Katsuaki Abe

Serial-parallel connection of direct sampling mixer

In this paper, a novel parallel connection for direct sampling mixer (DSM) and its design method have been proposed. The transfer function of IIR in the conventional DSM can be designed only for the second order that leads to a poor skirt characteristics. To alleviate this problem, a parallel connection of DSM for the higher order of IIR has been proposed. By this structure, higher order of polynomials both in the denominator and numerator can be designed. So, an excellent attenuation characteristic can be achieved by specifying frequencies of attenuation pole.

Soft-decision decoder employing eigenvalue of channel matrix in MIMO systems

This paper proposes a new soft-decision decoder employing the eigenvalue of the channel matrix as a weighting factor for conventional codes in MIMO (multi-input multi-output) systems. As is generally known, sufficient coding gain in a soft-decision decoder can only be obtained by employing the square Euclidean distance as a branch metric under AWGN (additive white Gaussian noise) channels. On the other hand, this gain cannot be obtained by simply doing the same under Rayleigh fading channels. This paper studies a suitable weighting factor for obtaining the coding gain in soft-decision decoders under Rayleigh fading channels in MIMO systems. First, we propose that the minimum eigenvalue power of the channel matrix indicates an effective carrier power in MIMO systems. Next, we propose the effective carrier power as a weighting factor for soft-decision decoders. We then calculate BER performance. According to the results, the proposed decoder gives a margin of about 5 dB at BER=10/sup -4/ compared to a conventional decoder employing received power as a weighting factor. The results also demonstrate that the proposed weighting factor can enhance the ability of soft-decision decoders under frequency non-selective Rayleigh fading channels in MIMO systems.