Applied Signal Technology and VLSI jointly develop single chip 64 256 QAM; APSG supplies demodulator design -- VLSI supplies layout and fab expertise; "Meets or exceeds performance of existing QAM and VSB solutions".

SAN JOSE, Calif.--(BUSINESS WIRE)--March 13, 1995--A single-chip 64/256-QAM Quadrature downconverter Equalizer Demodulator (QED) subsystem, a key component in the production of affordable digital-video set-top boxes, has been jointly developed by Applied Signal Technology Inc. (NASDAQ:APSG) and VLSI Technology Inc. (NASDAQ:VLSI).

The QED Subsystem extracts the digital signal from the cable and passes it on to circuits which format the digital video or data for presentation to the viewer.

The subsystem provides the heart of a cost-effective digital set-top system for 64- and 256-QAM applications, and reduces both the price and number of external components required as well as increasing the performance and reliability of such a system. Quadrature Amplitude Modulation (QAM) is accepted worldwide as a reliable digital modulation standard, with 256-QAM providing in excess of 40 Mb/s in the space of an analog television channel, one-third again as much data as the 64-QAM format delivers.

Based on APSG's field-proven technology, the QED Subsystem implements the necessary functions required for all-digital downconversion and demodulation of QAM for CATV-based applications. These functions extract the digital stream containing video, audio and data from the signals on the cable and pass it to decompression circuitry, such as MPEG 2. The QED chip will operate at a 43.75 Mhz IF from inexpensive, off-the-shelf CATV tuners, and will offer symbol rates of up to 5.4 MBaud, compatible with proposed U.S. digital CATV implementations.

With digital set-top costs directly tied to the number of complex chips required, the QED Subsystem is designed to be an extensible core, permitting low-cost integration of other related functions onto a single chip. Functional System Block (FSB) cells from VLSI Technology, such as forward error correction, decompression, analog-to-digital conversion and a wide range of control and interface functions, can be included to match a customer's specific application.

According to Jeff Hendy, vice president of VLSI's Consumer Products Group: "This single-chip device is a significant step forward in demodulation and integration. It's designed to drive down system-level costs for set-top boxes, and to meet or exceed the performance of existing commercially available QAM and VSB solutions."

"Applied Signal Technology is no stranger to the demodulation of QAM signals, which is why we were able to supply off-the-shelf QAM equalizer/demodulators for the recent Grand Alliance HDTV tests," said Dr. Ernest Tsui, director of Applied Signal Technology's Commercial Telecommunications Division. "The expertise gained in a decade of developing our successful line of off-the-shelf ultra-wideband demodulators is directly embodied in the QED 64/256-QAM Subsystem."

By employing a blind-equalization approach, pioneered by Applied Signal Technology, the QED 64/256-QAM Subsystem does not require a training sequence, increasing effective throughput and permitting acquisition of signal without delay. With CCITT-recommended Reed-Solomon Forward Error Correction, the QED Subsystem attains virtually error-free performance in even highly perturbed cable environments.

The level of reliability represented by the QED Subsystem cannot be achieved using "textbook" solutions; with the many interacting feedback loops in a typical demodulator, more robust design approaches are needed. Applied Signal Technology has demonstrated capabilities in delivering products to meet these stringent design requirements while VLSI has proven their abilities to manufacture such devices.

VLSI Technology Inc. designs and manufactures application-specific integrated circuits (ASICs) and application-specific standard products (ASSPs) based on its library of functional system blocks (FSB). Targeting its offerings toward the computing, communications and entertainment marketplaces, the company offers its customers advanced system-level integration capabilities. The company is based in San Jose, Calif., with 1994 revenues of $587 million, and has approximately 2,700 employees worldwide.

Applied Signal Technology Inc. is an industry leader in the design and manufacture of communications and signal processing equipment. Applied Signal Technology's line of products cover virtually all of the RF spectrum (including cellular telephone, microwave and satellite), as well as telecommunications switch monitoring and signal processing equipment. Complete acquisition and processing systems are supplied for all types of modulation, from voice-grade channels through ultra-wide bandwidth digital systems, along with a full line of ancillary equipment. They provide consulting services and custom system designs to solve problems in all arenas of the communications market. Applied Signal Technology, with over US $64M in sales, is headquartered in Sunnyvale, Calif., and has additional engineering offices on the East Coast.

