Testing Frequency-Hopping Spread Spectrum Devices

Frequency-hopping spread spectrum (FHSS) is an essential wireless communication method used for improving security, minimizing interference, and optimizing bandwidth utilization. It is applied in Bluetooth technology, consumer walkie-talkies, and military communication. In FHSS systems, the carrier frequency jumps swiftly to different frequency channels according to a pre-agreed, synchronized, and predictable pattern known by both the transmitter and receiver. This technique is useful in minimizing the potential for interception and interference, making it advantageous for needs requiring robust and secure communications.

Like with any other wireless technology, testing devices that operate using frequency hopping presents unique problems because of the dynamic nature of the signals. Areas such as accuracy of frequency, speed of switching, LO settling time, dwell time, duty cycle off-time, and power level stability require stringent control, which makes these systems difficult to evaluate. Testing those devices with traditional methods like switched synthesisers or stand-alone arbitrary waveform generators does not work due to insufficient sequencing capabilities, inadequate adjustable playback memory, failure in signal sequencing, and lack of coverage for frequency or switching speed.

To mitigate these challenges, Keysight Technologies created an integrated solution for generating and testing frequency-hopping signals with high precision and repeatability. This system provides an advanced, flexible, and FHSS scalable framework that utilizes COTS hardware in conjunction with advanced software tools. At the core of the system is an AWG VSG, integrated with VSG, and waveform creation software, typically MATLAB, capable of generating ideal mathematical I/Q-modulated signals for frequency-hopping.

The AWG is critical to execute the modulating in-phase (I) and quadrature (Q) signals, thus controlling the FHSS pattern. Also, the VSG acts as an upconverter equipped with wideband I/Q modulation, translating the baseband signals to the desired radio frequencies. For this configuration, the primary VSG used is Keysight’s E8267D PSG vector signal generator, which supports frequencies up to 44 GHz and offers 2GHz of RF modulation bandwidth. With sampling rates of up to 12 GSa/s and sophisticated waveform memory, the AWG options of the Keysight 81180A, and the high-performing M8190A, can store complex, greater-than-real-time frequency-hopping sequences.

Perhaps the most notable improvement this solution offers is the ability to attain near-zero settling time during frequency hops, which is important to maintain the fidelity of the signals generated. This capability greatly assists R&D centers, particularly for developing and validating sophisticated FHSS receivers. It is also possible to move test signals developed during R&D directly to automated production test environments, thus increasing efficiency and reducing overall testing costs. 

Incorporating aggressive frequency hopping or custom hop sequences into tests is versatile and can be incorporated into a multitude of systems, which requires special consideration for the overall system design. Such features are offered by MATLAB, including defining and customizing the signal and modifying parameters such as hop frequencies, dwell times, and sequencing logic so that real-world frequency hopping behavior can be replicated in tests. 

The modular nature of the solution allows seamless upgrades to be implemented, like accommodating higher frequencies, wider bandwidths, or more complex modulation schemes. Because of this, the solution is advantageous for laboratories and manufacturers as it serves as a future compatible investment. The scalability of the solution is a feature that is highly sought after, as it can adapt to future needs for tests and changing wireless standards.

Within the realm of manufacturing, this specific frequency-hopping test solution guarantees consistent and dependable measurements vital for maintaining quality and adhering to compliance standards. Furthermore, the system's automation features, along with fast switching, enable high-throughput testing, significantly streamlining product validation processes and accelerating market readiness for devices equipped with FHSS. 

In summary, the comprehensive testing solution developed by Keysight Technologies for frequency-hopping spread spectrum devices is pivotal in addressing the critical concerns posed by heterogeneous and dynamically evolving RF signal evaluation. The seamless integration of high-performance arbitrary waveform generators (AWGs), agile vector signal generators, and sophisticated software for waveform generation enables the system to conduct precise and dependable tests, fulfilling the rigorous demands of contemporary FHSS applications while providing scope for future innovations in wireless communication technologies. 

This framework demonstrates the capability of integrated software and hardware to aid in the generation and analysis of frequency hopping signals. Its impact on the development, validation, and production of FHSS devices is paramount towards fostering advanced secure wireless communications systems.