| Personal mobile communication started from first generation (Based on FDMA), second generation (Based on TDMA) to third generation (Based on CDMA) and fourth generation (CDMA, MIMO ,SDMA & OFDM etc) with the rapid development of wireless communication. One of the main problems faced by future mobile communication systems is the rapid increase in the demand for wideband services and applications. As the available frequency spectrum is limited, new systems have to look at new means to overcome spectrum congestion in multi-user environment. In addition to conventional frequency/time and code multiplexing, the only extra means available to the wireless-communication system designer is the space or angular domain. Utilization of the space/angle domain requires the employment of multi-element antennas with a suitable signal processing algorithm. Such antennas are known as adaptive or smart antennas.Up to now, research on smart antenna has been restricted to narrowband wireless systems. The beamforming techniques used in narrowband systems are inadequate for wideband systems because they result in main-beam squinting and null shifting. As a result, smart antenna with narrowband beamforming schemes are unable to track a desired user or form nulls or form low side lobes towards interfering sources over a large frequency band. With the development of wireless communications, the requirements on bandwidth become higher and higher, the wideband beamforming of smart antenna is becoming the next hot spot.This thesis is mainly focus on algorithm research of the beamforming in the wideband smart antenna. In order to turn away the problem mentioned above, suitable algorithm needed to be found to keep the constant beam pattern over a range of frequency. This thesis mainly discuss... |
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