The Agilent CXA Signal Analyzer
Bringing the Power of Sophisticated RF Spectrum Analysis to a Wider Audience of Users
September 28, 2009
Spectrum analyzers are usually the engineer's preferred tool of choice for testing and evaluating the wide variety of RF communication signals and technologies.
This preferred instrument of the communications industry is valued for its broad frequency range, from less than a few Hertz to beyond 1000's of MHz, and wide amplitude measurement range, from close to the fundamental limits of random noise to +30 dBm coupled with accuracy approaching that of power meters. Also valued is the ability to separate complex signals into their component pieces driven by an extensive selection of digital resolution bandwidth filters from 1 Hz to over 8 MHz. A large distortion-free dynamic range enables measurement of tiny nonlinearities and leakage in the presence of large signals. This compelling performance, combined with diminishing measurement time, has led to the spectrum analyzer's popularity among RF engineers.
To meet the escalating needs of wireless technology to thrust more data through limited frequency and bandwidth channels by exploiting ever more complex modulation schemes, current-generation signal analyzers like the Agilent X-Series have increased their measurement sophistication substantially beyond just the analysis of power versus frequency and time. Now, powerful modulation analysis tools evaluate complex modulation schemes and their underlying parameters while providing application-specific displays and metrics. Built-in, single-button activated, test routines, advanced measurement algorithms and standards-specific software simplify the setup and automation of modulation testing.
Also, by leveraging its potent RF hardware performance and computational capabilities, the spectrum analyzer can perform the tasks of multiple instruments more economically within a single platform. For example, the Agilent X-Series signal analyzers can emulate a noise-figure meter, phase-noise test set, EMC pre-compliance analyzer, a vector signal analyzer, and more. This evolving combination of powerful performance and analysis has been matched with a user interface honed over multiple Agilent analyzer generations and modern connectivity like LAN and USB, making it easier than ever to utilize and access these sophisticated capabilities.
However, this sophisticated level of analysis capability has generally been unavailable to budget constrained and low-cost R&D, manufacturing and educational organizations. For example, with cost-sensitive-driven manufacturing test engineers, their biggest challenge is often the relentless cost reduction combined with limited capital equipment budgets. The new Agilent CXA signal analyzer model, as the most affordable member of the Agilent X-Series signal analyzers, makes possible the first low-cost access to these powerful and sophisticated analysis tools (Figure 1).
Figure 1: The Agilent N9000A CXA signal analyzers offer a pair of low-cost models that deliver frequency coverage up to 7.5 GHz.
Power Suite: The Power of One-button RF Measurements in CXA
The measurement of 2G/3G wireless carrier envelopes for power, channel leakage and other standards-based parameters can often be complicated to set up and difficult to measure correctly with the needed accuracy and repeatable results.
Power Suite, standard in the Agilent CXA signal analyzer, provides standards-based, intricate power measurements through a comprehensive set of flexible, one-button RF power measurement routines. A simple and intuitive interface offers quick, consistent and accurate answers no matter who presses the button to activate the measurement routine.
Power Suite measurements include; Adjacent Channel Power (ACP) measuring up to 12 carriers at once, Channel Power, Occupied Bandwidth (OBW), Spectrum Emission Mask (SEM), Complementary Cumulative Distribution Function (CCDF), Burst Power, and Spurious Emissions. Wireless standards-based setups include: 2G/3G cellular, Bluetooth®, UWB, and S-DMB. More than 75 quick setups or custom settings are available for specific power measurements.
Analog-Demodulation Measurements in CXA
AM and FM are still a principal form of wireless communications worldwide, ranging from commercial broadcast stations to business radios. Analog radio manufacturers are challenged to test, evaluate and troubleshoot their products with increasingly more efficient and comprehensive tools.
The optional W9063A analog demodulation measurement application for the CXA signal analyzer offers easy-to-use, one-button measurements to analyze analog modulated signals such as AM, FM and PM with unprecedented insight and measurement speed. The application provides a quad view showing the RF spectrum, AF spectrum, demodulation waveform, and FM demodulation metrics simultaneously. By watching these traces in the various domains along with the metrics, engineers can understand the signal characteristics precisely and, especially during troubleshooting, quickly and easily identify the cause of a problem.
Noise-Figure Measurements in CXA
A key measurement in the development of devices and systems is noise figure. The overall noise figure of a system is one of the limiting factors in performance. Making noise-figure measurements can also be a tedious manual process. However, with CXA's optional W9069A noise figure application, these measurements can be made quicker and easier with accurate results.
The W9069A noise figure measurement application provides a suite of fast, one-button noise figure and gain measurements from 200 kHz up to 7.5 GHz, depending on which CXA model is chosen. The CXA analyzers offer an optional 3- or 7.5-GHz preamplifier required to reduce instrument uncertainty so low-gain devices can conveniently and accurately be measured. In addition, setup menus help guide engineers through amplifier and mixer measurements. A built-in measurement uncertainty calculator makes it easy to qualify a measurement system.
