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High-Speed Wideband Testing Technology Goes Mainstream

October 1999
By Henry S. Kenyon

A California-based firm is cashing in years of military communications experience to enter commercial markets.

Technology derived from military signal analysis work is producing testing equipment for wideband applications in the private sector. These devices are capable of both storing and analyzing large amounts of data while generating a variety of broadcast waveforms.

This capability meets the test needs of a rapidly growing commercial environment whose numerous new technologies demand increased bandwidth and modulation complexity. These new markets include wideband communications satellites, wideband satellite components, high definition television, wireless local area networks, wireless local loop, local multipoint distribution service, multichannel multipoint distribution system, wideband code division multiple access, and wavelength multiplexed fiber.

The explosion of commercial communications has opened up a variety of opportunities for companies to apply what were once exclusively defense-related methods. As defense budgets continue to shrink, firms that had contracted with the government and armed forces are using their knowledge and expertise to move into new and lucrative civilian markets. Now, new wideband technologies appear and demand increasing amounts of bandwidth, creating a vital niche for this new testing equipment.

One example of this trend is Celerity Systems Incorporated. When it was founded in 1994, the Cupertino, California-based company produced wideband technology to support strategic and tactical reconnaissance systems. Though the firm continues to enjoy steady business with its military clients, it has moved into the civilian business sector. According to Celerity President and Chief Executive Officer John L. Anderson, 60 to 65 percent of the company’s business now comes from the commercial sector.

Celerity’s specialty is wideband test equipment for a variety of broadcast and Internet applications. Anderson believes that growing commercial wireless markets are creating a need for test instrumentation that is not being met by existing products. His firm’s background in military signal intercept and reconnaissance technology, where devices with a large amount of memory are needed to record and analyze waveforms, is proving to be useful in developing civilian products. He notes that a decade ago, nearly all of the advances in the wireless world came from the military. Now commercial satellite and communications markets are driving technological development, he says.

The company makes testing equipment for generating and receiving a variety of wideband signals. Anderson believes that what sets his company’s products apart from those of its competitors is that they record data and produce waveforms across a broad range of frequencies. He notes that an average commercial spectrum analyzer only detects narrowband signals. Even though these instruments sweep across 3 gigahertz, their instantaneous bandwidths are at any given time in the area of 1 to 3 megahertz. Other tools such as network analyzers test communication devices by generating a signal and receiving a reply from the equipment being examined. By using a tone on the input side, a range of frequencies are swept through the device and the results are then measured for factors such as magnitude and phase. One of the drawbacks to these traditional methods is that they only deal with a single tone, signal or sine wave, observes Anderson.

By contrast, Celerity’s equipment can generate up to 30 megahertz of complex waveforms and test a piece of equipment under more realistic signal conditions. Anderson notes that as communications devices such as modems and amplifiers all begin to operate in higher bandwidths, there will be a growing need to test those devices with more authentic transmissions rather than artificial sine waves.

The firm’s latest product, the CS29010 distortion measurement test set, is designed to fit these needs. According to Anderson, it is the first instrument the company has produced that takes full advantage of its experience in wideband receiving and generation technologies. This is also the first offering aimed at the microwave measurement markets, he adds. The product is now beta marketing as a device to test travelling wave tube amplifiers, which are high-powered amplifiers for ground and space applications.

The CS29010 features a wideband high-performance arbitrary waveform generator module, wideband data acquisition module, radio frequency up/down converter module, a Pentium processor operating Windows NT, and measurement and control software. Unlike network analyzer instruments that use a single swept tone for analysis, the CS29010 can generate and receive signals with bandwidth of over 30 megahertz, allowing advanced signal types such as biphase shift keying, quadrature phase shift keying, quadrature amplitude modulation, time division multiple access, code division multiple access (CDMA) and eight-level vestigial sideband (8VSB) to be used in testing. The device can also synthesize any new signals in software and use them for testing through the arbitrary waveform generator.

The CS29010 can make a number of measurements to determine the linearity of microwave communications devices. These include noise power ratio, third order intermodulation distortion, adjacent channel power ratio, pin versus pout, noise figure, magnitude response and phase response.

