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Dual FFT Analyzer

Reference: Documentation

Found in these Apps
Features
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User-friendly Frequencies: Traditional FFT-based spectrum analyzers use FFT's (Fast Fourier Transforms) with lengths that are powers of 2 (e.g. 2 to the 12th power = 4096). With typical audio sample rates, such as 48 kHz, this yields non-integer (awkward) frequency resolutions, such as 11.71875 Hz (48000/4096 = 11.71875). SignalScope's Dual FFT Analyzer uses mixed-radix FFT's that yield frequency resolutions that are more than just user-friendly—they allow for precise amplitude measurement at frequencies such as 1000 Hz (a frequency commonly used for calibrating sound level meters and measuring total harmonic distortion, or THD). For example, an FFT length of 4800, when used with a sample rate of 48 kHz, yields a frequency resolution of exactly 10 Hz (48000/4800 = 10).
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Real-time SIMO Analysis: Measure 2 DUT's or SUT's at a time, with a single reference channel. (DUT = Device Under Test, SUT = System Under Test, SIMO = Single Input, Multiple Output)
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Save Data: Export frequency and time domain data and metadata to a data file (.csv, .mat, or .txt). Or, generate a high-resolution image of the graph and save it to a PDF file.
Specifications
  • Input: Up to 2 system or device measurements simultaneously, with X input (reference) and Y inputs (DUT/SUT outputs) selected from any available input, output, or virtual output channels
  • Measurement Types:
    • Frequency Response (FR) Magnitude
    • Frequency Response (FR) Phase
    • Coherence
    • Phase Delay
    • Group Delay
    • Impulse Response (IR)
    • Squared IR
    • Cross-correlation
  • FFT Type: Mixed Radix
  • Frequency Resolution (Hz), per sample rate:
    • Sample rate > 48000 Hz
      • 10, 8, 5, 4, 2, 1, 0.5, 0.25, 0.2
    • Sample rate <= 48000 Hz, physical memory > 600 MB
      • 10, 8, 5, 4, 2, 1, 0.5, 0.25, 0.2, 0.125, 0.1, 0.08, 0.0625
    • Sample rate <= 48000 Hz, physical memory > 400 MB
      • 10, 8, 5, 4, 2, 1, 0.5, 0.25, 0.2, 0.125, 0.1
    • Sample rate <= 48000 Hz
      • 10, 8, 5, 4, 2, 1, 0.5, 0.25, 0.2
  • Measurement Length (s), per sample rate:
    • Sample rate > 48000 Hz
  • 0.1, 0.125, 0.2, 0.25, 0.5, 1, 2, 4, 5
  • Sample rate <= 48000 Hz, physical memory > 600 MB
    • 0.1, 0.125, 0.2, 0.25, 0.5, 1, 2, 4, 5, 8, 10, 12.5, 16
  • Sample rate <= 48000 Hz, physical memory > 400 MB
    • 0.1, 0.125, 0.2, 0.25, 0.5, 1, 2, 4, 5, 8, 10
  • Sample rate <= 48000 Hz
    • 0.1, 0.125, 0.2, 0.25, 0.5, 1, 2, 4, 5
    • FFT Length: Set automatically, based on frequency resolution and current sample rate (e.g. at 48 kHz, a frequency resolution of 5 Hz requires an FFT length of 9600 points)
    • Data Windows (Independently selectable for X and Y input):
      • Uniform (rectangular)
      • Bartlett
      • Blackman
      • Flat Top
      • Hamming
      • Hann
      • Rife-Vincent 2
      • Exponential Decay
      • Force
      • Force Exponential
      • Exponential Window: User defined time constant and final value
      • Force Window: User defined window length in seconds or percent
      • Window Preview: In-menu graph of the window shape
    • Overlap (%): Off (0), 50, 75, 80, 90, Max (automatically calculated, limited to approximately 20 FFT calculations per second)
