Electronic Design

New Apps, Rising Clock Rates Test The T&M Arena

It's a pressure cooker for today's test-and-measurement equipment manufacturers. With electronics penetrating further into automotive, consumer, medical, industrial, and military applications, innovative test equipment is essential to ensure success in today's competitive marketplace.

T&M equipment users demand more capabilities, but they don't want to pay higher prices. That's why low-cost PC-based instruments are flourishing. But there's no substitute for the latest gear in leading-edge markets, like silicon-on-chip and RF ICs, where signal integrity is paramount. The instrument designer's task is especially challenging because signal-integrity interpretation involves the analog domain.

Signal integrity is vital in T&M. The boundaries between the digital and analog worlds is blurry, now that digital data rates have reached the gigabit-per-second range. While T&M equipment tries to keep pace with digital circuitry advances, it lags behind for analog signals. Thus, analog signal integrity is even more critical.

The faster rise times of signal transitions cause interconnect analog effects to dominate system performance. But these effects are no longer restricted to the transmission medium. Connectors, sockets, pc boards, and other hardware associated with transmission systems also come into play. All of this points to the need to develop practical methods to quantify a given design, be it analog, digital, or mixed signal, through accurate measurements. The biggest challenge again lies in the analog domain.

Last year, several signal-integrity instruments offered leading-edge jitter-measurement capabilities.

Agilent Technologies' 81142A/81141A 13.5/7-GHz serial data pulse generators provide output-pulse transition times under 20 ps and jitter of less than 1 ps rms. Also, Agilent's N4903A combo generator/bit-error-rate tester (BERT) simplifies jitter-tolerance testing up to 12.5 GHz.

Anritsu unveiled a 39.8-GHz instrument, the MP1797A, which serves as a single-box solution for jitter testing. It consists of a jitter generator/receiver as well as optical-to-electrical and electrical-to-optical conversion modules. Also, LeCroy delivered the SDA 100 digital storage oscilloscope (DSO) last year. This four-channel, 11-GHz bandwidth pattern-analysis instrument can sample data at 40 Gsamples/s.

Software even chimed in to help with signal-integrity measurements. Last year, Tektronix unveiled a software package for its spectrum analyzers that quantifies measurements. With the software, designers can better characterize phase noise, jitter, frequency deviation, and transient times for high-frequency signals.

One of 2005's most important T&M advances again came from Anritsu with its MT8860B—a single-unit, protocol-based, wireless local-area network (WLAN) tester. It analyzes the performance of 802.11b/g devices and consumer products, a task that required several separate instruments. Simulating an access point, the MT8860B creates a standard connection to the device under test (DUT), eliminating special DUT test mode software or signal-generator programming used by other WLAN test systems.

Many new T&M instruments target communications protocols, such as the controller-area-network (CAN) bus used in automotive applications. For instance, LeCroy's Vehicle Bus Analyzer makes it easy to view CAN networks by decoding the CAN protocol in a symbolic format. It decodes serial CAN data into symbolic ( application layer) signals. This not only provides test engineers with the first full range of CAN protocol stack information (symbolic, hexadecimal, and electrical formats), it also lets them view other in-circuit information that influences CAN-bus behavior.

Rising clock rates in serial communications systems perpetually drive manufacturers to come up with state-of-the-art T&M instruments. That said, we're seeing the deployment of next-generation synchronous optical network (Sonet) equipment that can transport data over the present Sonet/SDH ( synchronous digital hierarchy) infrastructure.

On another front, the move is on from legacy asynchronous transfer mode/frame relay (ATM/FR) systems to Internet Protocol/multiprotocol layer switching (IP/MPLS) systems. As a result, demand is on the rise for test equipment that's best suited for current and next-generation networks.

A major challenge in communications testing is to implement complex test measurements for Voice-over-IP (VoIP) networks. With the call for VoIP test equipment growing louder daily, market analyst Frost & Sullivan sees the market for such equipment ballooning to $640 million in 2008, up from $215.8 million in 2004.

However, evolving VoIP standards create quite a challenge in VoIP testing. Thus, equipment must be able to interpret protocols, as well as detect interoperability issues arising from these protocols.

It's important for such equipment easy to use, too, which is difficult to achieve given VoIP technology's complex nature. In addition, it must go beyond testing and include voice quality quality-of-service (QoS) measurements networks as well (see the figure).

Not many T&M systems on the market can handle such a tall order. One of few is the Abacus 5000 test system Spirent Communications. It can manage analog, time-division-multiplexed (TDM) switched circuit, and VoIP signals with 50,000 IP phone calls under test.

T&M equipment suppliers continually look to integrate greater within limited bench space. of this trend abound, but one standout is LeCroy's WaveSurfer oscilloscope.

Measuring 10.25 in. high by 13.25 in. wide by just 6 in. deep, it packs lots of power as well as a 10.04-in. diagonal LCD screen. Available in 200-, 350-, and 500-MHz models, the WaveSurfer offers a 250-Msample/s standard rate on each one of its four channels.

The more-in-less-space trend closely parallels the move to PC-based testing systems that use advanced graphical user interfaces, like LabView, and state-of-the-heart PCI-bus and PXI-bus hardware plug-in boards. Such an approach offers lower-cost testing plus greater flexibility to adapt to different and constantly changing enduser test requirements.

The latest PC-based plug-in boards continue to add more capabilities to the mix. Aware of this, many leading T&M instrument companies now work closely with hardware and software PC-based measurement products.

Beyond PCs, we're already witnessing T&M systems based on laptop and notebook computers, pocket computers, personal digital assistants (PDAs), and palmtop computers. Just take a look at the powerful PDA-based and pocket-PC-based laser meters from Coherent Technologies.

With PCI Express' quick adoption rate, its impact on T&M systems may rival that of the general-purpose interface bus (GPIB) from 30 years ago. The story will unfold as the PXI standard evolves into the recently announced PXI Express standard and as more test equipment begins to support it.

The PCI Industrial Computer Manufacturers Group (PICMG) and the PXI Systems Alliance (PXISA) are moving to integrate PCI Express into both CompactPCI and PXI with backward compatibility. A key feature of PCI Express is its hybrid slot. It supports signaling for both PCI Express and PCI modules—PXI modules that use PCI signaling can be installed as well as future high-performance PXI Express modules.

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