다상회로와 고속DCT를 이용한 12채널의 TDM/FDM변환

The 12 Channel TDM/FDM Translator with Polyphase Network and Fast DCT

12채널의 TDM/FDM變換時間을 단축시키기 위하여 14點高速DCT와 多相回路를 사용하였다. 이러한 多相回路는 原試型필터를 各채널의 채널 필터로 變換하여 設計되었고 原試型필터에 대하여 分子의 次數는 168次로 對稱性을 갖도록 하였고 分母의 次數는 6次로 하여 CCITT規定을 만족하도록 하였다. 變換에 필요한 곱셈回數는 $0.12267{\times}10^2$ multiplications/sec channel로써 기존의 결과보다 약 15%~40% 단축하였다. 또한 간단한 檢波시스템을 포함하여 PRIME750컴퓨터에 의한 시뮬레이션過程을 거쳐 理論의 타당성이 확인되었다.

For the reduction of the 12-channel TDM/FDM translation time the 14-point fast DCT algorithm is used and the polyphase network which translates the prototype filter into the channel filters required in each channel is designed. For the prototype filter the degree of the numerator is 168 and the coefficients have symmetry values, the degree of the numerator is 6. Such a prototype filter is consistant with the CCITT requirements. In this case the required multiplication rate is CCITT requirements. In this case the required multiplication rate is $0.12267{\times}10^2$ multiplications/sec. channel and reduces to about 15-40% of the rate required in the exising systems. The proposed 12-channel TDM/FDM translation system is simulated using a demodulation system with a computer (PRIME 750) and the results show that the proposed conversion method is valid.