Signal sources for high resolution radar applications

Abstract

The increasing demand for high resolution target detection in short range radar applications requires the use of an ultra wide band (UWB) signal. The UWB signal can be generated by a pulsed wave or by a frequency modulated continuous wave. For the resolution of several centimeters, a sub-nanosecond pulse or a frequency sweep up to several GHz is required. A UWB signal source is an important building block in such systems because it determines the pulse width and the bandwidth of the transmitted signal. In this thesis, a UWB pulse generator and a UWB PLL are presented for the UWB signal generation. A fast transient response pulsed oscillator is proposed for the implementation of the UWB pulse generator. The pulsed oscillator is switched on by a glitch signal only for a short duration, so as to make a UWB pulse. A pulse shaping filter makes the oscillator output fall into the Federal Communications Commission (FCC) spectral mask. The pulse generator is fabricated using a 0.18 μm CMOS process. The core chip has a size of 0.11 $mm^2$. The measurement results demonstrated sub-nanosecond pulse duration with low energy dissipation and high-peak amplitude. It shows pulse duration of about 500 ps with -10 dB bandwidth of 4.5 GHz from 5.9 to 10.4 GHz. The energy consumption is 27.6 pJ per pulse with a peak-to-peak amplitude of 673 mV on a 50Ω output load. A UWB ring VCO with a level shifter is proposed for the implementation of the UWB PLL. A design guide for the optimization of the UWB ring VCO is presented to maximize the tuning range and to minimize the power consumption. The UWB ring VCO with the level shifter is fabricated using a 0.18 μm CMOS process. The VCO demonstrated ultra wide tuning range from 0.85 to 10.01 GHz with the power consumption from 2.2 to 32.4 mW. The VCO requires 0V tuning voltage that can be a problem in a PLL application because a charge pump output can not operate properly with 0V tuning voltage if a negative supply is not used. This pro...