DIGITAL MODULATION APPARATUS

Disclosed is a digital modulation apparatus which comprises a quadrature amplitude modulation unit for modulating first and second baseband digital signals orthogonal to each other by means of digital cosine/sine information obtained based on information regarding a carrier frequency which is n multiple of a local frequency and a phase rotation unit provided in the input side of the quadrature amplitude modulation unit for performing phase rotation for the first and second baseband digital signals by using a difference frequency equivalent to a difference between the local frequency and a a baseband frequency. A frequency is converted into a transmitted frequency without using an analog circuit for conversion into a second frequency, a limit value of this transmitted frequency is increased, and a circuit is fully digitized to simplify and miniaturize a circuit configuration. As a result, the turning of the circuit into LSI can be facilitated, and high accuracy and high cost effectiveness can be promoted.