| Recent allocation of the Ultra WideBand (UWB) 3.1 to 10.6 GHz frequency spectrum for unlicensed use has opened many new opportunities for radio communications. Providing unique advantages as well as interesting design challenges makes UWB an attractive technology to pursue. Furthering the challenge is the desire to monolithically integrate an UWB radio with an antenna. Such a feat would reduce manufacturing complexity, while maintaining a high level of cost effectiveness. With these two technologies in mind, as well as traditional methods, design considerations for the development of an on-chip ultra wideband antenna in CMOS are discussed. After a review of current UWB antennas, an electrically small square loop radiator integrated in a 0.13 mum CMOS process is proposed for use as an UWB antenna. An UWB LNA and pulse generator are monolithically included with the antenna. Simulation results of this antenna show it to perform as expected, having a relatively constant, but poor return loss of less than 1 dB, an omnidirectional radiation pattern, low dispersion, and a maximum gain ranging from -25 dBi to -35 dBi over the UWB spectrum. Due to complications with the on-chip circuitry, measurements are unable to confirm the radiation patterns and transient response of the antenna. Despite this, measurements show the maximum gain is in good agreement with simulation over the entire band, while the return loss is less than 10 dB, but shows multiple unexpected resonances. Phase response of the antenna was linear with an R2 value of 0.99, indicating the antenna may be a good device for use with impulse radios. Although the results are somewhat inconclusive, data does indicate the antenna is still potentially a viable candidate for use with UWB. |
