Spread spectrum receiving device

DETAILED DESCRIPTION In order to achieve the above object, according to the present invention, in a spread spectrum communication device there is disposed means for removing excessive components generated by disturbance, etc.
in an efficient and simple manner other than the desired correlation peak after having inversely spread the spread spectrum signal on the receiver side.
For this means a first invention is constructed by using a mixer having squaring characteristics.
According to a second invention the reference signal for the correlator is FM-modulated and a third invention is so constructed that the center of the spectrum of the spread spectrum signal, which is weak against disturbance, is removed by means of a filter.
Each of these constructions of the first to the third invention is efficient alone, but combinations thereof are more efficient.
By the construction of the first invention described above the disturbing wave components are removed by squaring the correlation output, on which the disturbing wave is superposed, and disposing band pass filters (B.
P.
F) in separated two groups.
This is because, since the disturbing wave components are concentrated in the neighborhood of DC and in the neighborhood of a frequency twice as high as the frequency of the disturbing wave components in the frequency by squaring them, the disturbing wave components are removed by removing these frequency components in the neighborhood of DC and the frequency components twice as high as that of the disturbing wave components by means of the band pass filters (B.
P.
F) and in this way the desired spread spectrum signal component can be detected with a high S/N ratio.
Next, by the reference signal FM-modulating method, which is the construction of the second invention, the central frequency of the reference signal inputted in the correlator is always deviated in time from the frequency component of the disturbing frequency by disposing means for FM-modulating it and in this way it is possible to prevent that the disturbing wave components are outputted at the output of the correlator at the correlation processing