Volume 19, Number 3, 2016
Saurabh CHATURVEDI, Mladen BOẐANIĆ, Saurabh SINHA
Abstract. The paper presents the effect of conductive or lossy silicon (Si) substrates on the frequency-dependent distributed series impedance transmissionline (TL) parameters, R(ω) and L(ω). The frequency variations of these parameters of the microstrip line for four different conductivities of Si substrate are observed and compared. Keysight Technologies (formerly Agilent’s Electronic Measurement Group) Advanced Design System is used for the electromagnetic simulations of the microstrip line structures. Scattering parameters based equations are used to plot the variations of series impedance parameters as a function of frequency. Furthermore, this paper explains a complete method to extract various parameters related to a TL. The work extracts the parameters of a microstrip TL model provided with the GlobalFoundries 0.13 mm SiGe BiCMOS8HP process design kit up to 100 GHz. Read the pdf
Valentin BUICULESCU, Ioana GIANGU
Abstract. Signal backscattering (BS) methods are normally used for gain and radiation pattern measurements of small antennas, mainly due to reduced disturbance from RF feeding cables. Most chipless RFIDs are based on passive structures with broadband, multiple resonances, therefore UWB antennas are best suited for these RFID applications. However, bandwidth of small antennas used in most RFID applications is inherently narrow, hence regular BS modulators used for their characterization work within limited bandwidths. A broadband BS modulator solution is proposed in this paper for covering non-standard and ultra wideband (UWB) antenna measurements. The basic component of this BS modulator can be any monolithic integrated single-pole double through (SPDT) switch with low current consumption and control voltages; both CMOS and pHEMT devices are suitable for this application. A bistatic arrangement provides improved measurement accuracy due to constant coupling factor between transmitting and receiving antennas placed in stationary positions. About 11 mW power consumption from a single 3 V battery was measured for the complete UWB BS modulator, therefore long term antenna characterization with 0.004 dB/day accuracy was possible. Read the pdf.
A.C. BUNEA, D. NECULOIU, A.M. AVRAM, A. MULLER
Abstract. In this paper we analyze the influence of extremely low temperatures on the operation performances of a hybrid integratedW-band (75 – 110 GHz) receiver based on a zero-bias GaAs diode. First, the zero-bias diode is investigated and modeled in the temperature range of operation. Then, a direct detection receiver consisting of a membrane supported folded slot antenna and a detection circuit based on a zero-bias diode is fabricated and characterized. The detection circuit is inserted in a cryogenic system and on-wafer measurements are performed in the temperature range 23 K – 295 K, in advanced vacuum conditions. The detection circuit is fed with a 1 kHz amplitude modulated W-band signal and both detected signal and i/v characteristic are compared for different temperatures. It is demonstrated that the receiver is capable of operating even at 23 K (-250.15°C), when the diode is biased at +0.25 V. Read the pdf
M. FANORO, S.S. OLOKEDE, S. SINHA
Abstract. This paper presents the design of a millimeter-wave low noise amplifier (LNA) realized using a 0.13 mm silicon germanium bipolar complementary metal oxide semiconductor process technology. The effect of input matching on an LNA is investigated. A small-signal equivalent circuit, which depicts the resistor-inductor-capacitor relationship of the input impedance network, is explored to determine its input impedance. A MATLAB code was written to understand the frequency response of the input matching network. The responses obtained are expected to be applied to the LNA to determine the input reflection coefficient (| S11 |). The equivalent circuit model (ECN) is verified numerically using 2D Advanced Design System (ADS) software. Thereafter, a step-by-step methodology that can be applied in realizing a 60 GHz LNA at the V-band is formulated. The amplifier is designed using lumped elements in a two-stage cascode topology based on a novel matching network. The matched network consists of an L-input and a T-output matching network as well as inductive emitter degeneration. The output network is designed to enhance maximum power transfer, whereas interstage matching is designed to optimize for high gain while minimizing the noise of the local area network. The transistor configuration is implemented by varying the length of the transistor to observe the minimal noise figure and the maximum gain, while keeping the voltage across the collector, emitter and the base constant. By utilizing the cascode topology and series peaking inductor, (| S11 |) of the LNA peaks at 14 dB, whereas the output reflection coefficient (| S22 |) achieved is 25 dB. The estimated value of S11 using the ECN was about 12 dB. The noise factor is 4.3 dB minimum at 60 GHz, whereas the forward gain (| S21 |) of the LNA is well above 26 dB. Read the pdf.
