| | 1 | [[TOC(DSP/Interpolation*, depth=3)]] |
| | 2 | |
| | 3 | = Interpolation Tutorials = |
| | 4 | |
| | 5 | == Introduction == |
| | 6 | Interpolation, also known as upsampling in the case of Digital Signal Processing, is a process that provides an approximation of the signal that would have been obtained if it had been sampled at a higher sample rate.[[BR]] |
| | 7 | |
| | 8 | Before continuing with this tutorial for further reading for understanding Interpolation read the following resources: |
| | 9 | * [http://dspguru.com/dsp/faqs/multirate/interpolation DSPGuru - Interpolation] |
| | 10 | * [http://en.wikipedia.org/wiki/Upsampling Wiki - Upsampling] |
| | 11 | == Materials Required == |
| | 12 | * [http://www.orbit-lab.org/userManagement/register Orbit Account] |
| | 13 | * Installation of GNURadio |
| | 14 | * Reservation on Orbit Lab |
| | 15 | * WAV File |
| | 16 | == Installing GNURadio == |
| | 17 | If running on a Ubuntu or Debian distribution of Linux use the following command for installation: |
| | 18 | {{{ |
| | 19 | sudo apt-get install gnuradio |
| | 20 | }}} |
| | 21 | |
| | 22 | For other OS's follow the instructions from this [http://gnuradio.org/redmine/projects/gnuradio/wiki/InstallingGR guide]. |
| | 23 | == Interpolation of a Sinusoidal Wave with GNURadio == |
| | 24 | In GNURadio on your computer implement the following flow chart to obtain the following FFT and Scope Plots: |
| | 25 | [[Image(img1.png)]] |
| | 26 | [[Image(img2.png)]][[Image(img3.png)]] |
| | 27 | |
| | 28 | Next add a Interpolation FIR Filter with an Interpolation of 3 as seen below: |
| | 29 | [[Image(img4.png)]] [[BR]] |
| | 30 | |
| | 31 | Verify that the Scope and FFT plots are: |
| | 32 | [[Image(img5.png)]][[Image(img6.png)]] |
| | 33 | |
| | 34 | The waveforms can be seen with 3 zeros inserted from the Interpolation FIR Filter between every sampled point. Next apply a Low Pass Filter as seen below to smooth out the waveform. |
| | 35 | [[Image(img7.png)]] |
| | 36 | |
| | 37 | Verify that the smoothed out signal plots resemble: |
| | 38 | [[Image(img8.png)]] [[Image(img9.png)]] |
| | 39 | == Interpolation of a .WAV File with GNURadio == |
| | 40 | For the following download the .WAV File and listen to the audio file. Then set up the following flowgraph in GNURadio: |
| | 41 | [[Image(img10.png)]] |
| | 42 | Go back to the original .WAV File and listen to the audio. Then listen to the output file and notice the difference and effects of upsampling an audio sample. |
| | 43 | == Interpolation of a Sinusoidal Wave with Octave == |
| | 44 | |
