On the design of an Ohmic RF MEMS switch for reconfigurable microstrip antenna applications

This paper presents the analysis, design and simulation of a direct contact (dc) RF MEMS switch specified for reconfigurable microstrip array antennas. The proposed switch is indented to be built on PCB via a monolithic technology together with the antenna patches. The proposed switch will be used to allow antenna beamforming in the operating frequency range between 2GHz and 4GHz. This application requires a great number of these switches to be integrated with an array of microstrip patch elements. The proposed switch fulfills the switching characteristics as concerns the five requirements (loss, linearity, voltage/power handling, small size/power consumption, temperature), following a relatively simple design, which ensures reliability, robustness and high fabrication yiel

Focal plane arrays for submillimeter waves using two-dimensional electron gas elements: A grant under the Innovative Research Program

This final report describes a three-year research effort, aimed at developing new types of THz low noise receivers, based on bulk effect ('hot electron') nonlinearities in the Two-Dimensional Electron Gas (2DEG) Medium, and the inclusion of such receivers in focal plane arrays. 2DEG hot electron mixers have been demonstrated at 35 and 94 GHz with three orders of magnitude wider bandwidth than previous hot electron mixers, which use bulk InSb. The 2DEG mixers employ a new mode of operation, which was invented during this program. Only moderate cooling is required for this mode, to temperatures in the range 20-77 K. Based on the results of this research, it is now possible to design a hot electron mixer focal plane array for the THz range, which is anticipated to have a DSB receiver noise temperature of 500-1000K. In our work on this grant, we have found similar results the the Cronin group (resident at the University of Bath, UK). Neither group has so far demonstrated heterodyne detection in this mode, however. We discovered and explored some new effects in the magnetic field mode, and these are described in the report. In particular, detection of 94 GHz and 238 GHz, respectively, by a new effect, 'Shubnikov de Haas detection', was found to be considerably stronger in our materials than the cyclotron resonance detection. All experiments utilized devices with an active 2DEG region of size of the order of 10-40 micrometers long, and 20-200 micrometers wide, formed at the heterojunction between AlGaAs and GaAs. All device fabrication was performed in-house. The materials for the devices were also grown in-house, utilizing OMCVD (Organo Metallic Chemical Vapor Deposition). In the course of this grant, we developed new techniques for growing AlGaAs/GaAs with mobilities equalling the highest values published by any laboratory. We believe that the field of hot electron mixers and detectors will grow substantially in importance in the next few years, partly as a result of the opportunity given us through this grant, which represents the major effort in the US so far. We note, however, that parallel research on hot electron mixers in thin film superconductors in Russia, and recently in Sweden, have demonstrated mixing up to 1 THz, with the potential for low-noise receivers for frequencies up to many THz. The three groups recently assessed the relative adtantages of 2DEG and superconducting film mixers in a joint paper (Kollberg et al., 1992; see Appendix II)

Millimetre-wave and Terahertz Electronics

Overview: The basic thesis for the advancement of millimetre-wave and terahertz electronics is represented in four sections: Signal Processing, Component Design and Realization, Modelling and Materials, and Paradigm Shift. The first section is at system and circuit levels and reports on complex signal process functions that have been performed directly on the millimetre-wave carrier signal, intended for realizing low-cost and adaptive communications and radar systems architectures. The second section is at circuit and component levels and reports on techniques for the design and realization of low-loss passives for use at millimetrewave frequencies. The third section is at component and material levels and reports on modelling techniques for passives for use at both millimetre-wave and terahertz frequencies. Finally, the fourth section introduces a revolutionary new technology that represents a paradigm shift in the way millimetre-wave and terahertz electronics (i.e. components, circuits and systems) can be implemented. As found with the new generation of mobile phone handsets, a fusion of two extreme technologies can take place; here, complex signal processing operations could be performed both directly on the carrier signal and with the use of a spatial light modulator. Based on a selection of 20 papers (co-)authored by the candidate †b, and published over a period of 15 years, it will be seen that a coherent theme runs throughout this body of work, for the advancement of knowledge in millimetre-wave and terahertz electronics

