J. Wenger

Low-noise pseudomorphic dual-gate cascode HEMTs with extremely high gain

Quarter-micron InGaAs-GaAs dual-gate HEMTs connected as a cascode MMIC in a compact manner have been fabricated and investigated. The devices show a high output impedance and a very low feedback capacitance, resulting in a high-voltage gain factor /sub gm///sub gd/ of 125 and a C/sub gs//C/sub gd/ ratio of 45. The current gain cutoff frequency f/sub T/ is 45 GHz and the maximum stable gain is 23.5 dB at 10 GHz and 19 dB at 20 GHz. The pseudomorphic cascode HEMTs show a low-noise figure of 1.1 dB with an associated gain of 22 dB at 10 GHz, at 18 GHz the minimum noise figure is 1.9 dB with 16-dB gain.<<ETX>>

Design, Fabrication, and Performance of Monolithic Dielectrically Stabilized PM-HFET Oscillators Up to 60 GHz

Monolithic HFET dielectrically stabilized oscillators (DROs) are designed based on results obtained, from hybrid HFET DROs /1,2/. The monolithic chips are fabricated using MBE grown 2¿ substrates. The employed low noise quarter micron InGaAs/GaAs pseudomorphic (PM) HFET devices yield fT and fmax values of the least 70 GHz and 140 GHz. State. of-the-art topology DROs show an output power of +11 dBm and +2.3 dBm. at 36 GHz and 62 GHz, respectively. Excellent phase noise data of ¿97 dBc/Hz at 100 kHz off carrier (Ka-band DRO) and ¿101 dBc/Hz at 1 MHz off carrier (V-band DRO) are obtained.

Ka- and W-band PM-HFET DROs

Dielectric resonator stabilized oscillators have been designed, fabricated, and investigated. The oscillators consist of microstrip matching and biasing circuits on alumina substrate, a dielectric resonator puck, and a low-noise quarter-micron InGaAs-GaAs pseudomorphic (PM) HFET as the active device. At 37 GHz and 81 GHz, output powers of 10 dBm and 0 dBm have been measured. The phase noise of the Ka-band and W-band oscillators has been determined to be -97 dBc/Hz at 100 kHz and -90 dBc/Hz at 1 MHz off carrier, respectively.<<ETX>>

Short range radar - being on the market

In 2005 in addition to forward looking long-range radar (LRR) used mainly for autonomous cruise control (ACC) short range radar (SRR) sensors with a coverage up to 30 meters have been introduced in the new Mercedes S-class enabling a variety of further driver assistance and safety applications today. SRR is used to expand ACC to stop-and-go operation, to perform pre-crash warning, to act as parking aid, to warn during backing up or changing lanes, or even for emergency braking. This contribution describes SRR specifications, design and packaging considerations, and the status of the worldwide frequency regulation situation.

Millimeter-wave imaging of traffic scenarios

Methods for the automatic interpretation of complex road traffic scenarios are currently developed on the basis of real measured data. The measurements are performed using a fully polarimetric instrumentation radar at 76 GHz. Results of those measurements will be presented, especially with respect to automatic image interpretation. The features of the measurement system are very similar to a prospective automotive radar with the exception of possible Doppler range and physical dimensions. In parallel to the measurement and algorithmic activities, a radar sensor for automotive applications using monolithic integrated millimeter-wave circuits (MMIC) is under development. Real aperture imaging is achieved with a focal plane multibeam array. The most important design criteria are low cost and compactness. System aspects of this radar sensor will be discussed including results of the millimeter-wave circuits.

MICROWAVE BLADE TIP CLEARANCE MEASUREMENT SYSTEM

This paper describes the development of a Microwave Tip Clearance Measurement System for use in the gas turbine environment Applications for this sensor include basic tip clearance measurements, seal wear measurement and active blade tip clearance control in gas turbine engines. The system being developed was designed for useful operation to temperatures exceeding 1093°F, since only ceramic materials are directly exposed in the gas path. Other advantages of this microwave approach to blade tip clearance sensing include the existence of an inherent self-calibration in the sensor that permits accurate operation despite temperature variations and possible abrasion by the rotating blades. Earlier experiments designed to simulate this abrasion of the sensor head indicated that rubs as deep as 1 mm (40 mils) were easily tolerated. In addition, unlike methods based upon phase measurements, this method is very insensitive to cable vibration and length variations. Finally, this microwave technique is expected to be insensitive to fuel and other engine contamination, since it is based on the measurement of resonant frequencies, which are only slightly affected by moderate values of loss due to contamination.Copyright

Prototypic Realisation of Millimetre Wave Radar Imaging

In future novel driver assistance, comfort, and safety systems the needs for environmental sensing and traffic scene interpretation are increasing. The reliability of these systems will be mainly determined by the perception of the sensors and the capability of automatic data interpretation, and it will be a differentiating factor in the competition amongst automotive OEMs. Automotive radar is expected to be a key sensor technology for future active safety systems, especially due to its specific physical properties (direct acquisition of range and velocity). This contribution demonstrates the potential of radar sensors with high resolution in azimuth and range in traffic environment and addresses some aspects of their practical implementation. A prototype of an automotive instrumentation radar is presented, which allows on-line acquisition and real-time visualisation of radar images with an update rate of up to 10Hz. The imaging capabilities of high resolution radar in traffic environment will be pointed out with respect to new comfort and safety features. In addition practical realisation approaches will be discussed.

Monolithic 60 GHz Amplifier using Low Noise Pseudomorphic HEMTs

The design and fabrication of a monolithic 60 GHz low noise amplifier is presented. As active device very low noise pseudomorphic HEMTs with Fmax ¿ 200 GHz have been developed and fabricated using a full monolithic technology. A two stage amplifier has been fabricated having reflexion losses below 10 dB and a gain of 5 dB at 58 GHz.

Microwave Performance of Dual-Gate Cascode MESFET and HEMT Devices with High Gain at Low Noise Levels

Quarter micron dual-gate MESFETs and pseudomorphic HEMTs connected as a cascode circuit have been fabricated and investigated. The devices exhibit a high output impedance and a very low feedback capacitance resulting in high voltage gain factors gm/gd up to 125 and a Cgs/Cgd ratio up to 45. The maximum stable gain obtained with dual-gate HEMTs is 23.5 dB 10 GHz and 19 dB at 20 GHz, the current gain cutoff frequency is 45 GHz. The cascode PHEMTs show a low noise figure of 1.1 dB with an associated gain of 22 dB at 10 GHz. These results represent the highest gain values and the best noise performance yet reported for dual-gate HEMT devices. With dual-gate MESFETs a dynamic range of more than 35 dB can be obtained for the insertion gain/loss up to 40 GHz by applying a DC voltage swing of 4 V at the second gate electrode. Thus these elements are very promising for gain controllable amplifiers for both low noise and high gain as well as for switching applications.

An MMIC-Based Microwave Sensor for Accurate Clearance Measurements in Aircraft Engines

A novel microwave sensor for accurate noncontacting clearance measurements in turbine engines has been designed, fabricated, and successfully tested. The sensor consists of a microwave resonant cavity probe, a MMIC based microwave module for signal generation and detection, and a signal conditioning and processing unit. To enable high temperature operation the probe is fabricated by using metal and ceramics, the operating frequency range is 22-24 GHz. The clearance measurement range is some millimeters, the achieved sensitivity and accuracy are very high.