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Getting Started with the USRP B205mini-i software defined radio platform

alexwonglik1

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The USRP B205mini-iUSRP B205mini-i is a flexible and compact platform that is ideal for both hobbyist and OEM applications. It is designed by Ettus ResearchTm and provides a wide frequency range (70 MHz to 6 GHz) and a user-programmable, industrial-grade Xilinx Spartan-6 XC6SLX150 FPGA. The RF front end uses the Analog Devices AD9364 RFIC transceiver with 56 MHz of instantaneous bandwidth. The board is bus-powered by a high-speed USB 3.0 connection for streaming data to the host computer. The USRP B205mini-i also includes connectors for GPIO, JTAG, and synchronization with a 10 MHz clock reference or PPS time reference input signal.

 

The getting started guide walks you through the steps you need to take in order to use the USRP B205mini-i.USRP B205mini-i. You will learn how to install the software driver and GNU radio in Windows or Ubuntu, connect the devices, run examples and create an FM radio receiver from scratch. When you start using the device, there are some examples that come with the driver. You can run the real-time Discrete Fourier Transform (DFT) example. The options for the executable (./rx_ascii_art_dft) are frequency (–freq), sampling rate (–rate), gain (–gain), bandwidth (–bw), and reference level (–ref-lvl). The terminal will show the flow of execution, list the parameters, and graph the result:

 

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Project Example - Using GNU Radio to Design a Frequency Modulation (FM) Receiver

The FM receiver takes the modulated signal (i.e. radio waves under the VHF band) as input and produces the original audio signal ranging from 20 Hz to 20 kHz.

First of all, in the terminal, the GNU Radio Companion will be open. Then, the following blocks will be added: Sample Rate, Frequency, USRP and QT GUI Sink. Next, a low pass filter is used.

Notice that the audio signal bandwidth ranges from 200 Hz to 20 kHz. Once the lowpass filter has been added, the next step is to perform the FM demodulation.

 

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Since the output signal is audible, this signal is sent to the sound card - which is actually a digital to analog converter with a sample rate of, in general, 96 kHz. A Rational resamples block is used, to perform an x/y operation, where x (interpolation) is the output frequency, and y (decimation), is the input frequency. Finally, Audio sink block is added, so that the output signal will be played through speakers. After being generated, the python script is sent to USRP B205mini-i and executed. The output signal is displayed in the time and frequency domain, as seen below.

 

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Find the complete getting started guide and project examples on the Digilent Reference Page.

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