    • Averaging: Off, Linear (Stable), Exponential, Peak Hold
    • Visible Frequency Limits: Min/Max, User-adjustable between 0 and Nyquist
    • Built-in Excitation Signal Generator
      • Enable/Disable
      • Output Channel A/B Selection: selected from any available output channels
      • Signal Type: Sweep, Pseudorandom Noise (each automatically configured with a length to match the measurement length, or FFT length)
      • Presends: User-definable value greater than or equal to zero
      • Level: specified in dBFS where 0 dBFS is the maximum (full scale) output amplitude
    • Unwrap Phase: Enable/Disable
    • Scale
      • Horizontal divisions: 10 (linear frequency scale)
      • Vertical divisions: 10
      • Autoscale: Off, Auto, Up, Down
      • FR Magnitude Vertical Axis: Lin, Log, dB
      • Squared IR Vertical Axis: Lin, Log, dB
      • dB Vertical Scale (dB/Div)
        • 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 9.0, 10.0, 12.0, 15.0, 16.0, 18.0, 20.0, 24.0, 25.0, 27.0, 30.0
      • Lin/Log Vertical Scale (Units/Div)
        • 1e-9, 2e-9, 3e-9, 4e-9, 5e-9, 6e-9, 8e-9, 10e-9, 20e-9, 30e-9, 40e-9, 50e-9, 60e-9, 80e-9, 100e-9, 200e-9, 300e-9, 400e-9, 500e-9, 600e-9, 800e-9, 1e-6, 2e-6, 3e-6, 4e-6, 5e-6, 6e-6, 8e-6, 10e-6, 20e-6, 30e-6, 40e-6, 50e-6, 60e-6, 80e-6, 100e-6, 200e-6, 300e-6, 400e-6, 500e-6, 600e-6, 800e-6, 1e-3, 2e-3, 3e-3, 4e-3, 5e-3, 6e-3, 8e-3,10e-3, 20e-3, 30e-3, 40e-3, 50e-3, 60e-3, 80e-3,100e-3, 200e-3, 300e-3, 400e-3, 500e-3, 600e-3, 800e-3, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 80.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 800.0, 1e3, 2e3, 3e3, 4e3, 5e3, 6e3, 8e3, 10e3, 20e3, 30e3, 40e3, 50e3, 60e3, 80e3, 100e3, 200e3, 300e3, 400e3, 500e3, 600e3, 800e3
      • Horizontal Axis (Frequency Scale): Lin, Log
      • Frequency Units: Hz, cpm
    • Spectral Smoothing: Enable/Disable (requires logarithmic frequency scale)
      • Smooth Bandwidth (fractional octave bandwidth): 1/6, 1/12, 1/24
      • Smoothing Type: Avg, Max, Min
    • Cursor
      • Harmonic Cursors: up to 128
      • Horizontal Bar: Hidden or drawn at the instantaneous amplitude of any available waveform
      • Peak Track: Off, Max, Min
        • The cursor can track the peak value of any channel which has been selected for analysis
    • Triggering (sourced from X reference input and applied to both X and Y inputs): Enable/Disable
      • Channel selection: Self or any available input or output channel
      • Mode: Auto, Normal, Single
      • Slope: Positive, Negative
      • Threshold
    • Data Export
      • Data File Format: CSV, MAT, TXT
      • Image: PDF
      • Optionally include current location in exported data files.
      • Option to export only visible frequencies.
    • Data Import
      • Data File Format: CSV, MAT, TXT (only files created by the FFT Analyzer tool)
      • The total number of loaded static spectra and live spectra cannot exceed 16 (8 on iPhone)
      • Trace Opacity: 0.25 - 1.0
      • Trace Thickness: 1, 2, 3
    • Average Curve
      • The total number of loaded static measurements (including average curves) and live measurements cannot exceed 16 (8 on iPhone)
      • Max Data Files Per Average Curve: 999999999
      • Data File Format: CSV, MAT, TXT (only files created by the FFT Analyzer tool)
    • Specifications Subject to Change
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