Design of Pulse Generator in 180nm Technology for GPR Applications

Abstract

In this work, we present a low-complexity and low cost pulse generator in 180nm technology for ground penetrating ultra-wideband (UWB) radar system applications. Here I have implemented an UWB pulse generator circuit. A UWB pulse generator is a method introduced in communication system to simplify the data transmission and remove disadvantages that occurs in other systems. This generator generates a Gaussian pulse for a small period of time of the order of some nanoseconds. As UWB pulses are generated for a short time, hence no carrier signal is required to send a base band or message signal. So power loss due to carrier signal doesn’t exist at all. These pulses are very high in frequency; hence it has very less chance to be got affected by noise. This pulse generator uses a delay generator along with a Gilbert XOR cell for generating a Gaussian pulse which can be shaped by using a FIR filter, and finally a Gaussian mono cycle pulse is observed at the output which has a pulse width of 97ps thereby give rise to a bandwidth of 10.3 GHz which meet the FCC requirements. The pulse generator comprises of three cascaded delay blocks, a XOR block, and a FIR filter. The interpolation delay blocks uses voltage for adjusting the delay time by the control of the gains of each path. By adjusting the delay time, pulse generator can achieve the required frequency. The XOR gate is implemented using a Gilbert cell. When the two signals given as input have opposite voltage levels at a given time, the XOR gate creates a pulse. After the XOR gate, a Gaussian pulse is generated and then it goes through the FIR filter to shape it to a Gaussian mono cycle pulse. The design and simulation of the pulse generator was performed using the Cadence UMC tool in 180nm CMOS process.