A 5.8 GHz Low Noise Amplifier for Wireless LAN Applications in Silicon Bipolar Technology

A monolithic integrated low-noise amplifier for operation in the 5.8-GHzband is described. Two different versions have been implemented where the biasing wasadapted to allow operation over a different range of supply voltage. At 5-V, theamplifiers gain is about 17-dB, with a noise figure of 4.2-dB and 1-dB compressionpoint at –15-dBm input power. The circuits have been designed utilizing a0.6-micron silicon bipolar production technology, featuring npn transistors with and of about20-GHz.     

Optimizing CMOS Transconductor-C Filters for Low Power Wide Band Operation

A novel figure of merit to describe the bandwidth power efficiency of CMOS transconductors— is proposed and optimized for cross-coupled differential pair transconductor structures. The optimization is done in two different ways: univariable unconstrained and multivariable constrained. It is revealed that not only dc biases but also ac input phases can affect the bandwidth power efficiency of the transconductor. The bias voltages which can lead to best ratio at different ac phase combinations are obtained and presented in the article. HSPICE simulations are conducted to verify the theoretical predictions. On the basis of the cross-coupled differential pair transconductor, a biquadratic transconductor-C filter configuration is implemented. The frequency vs. power characteristic of the filter is studied for both optimally- and non-optimally-biased transconductor. It is shown that the optimization of the transconductor structure can result in performance improvement of the transconductor-C filter. The deviation of the optimal bias condition between the transconductor alone and the transconductor-C filter due to the inclusion of peripheray circuitries in the filter is discussed in the article.     

Current-Mode High Output Impedance Multifunction Filters Employing Minimum Number of FTFNs

In this study, five current-mode FTFN-based multifunction filters are proposed, which realize the same transfer functions in ideal case. All circuits employ two capacitors and three resistors. For each circuit R-C:C-R transformation increases the number of realization possibilities to ten. The proposed topologies simultaneously realize three basic filtering functions using minimum number of FTFNs and provide high output impedances that enable easy cascading in current mode. Sensitivity analysis of the filters show that they have low passive sensitivities, and of the filters are insensitive to current tracking errors, furthermore of the filters are insensitive to voltage tracking errors of the FTFNs. The proposed circuits do not require component matching condition except for notch and allpass responses and permit independent adjustment of without disturbing . Experimental and simulation results are given to verify the theoretical analyses.     

A Small Area Charge Sensitive Readout Chain with a Dual Mode of Operation

A charge sensitive readout chain has been designed and fabricated in acommercially available 0.8 m CMOS technology. The readout chain is optimizedfor pixel detectors measuring soft X-ray energies up to 20 KeV. In the first modean analog signal proportional to input charge is generated and processed in realtime. In the second mode a peak-and-hold operation is enabled and therelevant signal is processed in later time. This dual mode of operation iscontrolled by an external digital signal. The readout chain consists of a chargeamplifier, a shaper, an operational amplifier which can either operate as avoltage amplifier or a peak detector and an output buffer. Its area is . The gain at the shaper output is 378 mv/fC, theENC is 16 rms at 160 nsec shaping time. The overall gainis 557 mV/fC, the ENC is rms with 240 nsec peaking timeand 1.4 sec recovery time. The overall power dissipation is 1.5 mWatt with aload capacitance of 25 pF.     

A Symbolic Circuit Analysis-Oriented Algorithm for Finding a Common Tree of the Current and Voltage Graphs

A fundamental problem of symbolic analysis of electric networks when using the signal-flow (SFG) graph method is to find the common tree of the current and voltage graph ( and , respectively). In this paper we introduce a novel method in order to determine a common tree of both graphs, which may be used to obtain the symbolic network transfer function when carrying out the small-signal analysis of linear(ised) circuits.     

A Fully Integrated, Low Noise and Low Power BiCMOS Front-end Readout System for Capacitive Detectors

Bipolar transistors are interesting for low noise front-end readout systems when high speed and low power consumption are required. This paper presents a fully integrated, low noise front-end design for the future Large Hadron Collider (LHC) experiments using the radiation hard SOI BiCMOS process. In the present prototype, the input-referred Equivalent Noise Charge (ENC) of 990 electrons (rms) for 12 pF detector capacitance with a shaping time of 25 ns and power consumption of 1.4 mW/channel has been measured. The gain of this front-end is 90 mV/MIP (Minimum Ionisation Particle: 1 fC) with non-linearity of less than 3% and linear input dynamic range is MIP. These results are obtained at room temperature and before irradiation. The measurements after irradiations by high intensity pion beam with an integrated flux of pions/cm² are also presented in this paper.     

