Relationship between Governance Structure and Financial Performance in Construction

Although corporate governance has emerged as an issue of considerable importance in shaping the organizational structure and the vision of the firm, this entity has yet to receive sufficient scrutiny in the construction industry. The purpose of this study is to determine the extent by which the configuration of corporate governance may impact on the financial performance of construction firms. The investigation utilizes 100 companies of differing sizes. The analysis reveals that a critical mass of outside independent directors and the dissociation of the roles of CEO and Chairmanship of the board do translate into superior financial market returns for the firms. Other corporate governance variables have no apparent impact on the financial performance of the firms. These findings are significant to construction firms that are already established or in the process of being formed.     

High-isolation CPW MEMS shunt switches. 1. Modeling

This paper, the first of two parts, presents an electromagnetic model for membrane microelectromechanical systems (MEMS) shunt switches for microwave/millimeter-wave applications. The up-state capacitance can be accurately modeled using three-dimensional static solvers, and full-wave solvers are used to predict the current distribution and inductance of the switch. The loss in the up-state position is equivalent to the coplanar waveguide line loss and is 0.01-0.02 dB at 10-30 GHz for a 2-μm-thick Au MEMS shunt switch. It is seen that the capacitance, inductance, and series resistance can be accurately extracted from DC-40 GHz S-parameter measurements. It is also shown that dramatic increase in the down-state isolation (20⁺ dB) can be achieved with the choice of the correct LC series resonant frequency of the switch. In part 2 of this paper, the equivalent capacitor-inductor-resistor model is used in the design of tuned high isolation switches at 10 and 30 GHz     

A 140-170-GHz low-noise uniplanar subharmonic Schottky receiver

A 150-GHz Schottky diode subharmonic receiver based on a coplanar-waveguide-fed double-folded-slot (DFS) antenna is presented in this paper. The DFS antenna is placed on an extended hemispherical high-resistivity silicon substrate lens to achieve a high directivity and a high coupling to a Gaussian beam efficiency. The uniplanar receiver results in a 12±0.5-dB measured double-sideband conversion loss at 144-152 GHz for a 8-10 mW local-oscillator power at 77 GHz, and has a wide-hand ⩽13-dB conversion loss over 30 GHz of bandwidth (140-170 GHz). The measured conversion loss includes silicon lens absorption and reflection losses, as well as IF mismatch losses. The applications are in new small aperture (7.5-cm lenses) collision-avoidance radars at 150 GHz     

Multi-Chroic Dual-Polarization Bolometric Detectors for Studies of the Cosmic Microwave Background

We are developing multi-chroic antenna-coupled Transition Edge Sensor (TES) bolometer detectors for Cosmic Microwave Background (CMB) polarimetry. Multi-chroic detectors increase focal plane area efficiency, and thus the mapping speed per focal plane area, and provide greater discrimination against polarized galactic foregrounds with no increase in weight or cryogenic cost. In each pixel, a silicon lens-coupled dual-polarized sinuous antenna collects photons over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into multiple frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization state. We will describe the design and performance of these devices and present optical data taken. Our measurements of dual-polarization pixels in multiple frequency bands show beams with percent-level ellipticity, and percent-level cross-polarization leakage. We will also describe the development of large arrays of these multi-chroic pixels. Finally, we will describe kilo-pixel arrays of these detectors planned for the future CMB experiments that will achieve unprecedented mapping speed.     

Design of Lange-couplers and single-sideband mixers usingmicromachining techniques

This paper reports on the design and performance of micromachined Lange-couplers and single-sideband mixers (SSB) on thin dielectric membranes at Ku-band. The micromachined Lange-coupler results in a 3.6±0.8 dB coupling bandwidth from 6.5 to 20 GHz. The Lange-coupler and an interdigital filter are used in a 17-GHz SSB. The SSB mixer requires 1-2 mW of local oscillator (LO) power without dc bias and achieves a 30 dB upper-sideband (USB) image rejection for an IF frequency of 1 GHz and above. The micromachined membrane technology can be easily scaled to millimeter-wave monolithic microwave integrated circuits (MMIC's) to meet the low-cost requirements in automotive or portable communication systems     

Polymer Concrete Using Coal Fly Ash

The disposal of coal combustion byproducts wastes has been a pressing issue during the past few decades. In parallel, the formulation of high-performance materials that are stronger and more durable than conventional cement-based materials has emerged as an issue of considerable importance in the construction industry. This paper shows that it is possible to utilize fly ash, a byproduct of coal burning, to produce a high-performance material at a potentially lower cost and without compromising its structural integrity. The high-performance material reported in this study is polymer concrete (PC) made with fly-ash fillers. The PC is investigated for its compressive strength, flexural strength, creep deformation, and bond strength of PC overlay on portland cement concrete under thermal cycling. The use of fly ash as an aggregate in PC is very promising because it enhances the physical properties of the material and particularly its compressive and flexural strength. PC using fly ash could be used as an overlay in pavement, bridges, and runways or in precast applications such as utility, transportation, and hydraulic components.     

