A monocycle pulse generator with variable capacitance diodes for radar target detecting application

Abstract

The high amplitude pulses played a crucial role and is of paramount importance for obtaining a good radar range, especially when performing the task of penetrating thick and lossy building walls. The outputs of monocycle pulse generator affect the performance directly. Aimed at increasing the output power of the transmitter and improving the present pulse generator, in this paper, we present a novel monocycle pulse generator. This generator can operate well at the pulse repetition frequency (PRF) up to 5 MHz and generate a monocycle pulse with good symmetry and very low ringing. It combines wideband bipolar junction transistors (BJTs), linear power amplifier transistor, step recovery diode (SRD), variable capacitance diodes (VCDs) as a unique pulse compressor, LC high-pass filter as a differentiator and short-circuited microstrip line to generate the monocycle pulse directly. Measurement results show that the output peak-to-peak amplitude of the monocycle pulse is 25V and the duration is 450ps. These characters has significant potential in applications where long detection range and a high resolution are concerned, especially when penetrating thick and lossy medium for applications in through-wall and ground penetrating radar sensors.