UCLA

As the number of wireless network users increases in the modern communication systems, cognitive radio becomes an attractive solution to the crowded communication spectrum. A key technology that enables the application of cognitive radio is the circuit that can sense the available spectrum for communication, as known as: Spectrum Scanner. Previous work has demonstrated a passive spectrum scanner using the sampled LPTV RC circuit that achieves 0-1Ghz scanning range and 40dB stopband attenuation. However, the parasitic capacitors in the resistor DAC limits the stop band attenuation from 60dB to 40dB. Chapter 1 and 2 will provide the background of sampled LPTV RC filter as a spectrum scanner. Chapter 3 will provide the analysis of parasitic capacitor's effect on filter's frequency response and a RDAC switching technique as a solution. Chapter 4 and 5 present the circuit design of a 0-3Ghz spectrum scanner using return-to-infinity RDAC to remove parasitic capacitor's influence on filter's stopband attenuation.