A CMOS Monolithic Image-Reject Filter

A CMOS inductorless image-reject filter based on active RLC circuitry is discussed and designed with the emphasis on low-noise, low-power, and gigahertz-range circuits. Two -enhancement techniques are utilized to circumvent the low characteristics inherent in the simple feedback circuit. The frequency tuning is almost independent of tuning, facilitating the design of the automatic tuning circuitry. The stability and the tuning scheme of the filter are also discussed. Simulations using 0.6 m CMOS technology demonstrate the feasibility of the tunable image-reject filter for GSM wireless applications. Simulation results show 4.75 dB voltage gain, 9.5 dB noise figure, and –20 dBm IIP3 at a passband centered at 947 MHz. The image signal suppression is 60 dB at 1089 MHz and the power consumption is 27 mW.     

Statistical Design of the Four-MOSFET Structure

The statistical design of the four-MOSFET structure is presented in this paper. The quantitative measure of the effect of mismatch between the four transistors on nonlinearity and offset current is provided through contours. Statistical optimization of the transistor and values is demonstrated. The four-MOSFET structure was fabricated through the MOSIS 2 m process using MOS transistor Level-3 model parameters. Experimental results are included in the paper.     

Planar defects and double-domain epitaxy in epitaxial YSi<Subscript>2−x</Subscript> and ErSi<Subscript>2−x</Subscript> thin films on Si substrates

Interfacial reactions of Y and Er thin films on both (111)Si and (001)Si have been studied by transmission electron microscopy (TEM). Epitaxial rare-earth (RE) silicide films were grown on (111)Si. Planar defects, identified to be stacking faults on planes with 1/6 displacement vectors, were formed as a result of the coalescence of epitaxial silicide islands. Double-domain epitaxy was found to form in RE silicides on (001)Si samples resulting from a large lattice mismatch along one direction and symmetry conditions at the silicide/(001)Si interfaces. The orientation relationships are [0001]RESi_2−x// Si, RESi_2−x//(001)Si and [0001]RESi_2−x/ Si, RESi_2−x//(001)Si. The density of staking faults in (111) samples and the domain size in (001) samples were found to decrease and increase with annealing temperature, respectively.     

Identification of prismatic slip bands in 4H SiC boules grown by physical vapor transport

Transmission electron microscopy (TEM) and KOH etching have been used to study the dislocation structure of 4H SiC wafers grown by physical vapor transport. A new type of threading dislocation arrays was observed. Rows of etch pits corresponding to dislocation arrays were observed in vicinity of micropipes, misoriented grains and polytypic inclusions at the periphery of the boules and extended along the directions. Plan view conventional and high resolution TEM showed that the arrays consisted of dislocations threading along the c-axis with Burgers vectors having edge components of the a/3 type. The Burgers vectors were parallel to the corresponding arrays. The dislocation arrays were interpreted as slip bands formed by dislocation glide in the prismatic slip system of hexagonal SiC during post-growth cooling.     

Finite-Memory Systems

Let K be a field, k and n positive integers and let matrices with coefficients in K. For any function

A kinetic study of structured surface relief patterning of GaP (\bar 1\bar 1\bar 1)

Orientation dependent etching of photolithographically patterned GaP was investigated using solutions of HCl:CH₃COOH:H₂O₂. The pattern was prepared using standard ultraviolet lithography and was a two-dimensional grid with an 18 μm repeat, consisting of 15 μm squares separated by 3 μm spaces. The mask sides were aligned along the and directions. Under appropriate etching conditions, high quality arrays of pyramids were prepared. These pyramids were defined by , and facets. It was shown that the etching process depended on the degree of solution aging after initial mixing. For a freshly prepared solution, the etching rate showed an inverse dependence on time. For short etching times (below 5 min), an intermediate etching profile was followed, while for long times (greater than 5 min) etching was kinetically controlled. We demonstrated that controlled etching at extremely low rates (0.1–0.5 μm/min) is feasible with this new approach.     

