| 摘要 |
PURPOSE:To ensure the reduction of multiplication frequency, i.e. processing duration per sampling by reversing the order of processing that is frequency conversion and filtration, i.e. by making the frequency conversion after resampling. CONSTITUTION:The analog signal subjected to band limitation when passing through an analog low-pass filter 201 is fed to the band-pass digital filters 205 having the impulse responses obtained by multiplying the impulse responses of a low- pass filter by sine and cosine waves respectively via a sample-hold circuit 202 and an A/D converter 203. The output of a complex filter is fed to a high-speed Fourier transformer 211 via a secondary sampling circuit after the complex multiplication by a frequency converter 207 consisting of 4 digital multipliers 208 and 2 digital adders 209 fed with the output of a digital sine.cosine function generator 210 and the result of frequency analysis is displayed on an indicator 212. Thereby, processing is possible at a high frequency with multiplication frequency reduced. |
