A multi band orthogonal frequency division multiplexing (MB-OFDM) compatibleultra wideband (UWB) receiver with narrowband interference (NBI) suppressioncapability is presented. The average transmit power of UWB system is limited to-41.3 dBm/MHz in order to not interfere existing narrowband systems. Moreover, itmust operate even in the presence of unintentional radiation of FCC Class-B compatibledevices. If this unintentional radiation resides in the UWB band, it can jam thecommunication. Since removing the interference in digital domain requires higher dynamicrange of analog front-end than removing it in analog domain, a programmableanalog notch filter is used to relax the receiver requirements in the presence of NBI.The baseband filter is placed before the variable gain amplifier (VGA) in order to reducethe signal swing at the VGA input. The frequency hopping period of MB-OFDMputs a lower limit on the settling time of the filter, which is inverse proportional tonotch bandwidth. However, notch bandwidth should be low enough not to attenuatethe adjacent OFDM tones. Since these requirements are contradictory, optimizationis needed to maximize overall performance. Two different NBI suppression schemesare tested. In the first scheme, the notch filter is operating for all sub-bands. In thesecond scheme, the notch filter is turned on during the sub-band affected by NBI.Simulation results indicate that the UWB system with the first and the second suppressionschemes can handle up to 6 dB and 14 dB more NBI power, respectively. The results of this work are not limited to MB-OFDM UWB system, and can beapplied to other frequency hopping systems.
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