Software Defined Radio (SDR) refers to a radio communication system where most of the traditional radio hardware components, such as filters, amplifiers, and modulators/demodulators, are replaced with software running on a general-purpose computer. In an SDR system, the analog signals received by the antenna are digitized by an analog-to-digital converter and then processed by software to perform the required signal processing tasks.
SDRs offer several advantages over traditional radio systems, such as flexibility, reconfigurability, and reduced hardware complexity. This makes them ideal for a wide range of applications, including military communication, amateur radio, wireless networking, and digital broadcasting.
The use of SDRs has become increasingly important in the modern battlefield, where the need for reliable and secure communication is critical. SDRs can adapt to changing mission requirements, support multiple waveforms, and operate in hostile environments, making them a valuable tool for military communication and intelligence gathering.
SDRs have several advantages over traditional military communication systems, making them increasingly important in modern warfare. Some of the advantages of using SDRs for military communications include:
- Flexibility: SDRs can be reprogrammed to support different waveforms, frequencies, and modulation schemes. This allows military units to quickly adapt to changing mission requirements and overcome spectrum management challenges.
- Reduced hardware complexity: SDRs replace many of the traditional radio hardware components with software, reducing the size, weight, and power requirements of military communication systems. This makes them more portable and easier to deploy in the field.
- Secure communication: SDRs can implement advanced encryption and authentication techniques to ensure secure and reliable communication between military units.
- Interoperability: SDRs can support multiple communication protocols, making it possible for military units from different countries or branches of the armed forces to communicate with each other.
- Spectrum efficiency: SDRs can operate on different frequency bands and adjust their transmit power and modulation to optimize spectrum usage, allowing military units to communicate with minimal interference and reduce the chances of detection by the enemy.
Overall, SDRs are becoming an increasingly valuable tool for military communication, allowing military units to communicate effectively and securely in even the most challenging environments.
SDR on satellites
One important aspect to consider when building any type of satellite is communications. Communication systems enable data transfer between sensor systems, satellites, and end users. A satellite’s communication system is basically a radio system that includes antennas, transceivers/transponders, and, in some cases, processors. A satellite radio system is responsible for generating, transmitting, receiving, and processing electromagnetic signals.
Furthermore, satellite communications use 1 to 50 GHz for transmission – the L, S, C, X, Ka, Ku, and V bands – with different satellite applications using different bands. Similarly, the various frequencies within a band are dedicated to specific applications. SDRs can operate normally with all the satellite bands (L, S, C, X, Ku, Ka, and V), thus there is a large range of applications in the satellite industry.
Using such high frequencies at Ka and V band require powerful radio receivers with high-end modulation/demodulation systems are required to extract the information from the signal with minimum noise. Moreover, rain fading is much higher in these cases, which increases the noise figure at the receptor.
Most kinds of communications systems are designed for worst-case scenarios, and satellite channel characteristics are highly variable due to atmospheric and ionospheric effects, especially in LowEarth Orbits (LEO). Designing for the worst-case leaves an expensive and overly-designed system that does not maximize channel capacity. To compensate for this, there is a need to develop enhanced communications systems that can adapt to variable characteristics, for instance, changing modulation, power levels, or carrier frequency on-the-ﬂy.
SDRs have traditionally been used in a wide variety of terrestrial applications. But with the rising demand for high processing power on-board satellites and space systems, SDRs have gradually gained momentum in the space industry. SDR is beneficial for space applications as it provides the flexibility that will allow deployed satellite communication equipment to be software upgradable to more advanced on-board algorithms and communication standards. This will allow communication functionality changes and multiple uses during the lifetime of the satellite mission.
Software Deﬁned Radio (SDR) is a ﬂexible technology that enables the design of an adaptive communications system. This means that a generic hardware design can be used to address different communication needs, with varying frequencies, modulation schemes, and data rates.
Applying this concept to small satellites can increase data throughput, add the possibility to perform software updates over the air, and make it possible to reuse the hardware platform for multiple missions with different requirements. Therefore, development time for future small satellite communication systems can be reduced, even though the development time of the ﬁrstimplementation might be longer than for a traditional radio system.
