Handheld direction of arrival finder with electronically steerable parasitic array radiator using the reactancedomain MUltiple SIgnal Classification algorithm

Reactance-domain multiple signal classification (RD-MUSIC) is a promising scheme for enabling ESPAR (electronically steerable parasitic array radiator) antennas to accurately estimate the DOAs (directions-of-arrival) of radio waves. The ESPAR antenna is a variable directional antenna designed for battery-operated mobile terminals, and is utilised for handheld DOA finder applications as well as for wireless communication systems. We present some experimental results showing that the RD-MUSIC with a conventional calibration obtains a sharp spectrum for accurate DOA estimation, although the ESPAR antenna is equipped with only a single-port output unlike a conventional array antenna. The results also demonstrate that RD-MUSIC works well even when exploiting fewer beam patterns than the number of antenna elements. Moreover, we have verified that a human body hardly generates any degradation of DOA estimation even holding the DOA finder close to the body. The degradation of DOA estimation because of a human body is kept to less than about 6deg, and removing beam patterns towards directions of reflections from the human body is found to be useful in decreasing the errors. Although the reduction in the number of beams results in reducing the total number of estimated waves, it can mitigate the influence of a human body for actual DOA estimation with the handheld DOA finder.