Kenneth W. Brown

W-band GaN power amplifier MMICs

An advanced high power, high frequency GaN semiconductor process has made possible the design and fabrication of W-band power amplifier MMICs with unprecedented performance. The key enabling semiconductor technology is a 150 nm T-gate GaN HEMT with an output power exceeding 300mW and a peak PAE (power added efficiency) of 37%. With this process, W-band power amplifier MMICs have been designed and fabricated that demonstrate output powers of 1.7 watts, power added efficiencies greater than 20%, and small signal gains of 21 dB. In addition, the compactness of these MMIC designs have allowed for MMIC power densities (MMIC output power relative to MMIC area) exceeding 1/2 watt/mm2.

High power, high efficiency E-band GaN amplifier MMICs

An advanced high power, high frequency GaN semiconductor process has been used to design high performance E-band power amplifier MMICs demonstrating unprecedented output power, PAE and reliability. To the authors knowledge, these power amplifier designs demonstrate performance beyond previously published results for E-band power amplifier MMICs.

W-band metamorphic HEMT with 267 mW output power

This paper reports the highest W-band power output of metamorphic HEMT (MHEMT) technology to date. 267 mW single stage performances at 90 GHz are achieved on a 0.15 micron GaAs-based production line with improved manufacturability over InP HEMT. The single stage circuits presented here are building blocks for future MHEMT power amplifier development.

Development of a 300 kW CW L-band industrial heating magnetron

An industrial heating magnetron operating in L-band (915 MHz) and capable of producing 300 kW of continuous microwave power has been developed and is available for commercial sale. This high average power magnetron design, model CWM-300L is based on the presently-available CTL model CWM-75L, an L-band magnetron that produces 75 kW of continuous microwave power. The 300L magnetron operates at 32 kV and 10 A with a conversion efficiency exceeding 90% when freshly conditioned. To address specific problems, a paper-design version of the 300L is available although that new design has been neither fabricated nor tested.

W- and G-Band Solid State Power Combining

Recent advances in semiconductor technologies have enabled the design and fabrication of mmW MMIC amplifiers with unprecedented gain, output power, and power added efficiency. However, individual mmW MMIC performance is ultimately limited by transistor size and on-die power combining losses. Therefore, in order to achieve significant solid state mmW amplifier power levels, low-loss off-die power combining is obviously necessary. This paper examines trade-offs between on-die, waveguide, and spatial power combining approaches. Several examples of mmW power combined amplifiers are discussed including 10W+ W-band GaN and 1W-class EHF InP amplifiers.

Efficient array-fed reflector antenna

This paper presents a method of maximizing antenna efficiency. The proposed method utilizes a specially configured antenna array as the prime-focus feed. By carefully configuring the array elements (spacing and excitation), the array illuminates only the non-blocked portion of the main reflector. In addition, the array pattern is optimized such that the non-blocked portion of the reflector antenna is quasi-uniformly illuminated. The illumination function from this feed array is similar to the sub-reflector pattern of an axially symmetric shaped reflector configuration, where the sub-reflector is designed to uniformly illuminate the non-blocked portion of the main reflector.

Simple meshing and efficient numerical analysis of curved surfaces using a new quadrilateral basis function

In this paper, a quadrilateral roof-top type of basis function is presented. Four arbitrary and not necessarily coplanar points establish the associated curved basis function surface. In addition to this, the defined current density is conveniently decomposed into sinusoidally excited strips, vastly reducing the computation time required to determine the associated near zone-field. Moderately curved geometries can be easily meshed by projecting a rectangular grid unto the surface, while fulfilling the objective of quasi-orthogonal current densities on each basis function. To demonstrate the capabilities of the proposed basis function, a case study is presented where the current density induced on the curved surface of a paraboloid is determined using the method of moments. The corresponding results are shown to agree very well with the known correct solution.

Long-range wireless link with fiber-equivalent data rate

Recent advances in both high power millimeter wave (mmW) Gallium Nitride (GaN) technology and high-speed System on Chip (SoC) modem technology has enabled the development, fabrication, and field testing of a high speed, long range wireless datalink with fiber equivalent speed. The link exhibited nearly an 80 Gbps bi-directional data rate (40 Gbps in each direction) over a range of 16km. This was accomplished by using a combination of frequency and polarization multiplexing to combine a total of eight ∼10 Gbps modem channels on the lower (71–76 GHz) and upper (81–86 GHz) E-band channels. Each modem channel was separately up-converted and amplified with a Gallium Nitride (GaN) power amplifier. Frequency multiplexing was accomplished at E-band (post-amplification) to maintain high Power Added Efficiency (PAE) in the power amplifiers.

Rigorous analysis of practical reflector antennas

Perhaps the most ubiquitous numerical tool used in the analysis of reflector antennas is the physical optics technique. Although this approximate technique typically predicts the radiation patterns of reflector antennas with excellent accuracy, there are numerous situations where rigorous analysis methods are desirable. The rigorous analysis of reflector antennas using the method of moments has been accomplished in the past. However, the majority of the work has been limited to electrically small reflectors, or antennas with axial-symmetry. In this work a technique for rigorously analyzing relatively large practical reflector antennas, with as many as 100,000 surface current elements, is presented. This tool is based on an iterative integral equation solver and can rigorously handle offset multireflector antennas in their entirety (including all reflectors, surfaces, struts, feed, and feed support hardware). To demonstrate the tools performance, computed radiation patterns are compared with measured and physical optics generated radiation patterns.

7kW GaN W-band transmitter

Recent advances in high power millimeter wave (mmW) Gallium Nitride (GaN) technology has enabled the development of a high power solid state W-band transmitter with an unprecedented 7kW Continuous Wave (CW) output power. The transmitter coherently sums a total of 8,192 1W+ GaN Power Amplifier (PA) Monolithic Microwave Integrated Circuits (MMICs) using spatial combining. This accomplishment represents a two-orders-of-magnitude improvement in W-band solid state power generation over previously published results.