High Resolution Direction of Arrival Estimation Analysis and Implementation in a Smart Antenna System

Book excerpt: The goal of this research is to equip the smart antenna system designed by the telecommunication group at the department of Electrical and Computer Engineering at Montana State University with high resolution direction of arrival estimation (DOA) capabilities; the DOA block should provide accurate estimates of emitters' DOAs while being computationally efficient. Intensive study on DOA estimation algorithms was carried out to pinpoint the most suitable algorithm for the application of interest, and the spectral methods were chosen for this study. The outcome of the study consisted of generating a novel algorithm, spatial selective MUSIC, which is comparable in accuracy to other high resolution algorithms but does not require the intensive computational burden that is typical of high resolution spectral methods. Spatial selective MUSIC is compared in terms of bias, resolution, robustness and computational efficiency against the most widely used DOA estimation algorithms, namely, Bartlett, Capon, MUSIC, and beamspace MUSIC. The design, troubleshooting, and implementation of the hardware needed to implement the DOA estimation in a real case scenario was achieved. Two design phases were necessary to implement the center piece of the hardware needed to achieve DOA estimation. The 5.8 GHz 8 channel receiver board along with a casing that egg crates the RF channels for channel-to-channel isolation was designed and built. A National Instrument data acquisition card was used to simultaneously sample all the 8 channels at 2.5 MSPS, the data was processed using the PC interface built in LabView. Phase calibration that accounts for the overall system magnitude and phase differences along with a novel calibration method to mitigate the effects of magnitude and phase variations along with mutual coupling was produced during this research and was imperative to achieving high resolution DOA estimation in the lab. The DOA estimation capabilities of the built system was tested within the overall smart antenna system and showed promising results. The overall performance enhancement that the DOA estimation block can provide cannot however be fully realized until the beamforming block is revised to provide accurate and deep null placing along with a narrower beam width. This cannot be achieved with the current system due to limitations in the number of the array elements used and the granularity in the phase shifters and attenuators used in the analog beamformer.