A 94-GHz aperture-coupled micromachined microstrip antenna

This paper presents an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -18 dB at 94 GHz for a 10-dB bandwidth of 10%. A maximum efficiency of 58±5% has been measured and the radiation patterns show a measured front-to-back ratio of -10 dB at 94 GHz. The measured mutual coupling is below -20 dB in both E- and H-plane directions due to the integration of small 50-μm silicon beams between the antennas. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies     

A high-performance W-band uniplanar subharmonic mixer

A uniplanar subharmonic mixer has been implemented in coplanar waveguide (CPW) technology. The circuit is designed to operate at RF frequencies of 92-96 GHz, IF frequencies of 2-4 GHz, and LO frequencies of 45-46 GHz. Total circuit size excluding probe pads and transitions is less than 0.8 mm ×1.5 mm. The measured minimum single-sideband (SSB) conversion loss is 7.0 dB at an RF of 94 GHz, and represents state-of-the-art performance for a planar W-band subharmonic mixer. The mixer is broad-band with a SSB conversion loss of less than 10 dB over the 83-97-GHz measurement band. The measured LO-RF isolation is better than -40 dB for LO frequencies of 45-46 GHz. The double-sideband (DSB) noise temperature measured using the Y-factor method is 725 K at an LO frequency of 45.5 GHz and an IF frequency of 1.4 GHz. The measured data agrees well with the predicted performance using harmonic-balance analysis (HBA). Potential applications are millimeter-wave receivers for smart munition seekers and automotive-collision-avoidance radars     

Strength and durability properties of polyester concrete using pet and fly ash wastes

Recycled poly(ethylene terephthalate), PET, mainly recovered from plastic beverage bottles, can be used to produce unsaturated polyester resins. In turn, these resins can be mixed with inorganic aggregates (sand and gravel and fly ash waste), to produce polyester concrete (PC). The strength and durability properties of plain and steel-reinforced polyester concrete (PC) using unsaturated polyester resins based on recycled PET and fly ash fillers are discussed in this paper. The recycling of PET and fly ash in PC helps in reducing the cost of the material and alleviating an environmental problem posed by waste materials. The material may effectively be used in many construction applications such as utility, transportation and building components, and the repair and overlay of pavements, bridges and dams.     

Chloroplast biogenesis. Net synthesis of protochlorophyllide from protoporphyrin IX by developing chloroplasts

Developing chloroplasts were isolated from greening Cucumis cotyledons in a co-factor-enriched medium and were incubated in the dark with 14C-labeled and unlabeled protoporphyrin IX. The metabolic pools between protoporphyrin and protochlorophyllide were monitored spectrofluorometrically. The incorporation of the 14C label into protochlorophyllide was also determined. It was shown that protoporphyrin IX, a postulated intermediate of the chlorophyll biosynthetic pathway, was convertible into protochlorophyllide. Since protochlorophyllide is the immediate precursor of chlorophyll a it was concluded that protoporphyrin IX was indeed an intermediate of the chlorophyll biosynthetic pathway.     

Micromachined circuits for millimeter- and sub-millimeter-waveapplications

Two approaches for the development of micromachined circuits for millimeter- and submillimeter-wave applications are discussed. These technologies provide a means to overcome the drawbacks typically associated with conventional planar transmission lines, such as microstrip and coplanar waveguides. Examples demonstrating the use of micromachining to effectively incorporate a third dimension into the geometry of monolithic circuits are presented. This introduces additional parameters in the design and results in structures with superior electrical performance, such as membrane-supported circuits, and reduced volume and weight, such as micromachined-shielded circuits. Micromachined circuits which incorporate miniaturized shielding packages in a monolithic design are described. The performance of these circuits shows that the low-volume, low-weight packaging is effective in reducing signal loss, without degrading the desired frequency response     

A 250 GHz planar low noise Schottky receiver

A planar quasi-optical Schottky receiver based on the quasi-integrated horn antenna has been developed and tested over the 230–280GHz bandwidth. The receiver consists of a planar GaAs Schottky diode placed at the feed of a dipole-probe suspended on a thin dielectric membrane in an etched-pyramidal horn cavity. The diode has a 1.2Μm anode diameter and a low parasitic capacitance due to the use of an etched surface channel. The antenna-mixer results in a measured DSB conversion loss and noise temperature at 258GHz of 7.2dB±0.5dB and 1310K±70K, respectively, at room temperature. The design is compatible with SIS mixers, and the low cost of fabrication and simplicity makes it ideal for submillimeter-wave imaging arrays requiring a 10–20% bandwidth.     

Low-Loss 5.15–5.70-GHz RF MEMS Switchable Filter for Wireless LAN Applications

Low-loss 3.6-GHz fixed and 5.15-5.70-GHz RF microelectromechanical systems switchable filters were designed and fabricated on quartz substrates. Detailed design equations for the capacitively loaded coupled open-loop lambda/2 resonators are given and the realization of the tunable filter using these equations is discussed. The use of capacitively loaded coupled open-loop lambda/2 resonators made it possible to realize the fixed and switchable filters with unloaded Q of around 150 resulting in a -1.4-dB insertion loss. The measured -1-dB bandwidth for the 3.6-GHz fixed and 5.15-5.70-GHz switchable filters were 4% and 5%, respectively. To our knowledge, this represents the lowest loss planar tunable filter to-date in the 4-6-GHz frequency range     

Integrated millimeter-wave corner-cube antennas

An integrated corner-reflector antenna has been designed, fabricated and measured at millimeter-wave frequencies. The structure consists of a traveling-wave antenna integrated on a 1.2-μm dielectric membrane, and suspended in a longitudinal cavity etched in a silicon wafer. A novel traveling wave antenna design, the modified-bend antenna, with an antenna length of 1.2 λ and spacing 0.96 λ from the apex, results in a wideband input impedance centered at 140 Ω and low cross-polarization levels. Measurements at 180-270 GHz show a well-defined pattern with low sidelobe levels, and a main-beam efficiency of 93% and 83% at 180 and 222 GHz, respectively. The monolithic approach allows the integration of a matching network and a Schottky-diode or SIS detector at the base of the antenna to yield a low-noise monolithic millimeter-wave receiver     

92 GHz dual-polarized integrated horn antennas

A dual-polarized two-dimensional imaging array was designed for millimeter-wave applications. The dual-polarized design consists of two dipoles perpendicular to each other and suspended on the same membrane inside a pyramidal cavity etched in silicon. The dual-polarized antenna is fully monolithic with room available for processing electronics. The IF or video signals are taken out through a novel bias and feeding structure. The measured polarization isolation is better than 20 dB at 92 GHz, and the orthogonal channels show identical far-field patterns. The antenna is well suited for millimeter-wave polarimetric synthetic aperture radars (SARs) and high-efficiency balanced-mixer receivers     

Integrated horn antennas for millimeter-wave applications

This paper reviews the development of integrated horn antennas since their introduction in 1987. The integrated horn is fabricated by suspending a dipole antenna on a thin dielectric membrane in a pyramidal cavity etched in silicon. Recent progress resulted in optimized low and high-gain designs with single and double-polarizations for remote-sensing and communication applications. A fullwave analysis technique have resulted in an integrated antenna with performance comparable to that of waveguide-fed corrugated horn antennas. The integrated horn design can be easily extended to large arrays for imaging and phased array applications while still leaving plenty of room for the rf and w processing circuitry. Theoretical and experimental results at microwave frequencies and at 90, 240 and 802 GHz will be presented.