The shape of self-assembled InAs islands grown by molecular beam epitaxy

We have determined the shape of InAs quantum dots using reflection high energy electron diffraction. Our results indicate that self-assembled InAs islands possess a pyramidal shape with {136} bounding facets. This shape is characterized by C_2v symmetry and a parallelogram base, which is elongated along the direction. Cross-sectional transmission electron microscopy images taken along the [110] and directions as well as atomic force microscopy images strongly support the {136} shape. Furthermore, polarization-resolved photoluminescence spectra show strong in-plane anisotropy, with emission predominantly polarized along the direction, consistent with the proposed quantum dot shape.     

Microstructure of GaN grown by lateral confined epitaxy 2. GaN on patterned sapphire

Transmission electron microscopy (TEM), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy were used in order to study the microstructure and optical properties of GaN films grown by metal-organic chemical vapor deposition (MOCVD) on c-plane sapphire by lateral confined epitaxy (LCE). In this method, the substrate is etched prior to growth to form uniform mesas separated by trenches for laterally restricting growth area. As previously observed for LCE GaN on Si(111), the density of threading dislocations was significantly reduced in the areas close to the edge of mesas due to the lateral propagation of the dislocations. Hence, the overall material quality improves with decreasing mesa size, which is consistent with the observed increase in photoluminescence band edge peak intensity. Electron diffraction indicated ∼1° rotation about the [ ] axis between the mesa and trench material, which was also observed in the image contrast of these two regions with g= . Additionally, LCE samples prepared in [ ] and [ ] cross sections were used for comparing the growth rates in these two perpendicular directions. As theoretically expected, growth in the [ ] direction appears to proceed considerably faster than that in the [% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9qqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaaig% daceaIYaGbaebacaaIWaaaaa!38D1!\[11\bar 20\]] direction.     

A DDS Synthesizer with Digital Time Domain Interpolator

A DDS type circuit structure for producing numericallyprogrammable square wave clock signal is presented. The high speed D/Aconverter needed in conventional DDS systems is replaced by an tap delay line time domain interpolator thateffectively increases the sampling rate by a factor of . Thus the circuit can be used up to full clock rate withoutimage filtering. A prototype IC with clock frequency of 30 MHz, 5 bitinterpolator and SFDR of –40 dBc up to 10 MHz and –33 dBcup to 15 MHz has been designed and tested.     

CORDIC-Based Computation of ArcCos

CORDIC-based algorithms to compute cos and are proposed. The implementation requires a standard CORDIC module plus a module to compute the direction of rotation, this being the same hardware required for the extended CORDIC vectoring, recently proposed by the authors [T. Lang and E. Antelo, IEEE Transactions on Computers, vol. 47, no. 7, 1998, pp. 736–749.]. Although these functions can be obtained as a special case of this extended vectoring, the specific algorithm we propose here presents two significant improvements: (1) it uses the same datapath width as the standard CORDIC, even when t has 2n bits (to achieve a granularity of 2^–n for the whole range). In contrast, the extended vectoring unit requires about 2n bits. (2) no repetitions of iterations are needed (the extended vectoring needs some repetitions). The proposed algorithm is compatible with the extended vectoring and, in contrast with previous implementations, the number of iterations and the delay of each iteration are the same as for the conventional CORDIC algorithm.     

BIBO Stability of D-Dimensional Filters

Consider the class of d-dimensional causal filters characterized by a d-variate rational function analytic on the polydisk . The BIBO stability of such filters has been the subject of much research over the past two decades. In this paper we analyze the BIBO stability of such functions and prove necessary and sufficient conditions for BIBO stability of a d-dimensional filter. In particular, we prove if a d-variate filter H(z) analytic on has a Fourier expansion that converges uniformly on the closure of , then H(z) is BIBO stable. This result proves a long standing conjecture set forth by Bose in [3].     

Can One Control the Vibrations of a Drum?

This paper considers the problem of constructing feedback stabilizing controllers for the wave operator on ⁿ (more generally AR systems determined by a hyperbolic operator). In order to accomplish this, it must first clarify the notion of an input-output structure on a distributed system, as well as what it means to interconnect two such systems. Both these notions are shown to be consequences of a structure which generalizes the standard causal structure of lumped systems determined by the flow of time. Given this apparatus, the paper then constructs feedback controllers which stabilize the wave equation along directions given by a proper cone in ⁿ.     

Orthogonal cycle transforms of stochastic matrices

In this paper we investigate new Fourier series with respect to orthonormal families of directed cycles , which occur in the graph of a recurrent stochastic matrixP. Specifically, it is proved thatP may be approximated in a suitable Hilbert space by the Fourier series . This approach provides a proof in terms of Hilbert space of the cycle decomposition formula for finite stochastic matricesP.