The lower investment cost and speed of this application also offer manufacturing engineers an efficient application for measuring any one of the following in their test racks without compromising speed: noise figure/factor, gain, effective temperature, Y-factor, and hot/cold power density. Agilent Smart Noise Sources are supported for easier setup and calibration.
Phase-Noise Measurements in CXA
Phase noise is still one of the most important characteristics when evaluating the short-term stability and purity of a signal. Signal stability is fundamental to successful modern digital wireless communication systems. Pressure to bring products to market more quickly does not allow time for executing multiple measurements across several instruments. Therefore, an accurate, fast, and easy-to-use phase noise measurement tool is critical in R&D and manufacturing environments.
The optional W9068A measurement application in CXA lowers the cost of phase noise analysis by providing a single instrument that does both spectrum and phase noise measurements. This flexible tool quickly and easily generates log plots of phase noise in dBc/Hz versus offset frequency; measures RMS, degrees, jitter and carrier frequency drift; and also makes continuous spot frequency phase-noise measurements.
EMC: Precompliance Measurements in CXA
All manufacturers planning to sell electronic products on the commercial market must pass EMC regulatory requirements prior to distribution. Proof of meeting various national EMC regulations is typically done by EMC compliance testing facilities.
Successful compliance testing of a manufacturers' final version of their product is, under of the best of circumstances, expensive and time consuming. However, waiting until the end of the development cycle to find out whether or not a product passes regulatory agency requirements can be a high-priced gamble. Failing to pass can result in costly redesign and introductory schedule delays.
Because of this, developers are justifiably concerned about the EMC performance of a new product from design investigation through preproduction units. Many manufacturers use less expensive EMI precompliance measurement systems to perform their own conducted and radiated EMI emissions tests prior to sending their product to a test facility for full compliance testing.
The N9000A-EMC Optional measurement application for CXA provides a less expensive precompliance solution for manufacturers wishing to avoid the risk of EMC compliance failures. Option EMC offers full CISPR 16-1-1 (2007) compliant detectors and bandwidths. The tune and listen feature can discriminate between ambient environment and DUT signals. The measure at marker feature allows measurements using up to three detectors. EMC regulatory limit lines and antenna corrections are available as standard features on the X-Series signal analyzers.
VSA: Vector Signal Analysis in CXA
The CXA is the only low-cost analyzer that can support both spectrum and complete vector signal analysis in a single tool, including both general and standard-specific digital modulation analysis. Within the limits of the CXA 10-MHz analysis bandwidth, R&D and manufacturing engineers can measure, demodulate, evaluate, and troubleshoot the complex, time-varying behavior of digitally-modulated signals.
CXA users have a choice of optional VSA analysis tools, the Agilent 89601A VSA software or the 89601X VXA measurement application.
The 89600 VSA software is the industry's leading signal analysis solution offering comprehensive, flexible signal visualization and advanced algorithms for analysis in the time, frequency and modulation domains (Figure 2). It supports over 70 signal standards and modulation types with tools that include: constellation and vector diagrams, IQ parameters, EVM, frequency and clock errors, and channel/impulse response with equalization, along with transient and time-selective statistics (e.g., burst analysis). This software runs on the CXA embedded PC utilizing keyboard and mouse control, Windows toolbar and menus, and with COM API remote programming.
Figure 2: Running on the X-Series signal analyzers, Agilent's 89600 VSA software offers premier analysis and troubleshooting.
The less expensive 89601X VXA measurement application, with its general-purpose modulation analysis, is focused on design verification, conformance and quality testing in R&D and manufacturing. More than 30 demodulators including 2-16 FSK, PSK and 16-1024QAM are available. Analysis tools include: constellation and vector diagrams, IQ parameters, EVM, frequency and clock errors, and channel/impulse response with equalization. The outstanding measurement speed of the CXA directly benefits manufacturing productivity. In addition, tests can be leveraged from programs developed in design verification and R&D from any members of the X-Series family. The VXA utilizes the familiar X-Series signal analyzer front-panel user interface along with easy-to-use SCPI programming.
With the sophisticated and powerful signal-analyzer capabilities available in the 3- and 7.5-GHz CXA models, a complete spectrum- and vector-based signal evaluation and troubleshooting toolset is now accessible to manufacturers at a lower price point than previously obtainable.
About Agilent Technologies
Agilent Technologies Inc. (NYSE: A) is the world's premier measurement company and a technology leader in communications, electronics, life sciences and chemical analysis. The company's 18,000 employees serve customers in more than 110 countries. Agilent had net revenues of $5.8 billion in fiscal 2008. Information about Agilent is available on the Web at www.agilent.com.
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For further information visit: www.agilent.com/find/CXA_backgrounder
Janet Smith, Agilent
Sarah Calnan, Europe
Iris Ng, Asia