Modulating device and modulation method

摘要

A modulating device including: a first convertor configured to generate a converted analog signal by analog conversion on a input digital signal, a modulator configured to generate a modulated signal by quadrature modulation, a phase shifter configured to generate a phase shift signal by phase rotation, a demodulator configured to generate a demodulated signal by quadrature demodulation, a second convertor to generate a converted digital signal by digital conversion, a calculating circuit configured to estimate a the first direct current offset based on the input digital signal and the converted digital signal, the first direct current offset being a noise of digital current component generated between the input digital signal inputted to the first convertor and the output signal inputted to the demodulator, and a correcting circuit configured to correct at least one among from the input digital signal to the output signal based on the first direct current offset.

主权项

1. A modulating device adapted to receive a digital input signal and produce an analog output signal, the modulating device comprising:
a first convertor configured to receive the digital input signal and generate a converted analog signal by analog conversion on the digital input signal; a modulator configured to receive the converted analog signal and generate a modulated signal by quadrature modulation on the converted analog signal based on a local signal from a first oscillator; a first phase shifter configured to receive the local signal from the first oscillator and a phase shift signal from a second oscillator, and generate a first phase rotated signal by performing a first phase rotation on the local signal using the phase shift signal from the second oscillator, the phase shift signal being a signal that is phase rotated by a phase shift amount that changes with a period; a demodulator configured to receive the analog output signal and the first phase rotated signal, and generate a demodulated signal by quadrature demodulation on the analog output signal using the first phase rotated signal, the analog output signal being based on the modulated signal; a second convertor configured to receive the demodulated signal and generate an analog-to-digital converted signal by digital conversion on the demodulated signal; a second phase shifter configured to receive the analog-to-digital converted signal and the phase shift signal from the second oscillator, and generate a second phase rotated signal by performing a second phase rotation on the analog-to-digital converted signal using the phase shift signal, by the phase shift amount in a direction opposite to a direction of the first phase rotation; a calculating circuit configured to estimate a first direct current offset based at least in part on the digital input signal and the second phase rotated signal, the first direct current offset corresponding to a noise component of digital current components generated in a signal path between the digital input signal inputted to the first convertor and the analog output signal inputted to the demodulator; and a correcting circuit configured to correct the digital input signal based on the first direct current offset.