Adaptive Array Employing Eigenvector Beam of Maximum Eigenvalue and Fractionally-Spaced TDL with Real Tap

Manuscript received December 10, 1999. Manuscript revised March 18, 2000. † The authors are with NTT Network Innovation Laboratories, Yokosuka-shi, 239-0847 Japan. SUMMARY This paper proposes a new digital beamforming adaptive array antenna (DBFAAA) that is effective in severe multipath environments in which timing and carrier synchronization circuits cannot function ideally resulting in the DBFAAA losing control. The proposed DBFAAA has two stages. In the first, the DBFAAA captures the desired signal and establishes synchronization. In the second, the DBFAAA optimizes the beam pattern of the signal. The proposed configuration employs an eigenvector beam of the maximum eigenvalue in the first stage beam-forming. In addition, a fractionally-spacedtapped-delay-line (FS-TDL) with real tap weights, which is placed after the beam-former, is applied to achieve timing synchronization. The behavior of the proposed DBFAAA for asynchronous sampling data is investigated and the results indicate that the proposed configuration enables asynchronous sampling at the A/D converter. A prototype of the proposed DBFAAA achieving 38-Mbps real-time data communication is introduced and the transmission performance is shown. key words: adaptive array, digital beamforming, eigenvector beam, high-speed wireless access, fractionally-spaced-tapped-delay-line