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Recent Advances in Radar Technology
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GEC Tests New Approach to Monolithic Filtering at Microwave Frequencies
UK contractor GEC is working on active filtering at UHF (0.3 to 1 GHz) and microwave frequencies using a silicon-on-insulator (SOI) bipolar IC process. At the heart of the effort is the use of pairs of silicon wafers (one of which is oxidized) that are bonded together using Van der Waals forces between flat structures (1 mm across a 100 mm wafer). The upper wafer then is chemo-mechanically polished down to a 2 mm active layer on top of an isolation oxide. The remainder of the processing follows a conventional bipolar route. While prebonded wafers remain expensive, GEC believes that the additional cost is recouped in the potential the approach offers for improved cost and volume performance.
The approach used reportedly meets the bipolar device requirement for good quality silicon in depth and provides the necessary electrical isolation (via the silicon dioxide underlay) at the bottom of the transistor well. The contractor further stresses the low parasitic capacitance of the collector to substrate (32 fF). The trial devices utilise a simple amplifier design that is integrated into a transconductor-capacitor structure and effectively is a variant of the type of biquadratic structure used commonly in low frequency applications. To overcome limitations in dynamic range, GEC also has produced a device that uses degeneration as a means of expanding dynamic range at the cost of increased noise levels. The company reports that this approach (when combined with digital on-chip tuning) offers relatively simple devices with adequate noise values and low power requirements for small signal area, low cost receiver applications. The company also envisages that bonded SOI technology will allow mixers, and RF and IF amplifiers to be integrated with few (if any) external components, thereby providing significant cost and volume savings in radio front-end design.
Rohde & Schwarz Launches Hand-held Search and Monitoring Receiver Package
Germany-based contractor Rohde & Schwarz has launched a 10 kHz to 3000 MHz search and monitoring receiver package that reportedly can detect interference sources and locate miniature transmitters in rough terrain where a man-portable system is the only viable deployment option. Central to the capability is the Miniport EB200 series receiver, a budget-priced, compact, hands-off unit that offers high input sensitivity, accurate frequency resolution and accurate level indications over a 120 dB dynamic range. The receiver is battery powered and incorporates an integral parameter display. Available options include a digitally controlled frequency spectrum mode and a differential mode that allows for the detection of miniature transmitters at close range. An IF option allows the operator to evaluate received signals visually.
The unit offers 15 bandwidths within the 150 Hz to 1 MHz range and is capable of demodulating amplitude- and frequency-modulated, lower and upper sideband, and continuous wave signals. Operator control is via a front plate with labeled keys. In addition, the equipment includes the hand-held HE200 series active antenna unit. Rohde & Schwarz also notes that the EB200 receiver is suitable for fixed site applications where control is exercised via RS-232-C or IEC625 interfaces, or an RJ45 standard local area network.
Sweden Plans Active Radar Array Demonstration
As part of an ongoing programme, Swedish contractor Ericsson Microwave Systems is planning a technology demonstration of an active electronically scanning array (AESA) for use in fighter radars by the end of 1999. Work on the project began in 1994 under the sponsorship of Sweden's Defense Materiel Administration with current activity reportedly focusing on the development of a prototype 205 mm-long transceiver module. Ultimately, a fully developed AESA-equipped radar will incorporate up to 1300 such modules and combine electronic scanning in elevation (+/-50° to 60º) with mechanical scanning in azimuth (+/-50° to 60°).
In addition to increasing overall system weight, the combination of electronic and mechanical scanning is intended to simplify the necessary development work and provide an over-the-shoulder operating mode. Once developed fully, the new array will be incorporated in Sweden's JAS 39 Gripen fighter aircraft as a midlife upgrade.
While Ericsson is determined to proceed to at least a flight demonstration of its AESA technology, the company would rather expand the programme to include collaborative partners. Negotiations have reportedly been opened with Raytheon-Hughes and Northrop Grumman in the US, and GTDAR in Europe. The GTDAR tri-national consortium of radar manufacturers (comprising GEC-Marconi Avionics in the UK, Thomson-CSF Radars & Contre-Mesures in France and Daimler-Benz Aerospace Sensor Systems in Germany) currently is developing a future airborne multirole, multifunction, solid-state active-array radar (AMSAR), which is scheduled to be applied to both the French Rafale and the four-nation (Germany, Italy, Spain and the UK) Eurofighter 2000 next-generation combat aircraft. The initial phase of the AMSAR programme (the development of a suitable GaAs-based MMIC transceiver module) is reportedly nearing completion with the consortium moving towards an in-flight technology demonstration.
Philips Enters Answering Machine/Cordless Telephone Market
Netherlands contractor Philips Semiconductors has launched its UBA1707 series line interface and analogue speech processing IC as a first step towards capturing a 50 percent slice of the world's fax, answering machine and cordless telephone line interface IC market. Defined by the company as the world's only fully integrated, fully programmable line interface device in its field, the UBA1707 series IC is equipped with an industry-standard three-wire bus interface (to ensure controllability by any microcontroller on the market currently), can be programmed for specific national voltage/current standards and provides independent control of its host's DC and AC set impedance.
Automatic gain control (AGC) using a line current control technique is provided for both transmit and receive channels and is programmable as to range and slope. According to Philips, in DC mode, the device's ability to operate at line voltages down to 1.2 V enables several telephones to operate in parallel on the same line. The UBA1707 IC also provides all the digitally controlled baseband audio transmit/receive functions required in cordless telephone base station, digital answering machine and fax machine applications. In addition, the device features drive circuitry for an external solid-state hook switch in order to facilitate electronic on/off hook switching, pulse dialing and register recall.
The device's input signal capability is between 350 mV (15 mA line current) and 750 mV (90 mA line current). An integral loudspeaker amplifier provides two selectable input channels, 3-bit volume control, rail-to-rail output voltage swing/dynamic output limiting and automatic gain reduction if the supply voltage falls below 2.7 V. Each input handles signals of up to 500 mV RMS with loudspeaker loads of 8 W at 3.3 V or 16 W at 5 V. Separate pins are provided for the two loudspeaker amplifier inputs and the auxiliary amplifier (used for intercom-type talk facilities) input and output. Programming is via four on-chip registers that control current/voltage regulation, AGC range and slope, loudspeaker volume, channel selection, dynamic limiting, amplifier muting and power-down modes. The device also incorporates three general-purpose switches for functions such as on/off light-emitting diode display switching and is available in 28 lead small-outline or shrink small-outline packaging. With a production rate of 1 million pieces per year, Philips estimates a UBA1707 unit cost of approximately $1.15.
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