Satellites equipped with SDRs are increasingly being used to provide reliable and efficient communication links between different parts of the world. SDRs on satellites can be reconfigured remotely to support different waveforms, frequencies, and modulation schemes, making them an ideal solution for a wide range of communication applications. For example, SDR-equipped satellites can provide voice and data communication services to remote areas that lack terrestrial infrastructure, as well as support military and government communication needs.
Both satellites and ground stations are completely dependent on radio systems, so the SDR is a crucial component in the satellite industry. Ground stations also employ SDR systems in the TT&C, receiving data, issuing commands, and uploading software to the satellite.
However, onboard SDR must withstand the orbital conditions while still providing sufficient performance to satisfy the satellite’s requirements. For instance, onboard SDRs must be designed to resist the extreme temperatures and radiation levels of space.
Moreover, the monitoring of space debris and satellites is becoming increasingly necessary as the number of debris increases in the earth’s orbit, especially in the context of satellite constellations. Finally, there is a crucial need for tight timing synchronicity between satellites and the ground stations, particularly in multiple satellite networks for navigation, maritime, and positioning systems.
Therefore, software-defined radios (SDRs) are one of the fundamental building blocks in any satellite. They are responsible for not only basic radio communications, but also more complex tasks, such as wideband spectrum monitoring for space situation awareness (SSA) and space domain awareness (SDA) applications, jamming and interference detection/avoidance, common clock sources, and ground station control/communication. In every one of these applications, the onboard radio of the satellites performs the primary function.
SDR also enables satellite internet, which is a fast-rising application of satellite systems and is a much larger scale of data communication, involving the transfer of enormous amounts of data. The configurable architecture can work across different satellite constellations and protocols without requiring any hardware changes.
In addition to requirements for frequency, bandwidth and regulations found in every communication system, Software Deﬁned Radios (SDR) are highly dependent on the hardware platform used to run the software. In small satellites, the main design drivers are size, mass, cost and power consumption. Moreover, the modular nature of SDRs allows device customization based on the size, weight, and power (SWaP) requirements, which is critical in the satellite industry – in particular nanosatellite applications.
In addition to communication, SDRs on satellites can also be used for a range of sensing applications. For example, SDRs can be used to collect and process data from remote sensors and imaging devices, enabling real-time monitoring of weather patterns, natural disasters, and other environmental factors. SDRs on satellites can also support remote sensing applications such as radar, lidar, and passive microwave sensing, providing valuable information for scientific research and resource management.
The flexibility and reconfigurability of SDRs make them an ideal solution for satellite applications, where the ability to adapt to changing mission requirements is critical. For example, SDR-equipped satellites can be reprogrammed to support different communication protocols or sensing applications as the mission evolves, reducing the need for costly hardware upgrades. Furthermore, SDRs on satellites can be used to support advanced networking and signal processing techniques, such as cognitive radio and software-defined networking, which can improve the efficiency and reliability of satellite communication and sensing systems.
In conclusion, SDRs are playing an increasingly important role in satellite communication and sensing applications. By providing flexibility, reconfigurability, and advanced signal processing capabilities, SDRs on satellites are enabling a wide range of applications, from remote communication and sensing to scientific research and resource management.
For in depth understanding on SDR technology and applications please visit: Software Defined Radio (SDR): Technology, Applications and Market Trends
Software Defined Radio plays a critical role in the Russia-Ukraine war
Software-defined radios (SDRs) have proven critical to electronic warfare, signals intelligence countermeasures and counter-unmanned aerial vehicles. Their ability to monitor the spectrum, intercept signals and record and store data for further signal analysis, especially in near-real time, is imperative in having the upper hand in a battle. There have been instances of Ukrainian hackers using HackRF and RTL-SDR to jam Russian signals, according to a report on Hackers-Arise.com.
On the battlefield, it’s also become essential for SDR to be implemented into tactical radios for the ground soldiers and command and control communication. Russian company NPO Angstrem has developed a radio communications system with an R-187-P1E Azart multimode portable SDR providing much of the system functionality. The SDR-based radio makes it possible to establish a tactical communications subsystem between commanding officers, ground forces and various other forces, all while ensuring a protected data exchange under many conditions, including in an electronic attack and countermeasures environment.
