TRW designs miniature radio component for satellite payloads

REDONDO BEACH, Calif. ? Engineers at TRW used improved packaging techniques and gallium arsenide technology to design a highly miniaturized radio component that improves the messaging capability of TRW communications satellite payloads, while decreasing size and weight.

By John McHale

REDONDO BEACH, Calif. — Engineers at TRW used improved packaging techniques and gallium arsenide technology to design a highly miniaturized radio component that improves the messaging capability of TRW communications satellite payloads, while decreasing size and weight.

The TRW low-noise amplifier (LNA) downconverter will first be used in TRW payloads for the Astrolink global broadband telecommunications system, slated to begin service in 2003.

It was designed specifically for the Astrolink program, but will also be used in other TRW programs, says Jack Pritchett, TRW spokesman. However, the device will be sold as a separate product, he adds.

The device detects and converts signals received by the satellite's antennas at frequencies of 30 billion cycles per second (30 GHz) to much lower frequencies that are easier to process electronically, TRW officials say. Astrolink's satellites receive signals from earth at 30 GHz and transmit to earth at 20 GHz, in a frequency range known as the Ka band.

"Our miniature package shows the advantages of TRW's advanced microelectronics for spacecraft use, where weight and size are always at a premium," says Paul Borzcik, vice president and program manager of the TRW Astrolink program.

"Our unit is about the size of a matchbook and weighs little more than an ounce, yet it contains extensive built-in redundancy for high reliability," Borzcik says. "Only five years ago, electronics to perform the same functions would have required a box weighing several pounds."

The LNA downconverter is packaged as an integrated microwave assembly, housing a number of TRW gallium arsenide integrated circuits designed for Ka band operation. Devices contained in the unit include low-noise amplifiers, filters, voltage regulators, frequency converters, low loss redundancy switches, and frequency multipliers.

Advances and price reduction during the last five years in gallium arsenide technology made the device possible, Pritchett says. Prices have decreased 10 to 20 fold for the chips, he adds.

TRW engineers also shrunk weight and cost of the downconverter by using proprietary packaging technology along with highly automated packaging lines, which helped create improved economies of scale, Pritchett explains.

Production takes place on an automated assembly line that reduces manual labor and shortens manufacturing times. The pre-production lots are identical to the flight lots and are being used to verify the mechanical and electrical design of the LNA downconverters and to validate the automated production processes.

Borzcik says that TRW is now completing the first pre-production lots of LNA downconverters. Production of the Astrolink flight units is set to begin in summer of 2000.

The boost to satellite performance results from the LNA downconverter's small size, which permits multiple LNA downconverter units to be mounted directly in the feed assembly of a densely packed multi-beam antenna. This direct feed mounting, rather than in a box remote from the feed, reduces signal loss between the antenna and low-noise amplifier, TRW officials explain.

In addition, the front-end conversion of the Ka-band receive signal to a lower intermediate frequency enables the use of coaxial cables to route the signal from the antenna for further signal processing. Coaxial cable avoids the weight, expense, and engineering associated with custom waveguide that would otherwise have to be employed.

Other key technical features of the LNA downconverter include the built-in voltage regulators, which result in higher spectral purity of the signals, and the need for only a single DC power supply, which simplifies payload integration.

For more information on the TRW's LNA downconverter contact the company by phone at 310-764-3000 or on the World Wide Web at http://www.trw.com.

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