Frequency response analyzers consist of a sweep oscillator, voltmeter, and phase meter. Digital Fourier transform calculations* allow voltage and phase to be obtained simultaneously and with high accuracy, with the oscillator as the reference(Note). When measurement at a frequency ends, the frequency is switched to the next frequency. Thus, an identical measurement is automatically repeated. This is similar to the operations which are performed by using an independent oscillator and phase meter. In this way, setting on the frequency response analyzer is easy. Furthermore, since the range of the voltmeter can be changed for each measuring point, a high dynamic range measurement far beyond the limit of bits of the A/D converter can be done. 

*Fourier transform calculations
The products of measured values and a reference (sine wave signal) are integrated. This is similar to operations for obtaining the basic waves of a Fourier series. An asynchronous element such as an external disturbance attenuates in proportion to the square root of integration time.
