Lambda SR1, Operation Manual, Page: 141 / 317

SR1 Operation 141
© 2014 Stanford Research Systems
2.4.4 FFT (Dual Channel)
The Dual-Channel FFT Analyzer (FFT2) computes the frequency spectra of both channels of the
selected input domain, analog or digital and additionally computes the magnitude and phase of the dual-
channel frequency response function and impulse response. Because the FFT2 analyzer computes
frequency response using a
relative measurement it can make highly accurate measurements of
frequency response magnitude and phase without the need for a perfectly flat reference source.
Typical Dual-Channel Response Measurem ent
The diagram above shows a typical two-channel measurement setup. SR1's Generator provides the
stimulus signal which can be a broadband source, such as noise or the FFT chirp signal, or can be
narrowband. The generator output is split and sent to both the DUT and the A-channel input of the
analyzer. The output of the DUT is sent to the B-channel input of the analyzer. The analyzer then
computes the quotient of the two complex FFTs which yields the magnitude and phase of the frequency
response.
FFT2 Analyzer Block Diagram
A block diagram of the FFT2 analyzer is shown above. Both input channels of the selected domain are
first optionally decimated by up to a factor of 2
10
depending on the user's bandwidth selection. Each