Patent ID: 8407545

Claim:
A communication device, comprising: a digital baseband circuit configured to modulate a baseband signal to be transmitted to the outside and demodulate a baseband signal received from the outside; a transmitter side analog circuit connected to the digital baseband circuit via a digital analog converter and including a transmission side quadrature modulator that quadrature modulates the baseband signal received from the digital baseband circuit to output an up-converted signal to be transmitted to the outside; a receiver side analog circuit connected to the digital baseband circuit via an analog digital converter and including a receiver side quadrature modulator that quadrature modulates a signal received from the outside to output the baseband signal to the digital baseband circuit; and a first loop back path circuit provided between the transmitter side analog circuit and the analog digital converter, wherein the digital baseband circuit includes: a reference signal generator configured to generate a reference signal including I signal and Q signal of a single tone that are different in phase by 90 degrees; a transmitter side correction circuit provided between the reference signal generator and the transmitter side analog circuit and configured to correct quadrature errors caused in the transmitter side analog circuit; and a correction calculator circuit provided between the analog digital converter and the transmitter side correction circuit and including a tone power calculator circuit that obtains a power envelope signal extracted from the reference signal that is quadrature modulated by the transmitter side quadrature modulator through the first loop back path circuit, calculates a correction parameter of the transmitter side correction circuit based on the extracted power envelope signal, and inputs the calculated correction parameter to the transmitter side correction circuit to correct quadrature errors, the tone power calculator circuit including: a partial Fourier transformation circuit programmed to calculate the power of a single one of frequency bins at a time to obtain the power of a signal component having the same frequency with the reference signal from the power envelope signal and the power of a signal component having a frequency twice the frequency of the reference signal, and the correction parameter calculated by the tone power calculator circuit is a value that minimizes the values of the powers obtained by the partial Fourier transformation circuit.