The ever-increasing need for smart wireless devices, broadband/broadband telecommunication systems, and global RF and digital systems is increasing the demand for Software Defined Radio (SDR) to levels never seen before. These applications vary widely in performance and cost, as well as size, weight, and power (SWaP). In this scenario, the test and measurement (T&M) industry is crucial in the process of developing new devices to ensure that the wireless equipment functions properly and meets the required standards and qualifications. Fortunately, SDRs offer a high level of flexibility and programmability, not only for the application but for the T&M process itself, reducing the amount of equipment needed and allowing the same device to perform several different functions without hardware modification. .
T&M is a well-known RF development process, required for various design stages of new devices, including proof of concept, pre-simulation, simulation, prototyping, and validation/certification for market release. A major challenge in T&M design is compliance with the wide variety of wireless devices that range from rugged aerospace and defense systems to mobile healthcare and agriculture solutions. In these applications, T&M equipment is needed to simulate different RF systems by testing and measuring:
- Modulation/demodulation schemes
- Transmit (Tx)/receive (Rx) performance parameters that include path loss, noise, dynamic range, and spurious-free dynamic range (SFDR)
- Antenna performance in terms of near field/far field measurements, antenna coupling, range and radiation pattern
- Electromagnetic compatibility
- Multiple RF evaluation functions, such as spectrum, signal and network analysis
In this article, we discuss how SDRs can help the T&M market keep pace with the rapid pace of technology development in the wireless industry. We discuss how SDRs can perform several functions found in traditional test benches, from signal generators to spectrum analyzers, while offering much more flexibility and reconfigurability than conventional RF test equipment. . Without any hardware modifications, SDRs can be adapted to work with different radio protocols, modulation schemes, frequencies and bandwidths, all of which are constantly evolving in the RF industry and exemplify the power and enduring utility that SDRs provide for T&M engineering.
What is DTS?
SDRs are essentially transceivers that perform most radio and signal processing functions in the software domain, implementing only the analog hardware needed for antenna coupling, amplification, and filtering. The analog part of the SDR is called the radio front end (RFE), which contains all the Rx and Tx channels of the design, operating over a very wide tuning range. The highest performing SDRs on the market provide RFEs with instantaneous 3 GHz bandwidth across multiple independent channels, each with a dedicated digital-to-analog/analog-to-digital converter for multiple-input, multiple-output (MIMO) operation. The digital back-end operates on the digitized signals, performing all on-board digital signal processing functions needed for RF applications, including modulation/demodulation, up/down conversion, and packetization of data over optical Ethernet links . The host connection is extremely important in SDRs for T&M because it integrates the device with the rest of the system, especially if high data throughput is critical. The industry’s highest bandwidth SDRs deliver 4 × 100 Gbps link rate over qSFP+ transceivers that can be connected to the host architecture via network interface cards, perfect for any high throughput test. Figure 1 shows the general SDR structure applied in T&M.
The combination of software-based operation and native host connection in SDRs enables the implementation of open source and custom software with readily available T&M functions. This dramatically increases the functionality of the equipment by taking advantage of built-in signal and RF processing functions and software libraries, without having to develop low-level coding and graphical interfaces. In this context, GNU radio is the best example of RF applications, with built-in functions such as frequency spectrum, spectrum cascade plots, constellation diagrams (important for DC offset and IQ phase imbalance ), scope traces, and waveform generation. It also provides out-of-the-box algorithms for calculating important RF parameters, such as SFDR, noise, and dynamic range. By applying a single MIMO SDR with GNU radio, T&M engineers can significantly reduce the number of devices in a test and centralize all RF configuration, further reducing cost, time, and human error.
SDRs are also capable of working with UHD-based tools and software, which includes custom programs based on Python and C/C++. This greatly increases the range of possibilities for T&M systems, as custom and proprietary software can be easily implemented to comply with different applications and protocols. For example, UHD powered SDRs can use GPS/GNSS simulation tools, according to different satellite constellations, while dealing with interference and jamming or even implement readily available open source LTE/5G base stations for testing. performance and compliance. A major advantage of UHD projects is their trend towards open source solutions, which reduces the need for proprietary licenses and fosters an active and resourceful community.
How are SDRs changing the face of T&M in various markets?
Due to their flexibility, programmability, inherent ability to work with multiple channels, and high performance, SDRs help engineers solve many challenges in the T&M industry. For example, capturing large instantaneous bandwidths is desirable in several T&M applications, but is very difficult to implement in conventional RF systems, especially when working with high frequencies (e.g. millimeter wave) . By providing software-based signal processing with very low latency, SDRs exhibit superior performance in terms of capturing bandwidth compared to conventional systems, while offering greater flexibility thanks to their wide tuning range. State-of-the-art SDRs implement high-speed host communication over optical Ethernet links, enabling the streaming of large amounts of data to a server system or storage solutions, which is fundamental in 5G networks and IoT. The flexibility and programmability of the FPGA not only provides better performance than existing radio systems, but allows the T&M system to be tuned to the device under test without any hardware modifications, providing a versatile and robust solution.
SDRs also reduce the need for specialized hardware, as a single device can provide a wide range of functionality, including future custom functions. Their modular nature also allows customization of the device to meet any performance and SWaP requirements of the application. T&M architectures can pair one or more SDRs to operate cohesively, each providing a different function, such as signal generation and spectrum analysis. Each SDR is a full-fledged RF world, offering total customization in terms of waveform, modulation scheme and frequency. High-speed SDRs can store and transmit massive amounts of data, providing plug-and-play solutions for network applications. Stand-alone RF solutions typically have a fixed number of RF channels, which limits their applicability and increases the number of devices. MIMO SDRs, on the other hand, provide a configurable amount of RF channels that can be used to perform different applications, such as waveform generation and signal reception, or to operate coherently in data networks. antennas, which is ideal for beamforming/beamsteering. Conventional T&M systems have fixed functionality and cannot be easily updated, while SDRs can be programmed to work with the latest protocols and algorithms without any hardware modifications.
The software nature of SDRs makes them naturally compatible with automated solutions, which requires a certain level of built-in intelligence and host interface. Automated T&M systems offer several advantages over conventional solutions. In the lab, tests can be programmed according to predefined power thresholds and task sequences, which reduces the risk of material damage and improves robustness and reliability by eliminating the risk of human error. In addition, it enables remote control of the test, which is especially important for cooperation between laboratories and testing in hard-to-reach remote locations, such as cell towers in remote areas. SDRs can also be pre-programmed to automatically transmit signals at specific time intervals, allowing the system to operate without human intervention.
In the era of 5G, the rapidly growing RF market requires robust and reliable T&Ms that can keep up with the constant technological innovations in terms of wireless devices and communication protocols. Conventional T&M systems are fixed and single-use and cannot provide the flexibility and versatility needed to cope with this ever-increasing evolution, making SDR-based equipment increasingly desirable in the T&M market. . SDRs can perform multiple functions at the same time through multiple RF channels that can be fully reconfigured to conform to different waveform, frequency, sensitivity, modulation, and latency requirements. They can be easily programmed to work with new protocols and algorithms, dramatically improving device longevity. SDRs are also compatible with open source software solutions for hosting with built-in T&M functions, including GNU Radio and UHD programs, improving their usability and reducing development time and cost.