Introduction About Software Defined Radio

It’s scarcely twenty years since the first-second generation (2G) digital mobile phones appeared on the market. By the mid–1990s texting was widely adopted, and further, GSM and GPRS based modems became available—albeit only providing slow connectivity no higher than a few kbps. This was the start of the wireless digital data revolution. By the end of the 1990s and into the 2000s, third-generation (3G)  mobile connections became available at speeds of a few 100kbps and WiFi emerged as a means of connecting devices to wireless access points over distances below 20 meters or so. From early WiFi speeds of just a few Mbps, by 2005 we were running at 54Mbps in most implementations and soon to speeds of  300Mbps and higher when MIMO methods emerged in the early 2010s. Smartphones also just keep getting smarter. WiFi and Bluetooth are now considered standard wireless connectivity requirements on smartphones alongside 2G, 3G, and likely fourth-generation (4G) LTE-Advanced connections. Homes and offices are now well served by superfast WiFi, and there are mobile base stations throughout cities,  towns and the countryside, all around the world. In many ways though, the ‘wireless revolution’ is still just beginning. With more Short Range Devices (SRDs) being produced, and the so-called Internet of  Things (IoT) continuing to evolve, we should expect very soon that there will be more than one wireless phone, laptop or tablet per person; and perhaps up to 10 other devices, ranging from keyfobs to sensors, GPS tracked objects, and so on. It will be wireless everything very soon. Many SDR module available in Market as shown in below Fig 1.1(range from 500KHz to 1.7GHz) and Fig 1.2(range 1MHz to 6GHz),

Fig. 1.1

Fig. 1.2

Software Defined Radio (SDR) is a generic term that refers to radio systems in which almost all of the functionality associated with the Physical Layer (PHY) is implemented in software using Digital Signal  Processing (DSP) algorithms. An ideal SDR receiver would have a very small hardware front-end; only an antenna and a high-speed GHz sampler that was capable of capturing and digitizing a  wide band of radio frequencies. Any demodulation, synchronization, decoding or decryption required to recover information contained within a received signal would be performed in software that is executed on a superfast, dedicated processing device.

Many smartphones and similar devices currently have up to around 8 different radios optimized for  receiving various signals from different frequency bands, such as those for WiFi (2.4GHz), LTE (Long  Term Evolution, 800MHz), GSM (Global System for Mobile Communications, 900MHz), UMTS  (Universal Mobile Telecommunications System, 2.1MHz) GPS (Global Positioning System, 1.5GHz), Blutooth (2.4GHz), NFC (Near Field Communications, 13.56MHz), and FM Radio (100MHz). Soon they may even include radios to receive IoT and TV White Space UHF (Ultra High Frequency at  400MHz) signals too. The ultimate solution here would be to utilize a single SDR that samples the spectrum at GHz rates to digitize and capture all signals from baseband to 2.5 or even 3GHz, and to implement all of these receivers in software code. illustrates the approximate frequency band positions for many of the broadcast radio signals that most of us receive and use daily.

In this series of MATLAB, I will provide many implementations works with RTL-SDR USB SDR hardware, and MATLAB & Simulink software to design and implement real-world desktop SDR systems. We will acquire signals from the frequency range  500KHz to 1.75GHz and digitize them with the hardware, then perform processing in software to demodulate and extract the signal’s information.RTL-SDR is what is termed an Intermediate Frequency (IF) sampling radio, rather than a Radio  Frequency (RF) sampling radio, however, we will demonstrate how this form of SDR can be used to receive signals from 500KHz all the way to 1.75GHz.

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