| 摘要 |
PURPOSE:To lower the power consumption by using only one piece of D/A converter whose operation speed is the same as that of a conventional constitution even at the time of obtaining a waveform output of I and Q channels by using the D/A converter by a time division, and converting a sampling frequency by using an interpolation filter. CONSTITUTION:A D/A converter 3 outputs serially data of each channel of I and Q by a time division. In this case, a sample frequency of a sample value corresponding to each channel of I and Q is 1/2 of a sampling frequency of a final output and an operation speed of the whole output data subjected to time division is equal to the sampling frequency. The output of this D/A converter 3 is divided into parallel signals of the I and the Q channels by using sample holding circuits 4, 5, and the sampling frequency is converted to two folds by using interpolation filters 6, 7. Subsequently, a sampling noise contained in the interpolation filters 6, 7 is suppressed by post-filters 8, 9, and as a result, a final waveform output of the I and the Q channels is obtained. |
