A Broadband Planar Magic-T Using Microstrip–Slotline Transitions

The improved version of a broadband planar magic-T using microstrip-slotline transitions is presented. The design implements a small microstrip-slotline tee junction with minimum size slotline terminations to reduce radiation loss. A multisection impedance transformation network is used to increase the operating bandwidth and minimize the parasitic coupling around the microstrip-slotline tee junction. As a result, the improved magic-T has greater bandwidth and lower phase imbalance at the sum and difference ports than the earlier magic-T design. The experimental results show that the 10-GHz magic-T provides more than 70% of 1-dB operating bandwidth with the average in-band insertion loss of less than 0.6 dB. It also has phase and amplitude imbalance of less than plusmn1deg and plusmn0.25 dB, respectively.     

A New Analytical Method for Robust Extraction of the Small-Signal Equivalent Circuit for SiGe HBTs Operating at Cryogenic Temperatures

We present a new analytical direct parameter-extraction methodology for obtaining the small-signal equivalent circuit of HBTs. It is applied to cryogenically operated SiGe HBTs as a means to allow circuit design of SiGe HBT low-noise amplifiers for cooled radio astronomy applications. We split the transistor into an intrinsic transistor (IT) piece modeled as a Pi-topology, and the quasi-intrinsic transistor (QIT), obtained from the IT after that the base resistance (R_b) has been removed. The relations between Z-Y-parameters of the IT and QIT are then established, allowing us to propose a new methodology for determining R_b. The present extraction method differs from previous studies in that each of the model elements are obtained from exact equations that do not require any approximations, numerical optimization, or post-processing. The validity of this new extraction methodology is demonstrated by applying it to third-generation SiGe HBTs operating at liquid-nitrogen temperature (77 K) across the frequency range of 2-22 GHz.     

Fractionation and Some Chemical Studies on Ailanthus excelsa Roxb. Seed Protein

The unavailability of protein foods, particularly in the context of population growth, has been an important factor in the protein malnutrition encountered in developing countries. The fractionation, gel filtration and polyacrylamide gel electrophoresis (PAGE) of Ailanthus excelsa seed (a nontraditional source containing 15.81% protein) proteins were carried out in the present study, and their solubility profiles, surface topographies and amino acid compositions were evaluated. The globulin fraction dominated the seed protein composition, accounting for 51.31% (w/w) of the total soluble proteins in the seeds. Protein isolate and protein fractions of A. excelsa seeds showed similar topographical structures to those of other plant seed proteins. Analysis of the isolated proteins identified 17 amino acids, of which nine were essential. Gel filtration on Sephadex G-200 revealed the presence of seven components. PAGE detected different polypeptide bands in the range of 28.8−154.9 kDa in the protein isolate as well as in protein fractions for A. excelsa. The amino acid compositions, the solubility patterns and the high abundances of low molecular weight proteins indicate that the isolated seed protein of A. excelsa may be a potential food protein.     

Power-Combining Transformer Techniques for Fully-Integrated CMOS Power Amplifiers

Fully integrated CMOS power amplifiers (PAs) with parallel power-combining transformer are presented. For the high power CMOS PA design, two types of transformers, series-combining and parallel-combining, are fully analyzed and compared in detail to show the parasitic resistance and the turn ratio as the limiting factor of power combining. Based on the analysis, two kinds of parallel-combining transformers, a two-primary with a 1:2 turn ratio and a three-primary with a 1:2 turn ratio, are incorporated into the design of fully-integrated CMOS PAs in a standard 0.18-mum CMOS process. The PA with a two-primary transformer delivers 31.2 dBm of output power with 41% of power-added efficiency (PAE), and the PA with a three-primary transformer achieves 32 dBm of output power with 30% of PAE at 1.8 GHz with a 3.3-V power supply.     

