Study Of Ultra Wide-band RAKE Receiver

Ultra-wideband (UWB) wireless communication technology has been proposed in the early1960s. UWB has low power consumption, high data rate, high processing gain, strongerdistinguishing property among multi-paths. Its low transmitting power can coexist with theconventional wireless communication systems. These characteristics have attracted muchattention and in-depth studies. At present, UWB wireless communication technology has beenone of the key technologies for high rate short distance wireless communications, which willprovide a charming application future for the short distance wireless communications.In conventional wireless communication systems, the normalized signal bandwidth isnarrower compared with center frequency. So there is no frequency-dependence in eachindividual path. However, the UWB pulse signals have huge normalized bandwidth (more thanor equal 0.2 percent), and the frequency-dependence in each individual path would cause pulsewaveform distortion. Base on electromagnetism wave diffraction theory, this thesis discusses thefrequency-dependence of individual path, derives the electric field intensity expression of theright angle cleave diffraction, and establishes the frequency-dependence channel model.Utilizing this model, the thesis simulates the effect to the waveform and spectrum caused by thedifferent frequency-dependence factors.The high-rate UWB wireless communication systems need a fast signal processing ability.Rapid synchronous reception is one of issues that the UWB receiver needs to resolve. Bases onpreviously synchronous search algorithms, the thesis proposes a half search algorithm based onmultiple units jump. The algorithm has lower computational cost with the existing linear searchalgorithm, random search algorithm and half search algorithm, and saves much synchronoussearch time.Considering multi-path effects, the UWB receiver uses RAKE technology usually. But theconventional RAKE receiver can not resolve the distortion of pulse waveform caused by thefrequency-dependence of single path. For this problem, the thesis proposes an Equalizing RAKEreceiver (E-RAKE, Equalizing Rake Receiver). The receiver is based on conventional RAKEreceiver and equalization processors are added. And then processing algorithms and Blockdiagram of the E-RAKE receiver is given. The E-RAKE receiver not only has the same ability ofthe conventional RAKE receiver, but also can combat the individual path frequency-dependence.The simulation results show that the E-RAKE receiver gives a better solution than that of the conventional RAKE receivers on processing pulse waveform distortion, and improves the BER(bit error rate) performance of the receiving systems.