To move a block on the canvas, grab it with the cursor, press the left mouse button, and move the block to the desired location. 3Ĥ Double-click on Signal Source to place a Signal Source on the GRC canvas as shown below. You can also use the search function (click on the looking glass on the top right) to enter a specific keyword, e.g., source, to see all blocks with source in their name. Click on a triangle next to a category, e.g., Waveform Generators, to see what blocks are available in that category. On the right side of the window is a list of the block categories that are available. Below the Options block is a Variable block that is used to set the sample rate, e.g., to F s = Hz in the GRC window above. 2ģ For now we will leave the default settings unchanged. Right-click on the block and click on Properties (or double-click on the block) to see all the parameters that can be set. The Options block at the top left is used to set some general parameters of the flowgraph, such as the graphical user interface (GUI) for widgets and result displays, or the size of the canvas on which the DSP blocks are placed. Start the GRC by typing gnuradio-companion in a terminal window in Linux and you will see an untitled GRC window similar to the following. 1Ģ 1.1 Getting Started with the GNU Radio Companion GNU Radio Companion (GRC) is a graphical user interface that allows you to build GNU Radio flowgraphs using predefined DSP blocks. The GNU Radio Companion (GRC) is a graphical user interface that makes it possible to build GNU Radio flow graphs in a user-friendly graphical tool environment. It is widely used in hobbyist, academic, commercial, and military environments to support wireless communications reearch, as well as to implement real-world radio systems. GNU Radio is a free software development toolkit that provides the DSP runtime blocks used to implement SDRs in conjunction with readily available low-cost external RF hardware. The use of these technologies allows new wireless features and capabilities to be added to an existing radio system without replacing or modifying its hardware. The main advantage of an SDR over a traditional radio is that (most of) the radio s operating functions (often referred to as physical layer processing) are implemented through modifiable and upgradable software and firmware on programmable devices such as field programmable gate arrays (FPGA), DSPs, general purpose computers (GPP), programmable System on a Chip (SoC), etc. Often the device that translates the digial baseband signal to the analog bandpass signal is referred to as the SDR and then the device (computer) that generates the digital baseband signal is referred to as the DSP. In modern practice, DSP is used for frequencies up to several tens or a few hundreds of MHz and analog hardware is used for frequencies of several hundreds of MHz and beyond. All the filtering and signal processing then takes place in the digital domain that can be more precisely controlled in an economic fashion than is possible for traditional analog signal processing. In its purest form, a SDR consists of an antenna and an analog-to-digital converter for the receiving part and a digital-to-analog converter connected to a power amplifier and an antenna for the transmitting part. Analog hardware is then used to translate between a (complex-valued) baseband signal and its corresponding (real-valued) bandpass signal in a frequency band that is suitable for wireless transmission and reception. SDRs, on the other hand, perform most of the complex signal processing needed for modern communications systems at baseband, using digital signal processing (DSP). Traditional radio devices are defined by their hardware and are typically only usable in a specific frequency band and for a particular type of modulation. A radio is any kind of device that transmits and/or receives signals wirelessly in the radio frequency (RF) spectrum from about 3 khz to 300 GHz. Mathys Lab 3: Introduction to Software Defined Radio and GNU Radio 1 Introduction A software defined radio (SDR) is a Radio in which some or all of the physical layer functions are software defined. 1 ECEN 4652/5002 Communications Lab Spring P.
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