Modeling and sensitivity analysis of circuit parameters for flip-chip interconnects using neural networks

This paper presents a neural network-based technique for modeling and analyzing the electrical performance of flip-chip transitions. A lumped element model using a simple pi equivalent circuit is used to characterize the electrical properties of the flip-chip bond. Statistical experimental design is used to extract the electrical parameters for flip-chip characterization from measurements and full-wave simulations up to 35 GHz. The extracted data is used to train back-propagation neural networks to obtain an accurate model of the pi equivalent circuit components and s-parameters as a function of layout parameters. The prediction error of the models is less than 5%. The models are used to obtain response surfaces for the entire range of variation of layout parameters. The neural network models are subsequently used to perform sensitivity analysis. All electrical parameters are shown to be sensitive to conductor overlap. The inductance and capacitance of the pi equivalent circuit are sensitive to the bump height. However, the return loss (S₁₁) is insensitive to the change in bump height. The coplanar waveguide width has a significant impact on the s-parameters, as it affects the matching of flip-chip transitions     

3-D-integrated RF and millimeter-wave functions and modules using liquid crystal polymer (LCP) system-on-package technology

Electronics packaging evolution involves system, technology, and material considerations. In this paper, we present a novel three-dimensional (3-D) integration approach for system-on-package (SOP)-based solutions for wireless communication applications. This concept is proposed for the 3-D integration of RF and millimeter (mm) wave embedded functions in front-end modules by means of stacking substrates using liquid crystal polymer (LCP) multilayer and /spl mu/BGA technologies. Characterization and modeling of high-Q RF inductors using LCP is described. A single-input-single-output (SISO) dual-band filter operating at ISM 2.4-2.5 GHz and UNII 5.15-5.85 GHz frequency bands, two dual-polarization 2/spl times/1 antenna arrays operating at 14 and 35 GHz, and a WLAN IEEE 802.11a-compliant compact module (volume of 75/spl times/35/spl times/0.2 mm/sup 3/) have been fabricated on LCP substrate, showing the great potential of the SOP approach for 3-D-integrated RF and mm wave functions and modules.     

Forward transit delay in In0.53Ga0.47Asheterojunction bipolar transistors with nonequilibrium electrontransport

The authors measured the microwave performance of high speed InP/In_0.53Ga_0.47As heterojunction bipolar transistors in the temperature range 55 K⩽T⩽340 K. The extrinsic unity current gain cutoff frequency is 130 GHz at 340 K, increasing to 300 GHz at 55 K. The intrinsic emitter-collector forward delay decreases with decreasing temperature from 0.5 ps at 340 K to a saturated value of 0.28 ps for ⩽150 K. Such behavior may be explained only by the presence of nonequilibrium electron transport in the base and collector of the device     

Experimental and theoretical investigation of the DC andhigh-frequency characteristics of the negative differential resistancein pseudomorphic AlGaAs/InGaAs/GaAs MODFET's

The authors investigated the negative differential resistance (NDR) in the I-V characteristics of pseudomorphic AlGaAs/InGaAs/GaAs modulation doped field-effect transistors (MODFETs) with gate lengths of 0.3 μm. They experimentally verified the existence of abrupt multiple NDR in both the input circuit and the output circuit. The NDR occurs over a short range of drain voltage (less than 200 mV) and gate voltage (less than 5 mV) for NDR induced by thermionic emission. The authors provide a general interpretation of the measured DC results based on tunneling real-space transfer (TRST) which occurs because of the formation of hybrid excited states across the InGaAs channel and AlGaAs donor layer. The existence of stable reflection is verified in both the input and output circuits with stable broadband frequency response in the output circuit to at least 49 GHz. These results show that NDR via TRST in pseudomorphic MODFETs can provide wideband frequency response not limited by the electron transit time from source to drain     

High-frequency noise in AlGaN/GaN HFETs

We present in this letter the benefits of GaN-based electronic devices for low-noise MMICs. A temperature-dependent two-temperature noise model for AlGaN/GaN HFETs is implemented on a wide range of bias conditions. This study enables to access the device high-frequency noise parameters, and allow a comparison of the noise performances with SiC and GaAs technologies.     

Copolymers of bulky fumarate: synthesis and their properties

The free radical copolymerization of di-n-docosyl fumarate with vinyl acetate and n-alkyl (meth)acrylates was carried out in toluene at 70°C using benzoyl peroxide as an initiator. ¹H NMR and carbon analysis was used to determine the copolymer compositions. Monomer reactivity ratios for high conversion polymerization were calculated by Fineman-Ross, Kelen-Tüdös and conversion extension Kelen-Tüdös methods. Gel permeation chromatography was used to determine the molecular weights and polydispersity indexes. In order to determine the stability of polymers against thermal degradation, the kinetics and mechanism of the thermal degradation of copolymers were investigated by differential scanning calorimetry and thermogravimetric analysis techniques. The energy of activation of the degradation process was determined by several thermogravimetric analysis models.