Direct conversion receiver

摘要

To solve such a problem of a conventional direct conversion receiver that an image rejection ratio is insufficient owing to analog processing employed to reject an image, the present invention provides such a direct conversion receiver that the image can be rejected by digital signal processing to improve the image rejection ratio and also reduce the hardware load and the processing load. A HILBERT filter of a digital signal processing section shifts a quadrature component digital signal by 90° by HILBERT conversion to provide an output, while a delay circuit delays an in-phase component digital signal by the same delay time as a delay time by the HILBERT filter to provide an output, both of which outputs undergo addition or subtraction at an adder to have the image rejected there and then enter a complex frequency converter, where an offset provided at a local oscillator is removed by frequency conversion processing to output the in-phase component and quadrature component signals.