What’s on the DFT & FFT poster
A definition and 6 facts worth remembering.
The DFT samples the spectrum of a finite record; the FFT is a fast algorithm for the same result.
- N samples in give exactly N frequency bins out
- Bin spacing is the sampling rate divided by N
- Bins above N/2 mirror the ones below
- The FFT costs N log N instead of N²
- The record is assumed to repeat forever
- A window trades resolution against leakage
- 1024 points at 48 kHz — 46.9 Hz per bin
- Record length — 21.3 ms
- Typical speed-up — About 100 times
- Doubling the record length halves the bin width; changing the sampling rate does not.
Resolution comes from record length, not point count. Zero-padding interpolates the plot without adding information.
Questions about the DFT & FFT poster
- What’s on the DFT & FFT poster?
- A definition and 6 facts worth remembering. The DFT samples the spectrum of a finite record; the FFT is a fast algorithm for the same result. N samples in give exactly N frequency bins out; Bin spacing is the sampling rate divided by N; Bins above N/2 mirror the ones below; The FFT costs N log N instead of N²; The record is assumed to repeat forever; A window trades resolution against leakage; 1024 points at 48 kHz — 46.9 Hz per bin; Record length — 21.3 ms; Typical speed-up — About 100 times; Doubling the record length halves the bin width; changing the sampling rate does not.. Resolution comes from record length, not point count. Zero-padding interpolates the plot without adding information.
- Who is the DFT & FFT poster for?
- DFT & FFT belongs to the Electrical Engineering section rather than to a school year, because engineering is not something one grade owns. Anyone learning signals & systems can pin it up — a beginner, a student mid-course, or someone revising years later.
- When should you use the DFT & FFT poster?
- Read it before trusting a spectrum plot: bin width and window shape decide what you see. A wall chart earns its place by being glanceable from where the work is happening, so DFT & FFT belongs on the wall where that engineering work actually happens, within glancing distance, rather than filed away.
- What other posters go with DFT & FFT?
- Filter Responses, Bode Plots and Convolution sit alongside DFT & FFT in the Electrical Engineering section. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.Filter ResponsesBode PlotsConvolution
- Is the DFT & FFT poster free to download and print?
- Yes. DFT & FFT downloads as a free PDF with no account, no email and no watermark, like everything else in the Electrical Engineering section. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
- What size does the DFT & FFT poster print at?
- DFT & FFT is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of DFT & FFT loses nothing.Printing guide
Related posters
Charts that sit alongside DFT & FFT on the same wall.
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