-wideband (UWB) sub-nanosecond monocycle pulse generator. The proposed circuit has a simple structure and low cost, and its core components are step recovery diodes (SRDs). It is composed of a power supply circuit, pulse drive circuit, short pulse-forming circuit, and pulse-shaping circuit. A transistor-based drive circuit is used to generate a drive pulse with sharp fall time. Then, a sub-nanosecond pulse width is realized through the combination of two SRDs in series and parallel. Finally, a monocycle pulse is directly formed by the inductance-based differentiator. This design achieves a full pulse width of 406 ps with a 260 mV peak-to-peak amplitude and a -10 dB bandwidth of 510 MHz to 6.1 GHz at a pulse repetition frequency of 10 MHz square waveform. The symmetry and ringing level are 96.9% and -25.3 dB, respectively, providing good symmetry and low ringing with a circuit size of 55 x 15 mm. In actual experiments, two identical UWB antennas with appropriate bandwidth are used to radiate a monopulse to breast phantoms. The results and uncertainty analyses of the test system show that there are distinguishable differences under diverse tumor phantoms and locations, proving that the proposed pulse generator is attractive for the application of UWB breast cancer detection.