Wireless and RF test equipment and systems are strong growth segments in the test and measurement (T&M) industry. But for wireless designers and production professionals, it's still a work in progress.
T&M equipment companies do a good job of staying on top of demand. Still, they face mounting pressures to produce even more accurate and faster systems. Here's a look at 10 factors that keep wireless T&M vendors on their toes to meet today's testing demands.
All wireless systems are based on standards provided by international bodies, as well as industry consortia. And every one of those standards is perpetually updated and revised.
Take the latest cell-phone standards. The cdma2000 standard developed by Qualcomm undergoes upgrades all the time to provide faster data services. The EV-DO version is now morphing into what is called Rev. A, which provides even faster downlink and uplink rates. But don't look now—Rev. B and C aren't far behind.
The ITU/3GPP 3G standard based on WCDMA is moving toward its higher datarate systems, HSDPA/HSUPA. These require new test systems that meet the new standards. However, they do provide backward-compatible test facility for the still widely used 2G standards like GSM/GPRS/EDGE.
Other wireless standards like Wi-Fi also face continuous change. The new 802.11n standard with MIMO (multiple input/multiple output) is creating a whole new class of testing systems for certification. Other standards force the T&M guys to constantly upgrade to stay current as well.
You'd think we had enough standards to cover almost any new wireless application. But that's not how the industry thinks. With so many standards to address, the T&M industry must be thrilled at the need. Think about all of the wireless stuff that must be tested based on existing standards like Bluetooth, Wi-Fi, Ultra-Wideband (UWB), ZigBee, RFID, near-field communications (NFC), and a mix of industrial-scientificmedical (ISM) band radios, not to mention more than a few proprietary systems.
And what about new radio technologies, such as those involved in testing HD, XM, and Sirius satellite radios? Then, even newer standards come along to push the innovation of new equipment and systems that can test them, such as the new Wibree and WirelessHD.
Test instruments are here to test upper-microwave products, but the frontier is expanding. UWB is moving from its below-5-GHz spectrum to the upper limits, where more space is available and there's less interference with other services. The WirelessHD standard works at 60 GHz. WiMAX and a few other services are pushing into higher frequencies. With chip geometries falling from 90 nm to 65 nm, and then to 45 nm, that trend will continue.
Faster Data Rates
Wireless services just get faster and faster. Wi-Fi will jump from its current maximum of 54 Mbits/s to near 300-Mbit/s range with the forthcoming 802.11n standard. Bluetooth will eventually move to a maximum of 480 Mbits/s as it adopts the UWB WiMedia standard. In addition, there's no holding back cellphone data rates as they ramp up with 3G speeds from 2 Mbits/s to near 20 Mbits/s. Some of the newer home networking technologies offer speed in excess of 1 Gbit/s.
Noise And EMC
Noise is the bane of all wireless. But as we reach higher frequencies, smaller IC geometries, and weaker signals, noise inside the instrument becomes a limiting factor. The push is on to solve traditional thermal noise problems, reduce digitizer noise, improve spurious-free dynamic range (SFDR), and deal more effectively with jitter.
Furthermore, the regulatory requirements for electromagnetic compatibility (EMC) continue to occupy the time of the wireless design and test engineer. Test equipment and systems that facilitate electromagnetic-interference (EMI) testing are mandatory in today's environment.
Some new technologies require T&M companies to come up with systems for testing special systems, such as mesh networks and MIMO. Orthogonal frequency-division multiplexing (OFDM), which is the modulation/ access scheme of choice for most new wireless systems, presents special problems for both test signal generation and analysis given the many different formats used. Another challenge involves testing systems like WiMAX, with adaptive modulation that adjusts to changing channel conditions.
Fixed And Mobile TV
A quickly emerging test challenge concerns wireless digital and high-definition television (HDTV). While a predominance of video comes to the TV set by cable, there's still a need to test over-the-air and satellite TV. Growing adoption of big-screen digital and HD sets, as well as Congress' mandate to get rid of analog TV in favor of digital TV in 2009, creates a need for wireless TV testing.
Another forthcoming testing challenge will be the video capabilities of cell phones. They're already present in some designs, but the major push hasn't really begun. Standard test techniques can be used to test video delivered over the existing networks, though some special measures will be required when separate TV receivers are built into cell phones. As usual, multiple standards will prevail, like Europe's DVB-H and Qualcomm's MediaFLO.
How do you test an SDR anyway? It has an RF section, meaning some basic RF tests will work. But the real challenge lies in the analog-to-digital converter/digital-to-analog converter sections, up/down conversion, and the baseband parts of the system. Here, software rules and multiple levels of operation occur, not to mention the use of multiple protocols in some cases. Obviously, SDR testing is largely software. Like some standards, testing procedures will be defined, and T&M companies will participate in creating test procedures.
Speed And Ease Of Use
Speed is becoming an even greater challenge as time-to-market gets shorter and margins fall. Reducing test time will make any manufacturer more competitive and profitable. With cell-phone handset sales slated to exceed 1 billion this year, how will all of those units get tested to the strict standards that define them in a timely manner?
On top of that, ease of use is essential. Setup time must be minimal, and a zero learning curve is desirable. With standards and testing getting more complex every day, speed and ease of use get tougher to achieve. But for customer satisfaction, these features are a must.
Test automation is common but becoming more important, particularly to achieve speed and ease-of-use goals. That means automated test systems are essential to achieve those volumes. In most cases, the key is better software.
To reach the goals set for wireless test equipment, vendors have begun to adopt a more modular approach to testing. PXIbased modular test solutions are smaller and lower in cost. They also offer the flexibility to be quickly set up, changed, and expanded thanks to the hundreds of modules available from multiple manufacturers.
Test time has become more critical in most wireless test systems. When analyzing test time, it becomes clear that it breaks out into four primary segments: device-under-test (DUT) setup, test-equipment setup, signal-acquisition time, and data-processing and analysis time. Instrument setup and signal-processing times tend to dominate, so any optimization of the equipment focuses on reducing those times.
One promising approach is to adopt an SDR architecture for building test systems, which can be done in a modular fashion. For signal analysis, an SDR receiver is a front end with downconversion and a fast IF digitizer. Software modules then demodulate and further analyze the resulting digitized signal. Analysis may be on a Pentium PC, a fast RISC processor, a DSP, an ASIC or FPGA, or some combination as the test situation requires.
For signal generation, an SDR architecture would use arbitrary waveform generators (AWGs), direct digital synthesizers (DDSs), and fast DACs. Again, modularity is the key, giving the instrument flexibility to be configured and reconfigured to the job.
Finally, overall performance means any new instrument must have ever-faster signal processing and analysis to speed test throughput, wide modulation and demodulation bandwidth, wide dynamic range, and low noise. While all test instruments manifest themselves as an expensive piece of hardware, the sophisticated software inside does the analysis and automates the process.