Lambda SR1, Operation Manual, Page: 155 / 317

SR1 Operation 155
© 2014 Stanford Research Systems
Nyquist but retains low frequencies.
The 240Hz-8kHz selection removes frequencies below 240Hz and above 8 kHz providing an
approximately 5 octave analysis range.
The 120Hz-16kHz selection removes frequencies below 120Hz and above 16 kHz providing an
approximately 7 octave analysis range.
Using the FFT2 Analyzer With the FFT Chirp Source
Like the FFT1 analyzer the FFT2 analyzer can be used with SR1's generator "FFT Chirp" waveform
which produces a signal with uniform power in each FFT bin. The FFT2 analyzer makes one-shot
frequency response measurements using the chirp source even easier— it's not necessary to store a
reference input curve for later normalization (as is the case with FFT1) because the FFT2 analyzer
normalizes each measurement individually. The magnitude and phase of the frequency response is
immediately available with no further computation.
As an example, the 2 plots above show the single-shot magnitude and phase of the frequency response
of an 8-pole 6-zero elliptical filter with a 5 kHz pass-band edge. The phase distortion (departure from
linear phase) characteristic of elliptical filters near the passband edge is apparent. Using the Graph
Calculator's "group delay" function we can directly calculate the group delay from the phase curve.