| 摘要 |
PROBLEM TO BE SOLVED: To reduce calculation amount in a reception FIR low-pass filter for the input IF signal of an arbitrary frequency and to highly accurately secure a base band signal. SOLUTION: Quadrature detection means 3 and 4 which detect a sample value signal which is A/D converted by a local frequency fs/4 and equivalently generate in-phase output and output, which have frequency offset Δf equivalent to the minimum value of |fc-(fs/4)| and whose sampling frequencies are fs/2, band-pass filters 5 and 6 which band-restrict the in-phase output and output and phase compensation means 7 and 19 compensating Δf included in the outputs of the band pass filters 5 and 6 are provided. When the carrier frequency of a signal after A/D conversion is considered to be fs/4 and it is detected, '0' is inserted into in-phase output and output at every other sample and the sampling frequency is equivalently reduced to 1/2. Thus, Δf by the consideration is compensated by the phase compensation means 7 and 19. |
