Ka-Band SiGe HBT Low Phase Imbalance Differential 3-Bit Variable Gain LNA

This letter presents the design and implementation of a differential Ka-band variable gain low noise amplifier (VG-LNA) with low insertion phase imbalance. The VG-LNA is based on a 0.12 mum SiGe heterojunction bipolar transistor process, and the gain variation is achieved using bias current steering. The measured VG-LNA gain at 32-34 GHz is 9-20 dB with eight different linear-in-magnitude gain states, and with a noise figure of 3.4-4.3 dB. The measured rms phase imbalance is < 2.5deg at 26-40 GHz for all gain states and this is achieved using a novel compensating resistor in the bias network. The VG-LNA consumes 33 mW (13.5 mA, 2.5 V) and the input 1-dB gain compression point is -27 dBm. The chip size is 0.13 mm² without pads.     

Submillimeter-wave antennas on thin membranes

Submillimeter-wave antennas have been fabricated on 1-μm thick silicon-oxynitride membranes. This approach results in better patterns than previous lens-coupled antennas, and eliminates the dielectric loss associated with the substrate lens. Measurements on a wideband log-periodic antenna at 700 GHz, 370 GHz and 167 GHz show no sidelobes and 3-dB beamwidths between 40° and 60°. A linear imaging array has similar patterns at 700 GHz. Possible applications for membrane antennas include wideband superconducting tunnel-junction receivers for radio astronomy and imaging arrays for radiometry and plasma diagnostics.     

Phase-noise analysis of MEMS-based circuits and phase shifters

The effect of Brownian, acceleration, acoustic, and power-supply noise on MEMS based circuits has been calculated for MEMS.-based circuits (phase shifters, delay circuits). The calculations are done for capacitive shunt MEMS switches and metal-to-metal contact series MEMS switches. It is found that these effects result in both an amplitude and phase noise, with the phase noise being around 100× larger than the amplitude noise. The phase noise due to Brownian motion is negligible for MEMS switches with k ≃ 1.0 N/m, g₀ > 2 μm, Q > 0.5, and f₀ ≃ 50 kHz. The effect of acceleration and acoustic noise is negligible for a total acceleration noise of 10 g or less and a total acoustic noise of 74-dB sound pressure level. The power-supply noise depends on the bias conditions of the MEMS element, but is negligible for MEMS switches with a bias voltage of 0 V and a total noise voltage of 0.1 V or less. It is also found that metal-to-metal contact series switches result in much less phase noise than standard capacitive shunt switches. The phase noise increases rapidly for low spring-constant bridges (k = 0.24 N/m), low-height bridges, and bridges with a large mechanical damping (Q < 0.3). Also, varactor-based designs result in 30-40 dB more phase noise than switch-based circuits. This paper proves that microwave passive circuits built using MEMS switches (with a proper mechanical design) can be used in most commercial and military applications without any phase-noise penalty     

A Low-Loss Double-Tuned Transformer

In this letter, we present a state-of-the-art, planar double-tuned transformer using high-, micromachined spiral inductors and integrated capacitors. This circuit provides a 4:1 impedance transformation over a 30% bandwidth centered at 4.06 GHz, with a minimum insertion loss of 1.50 dB. The fabricated circuit occupies a total area of 440 times 500 mum²and finds application in power amplifier and other matching applications. An accurate lumped-element circuit model and design tradeoffs are presented. We believe this is the first implementation of a planar microwave double-tuned transformer.     

Boardrooms of Energy Firms in the Post-Enron Era

Corporate governance has emerged as a topic of significant importance, particularly in the aftermath of the Enron scandal. Undoubtedly, the renewed scrutiny of this entity is not without justification. Enron’s failure is largely attributed to a breakdown of corporate governance with the inability, or unwillingness, of the board of directors to hold management accountable on behalf of the shareholders. Meanwhile, the academic and popular literatures have yet to provide unequivocal guidance as to the appropriate modus of operandi in the boardroom. Based on survey and interview results, this paper provides some suggested practices regarding the proper functions, optimum configurations, and appropriate incentive schemes of the boardrooms belonging to the energy industry. The importance of the energy sector stems from its prominent role as a main contributor to the production of goods and services. The guidelines presented in this study would enable the boardroom to be vigilant and adopt preventive measures not just in crisis situations, but also continually.     

Microstrip antennas on synthesized low dielectric-constantsubstrates

Micromachining techniques using closely spaced holes have been used underneath a microstrip antenna on a high dielectric-constant substrate (ϵ_r=10.8) to synthesize a localized low dielectric-constant environment (ϵ_r=2.3). The measured radiation efficiency of a microstrip antenna on a micromachined 635-μm thick ϵ_r=10.8 Duroid 6010 substrate increased from 48±3% to 73±3% at 12.8-13.0 GHz (including 3.3-cm feed line losses). We believe that this technique can be applied to millimeter-wave antennas (microstrip, dipoles, slots, etc.) on silicon and GaAs substrates to result in relatively wideband (3-6%) monolithic microwave integrated circuits (MMIC) active antenna modules for phased-arrays and collision-avoidance systems     

Strategies for corporate governance in engineering corporations

Although corporate governance plays a crucial role in shaping the vision, image and reputation of a corporation, this subject has been largely ignored in the prevailing engineering and technology management literature. In the wake of scandals like Enron and WorldCom, the call for effective corporate governance echoes across the boardrooms of many corporations. It is the intent of this paper to close the gap between the myth and the reality of US corporate governance effectiveness in engineering companies and to suggest some improvement strategies regarding the modus operandi and optimum structure of this entity. This study would benefit the board of directors of engineering companies that are already in existence or those that are in the process of being formed. It relies on survey results with individuals who, by virtue of their significant experience in the boardroom of engineering corporations, can offer unique insight and provide valuable data to the topic of corporate governance.     

An X- to ku-band 3-bit digital MEMS varactor

A 3-bit digital microelectromechanical system (MEMS) varactor bank is demonstrated on a low-cost glass substrate. It is composed of three discrete-position varactors, each of them achieving a capacitance ratio close to 3:1. The total capacitance of the varactor bank is tunable from 146 fF to 430 fF in eight states and is suitable for X- or Ku-band operation. The design can be easily scaled to Ka-band frequencies.