CROSS-CORRELATION ARRANGEMENT

摘要

Cross-correlation arrangement for determining the presence or absence of a signal x2(t) of known frequency in an unknown signal x1(t) if this signal x2(t) is present for at least a period of time ?o with an unknown starting instant. An auxiliary signal a1(t) is added to the signal x2(t). The sum signal is converted into one-bit code words s(nT) which are multiplied in at least a first correlation channel by one-bit code words yper(kT) which are stored in a storage medium having at least N/2 addressable storage locations. The code words yper(kT) are elements of a series {yper(kT which is formed by the code words which occur in a predetermined time interval having a length NT and which are of a non-periodical signal of the form sign ¢x2(t) + a2(t)!. The product code words obtained are added together in an integrator. This integrator is read each time after a time interval NT and reset. The absolute value of an output code word of the integrator is optionally added to corresponding code words of other correlation channels. The sum code words obtained in this way are integrated in a second integrator whose contents is continuously compared with a detection level. If No = ?o/T, N is smaller than No for example a factor of 3. The value of N determines the width of the detection characteristic.