A low-cost frequency response analyser

The standard Fourier technique for the extraction of the real and imaginary components of a frequency response has been used for many years in commercially available instruments, but their high cost has greatly restricted their use. The paper describes a simple implementation of the Fourier technique which, by use of ingenious circuitry and the rejection of some non-essential facilities, achieves good performance over the most useful frequency range at a fraction of the cost of the more ambitious instruments.