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Test & Measurement 2012-01-30
Frost & Sullivan : Understanding the True Performance of Time-Varying RF and Microwave Signals
Nowadays, there is ongoing discussion in the field of testing capabilities for real time spectrum analyzers, as issues have appeared with factors limiting key capabilities in terms of higher bandwidth capture and processing capabilities to capture events that are missed or not efficiently measured by traditional instruments. While real-time spectrum analysis for RF and microwave will bring a new set of benefits in the field, and enable users to obtain more information about a signal than with other analyzers, shortcomings over traditional swept analyzers are still significant.
Real-time Spectrum Analyzers’ Benefits
The increasing complexity of what they need to test is bringing about new challenges to technicians. Compared to traditional swept spectrum analyzers, real-time spectrum analyzers have taken a whole new meaning in measurement analysis to deal with the difficulties to detect the spectrum and find infrequent events and ultra-short signals that appear for very short periods of time in a defined bandwidth and certain input frequency.
The adoption of a real-time approach in the domain of spectrum analyzers presents a number of key benefits as described below.
One of the key benefits of real-time spectrum analyzers is their capability to analyze the performance of signals when frequency varies or digital adjustments take place. A real-time spectrum analyzer ensures that the whole bandwidth is captured at once without the need to sweep over each frequency to perform the processing of analysis of data. Some RF and microwave analyzers capture the frequency spectrum from the time domain data and are able to allow time-aligned triggers in a defined input frequency to capture sporadic signals.
Due to the increased ability to process large masses of data, another benefit is the evolution in capture capabilities of some instruments to complete modifications in the frequency and span once the signal is captured. Moreover, while a key benefit of real-time spectrum analyzers is to capture all events in a way that traditional instruments cannot, some leading companies are also making significant inroads using them to further exploit real-time signal analysis capabilities, adding user algorithms with flexible and modular instrumentation. "The modular approach of using FPGAs for real-time spectrum analysis offers some of the greatest benefits," said Raajit Lall, Product Manager for RF and wireless test at National Instruments. "Rather than being limited by box instrument capabilities, the use of FPGAs makes it possible to benefit from real-time processing and the ability to reconfigure for custom algorithms."
Current Challenges
Real-time spectrum analyzers will certainly lead to the need for new types of tests as users strive to capture every event and keep up with any changes in a certain input frequency. At the same time, even though the importance of understanding the true performance of time-varying signals has soared, real-time spectrum analyzers remain limited by their bandwidth capture and processing capabilities.
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Today, “the bandwidth limitation in spectrum analyzers is typically brought about by the analog to digital converter (ADC) that is used in spectrum analyzers,” added Lall.
The current technology of real-time spectrum processing is restricted to 100 MHz and presents a number of challenges to analyze sporadic events in much higher portions of spectrum. However, ADC manufacturers are continuously working to increase bandwidth options.
“I’d expect the universe of choices (various combinations/tradeoffs of speed or bandwidth and dynamic range) to continue to expand”, said Ben Zarlingo, Product Manager for Communications Test in Agilent Technologies’ Microwave and Communications Division. “There is a lot of room for more powerful and flexible processing of captured information including better and faster and more data-dense displays, more sophisticated post-capture processing, and for replay of selected signals from the capture”.
Viewing Methods
The pace at which real-time spectrum analyzers go through the quick detection of time varying RF and microwave events is increasing. Therefore, there have been a number of advancements made in the last years concerning viewing methods. Some of the technology trends that specifically impact real-time spectrum analyzers are the multiple simultaneous views and the 2D waterfall graph (i.e. spectrogram). The spectrogram allows the capture of every event that occurs within the span of interest in real time or the observation of the extent of every event. This viewing method enables to better analyze information in the spectrum in a longer period of time and is possible through the use of color pixels that depict each spectrum at a certain input frequency and time.
Growing Markets for Real-Time Spectrum Analysis
“The market potential will continue to gradually grow and the capabilities related to real time (trigger, capture, playback, post-processing, advanced displays, faster spectrum) will be in more widespread use. The presence of some sort or degree of real time capability will gradually be seen as less separate from “normal” signal analysis,”predicts Zarlingo.
However, while the issue of real-time analysis is not new, only a few leading companies are working in this space today. br>
Rohde & Schwarz’ FSVR is well positioned, providing a combined full signal and spectrum analyzer with a frequency range of up to 40 GHz.
Tektronix’s RSA 6000 series combined with DPX™ Live RF spectrum display is focused on advanced viewing systems for real-time analysis through the use of live color view of signal transients varying over time in a defined bandwidth and rapidly exhibiting a fault in real time.
National Instruments is well positioned providing real-time spectrum analyzers, through a modular, flexible approach that uses an optional NI FlexRIO module featuring an onboard FPGA. The company is expected to remain committed to this arena, ensuring that engineers are not limited to a box and can upgrade RF instruments to higher frequencies / bandwidths while maintaining the FPGA code that is used for processing.
Agilent Technologies is well positioned in the market with the 89600 VSA software to provide reliable insights into real-time analysis. According to Agilent Technologies, it can provide highly-customizable signal analysis views for both digital persistence displays and cumulative history.
There is a number of growth opportunities based on the analysis of end-user applications. Military and aerospace markets are seeing increasing adoption of real-time spectrum analyzers due to increased demand to capture events and signal intelligence. The mobile and electronic markets are seeing growth opportunities through Fast Fourier transforms (FFT).
Overall, the use of real-time spectrum analyzers is likely to accelerate, due to their ability to provide precision and the understanding of the true performance of time-varying signals, which address end-user demands more effectively than traditional swept analyzers.
Final Word
Despite the compelling capabilities, challenges in the real-spectrum analyzer market remain and include the need of a more accurate understanding of signal dynamics, bandwidth capture and processing capabilities. Even though real-time spectrum analysis is still at an early stage of development and progress needs to be made, ADC manufacturers are going to spend much more to develop and support further advances in spectrum infrastructure over the next few years for effective real-time analysis to occur.
For further information: www.testandmeasurement.frost.com.
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