Receiving device and automatic gain control method

A signal receiving method for a receiving device, the receiving device receiving a radio signal and including:

• a frequency converter converting a frequency of an analog signal from the receiver;
• an A/D converter converting the analog signal into a digital signal;
• and a digital signal processor processing the digital signal to obtain received data,
• the method comprising:
• adjusting a signal level of the analog signal from the frequency converter;
• separating a signal from the variable gain amplifier to an in-phase component and a quadrature component;
• removing higher harmonic waves included in the in-phase component of the analog signal from the quadrature detector;
• removing higher harmonic waves included in the quadrature component of the analog signal from the quadrature detector;
• converting an analog signal from the first low-pass filter into an m-bit digital signal of the in-phase component and an n-bit (n>m) digital signal of the in-phase component and outputting the m-bit digital signal and the n-bit digital signal of the in-phase component, the n-bit digital signal of the in-phase component serving as an output signal to the digital signal processor;
• converting an analog signal from the second low-pass filter into an m-bit digital signal of the quadrature component and an n-bit digital signal of the quadrature component and outputting the m-bit digital signal and the n-bit digital signal of the quadrature component, the n-bit digital signal of the quadrature component serving as an output signal to the digital signal processor;
• calculating a coarse adjustment gain of the variable gain amplifier on the basis of a power of the m-bit digital signal of the in-phase component and the m-bit digital signal of the quadrature component to control the gain of the variable gain amplifier and calculating a fine adjustment gain on the basis of a power of the n-bit digital signal of the in-phase component and the n-bit digital signal of the quadrature component to control the gain of the variable gain amplifier.