Wireless Technologies Demand Advanced Measurement Solutions.
The Next-Generation Signal Analyzer Enables Today’s Engineers to Quickly and Efficiently Test Emerging Wireless Technologies
By Taka Hando, Product Marketing Engineer, Agilent Technologies

With new and diverse wireless technologies like WiMAX, 3G LTE and TD-SCDMA continuing to emerg

e at a steady pace – driven by successful deployments of 2G/2.5G/3G cellular communication and WLAN – the issue of Time-To-Market (TTM) is garnering increasing attention. In fact, it now stands as a key factor in the success of today’s wireless businesses. Engineers ,therefore, are continually on the lookout for solutions that can help them achieve a fast TTM. One area where significant gains can be realized is test and measurement, and in particular, in the area of spectrum and signal analysis.

The Driving Force
The wireless industry is today experiencing a strong demand for cheaper wireless communications, as well as increased capacity to handle new functionality such as video via cellular handset. In order to support this demand, technology needs to be at its best – whether it is with regard to the DSPs which are heavily utilized in today’s wireless communications applications or the measurement instrumentation that is used to test them. Of course, this is no easy task, especially considering the complexity of wireless signals, which are time varying and therefore not especially compatible with more conventional frequency-domain test solutions.

This situation is further complicated by the fact that while general-purpose RF spectrum analyzers have traditionally been used to perform required analog/RF signal measurements, when it comes to digital measurements no such solutions exist. Instead, engineers are forced to create customized solutions to demodulate the different wireless signals. These measurements typically require the use of two separate test instruments. Given the challenges that an engineer normally faces during the product lifecycle – from system design, product development and initial production to volume production – this added work just makes the measurement task ever more daunting.

What today’s wireless engineers require is a single measurement solution that can make both analog/RF and digital signal measurements, while at the same time reducing test time and increasing test efficiency. A next-generation of signal analyzers is now emerging that addresses these issues head on, by helping to not only drastically improve measurement speed, and therefore TTM, but also by delivering a slew of benefits that can be realized throughout the entire product lifecycle.

A New Alternative
The next-generation signal analyzer is a new type of measurement solution that offers wireless engineers the performance and capabilities they need to quickly and accurately test complex wireless signals. It is fast, easy to use and offers outstanding performance. More importantly, it can address the engineer’s analog/RF and digital measurement needs with a single instrument. As a result, it is playing an increasingly important role throughout the entire product lifecycle (see Table 1, pg 60). To better understand that role, consider the various stages of the product lifecycle:

• System’s View
Challenge: In the early stages of any new wireless technology development, the engineer will typically face a number of different challenges. To begin with, there are fewer dedicated instruments for test and measurement. Additionally, at this stage, there is a strong need to protect any intellectual property.

Solution: The next-generation signal analyzer can address these challenges in a number of ways. Running an Open Windows XP Professional Operating System, for example, it allows the user to connect the signal analyzer with their custom measurement program and simulation tools in a much more efficient way than ever before. In turn, this accelerates the system design phase. It also allows the instrument to operate popular software tools like MATLAB. Included MATLAB drivers enable the user to easily create and execute custom measurement programs within a single instrument.

In addition to MATLAB, the next-generation signal analyzer supports modulation analysis software like Vector Signal Analysis (VSA) from Agilent Technologies (see Figure 1). When coupled with the company’s Advanced Design System (ADS), the engineer can make simple and reliable linkages between simulation and the real world.

• Product Development
During the product development stage, the engineer faces challenges in design verification, quality assurance (QA) and troubleshooting.

Challenge: A variety of emerging standards (e.g. EV-DO, 802.11n WLAN, HSDPA/HSUPA, WiMAX, ZigBee, and the WiMedia-based Ultra Wideband) are creating new opportunities for an increasing number of consumer devices to incorporate wireless capabilities. To take advantage of these opportunities while remaining cost competitive, many manufacturers are looking to address conformance, regulatory and interoperability testing requirements across the entire product lifecycle. With regard to design verification during product development, for example, the engineer must ensure that the device in question meets regulatory requirements and that it is interoperable with other devices. Regulatory testing requires power and spectrum measurements, while interoperable testing (e.g., conformance test) requires power, spectrum and demodulation analysis measurements.

Solution: The next-generation signal analyzer offers a comprehensive one button/SCPI compatible measurement application within the mainstream technology such as W-CDMA and mobile WiMAX. These measurement applications are comprised of up-to-date standard setup and test capabilities required for interoperability testing. They also include the performance and presets required for conformance testing. With these measurement applications, the user can execute design verification test by automated program and manual testing.

