specifically c 0 is the coefficient for the center tap of the fir filter 100 the coefficient input terminals c u2212 2 to c 2 are coupled to respective first input terminals of subtractors 210 212 214 216 and 218 a register 240 has had nominal i e no multipath component as described above values of the coefficients previously stored in it respective output terminals of the register 240 are coupled to corresponding second input terminals of the subtractors 210 212 214 216 and 218 that is the nominal coefficient n u2212 2 is coupled to the second input terminal of the subtractor 210 receiving the current coefficient c u2212 2 the nominal coefficient n u2212 1 is coupled to the second input terminal of the subtractor 212 receiving the current coefficient c u2212 1 and so forth respective output terminals of the subtractors 210 212 214 216 and 218 are coupled to corresponding input terminals of absolute value circuits 220 222 224 226 and 228 respective output terminals of the absolute value circuits 220 222 224 226 and 228 are coupled to corresponding input terminals of an adder 230 an output terminal of the adder 230 generates the multipath representative signal and is coupled to the output terminal 25 in operation the subtractors 210 212 214 216 and 218 respectively calculate the difference between each current coefficient c u2212 2 c u2212 1 c 0 c 1 and c 2 and the nominal value of the corresponding coefficient n u2212 2 n u2212 1 n 0 n 1 and n 2 the magnitude of each resulting difference represents.