A simple FM radio transmitter based on FPGA
May 7th - Radio Day!
I hope this note will be just the way.
Most recently, an article about a project based on the Raspberry Pi board was on Habré - just a piece of wire was connected to it and ... that's all. A program running on the Raspberry Pi managed to broadcast in the FM band simply through this piece of wire.
Here is a link to the article on Habré.
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Now a similar project has appeared for the Altera Cyclone III FPGA. Again, a short piece of wire is connected directly to the chip output, in this case the FPGA chip.
Audio file in WAV 22050Hz format, 8 bits, MONO is simply transferred to the board via the serial port. The board accepts bytes and broadcasts this stream in the FM range at a frequency of 90 MHz.
There is a demo video broadcast on youtube, though the music is somewhat sleepy.
It can be seen that the melody is received not only by a domestic radio receiver next to the board, but also in a car in the courtyard, about fifteen meters away.
The original project for the Mars Rover 2 with a detailed description appeared here .
The frequency modulator itself is written in Verilog HDL and is very simple. The project uses the original frequency of 450 MHz and is almost always divided by 5 with the resulting frequency of 90 MHz. Since for frequency modulation it is necessary to change the frequency in a small range, sometimes after many divisions by 5 the insertion “division by 4” is made. The more such inserts, the higher the average frequency of the digital sequence. This is sufficient for the receiver to detect the signal.
It is good that there are fairly detailed explanations for the project and testbenches and timing diagrams of signals. Now it's pretty easy to figure out the transfer method.
I hope this project will be of interest to anyone who is interested in radio, as well as FPGA digital circuitry.
I hope this note will be just the way.
Most recently, an article about a project based on the Raspberry Pi board was on Habré - just a piece of wire was connected to it and ... that's all. A program running on the Raspberry Pi managed to broadcast in the FM band simply through this piece of wire.
Here is a link to the article on Habré.
')
Now a similar project has appeared for the Altera Cyclone III FPGA. Again, a short piece of wire is connected directly to the chip output, in this case the FPGA chip.
Audio file in WAV 22050Hz format, 8 bits, MONO is simply transferred to the board via the serial port. The board accepts bytes and broadcasts this stream in the FM range at a frequency of 90 MHz.
There is a demo video broadcast on youtube, though the music is somewhat sleepy.
It can be seen that the melody is received not only by a domestic radio receiver next to the board, but also in a car in the courtyard, about fifteen meters away.
The original project for the Mars Rover 2 with a detailed description appeared here .
The frequency modulator itself is written in Verilog HDL and is very simple. The project uses the original frequency of 450 MHz and is almost always divided by 5 with the resulting frequency of 90 MHz. Since for frequency modulation it is necessary to change the frequency in a small range, sometimes after many divisions by 5 the insertion “division by 4” is made. The more such inserts, the higher the average frequency of the digital sequence. This is sufficient for the receiver to detect the signal.
It is good that there are fairly detailed explanations for the project and testbenches and timing diagrams of signals. Now it's pretty easy to figure out the transfer method.
I hope this project will be of interest to anyone who is interested in radio, as well as FPGA digital circuitry.
Source: https://habr.com/ru/post/178903/
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