An X- and Ku-Band 8-Element Phased-Array Receiver in 0.18-$mu{hbox{m}}$ SiGe BiCMOS Technology

This paper demonstrates an 8-element phased array receiver in a standard 0.18-mum SiGe BiCMOS (1P6M, SiGe HBT f_t ap 150 GHz) technology for X- and Ku-band applications. The array receiver adopts the All-RF architecture, where the phase shifting and power combining are done at the RF level. With the integrations of all the digital control circuitry and ESD protection for all I/O pads, the receiver consumes a current of 100 ~ 200 m A from a 3.3 V supply voltage. The receiver shows 1.5 ~ 24.5 dB of power gain per channel from a 50 Omega load at 12 GHz with bias current control, and an associated NF of 4.2 dB (@ max. gain) to 13.2 dB (@ min. gain). The RMS gain error is < 0.9 dB and the RMS phase error is < 6deg at 6-18 GHz for all 4-bit phase states. The measured group delay is 162.5 plusmn 12.5 ps for all phase states at 6-18 GHz. The RMS phase mismatch and RMS gain mismatch among the eight channels are < 2.7deg and 0.4 dB, respectively, for all 16 phase states, over 6-18 GHz. The 8-element array can operate instantaneously at any center frequency and with a wide bandwidth (3 to 6 GHz, depending on the center frequency) given primarily by the 3 dB gain variation in the 6-18 GHz range. To our knowledge, this is the first demonstration of an All-RF phased array on a silicon chip with very low RMS phase and gain errors at 6-18 GHz. The chip size is 2.2 times 2.45 mm² including all pads.     

High-Efficiency Angled-Dipole Antennas for Millimeter-Wave Phased Array Applications

A high-efficiency microstrip-fed endfire angled-dipole antenna has been developed for millimeter-wave phased array applications. The antenna is built on both sides of a Teflon substrate (epsiv_r = 2.2) and this allows a wideband feed from the single-ended microstrip line to the differential dipole. The design results in wide radiation patterns for scanning purposes with a gain of around 2.5 dB at 20-26 GHz and a cross-polarization level of < -15 dB at 24 GHz. A mutual coupling of < -23 dB is measured between adjacent elements with 6.8 mm center-to center spacing (0.50-0.54 lambda₀ at 22-24 GHz). A variant of the angled-dipole antenna with a magnetic ground plane edge was also developed, and shows a measured gain of > 6 dB at 23.2-24.6 GHz and very low mutual coupling between elements (<-23 dB for a 6.8 mm spacing). Both antennas result in a radiation efficiency of > 93% when referenced to the microstrip line feed (including mismatch loss). The usefulness of these antennas as phased array radiators is demonstrated by several eight-element linear arrays at 22-24 GHz with scan angle up to 50 degrees. The application areas are in automotive radars and high data-rate communication systems.     

A high-performance integrated K-band diplexer

This paper describes the design and measurement of a planar diplexer integrated on a single silicon substrate. The diplexer channels are 5% and 6.5% relative bandwidth at 28 and 31 GHz, respectively. The diplexer is based on a micropackaged membrane supported capacitively coupled microstrip structure and is 1.5 cm×1.6 cm and only 1.4 mm thick. The measured insertion loss is 1.4 dB (5%) and 0.9 dB (6.5%) for the two channels with better than 35 dB isolation in the 28 GHz band and better than 50 dB isolation in the 31 GHz band. The measured results include all transition and packaging effects. The diplexer has coplanar-waveguide ports and can easily be integrated with other elements such as planar antennas, low-noise amplifier, and power amplifiers     

A wide-band monolithic quasi-optical power meter for millimeter and submillimeter-wave applications

A novel monolithic power meter has been developed for submillimeter-wave applications (100 GHz to 10 THz). The detector is a large-area bismuth bolometer integrated on a 1.2-μm-thick dielectric membrane. This approach results in a wide-band, high-responsivity detector. The power meter is simple to fabricate, is inexpensive, and can be easily calibrated using a low-frequency network. Quasi-optical measurements at 90, 140, and 240 GHz show that the bolometer is polarization-independent and could be modeled by a simple transmission line model. Absolute power measurements at 90, 140, and 240 GHz show a ±5% accuracy and agree well with a calibration Anritsu power meter at 90 GHz. Potential application areas are power calibration, antenna coupling efficiency measurements, and absolute power measurements from solid-state devices and far-infrared lasers at submillimeter wavelengths. Absolute output power measurements on a 220-280 GHz tripler using the quasi-optical power meter are presented as an application example