Advanced digital modulation: Communication techniques and monolithic GaAs technology

Communications theory and practice are merged with state-of-the-art technology in IC fabrication, especially monolithic GaAs technology, to examine the general feasibility of a number of advanced technology digital transmission systems. Satellite-channel models with (1) superior throughput, perhaps 2 Gbps; (2) attractive weight and cost; and (3) high RF power and spectrum efficiency are discussed. Transmission techniques possessing reasonably simple architectures capable of monolithic fabrication at high speeds were surveyed. This included a review of amplitude/phase shift keying (APSK) techniques and the continuous-phase-modulation (CPM) methods, of which MSK represents the simplest case

Boundary layer flow and heat transfer over a permeable shrinking sheet with partial slip

The steady, laminar flow of an incompressible viscous fluid over a shrinking permeable sheet is investigated. The governing partial differential equations are transformed into ordinary differential equations using similarity transformation, before being solved numerically by the shooting method. The features of the flow and heat transfer characteristics for different values of the slip parameter and Prandtl number are analyzed and discussed. The results indicate that both the skin friction coefficient and the heat transfer rate at the surface increase as the slip parameter increases

Linear characterization and modeling of GaN-on-Si HEMT technologies with 100 nm and 60 nm gate lengths

Motivated by the growing interest towards low-cost, restriction-free MMIC processes suitable for multi-function, possibly space-qualified applications, this contribution reports the extraction of reliable linear models for two advanced GaN-on-Si HEMT technologies, namely OMMIC’s D01GH (100 nm gate length) and D006GH (60 nm gate length). This objective is pursued by means of both classical and more novel approaches. In particular, the latter include a nondestructive method for determining the extrinsic resistances and an optimizaion-based approach to extracting the remaining parasitic elements: these support standard DC and RF measurements in order to obtain a scalable, bias-dependent equivalent-circuit model capturing the small-signal behavior of the two processes. As to the noise model, this is extracted by applying the well known noise-temperature approach to noise figure measurements performed in two different frequency ranges: a lower band, where a standard Y-factor test bench is used, and an upper band, where a custom cold-source test bench is set up and described in great detail. At 5 V drain-source voltage, minimum noise figures as low as 1.5 dB and 1.1 dB at 40 GHz have been extracted for the considered 100 nm and 60 nm HEMTs, respectively: this testifies the maturity of both processes and the effectiveness of the gate length reduction. The characterization and modeling campaign, here presented for the first time, has been repeatedly validated by published designs, a couple of which are reviewed for the Reader’s convenience

Design and characterisation of electromagnetic bandgap filters

Most signal processing / communications applications heavily rely on filters. For adaptive spectrum filtering and for applications that switch between sets of different filter implementations, it would be beneficial to utilize just one, tuneable band-pass filter. In recent years, the study of metamaterials emerged as an area of scientific research due to the unique attributes of metamaterials. Metamaterials typically are artificial structures with properties not found in nature, for instance negative refraction indexes. Their feature sizes span a fraction of the wavelength corresponding to their frequency of operation. A sub group of metamaterials, the electromagnetic bandgap (EBG) structures, exhibit stopbands for electromagnetic waves irrespective of polarization or angle of incidence. EBG structures prominently achieved surface wave suppression to minimise cross talk between neighbouring devices and improving antenna efficiency by acting as a perfect magnetic conductor within a certain frequency range. The thesis investigates the suitability of EBG structures for filter implementations. The goal is to provide a tuneable band-pass filter for adaptive spectrum filtering and communication applications. The bandgap of an infinite array of EBG cells is numerically determined. Based on those results, an EBG band-pass filter implementation on a printed circuit board (PCB) is designed, fabricated and characterized. Different tuning methods were incorporated into the PCB design to create a tuneable EBG band-pass filter. An EBG filter was built on a fused silica wafer, in order to shift the passband to higher frequencies