The
matched filter unit of the present invention is used for finding a value of correlation between each of a plurality of digital signals synchronized with a
clock and each of a plurality of digital code strings consisting of M (M: plural) digital codes respectively. The
matched filter unit comprises a circuit for
multiplexing a plurality of the digital signals, a storage circuit composed of
delay circuits disposed in M stages and used for entering a
signal output from the
signal multiplexing circuit to the first stage
delay circuit, then shifting the
signal to the subsequent
delay circuits sequentially in synchronization with the
clock, and a plurality of computing devices for finding a value of correlation between each of the digital signals and a digital code string respectively using a signal output from each of the delay circuits disposed in M stages. Each of a plurality of the computing devices is composed of M multipliers (M: plural) for multiplying a signal output from each of the delay circuits by each digital code of a digital code string and an
adder for adding results of multiplication from the M multipliers to find a value of the correlation. According to this configuration of the
matched filter unit, a plurality of the digital signals that are
diffusion-modulated with different code values are not correlative with each other. Those non-correlative digital signals are multiplexed by a
signal multiplexing circuit, then the multiplexed signal is computed for back-
diffusion in the storage circuit, the multipliers, and the
adder using different digital code strings, thereby to detect a value of correlation between digital signals entered from a plurality of channels using the same storage circuit. It is thus possible to provide a matched filter unit that can be reduced significantly in circuitry size, thereby to satisfy the miniaturizing, lower manufacturing cost, and
power saving prerequisites.