A new block demodulator for DS/SS signal with carrier frequency offset

We present a new direct-sequence spread-spectrum demodulator using the block signal processing in the presence of large carrier frequency offset such as Doppler shift in low Earth-orbital satellites systems. The proposed demodulator employs the initial acquisition scheme which can roughly estimate both the timing and the carrier frequency offset. This scheme realizes the maximum likelihood estimation with the help of the FFT. As the result of the analytical discussion, it is shown that the proposed scheme makes the initial acquisition possible even in the presence of a large frequency offset where the conventional demodulator cannot achieve the acquisition