The radio also has a mode for frequency hopping—up to 20,000 hops per second—and thus severely hindering the possibility of communications countermeasures or signal intercept or direction finding by adversaries in this mode. On the Ukrainian side—nearly every Ukrainian ground unit was supplied with and trained on the NATO Single-Channel Ground and Airborne Radio System, which provides over 2,000 channels to choose from and replaces previous Russian-built radios that would be a liability due to espionage.
While Russia was originally expected to have the upper hand in electronic warfare and military capabilities, Ukraine has been viciously fighting back with equipment supplied by allied forces, including SDR-based technologies. For example, Ukraine has been conducting electronic attack and countermeasures operations using counter-drone systems containing SDR transceivers provided by the United States. It has downed hundreds of Russian drones by jamming their GPS signals and, reportedly, even by damaging their electronics with high-power microwave beams.
Elon Musk’s Starlink proved to be an asset in combating jamming attacks on Ukrainian forces. Its constellation of low-orbiting satellites has provided broadband internet to more than 150,000 Ukrainian ground stations, including many of the Starlink ground station terminals, according to hackaday.com. At the heart of these terminals is an SDR of sorts for various means of steering the phased array antenna, tuning to near-microwave frequencies, as well as sending and receiving the data packets during use. As a further blow to Russia, it is very challenging to jam these connections, as it is a far more difficult challenge to jam low-earth-orbiting satellites than geostationary ones.
Software Define radio technology
Software Defined Radio is essentially a transceiver with complex embedded processing capabilities and a flexible/reconfigurable platform for changing radio parameters via software. The generic SDR is divided into three stages: the radio front-end (RFE), the digital back-end (DBE), and the mixed signals interface (MSI).
The RFE contains the receive (Rx) and transmit (Tx) functions of the SDR, through one or more receive (Rx) and transmit (Tx) channels, capable of working with signals in a wide tuning range of tens of gigahertz (GHz). Moreover, the highest-bandwidth SDRs in the market can provide 1 – 3 GHz of instantaneous bandwidth per channel and work with up to 8 gigasamples/second (GSPS), and 16 GSPS independent Rx/Tx signal chains.
The DBE handles modulation, demodulation, up/down-converting, signal processing, control, intelligence, data storage, and communication protocols. This step uses a high-end FPGA with an on-board DSP for modulation, demodulation, up-converting, down-converting, data packetization, and other application-specific tasks, such as security schemes or AI. The FPGA communicates with a host or network by packetizing data into Ethernet packets and sending them via SFP+/qSFP+ links at a 10 to 100 Gbps transmission rate.
SDRs are capable of having very high bandwidths of up to 1 GHz per radio chain. Onboard FPGAs [field-programmable gate arrays] and DSPs [digital signal processors] enable rapid and power-efficient processing; both of these enable SDRs to quickly transfer huge amounts of data handled by satellites without significant latency.
The SDR is based on FPGA and DSP technology, which means the backend can be easily reprogrammed to accommodate different radio protocols, DSP algorithms, and even artificial intelligence, without any hardware replacement. This increases the flexibility, adaptability, and upgradability of the system.
Finally, the MSI is composed of dedicated digital-to-analog convertors (DACs) and analog-to-digital convertors (ADCs) channels, which convert the signals from digital to analog and vice versa. Furthermore, precise timing can be obtained through dedicated clock sources, based on internal time boards. High-end SDRs use oven-controlled crystal oscillators (OCXO) to obtain extremely stable and accurate clock frequencies for the FPGA, the ADCs/DACs, and channel synchronization.
They have evolved, not only in technology, from being solely receivers to transceivers but also in size, mass and power requirements. This range of options is continually increasing and some of these are finding mainstream acceptance in one form or another in the future terrestrial/space SDRs.
Projects are also underway to further reduce the size and operating power of SDR systems, through the use of more powerful electronics, innovative materials, and more advanced system setups.