| There is no single answer to how to improve the efficiency of wireless transmitter while maintaining its linearity and satisfying all other design specifications. More realistic approach to this problem should be thinking about how to combine similar elements in a right proportion to maximize the overall performance.;The conflicting requirements of high linearity and high efficiency impose an enormous challenge for the RF transmitter design. In this research, switching modulation technique is investigated, and the experimental results shows that the spurious noise from the switching converter can be reduced more than 53 dBm by periodically or randomly modulating the switching frequency of the switching converter.;To improve the efficiency of the switching converter without degrading its closed-loop transient response speed, the dual switching converter that incorporates two different types of switching converters is designed. Simulation and experimental results show that the dual switching converter topology has high performance without large hardware penalties.;The proposed current-sensing circuit can sense the average current out of the fast converter with a high switching frequency (> 30MHz), and the sensed voltage output effectively control the output current of the slow converter. Experimental results shows that, when a wide bandwidth triangular pulse, sine wave, and saw-shaped signal are applied to the dual converter, the fast converter effectively provides the high frequency part of the output current and the slow converter provides the low frequency part of the output current. The large ripples from the slow converter are effectively absorbed by the fast converter, so the actual ripple voltage was less than 50mV with 150nF load capacitor. The dual converter is fabricated in a standard 0.18 mum CMOS process. |
