W-band waveguide-packaged InP HEMT reflection grid amplifier

This letter presents a 79-GHz broadband reflection-type grid amplifier using spatial power combining to combine the power of 64 unit cells. Each unit cell uses a two-stage cascade configuration with InP HEMTs arranged as a differential pair. A broadband orthogonal mode transducer (OMT) separates two orthogonally polarized input and output signals over a 75 to 85GHz range. In conjunction with the OMT, a mode converter with quadruple-ridged apertures was designed to enhance the field uniformity over the active grid. Measurements show 5-dB small signal gain at 79GHz and an 800-MHz 3-dB bandwidth. The amplifier generates an output power of 264mW with little evidence of saturation

A 100-Element MODFET Grid Amplifier

A 100-element quasi-optical amplifier is presented. The active devices are custom-fabricated modulation-doped field-effect transistors (MODFETs). Common-mode oscillations were suppressed using resistors in the input gate leads. The grid has 9 dB of gain at 10.1 GHz. The 3-dB bandwidth is 1.2 GHz. We present a model for the gain of the grid versus frequency and compare measurement with theory

Gain and Stability Models for HBT Grid Amplifiers

A 16-element heterojunction bipolar transistor (HBT) grid amplifier has been fabricated with a peak gain of 11 dB at 9.9 GHz with a 3-dB bandwidth of 350 MHz. We report a gain analysis model for the grid and give a comparison of the measurement and theory. The measured patterns show the evidence of a common-mode oscillation. A stability model for the common-mode oscillation is developed. Based on the stability model, a lumped capacitor gives suitable phase shift of the circular function, thus stabilizing the grid. A second 18-element grid was fabricated, using this theory, with improved stability

Mechanistic Studies of [AlCp*]4 Combustion

The article of record as published may be found at https://doi.org/10.1021/acs.inorgchem.8b00589The combustion mechanism of [AlCp*]4 (Cp* = pentamethylcyclopentadienyl), a ligated aluminum(I) cluster, was studied by a combination of experimental and theoretical methods. Two complementary experimental methods, temperature-programmed reaction and T-jump time-of-flight mass spectrometry, were used to investigate the decomposition behaviors of [AlCp*]4 in both anaerobic and oxidative environments, revealing AlCp* and Al2OCp* to be the major decomposition products. The observed product distribution and reaction pathways are consistent with the prediction from molecular dynamics simulations and static density functional theory calculations. These studies demonstrated that experiment and theory can indeed serve as complementary and predictive means to study the combustion behaviors of ligated aluminum clusters and may help in engineering stable compounds as candidates for rocket propellants.Defense Threat Reduction Agency (DTRA)Air Force Office of Scientific Research (AFOSR)Grant No. HDTRA1-15-1-0031Grant No. FA9550-15-1-025

Mechanistic Studies of [AlCp*]₄ Combustion

The combustion mechanism of [AlCp*]₄ (Cp* = pentamethylcyclopentadienyl), a ligated aluminum­(I) cluster, was studied by a combination of experimental and theoretical methods. Two complementary experimental methods, temperature-programmed reaction and T-jump time-of-flight mass spectrometry, were used to investigate the decomposition behaviors of [AlCp*]₄ in both anaerobic and oxidative environments, revealing AlCp* and Al₂OCp* to be the major decomposition products. The observed product distribution and reaction pathways are consistent with the prediction from molecular dynamics simulations and static density functional theory calculations. These studies demonstrated that experiment and theory can indeed serve as complementary and predictive means to study the combustion behaviors of ligated aluminum clusters and may help in engineering stable compounds as candidates for rocket propellants