Electronic Design

High-Frequency Testing Drives Modern Instrument Design

It may be stating the obvious, but the prevailing trend in instrumentation surrounds the expanding array of instruments that addresses the growth of high-speed serial interfaces and the wide range of new wireless standards and products.

Both of these areas require microwave capability, something that was only needed in more esoteric RF test instruments of past years. No more. Instruments with gigahertz and higher capability are becoming the norm. And let’s not forget video with its higher definition and speed as required by TV and gaming.

High-Speed Serial Interface Test
The onslaught of new high-speed serial interfaces for linking processors to memory and peripherals (PCI Express, XAUI, 10Gigabit Ethernet, etc.) has unleashed a new breed of instrumentation, from oscilloscopes and logic analyzers to BER testers and signal generators (Fig. 1).

These instruments feature input sampling rates up to 20 to 50 Gbits/s and huge internal RAM to store millions of samples. Then, special test software not only lets you measure the usual speed and rise/fall times, it also provides sophisticated jitter measurement and analysis as well as BER testing. Best of all, instrument manufacturers are providing automated testing software targeting specific interfaces, making standards testing faster and easier.

Serial data testing has always been a bear, having to look at lots of bits to figure out the protocol and to identify headers, addresses, special codes, data, and error codes. Today, that’s all automated by the software and given to you in a variety of display options.

Tests for high-speed serial interfaces have led to the creation of automated testing software for other slower serial interfaces and protocols, such as RS-232, SPI, CAN, I2C, USB, and others that make serial communications and networking test faster and simpler. And what product today doesn’t use at least one of these?

Wireless Test
The massive growth of the cell-phone market has created a whole new class of test and measurement requirements. Add to that the dozens of new wireless standards and applications with extensive volume and severe compliance tests, and some critical needs become clear.

Today, we have test equipment that can handle these issues. Let’s take a look at some of the trends driving this fast-growing sector:

Increased integration: More circuits and functions are packed into every chip, including the ultimate in mixedsignal digital/radio/ linear. On top of that, there are more radios per product, such as Bluetooth, GPS, and Wi-Fi in a cell phone.

Pushing into the higher reaches of the spectrum: Today, 2.4 GHz is common. But the newer radios operate in everincreasing bands—5.8 GHz for 802.11a WLANs and many cordless phones, the 3.1- to 10.6-GHz UWB band, and the forthcoming 60-GHz radios.

More complex modulation schemes: There’s little use of plain-old AM or FM. Currently, it’s purely sophisticated digital modulation that improves spectral efficiency of digital data transmission. Even BPSK and QPSK are simple compared to the higher-level modulation schemes like M-QAM and CDMA with advanced coding. The newest king of them all is OFDM—the base of almost every new wireless technology that requires high speed FFT and IFFT.

Special antenna technologies: Multiple-input multiple-output (MIMO) is being incorporated into the latest LAN standards as well as WiMAX. In addition, special beam-forming antennas are finding their way into updated cellular systems to improve performance and system capacity. Only recently have test systems for these advanced methods been available.

Increasing number of complex wireless standards: Here’s the short list: GSM/GRPS/EDGE, WCDMA, HSPA, cdma2000, EV-DO, LTE, UMB, WiMAX, Wi-Fi 802.11n, Bluetooth, UWB, ZigBee, RFID, GPS/Galileo, satellite radio, satellite TV, HDTV, MediaFLO, and DVB-H.

Video Test
The immersion of video in myriad applications adds even further high-frequency testing demands (Fig. 2). Consider these not-so-subtle trends:

The rise of digital TV: We’re seeing a much quicker pace for HDTV adoption these days. In part, it’s due to the FCC mandating that analog TV broadcasting end on Feb. 17, 2009. Millions of digital-to-analog converter boxes will be needed by those who don’t immediately buy a new set. Furthermore, satellite TV (which is also all-digital) has grown remarkably over the years, stealing business away from cable TV companies.

Cheap big screens: Affordable plasma, LCD, DLP, and other large-screen TV sets are triggering the consumer trend toward bigger and higher-quality home-entertainment centers. This is just the beginning of even larger movements toward improved video performance and Internet TV.

Internet Protocol TV: IPTV is digital video and audio delivered via the Internet. Major companies like AT&T (U-verse) and Verizon (FiOS) already offer it. But more is on the way as the broadband connections to homes multiply and become capable of handling the speed required for streaming video.

Video on demand: VOD will also gain popularity once the digital rights management mess is solved. It’s more a content protection problem than a communications technology problem. VOD is now available, but in a limited capacity.

Re-awakening of videoconferencing: This application has been born and reborn several times. With all digital technology and the Internet, it should finally become mainstream.

TV on cell phones: It’s available in limited form right now via the cell-phone networks. But soon, cell phones will have separate built-in TV receivers that will pick up broadcasts from stations designed especially for this purpose.

Surveillance explosion: One trend, perhaps below the surface, is wiring the world for video monitoring. Terror threats and the need for better security in buildings and on the streets has become crucial, if not essential, for human safety. Small, inexpensive cameras and Internet technology make this easy to do on a broad scale.

The testing of analog video was always a challenge. However, it’s a whole new ballgame with digital video and its multiple formats, compression methods, screen sizes, and other variations.

TAGS: Components
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