Patent ID: 8509294

Claim:
A signal generator for testing a wireless communication device comprising: waveform data storage means for storing waveform data of a digital baseband signal including M sample data items and repeatedly and continuously outputting the waveform data; digital-to-analog conversion means for performing digital-analog conversion on the waveform data; frequency conversion means for performing frequency conversion on the digital-analog-converted baseband signal using a carrier signal with a predetermined frequency and outputting the frequency-converted signal as an RF test signal for testing the wireless communication device; and phase shift means that receives the waveform data which is repeatedly output n times from the waveform data storage means, shifts the phase of each sample data item in an n-th waveform data item by a phase shift amount φ n corresponding to the number of times n the waveform data is repeatedly output, and outputs the waveform data to the digital-to-analog conversion means, wherein the phase shift amount φ n is calculated from a reference phase difference θ, which is a phase difference between an (n−1)-th waveform data item and the n-th waveform data item, and the number of times n the waveform data is repeatedly output in order to obtain a continuous phase change between the tail of the (n−1)-th waveform data item and the head of the n-th waveform data item, and wherein the sample data items of the waveform data are a complex I-phase sample data item and a complex Q-phase sample data item, and the phase shift means includes: phase shift amount calculating means for obtaining the phase shift amount φ n from the reference phase difference θ and the number n of times the waveform data is repeatedly output, and outputting a first phase shift data item represented by cos φ n and a second phase shift data item represented by sin φ n ; a first multiplier which multiplies the first phase shift data item by the I-phase sample data item output from the waveform data storage means and outputs; a second multiplier which multiplies the first phase shift data item by the Q-phase sample data item output from the waveform data storage means and outputs; a third multiplier which multiplies the second phase shift data item by the Q-phase sample data item output from the waveform data storage means and outputs; a fourth multiplier which multiplies the second phase shift data item by the I-phase sample data item output from the waveform data storage means and outputs; a first calculator which subtracts the output of the third multiplier from the output of the first multiplier and outputs to the digital-to-analog conversion means; and a second calculator which adds the output of the second multiplier and the output of the fourth multiplier and outputs to the digital-to-analog conversion means.