A circuit comprises a vector separator circuit to generate a first extracted signal according to (i) a first correlation signal, (ii) a second correlation signal, and (iii) a relative response signal. The first correlation signal corresponds to a first correlation between an input signal and a first test signal. The first test signal has a first frequency, and the input signal includes a first spur having the first frequency. The second correlation signal corresponds to a second correlation between the input signal and a second test signal. The second test signal has a second frequency. The relative response signal corresponds to a relative response of the second frequency in the first correlation signal.