Abstract. This paper presents an extension of , by the same author, on an advanced body reference frame calibration method for 3-axis MEMS accelerometers using the total field approach. The extension consists in improving the calibration method by removing restrictions imposed on the positioning apparatus, providing a detailed comparison between several sensor frame error models, and providing additional details on the suggested thermal model with a study of its performance in the thermal compensation of MEMS accelerometers. As mentioned in , the proposed method solves the misalignment between the sensor reference frame and body reference frame without known stimuli, unlike prior work by other authors. Thermally compensated body reference frame calibrations are an absolute must in demanding applications such as inertial navigation and directional drilling.
R-C. VOICU, C. Tibeica, R. MÜLLER, A. DINESCU, M. PUSTAN, C.BIRLEANU
Abstract. This paper presents the design, simulation, fabrication, and characterisation of polymeric microgrippers based on V-shaped electrothermal actuators with two normally operation modes (open and closed) for bio-micromanipulation and micro assembly applications. The microgrippers were simulated using FEM in order to determine the electro-thermo-mechanical behaviour. The microgrippers were fabricated using the SU-8 biocompatible polymer as structural material. The metallic microheaters were embedded in the polymeric structural layers of the microgrippers to improve thermal efficiency and to reduce the undesirable out-ofplane displacement of the gripper. Electro-mechanical testing and characterisation have been performed to determine the openings of the microgripper tips as function of electrical current. For the evaluation of the microgripper displacement, a measurement based on an optical image approach was used. A displacement of 40 m can be obtained for an electrical current of around 25 mA. Over 26 mA the heaters are still working but a softening and a damaging status in the polymer were observed. A comparison between the simulation results and the displacement measurements is presented. Read the pdf
Anca-Ionela ISTRATE, Monica VECA, Florin NASTASE, Angela BARACU, Raluca GAVRILA, Florin COMANESCU, Vasilica TUCUREANU, Adrian DINESCU, Titus SANDU
Abstract. The current work presents the fabrication and characterization of graphene-silicon heterojunctions with various contact areas. First, we transferred the graphene from copper to Si and SiO2 substrates using Electrochemical Delamination and then we processed and characterized the transferred graphene. Second, we manufactured graphene-Si heterojunctions with several contact areas made by opening windows of various sizes in Si. Microscopy and spectroscopy analysis confirms the successful graphene transfer which is also revealed by a relative high carrier mobility of 2327 cm2/Vs measured in a field effect transistor configuration. We test the quality of graphene-Si Schottky contacts by measuring the I-V characteristics of heterojunctions established within Si windows with linear sizes ranging from up to 70 m to down to 6 m. All our structures exhibit rectifying I-V curves behavior from which we were able to extract junction parameters like the ideality factor, the barrier height and the series resistance. This work provides a route to engineer graphene-based devices like Schottky diodes and field effect transistors (FETs) by relatively simple procedures. Read the pdf
Andrei ENACHE, Ion RUSU, Florin DRĂGHICI, Gheorghe PRISTAVU, Gheorghe BREZEANU, Florin ENACHE
Abstract. A system used for measuring the concentration of chemical compounds in fluids/solutions is designed, implemented and tested. The system comprises a Sense and Control Circuit formed with a potentiostat for three-electrode electrochemical cell (biosensor) biasing and a transimpedance amplifier for cell current processing. The stability of the potentiostat and the linearity of the transimpedance amplifier are theoretically and experimentally investigated. The high accuracy of the system is demonstrated by simulations and measurements. A comparison with a commercially available system is carried out. Read the pdf