| 摘要 |
PURPOSE:To provide a quadrature modulator capable of obtaining a modulated wave for an input signal having plural coding speeds without changing the circuit constant of an analog circuit such as a filter. CONSTITUTION:This quadrature modulation device has a digital filter 1 for shaping the waveform of a digital input signal consisting of an I channel and a Q channel, a digital/analog converter 4 connected to the output of the filter 1, a quadrature modulator 2, and a band pass filter 5 for removing spurious wave. An input signal has plural coding speeds, and when an external control signal indicating the coding speed of the input signal is impressed to the filter 1, the sampling interval of the input signal is converted and a quadrature modulated wave with the same center frequency is generated by digital signal processing independently of the coding speed of the input signal. |
