DS-2000 Frequently Asked Questions

The operation of performing an inverse Fourier transform (IFFT) on a frequency-limited Fourier spectrum is as follows:

■Operating Procedure

• Open a new project.
• Click on "Window (Window Function) Settings" in the input menu to open the window settings page.
• Select the rectangle window and click OK.

Figure 1

Display the time axis for which you want to perform the IFFT and the Fourier spectrum on two separate screens, then stop the measurement.
To display the Fourier spectrum, click "Input Source Settings" in the Data Display menu and select "Fourier Spectrum" on the "Input Source Settings" page.

Figure 2

In the data display menu at the bottom of the screen, change the "Cursor" item from Peak to "Delta". Select !--.

Figure 3

• On the Fourier spectrum screen, click the mouse or use the left/right arrow keys to move the cursor (red vertical line) to the lower frequency limit you want to band-limit, and then click "Delta Position". The red vertical line will turn pink, and the lower frequency limit will be set. (Figure 3)
• Similarly, click the mouse at the lower frequency you want to limit the bandwidth to, and use the left and right arrow keys to fine-tune the cursor (red vertical line). The bandwidth will be limited by the pink and red lines. (Figure 3)
• Click [IFFT Settings] in the analysis menu to open the "Data Secondary Processing" page.

Figure 4

On the "Data Secondary Processing" page, check the box for "Bandwidth limit using the current delta cursor." Then, check the "Execute" box and click "OK." This will perform an IFFT on the Fourier spectrum and display the frequency-bandwidth limited time-domain waveform. (Figure 4)

Top screen: Original time-axis data. Bottom screen: IFFT results with frequency bandwidth limited.

Figure 5

If you want to change the frequency band, click [IFFT Settings] in the analysis menu to open the "Data Secondary Processing" page, uncheck "Execute", and click OK to return to the Fourier spectrum display. Then, repeat the operations in steps (6), (7), and (8) above.

supplement
Data obtained using IFFT cannot be treated as a time-domain waveform in its current state. Please refer to "How to treat IFFT-obtained waveforms as time-domain waveforms."​