Another aspect of the CS29010 is that it is the company’s first integrated test instrument to possess the software and recording, collection and analysis algorithms necessary to run by itself. Compared to the firm’s previous products, it is fully self-contained. With the company’s other instruments, the end-users put their own software into the test devices. Anderson describes these products as blank pieces of paper on which customers can write their own algorithms. In the case of the CS29010, while it can be modified by users, it already comes with the necessary software and algorithms.

Hughes Space and Communications Company has been a steady commercial purchaser of Celerity’s semicustomized equipment. As Hughes switched from defense to commercial satellites, Celerity was able to meet the company’s testing requirements with its arbitrary waveform generators and data recorders. He notes that this adds up to several million dollars in sales from Hughes and other customers in need of devices for complex satellite testing.

While the CS29010 is a self-contained device, it can sit in an equipment rack and operate as part of an integrated testing suite. For example, Anderson notes that Hughes uses multiple systems placed in two racks for satellite testing. Most of it is Hewlett-Packard equipment and Celerity’s unit for waveform generation and recording. The Celerity device sits on a network where it is loaded with and plays out data. This resulting information flows into other analysis equipment and over the network to Hughes’ own computers, which then process the raw data.

One advantage inherent in the company’s waveform generators is memory, says Anderson. Conventional devices tend to have only 4 to 8 megabytes of memory, while Celerity’s have from 1 to 4 gigabytes, which Anderson calls deep memory. This allows the firm’s equipment to record or generate contiguous data to analyze a signal in recording mode. If the item is generating waveforms, deep memory allows it to create realistic signals. He believes this capability will become increasingly important as the commercial world develops more complex signals and communications devices.

The company’s test equipment is designed for cross-platform use on a variety of computers, from SPARCs to Pentiums. Celerity uses LabVIEW software, which is a graphical user interface application developed by National Instruments. For signal simulation and analysis, MATLAB software was chosen. Anderson notes one reason these two packages were selected is that they are popular and available across a variety of different platforms. All of Celerity’s products come with some type of graphical user interface software. Also provided are capabilities to look at information being recorded with devices such as digital oscilloscopes as well as spectrum or logic analyzer displays. These capabilities allow the person testing the device to view information in a number of different signal modes: time, frequency, logic, phase and magnitude. The company’s testing equipment also features built-in data libraries written in ANSI C++. These libraries let customers easily integrate the equipment into their testing systems. ANSI C++ allows the equipment to be compatible with a number of different computer platforms, says Anderson.

The firm’s products have applications beyond radio and satellite communications. Because its hardware is capable of recording large amounts of data, with the proper software and algorithms, the company’s test equipment can take recorded data and distill it to look at specific things such as bit sample rates, data rates or modulation. This can be applied to Internet or cellular telephone applications because it is possible to go down to voice or bit levels, Anderson says. He claims that his firm’s equipment is capable of recording analog bandwidths of up to 300 megahertz and adds this capability will soon increase to 500 megahertz.

Celerity is currently looking into various Internet-related markets and sizing-up the competition where specialized, focused instruments are needed. It is currently building analysis-type instruments for customers developing high definition television (HDTV). With a signal at 6 megahertz, HDTV has very little equipment to support testing and analysis, Anderson says. HDTV uses the complex digital waveform 8VSB. He adds that while there are several other vendors making testing products, they are still trying to fully understand the technology because HDTV signals are still not as well understood as analog broadcasts. The testing devices Celerity is using are compact solid-state recorders capable of collecting and playing back data from the field. Other applications then analyze the multipaths of HDTV signals. One problem with HDTV is that the signals are so complicated that analysis may prove to be difficult, he adds.

Despite these technical hurdles, Anderson would like to see Celerity gain a niche in this market. He speculates that this could potentially become a multibillion dollar industry as broadcasters switch from analog to digital formats in the next decade.

Another promising technology in need of test equipment is local multipoint distribution service, also known as wireless cable. This broadband technology will be competing with next-generation communication satellites, high-speed telephone, video and Internet services, wireless local loops, wireless local area networks, and wideband code division multiple access (WCDMA)—the next generation of CDMA.

Using CDMA as an example, Anderson notes that wideband CDMA is moving to 6 megahertz of bandwidth and could potentially get to 10 megahertz because of a desire to have increased capacity and the ability to put digital networking on the signals as well. All of this is putting stress on today’s testing equipment, he observes. Celerity is looking into these markets to determine the specific needs and types of testing applications.