A comparison of adaptive antennas on desired signal arrival angle errors
Manabu Ohmiya, Yasutaka Ogawa, Kiyohiko Itoh · Electronics and Communications in Japan (Part I Communications) · 1985
Abstract In the Howells‐Applebaum adaptive antenna (H‐A) and the directionally constrained least mean‐squares adaptive antenna (CLMS) their abilities are degraded due to an angular error in the assumed direction of a desired signal. In this paper, several methods of preventing the angular error are compared. One of them is the decrease of the amplifier gain in H‐A, or in the increase of pseudo‐noise in CLMS so that the diagonal elements of the correlation matrix derived from input signal S are equivalently increased. Another is the use of multiple directional constraints in CLMS (multidirectional CLMS) where the number of constrained directions is increased. The effects of these methods are checked by numerical calculations. The evaluation criteria are set so that the angular error is 5 degrees, the upper limit of the dynamic range of the input SNR is. 20 dB, and the lower limit of the output SNR or SINR is 10 dB. Comparison is performed under the condition that the degrees of freedom for the antennas are kept constant. The multiple CLMS is the best way to satisfy the evaluation criteria in a wide range of arrival of interference if interference power is equal to or smaller than the desired signal power. On the other hand, the method for effectively increasing the diagonal elements of the correlation matrix is the best if interference power is larger than the desired signal power. However, when the countermeasure for the angular error suitable for signal environments is chosen from the above two, the choice depends on the evaluation criteria.