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Backgrounder QED 64/256 QAM Subsystem, March 1995 follows:

Advanced methods of digital compression are bringing a new era of interactive and on-demand television to households worldwide. One of the greatest challenges faced in implementing these new services is how to transmit the much higher data rate required for these services over the existing cable infrastructure. Transmission of digital signals usually involves a trade-off between data rate and robustness. With cable operators driven to increase the number of channels by both market and regulatory pressures, data rates are being pushed closer and closer to their ultimate limits. As the margin between practice and theory shrinks, the innovative design of the QED 64/256-QAM Subsystem ensures that maximum channel capacity can be reached without sacrificing picture quality.

Drawing directly form the experience Applied Signal Technology Inc. (APSG) has gained from both their digital-CATV field testing and a decade of developing and producing ultra-wideband demodulators, the QED 64/256-QAM Subsystem provides demodulated data for the crystal-clear picture demanded by cable viewers. VLSI Technology Inc. applies their state-of-the-art layout and fabrication abilities to bring this level of performance to the cable equipment suppliers at a price which makes digital-CATV an economic reality rather than just a futuristic dream.

What is QAM?

The keys to transmission of digital data over cable are appropriate modulation and demodulation. While the basic theory and approach to these functions has been well known for over a quarter of a century, it has only been in the past few years that data rates have been pushed to the limits of this theory. Take for example, modems (modulator/demodulators) for linking computers over a phone line. Ten years ago 300 bit-per-second (bps) modems were common with "exotic" 2400 bps modems selling for upwards of $1000. With a 3000 cycle-per-second (or Hz) bandwidth limitation on a voice-grade telephone line, this seemed to many about as fast as you could go. Today 14,400 bps modems are available for under $100, and manufacturers are now selling consumer-grade 28,800 bps modems -- over ten times faster than a decade ago. How was the barrier of one bit per Hz broken? Quadrature Amplitude Modulation (QAM) was employed, sending 2, 4, 6 and up to as many as ten bits per symbol in the same time that less sophisticated methods send one bit.

QAM has certainly proven itself reliable in the consumer computer marketplace. As the distinction between video and data becomes blurred by all-digital television production and distribution systems, QAM becomes an obvious choice for digital-CATV. With the 6 MHz bandwidth of a conventional analog television signal (NTSC) available for each digital channel, a 256-QAM signal (8 bits per symbol) can carry well over 40 Mb/s, enough for six or seven different digital-quality television signals per channel.

The challenge of meeting the demands of both the cable providers and cable viewers has brought up many proposed solutions. The Advanced Television Test Center (ATTC) is a private non-profit corporation created and supported by a coalition of broadcasting companies and television industry organizations to test and report on proposed systems for advanced television, including high-definition television (HDTV). The ATTC has found that 64-QAM and 256-QAM perform at least as well as any of the proposed modulation types for digital CATV. These tests include not only data-rate measurement, but also how robust the demodulator is under the stresses of "real-world" impairments. A properly-designed demodulators like the Applied Signal Technology Model 242 used for the tests, doesn't cause errors which appear in the picture when the quality of the cable connection is marginal or poor. "Textbook" solutions for QAM demodulation just don't work reliably at these rates in the environment found in many homes already wired for cable.

The QED 64/256-QAM Subsystem

The QED Subsystem is a direct descendant of APSG's line of off-the-shelf telecommunications demodulators, incorporating the knowledge gained during successful ATTC and field testing. The QED employs an innovative internal design, improving on conventional QAM demodulation approaches. Careful attention has been paid in the design to ensure its tolerance of severe levels of impairments seen on current CATV systems, including micro-reflections, residual FM and phase noise, AM hum, and distortion. By employing a blind-equalization approach, pioneered by Applied Signal Technology, the QED does not require a training sequence, increasing effective throughput and permitting acquisition of signal without delay. With CCITT-recommended Reed Solomon Forward Error Correction, the Subsystem attains virtually error-free performance in even highly perturbed cable environments.

QED Subsystem Application

To keep total set-top costs down, the QED already contains most of the functions required for demodulation of the QAM signal and requires minimal external circuitry. With its on-chip quadrature downconverter and internal baud and carrier oscillators, the external components required are primarily those found in existing analog set-top boxes. With set-top costs directly related to the number of chips required, further cost reduction can be gained by integrating onto a single chip the QED and other members of VLSI's Functional System Block (FSB) libraries, including forward error correction, decompression, ADCs, and the ARM RISC microprocessor.

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Note to Editors: FSB is a trademark of VLSI Technology Inc.

CONTACT: VLSI Technology Inc.

Greg Kaufman, 408/434-3070

Applied Signal Technology Inc.

Gary Yancey, 408/522-3300