John W. Archer

Low-parasitic, planar Schottky diodes for millimeter-wave integrated circuits

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 mu m/sup 2/ and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Omega . Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested. >

An indium phosphide MMIC amplifier for 180-205 GHz

This paper describes a high-performance indium phosphide (InP) monolithic microwave integrated circuit (MMIC) amplifier, which has been developed for application in radioastronomy and imaging-array receivers. Implemented using coplanar waveguide, the six-stage amplifier exhibits 15 db gain, 10 dB input and output return loss, and low noise figure over the 180-205 GHz frequency range. Only one design pass was needed to obtain excellent agreement between the predicted and measured characteristics of the circuit, a unique achievement in this frequency band. The circuit is also the first 180-205 GHz amplifier designed for and successfully fabricated using TRWs standard 0.1-/spl mu/m InP HEMT process.

A beam-scanning dual-polarized fan-beam antenna suitable for Millimeter wavelengths

The design and testing of a beam-scanning pillbox antenna for use in a 200 GHz imaging system is presented. The antenna features a rotating subreflector that scans the antennas fan beam and a multimode structure that reduces ohmic loss and allows use of two orthogonal polarizations. The antenna has an aperture size of 450/spl times/5 mm, half-power beam widths of approximately 0.4/spl deg/ and 18/spl deg/ and a beam-scan range of 10/spl deg/. The gain of the antenna was measured to be greater than 33 dBi for both polarizations. The radiation patterns of the pillbox antenna have been measured in the radiating near field using an outdoor range. Good agreement between measured and calculated patterns has been obtained.

Fully automated on-wafer noise characterization of GaAs MESFETs and HEMTs

A technique is described that permits the rapid determination of all four noise parameters of a MESFET or HEMT at wafer level. The fully automated procedure, which has been implemented in the 2-8 GHz range, uses 16 accurately measured, very repeatable source impedance standards. The standards have been selected for optimum coverage of the input impedance plane to result in stable and rapidly convergent least-squares solutions for the minimum noise figure, optimum source impedance, and noise resistance of practical devices. The resultant system is very stable and produces accurate noise parameters for a wide range of devices. >

Ultra-low-noise indium-phosphide MMIC amplifiers for 85-115 GHz

This paper describes a high-performance indium-phosphide monolithic microwave integrated circuit (MMIC) amplifier, which has been developed for cooled application in ultra-low-noise imaging-array receivers. At 300 K, the four-stage amplifier exhibits more than 15-dB gain and better than 10-dB input and output return loss from 80 to 110 GHz. The room-temperature noise figure is typically 3.2 dB, measured between 90-98 GHz. When cooled to 15 K, the gain increases to more than 18 dB and the noise figure decreases to 0.5 dB. Only one design pass was required to obtain very good agreement between the predicted and measured characteristics of the circuit. The overall amplifier performance is comparable to the best ever reported for MMIC amplifiers in this frequency band.

Performance Evaluation of a Passive Millimeter-Wave Imager

A cross-correlating 186-GHz passive millimeter-wave imager has been built. The key components in the signal processing hardware are two 186-GHz receivers and a broadband complex correlator. To evaluate the performance of this imager, its point-spread function, beam pattern, baseline vector, and their variations with the scanning direction have been experimentally measured and derived. Some of these results are needed for optimizing the imagers parameter settings. Others are required for implementing the modulated-beam and modulated-scene algorithms proposed in a previous paper dealing with the imagers fringe in its point-spread function. These results will also reveal any problems in the construction process of the imager. The theoretical bases for these measurements are analyzed. Novel algorithms for deriving each antennas point-spread function and beam pattern, as well as the imagers baseline vector from the measurement results of the imagers point-spread function and beam pattern are proposed and successfully applied in the measurements. Experimental results are presented and discussed.

W-Band GaAs Schottky Diode MMIC mixers for Multi-Gigabit Wireless Communications

This paper describes the design and measured performance of wideband sub-harmonically pumped mixers suitable for the millimeter-wave multi-gigabit wireless communication systems. It represents the first development of W-band mixers using a commercial Schottky diode process published so far.

A Millimeter-Wave Antenna Amplitude and Phase Measurement System

We describe the design and application of a system for measuring the magnitude and phase of antenna radiation patterns in the 182-194 GHz frequency range. A heterodyne receiver comparing antenna and reference signals is designed from readily available components and incorporated into a 12-m anechoic chamber. The chamber is used with or without a compact-range reflector for compact-range or far-field measurement of antennas up to 0.6 m in diameter. The measured phase variation of the system, when idle, averages 0.3° over 227 s and 4.5° over 30 min. The amplitude stability is better than ±0.15 dB over a 63-h period. Verification of the system is obtained through comparison with other measurements and calculated results on horn and pillbox antennas. The applications of the system are illustrated through its use in characterizing the magnitude and phase radiation patterns of a new beam-scanning pillbox antenna for a 186-GHz imaging system.

Bi-directional amplifiers for half-duplex transceivers

This paper reports a unique bi-directional amplifier (BDA) circuit that combines the symmetry of common-gate connected HEMTs with topologically mirrored input and output matching, Bi-directional behavior of the BDA is demonstrated on fabricated circuits, with identical performance in forward and reverse directions. Between 40 and 45 GHz, 10-dB gain and 8-dB input and output return losses have been measured.

A 190GHz active millimeter-wave imager

The design and testing of a 190 GHz imaging system is presented. The system features two beam-scanning antennas; the first transmits a horizontal fan beam and the second receives a vertical fan beam. By correlating the signals from the antennas, an estimate of the millimeter-wave reflectivity at the intersection of the fan beams is obtained. Each fan beam is scanned by rotating a small subreflector within the antenna; this simple rotation motion allows rapid scanning. The system is portable, currently approximately 0.6m × 0.6m × 2m high; the key size constraint is imposed by the 450 mm aperture length of the antennas. The imager has an angular resolution of 0.25° and a field of view of 14°×14°, resulting in a raw image of approximately 50 × 50 pixels. The raw image is processed using super-resolution techniques. Images will be presented which show the capability of the system to image metallic and ceramic objects beneath clothing. These images were obtained by illuminating the scene with signals from a frequency-doubled Gunn oscillator. While this paper focuses on active imaging, the system can also operate in passive mode with reduced sensitivity.