Lambda SR1, Operation Manual, Page: 147 / 317

SR1 Operation 147
© 2014 Stanford Research Systems
Summary of FFT2 Outputs
Measurement Description
Level A, B Peak-based levels of both channels of the selected input domain.
Time Record A,B The underlying time data used to compute spectra. When displayed on a graph
this measurement produces an "oscilloscope" type display.
Power Spectrum
Amplitude A,B The amplitude of the power-averaged spectra for each channel.
Linear Spectrum
Amplitude A,B The amplitude of the synchronously averaged spectra. The amplitude of signals
that are synchronous with the time record is preserved, other uncorrelated signals
average away.
Frequency
Response Mag. The magnitude of the averaged frequency response.
Frequency
Response Phase The phase of the averaged frequency response.
Coherence 2-channel coherence of the A and B signals. Values near one indicate good input/
output correlation while values near zero indicate the output consists mostly of
uncorrelated noise.
Impulse
Response The Inverse FFT of the Frequency Response. This time-domain signal represents
the response of the system to a narrow "impulse" excitation even though it can be
measured using any broadband source.
Anechoic
Response
(Magnitude) The frequency response magnitude calculated from the time-gated (no reflections)
impulse response. Multiple reflection paths introduce can produce interference
which obscures the true frequency response of the DUT.
Anechoic
Response
(Phase) The frequency response phase calculated from the time-gated (no reflections)
impulse response. Multiple reflection paths introduce can produce interference
which obscures the true frequency response of the DUT.
Energy-Time
Curve The magnitude of the analytic impulse response, or the "envelope" of the impulse
response.