Receiving device and signal demodulating method

A method for demodulating signals modulated by spread codes, comprising:

• a signal receiving step in which a signal receiving section receives signals modulated by spread codes and transmitted;
• a frequency converting step in which a frequency converting section converts frequencies of received signals received by the signal receiving section into intermediate frequencies;
• an A/D converting step in which an A/D converting section converts the received signals whose frequencies are converted into intermediate frequencies into digital signals to produce sample values of the received signals;
• a local code producing step in which a local code producing section produces local codes identical to the spread codes used by transmission side of the signals;
• a correlation value calculating step in which a plurality of multipliers each of which multiplies the sample values by the local codes and outputs a correlation value between base band signals reproduced from the sample values and the local codes;
• a correlation value adding step in which an adder adds the plural correlation values outputted from the plural multipliers;
• and
• an integral value calculating step in which an integrator integrates the outputs from the adder for one cycle of the spread code and outputs the integral value of the correlation values, wherein:
• each of the plural multipliers receives sets of the base band signal reproduced from the sample value and the local code, which sets received by the multipliers are produced at different chip positions for each of the plural multipliers in the correlation value calculating step.