NF FRA51615, Instruction Manual

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1.3 Operating principles
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FRA 51615
1.3 Operating principles
1.3.1 Basic principles
The Frequency Response Analyzer (FRA) measures the frequency transfer characteristics of the equipment
under test (EUT) with high accuracy over a wide dynamic range. It is equipped with a sweep oscillator and
two analysis input channels (CH1,CH2), and makes highly-accurate calculations of analysis frequency
component vectors (amplitude and phase) from Fourier coefficients obtained from a discrete Fourier
transform of the input signals. By measuring the EUT input signal (Vin) and output signal (Vout) with the
analysis input channels (CH1 and CH2) and calculating the vector ratio (CH1/CH2), the gain and phase at
the analysis frequency (f) of the EUT can be obtained.
Figure 1-4 Principal of frequency transfer characteristic measurement with the FRA 51615
The loop characteristic measurement and impedance characteristic measurement both differ from the
gain-phase measurement only in the connections and the units of the measurement results, so the
measurement principle is the same as for the gain-phase measurement described above.
One round of measurement produces the gain and phase values at the analysis frequency (f). By measuring
the gain and phase while sweeping the oscillator and analysis frequencies, frequency characteristics such as
Bode plots can be obtained. Also, when auto-range is set, the range of the analysis module is optimized for
each frequency being measured, so the dynamic range is greatly increased for measurement of A/D
converters.
～
A/D A/D
OSC CH1 CH2
EUT
DFT DFT
Frequency
= f
V2(f) V1(f)
|Gain(f)| = |V1(f)|
÷
|V2(f)|
Phase(f) =
∠
V1(f)
－ ∠
V2(f)
Vin Vout
FRA51615