• Quality Assurance
Challenge: At the QA phase, the typical challenge the engineer faces is how to manage the length of test. To ensure a certain level of product quality, device testing must be done iteratively, under ever slightly distinct conditions and by varying the product’s temperature. The problem stems from the fact that most of today’s wireless communication signals are either burst or time-varying. The common measurement approach is to simply use Time Gating for spectrum analysis. While it helps to ensure the signal is valid and significantly reduces measurement time, it only sweeps the frequency. Another common approach is List Sweep to configure the analyzer to make a list of single-point measurements. By doing so, the analyzer can run through the list without requiring the user to set it up for each measurement iteration.

Solution: The next-generation signal analyzer features a unique split-screen mode. This allows the user to view both time domain and frequency domain simultaneously in order to easily set up the proper gating for a Time Gating measurement (see Figure 2). Additionally, the next-generation signal analyzer offers support for both Time Gating and List Sweep.

• Troubleshooting
Challenge: Troubleshooting requires the engineer’s creativity, as well as imagination – especially when facing the problem of working in the digital modulation domain. That’s because today there is no single approach. However, there is an approach with a high probability of success. It is comprised of four checkpoints.

1. Band spurious or unwanted signals
2. In-channel spectrum and power
3. Analyze basic digital demodulation
4. Analyze advanced and format specific demodulation

Solution: In order to facilitate this approach, the ideal next-generation signal analyzer must provide the user with pieces of information from various angles. The Agilent MXA Signal Analyzer is an example of one such solution. Fully calibrated, with up to 26.5 GHz pre-amplifier and featuring advanced markers, six traces and simultaneous detectors, it is well suited for the 1st checkpoint. When combined with VSA software, it can also address checkpoints 2 through 4.

• Initial Production
Challenge: In general, the smoother the transfer from research and development, the more successful and rapid the ramp-up for the manufacturing team. Oftentimes though, new test equipment is introduced during production which sometimes creates measurement inconsistencies, resulting in production slowdowns.

Solution: Addressing this challenge requires a measurement solution that can be used during development as well as in production. The next-generation signal analyzer offers just such a capability. Outstanding speed, performance and usability make it affordable for manufacturing. Yet, it is also suitable for cases where only power and spectrum measurements are needed, featuring a set of common measurements and standard presets like Channel Power, Occupied Bandwidth (OBW), Adjacent Channel Power (ACP) and, Spectrum Emission Mask (SEM) (see Figure 3).

• Volume Production
Challenge: As production volume increases, so too, does the pressure on the engineer to reduce overall test time as a means of lowering cost and potentially catching other business opportunities. Of course, using traditional signal analyzers, this is not always an easy task to accomplish.

Solution: The next-generation signal analyzer is extremely fast. In fact, it is significantly faster than more conventional signal analyzers for every aspect of use cases, as opposed to just for a corner case. As an example, consider that the MXA signal analyzer is characterized by:

1. Mode / Measurement switch < 75 ms
2. Marker Peak Search < 5 ms
3. Center Frequency Tune and Transfer Data < 51 ms
4. Fast W-CDMA ACLR < 14 ms
5. W-CDMA Modulation Accuracy < 850 ms

Note that next-generation signal analyzers like the MXA can also be optimized via fine tuning to achieve even faster measurement speeds without compromising dynamic range. In the case of the MXA, that equates to 10 percent incremental 160 RBW settings realized by all digital IF, 2 dB step mechanical and 1 dB step electronic attenuator, selectable swept or FFT spectrum analysis feature.

Also note that, more recently, LXI-based test systems have garnered increasing attention thanks to their ability to deliver significantly improved test throughput as compared to more traditional GPIB-based test systems. LXI-based test systems include LXI Class C compliant general-purpose instruments like signal analyzers and signal sources. As a result, it may be wise to consider using a solution that is LXI Class C compliant.

The Bottom Line
There is no shortage of measurement challenges facing today’s engineers, especially those working in the dynamic, fast-paced and highly complex world of wireless communications. The next-generation signal analyzer can and will play an increasingly important role in addressing these challenges at every stage of the product life cycle. It is creating a new test paradigm in which multiple test instruments are no longer required for both analog/RF and digital measurements. Instead, these measurements can now be handled by a single, high-performance, easy to use instrument. In the process, the next-generation signal analyzer is not only reducing test time and increasing efficiency – both of which lead to significantly improved time-to-market - but also opening up a range of potential new business opportunities.

About the Author
Taka Hando is a product marketing engineer at Agilent Technologies. He joined HP in 1984 and was transferred to Agilent when it spun off from HP. Hando graduated from Hiroshima University in Japan with his Masters Degree in applied physics engineering in 1984.

Agilent Technologies
www.agilent.com
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