Signal Generation for FMCW Ultra-Wideband Radar

Abstract

One of the greatest concerns facing the planet earth today is global warming. Globally the temperatures have risen and this has caused rise in sea level. Since a large percentage of the population lives near the coast sea level rise could have potentially catastrophic consequences. One of the largest uncertainties in projections of sea level rise is the changes of mass-balance of the ice sheets of Greenland and Antarctica. To predict the rise in sea level we need accurate measurements of mass-balance. One of the methods of determining mass-balance is through surface ice elevation measurements. In order to measure surface ice elevation, map near surface internal layers and measure the thickness of snow over sea ice Ultra-Wideband (UWB) Frequency-Modulated Continuous-Wave Radars are being developed at CReSIS. FMCW radars are low-cost low-power solution to obtain very fine range resolution. However, nonlinearities present in the transmit frequency sweep of the FMCW radar can deteriorate the range resolution. The main objective of the thesis was to produce an ultra linear transmit chirp signal for UWB Radars. This was done by using the Voltage-Controlled-Oscillator (VCO) in a Phase-Locked Loop configuration. To check the linearity of the chirp beat frequency was generated using delay line as a synthetic target and captured on the oscilloscope. This beat signal data were further analyzed for linearity and we found that the frequency response of the beat signal was a focused Sinc wave as opposed to a smeared signal in case of nonlinear chirp. Also the phase of the beat signal data was linear with respect to time.