| 摘要 |
<p>PURPOSE:To facilitate the frequency conversion by converting a sampled signal into double sampling frequency and multiplying the result with a carrier having a frequency which is below the sampling frequency and is in an integral ratio to the sampling frequency. CONSTITUTION:A 1:2 DD converter 1 converting a digital signal having a sampling frequency fs into a digital signal of a sampling frequency 2fs consists of a low-pass filter (LPF) 2, a delay device 3 retarding the signal by a time 1/2fs and a switch 4 thrown alternately to two upper/lower circuits at each time 1/2fs. A multiplier 5 operated at the sampling frequency 2fs multiplies the carrier fc required for the frequency conversion with the input signal converted into the sampling frequency 2fs. The band of the output of the multiplier 5 is limited at least to the frequency fs/2 and inverted into the sampling frequency fs by a 2:1 DD converter 7 to form an output signal.</p> |
