Matched filter

A matched filter, for inversely spreading a received signal using spreading signals in a spread spectrum communications receiver, comprising:

• a plurality of correlating means for determining cross-correlation functions of the received signal which has been sampled at a certain timing and spreading signals having a certain section length;
• spreading signal delaying means for successively transferring the spreading signals having the certain section length to said plurality of correlating means by delaying timings of the transfer by a period equal to the section length of the spreading signals;
• and
• selecting means for successively selecting one of the cross-correlation functions outputted from said plurality of correlating means, for each period equal to a sampling interval of the received signal,
• wherein:
• said plurality of correlating means are divided into a plurality of groups, each group composed of K correlating means for determining a cross-correlation function of (1) the received signal which has been oversampled with an interval equal to 1/K (K being an integer of not less than 2) times the section length of a spreading signal and (2) the spreading signal having a certain section length,
• said spreading signal delaying means successively transferring the spreading signal having the certain section length to each group of said plurality of correlating means by delaying the timings of the transfer by the period equal to the section length of the spreading signals, and
• said selecting means successively selecting one of the cross-correlation functions outputted from said plurality of correlating means for each period equal to 1/K times the section length of the spreading signals.

A matched filter, for inversely spreading a received signal using spreading signals in a spread spectrum communications receiver, comprising:

• a plurality of correlating means for determining cross-correlation functions of the received signal which has been sampled at a certain timing and spreading signals having a certain section length;
• spreading signal delaying means for successively transferring the spreading signals having the certain section length to said plurality of correlating means by delaying timings of the transfer by a period equal to the section length of the spreading signals;
• and
• selecting means for successively selecting one of the cross-correlation functions outputted from said plurality of correlating means, for each period equal to a sampling interval of the received signal,
• wherein:
• said plurality of correlating means determine cross-correlation functions of (1) the received signal which has been sampled with an interval equal to the section length of the spreading signals and (2) the spreading signals having the certain section length,
• said output of said each correlating means is selected by said selecting means, per period equal to the section length of the spreading signals, and
• said plurality of correlating means include:
• multiplying means for calculating products of the received signal and the spreading signals;
• and
• integrating means for integrating the products of the received signal and the spreading signals,
• said integrating means carrying out damping by a period equal to L (L being a natural number) times the period by which one of the cross-correlation functions outputted from said plurality of correlating means is selected by said selecting means, and
• the number of correlating means in said plurality of correlating means exceeding a spread ratio of the spreading signals by a number in accordance with a time required for damping by said integrating means.