FFT Sink and Low Pass Filter

Open GNU Radio Companion using this command

$ gnuradio-companion

An untitled GRC window should open.


1. Double click on the options block. Type project title and Author Name. Set General options to WX GUI. Click OK.

2. Double click on variable and change the sample rate to 10Khz.

3. On the right side of the window by expanding the wave generator category click on signal source. Place two signal sources. Double click on the signal source and set frequency 1KHz and 2KHz.

4. Place Multiply Block and connect the signal sources to the multiply block and place FFT Sink and Scope Sink.

5. Place throttle block to control the flow between the multiply block and the sinks block.

6. Press F5 to generate the flow graph and F6 to execute the flow graph. You will see two peaks one at 1Khz and other at 3Khz.

 

 

Now we want to low pass the signal to get only 1KHz signal at the output.

7. On the right hand side of the window click on Filters-> Low pass filter. Double click on Low pass filter block and set the cut off frequency and transition bandwidth. Set cut off freq to be 1.2Khz and transition bandwidth to be 200.

8.  Fir filter type be Float-Float. Now place FFT sink and scope sink at the output of the filter.

9. Press F5 to generate and F6 to execute the Flow graph.