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The codesign of an impulse generator and miniaturized antennas for ultra-wideband impulse radio is described. The impulse generator, discussed by Bragga in 2004, is designed with differential outputs that are fed to the antenna, producing an optimum match of the generator to the antenna, an improved magnitude response, and reduced ringing of the radiated pulse. The impulse generator is preceded by a programmable pulse-position modulator and consists of a triangular pulse generator and a cascade of complex first-order systems, which, in turn, are made up of differential pairs employing partial positive feedback to approximate a Gaussian monocycle waveform. The complete pulse generator is fabricated in IBM 0.18-μm Bi-CMOS IC technology. Measurements show the correct operation of the circuit for supply voltages of 1.8 V and a power consumption of 45 mW. The output pulse approximates the Gaussian monocycle having a pulse duration of about 375 ps. Proper modulation of the pulse in time is confirmed. A number of antennas with differentially fed baluns and input impedances of 100 Ω have been designed. From measurements, it can be seen that ringing is considerably smaller as compared to conventionally fed antennas.
Microwave Theory and Techniques, IEEE Transactions on (Volume:54 , Issue: 4 )
Date of Publication: June 2006