本稿では，微弱無線及び超再生回路を使用するRF認識システムを用いて，並列組合せスペクトル拡散方式（PCSS：Parallel Combinatory Spread Spectrum）伝送を行う場合の伝送特性に関する検討を行う．これまでPCSSの伝送特性改善法として，直交した周波数を用いて伝送帯域を2つに分割し，各周波数でPCSSを用いる方法を提案してきた．しかし帯域分割を行うとチップ幅が長くなる．そのため従来法と伝送速度をほぼ等しくするために，片側の周波数において多重化を行う必要があり，伝送特性の改善がわずかとなる問題がある．そこで多重化を行わない周波数では従来通りの判定を行い，多重化を行った周波数では最尤系列推定を行う方法を提案する．計算機シミュレーションにより伝送速度を維持しながら伝送特性を改善できることを示す．%In this paper, we study a transmission characteristic of Parallel Combinatory Spread Spectrum (PCSS) for an RF recognition system which consists of a low power radio and a superregeneration circuit. We have already proposed a sub-band PCSS which uses two orthogonal transmission frequency bands to improve the transmission rate. However, the sub-band PCSS has a problem that the tip width becomes longer. Hence, the multiplexing has to be introduced into one of the two sub-bands to obtain the same transmission rate as the conventional PCSS. In this case, the transmission characteristic can be improved slightly. The proposed method therefore apply the hard-decision to the non-multiplexing sub-band and MLSE to the multiplexing sub-band. We show that the proposed method can maintain the transmission characteristic and improve the transmission rate through some computer simulation results.
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