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Articles 1 - 30 of 30
Full-Text Articles in Engineering
Asymptotic Spectral Efficiency Of Multiantenna Links In Wireless Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin
Asymptotic Spectral Efficiency Of Multiantenna Links In Wireless Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin
Siddhartan Govindasamy
An asymptotic technique is presented for finding the spectral efficiency of multiantenna links in spatially distributed wireless networks where transmitters have channel-state-information (CSI) corresponding to their target receiver. Transmitters are assumed to transmit independent data streams on a limited number of channel modes which limits the rank of transmit covariance matrices. An approximation for the spectral efficiency in the interference-limited regime as a function of link-length, interferer density, number of antennas per receiver and transmitter, number of transmit streams, and path-loss exponent is derived. It is found that targeted-receiver CSI, which can be acquired with low overhead in duplex systems …
Terahertz And Microwave Detection Using Metallic Single Wall Carbon Nanotubes, Enrique Carrion
Terahertz And Microwave Detection Using Metallic Single Wall Carbon Nanotubes, Enrique Carrion
Enrique A Carrion
Carbon nanotubes (CNTs) are promising nanomaterials for high frequency applications due to their unique physical characteristics. CNTs have a low heat capacity, low intrinsic capacitance, and incredibly fast thermal time constants. They can also exhibit ballistic transport at low bias, for both phonons and electrons, as evident by their fairly long mean free paths. However, despite the great potential they present, the RF behavior of these nanostructures is not completely understood. In order to explore this high frequency regime we studied the microwave (MW) and terahertz (THz) response of individual and bundled single wall nanotube based devices. This thesis is …
Power Mems And Microengines, Alan Epstein, Stephen Senturia, G. Ananthasuresh, Arturo Ayon, Kenneth Breuer, Kuo-Shen Chen, Fredric Ehrich, Gautam Gauba, Reza Ghodssi, C. Groshenry, Stuart Jacobson, Jeffrey Lang, Chuang-Chia Lin, Amit Mehra, José Oscar Mur-Miranda, Steve Nagle, D. Orr, Ed Piekos, Martin Schmidt, Gregory Shirley, Mark Spearing, Choon Tan, Sheng-Yang Tzeng, Ian Waitz
Power Mems And Microengines, Alan Epstein, Stephen Senturia, G. Ananthasuresh, Arturo Ayon, Kenneth Breuer, Kuo-Shen Chen, Fredric Ehrich, Gautam Gauba, Reza Ghodssi, C. Groshenry, Stuart Jacobson, Jeffrey Lang, Chuang-Chia Lin, Amit Mehra, José Oscar Mur-Miranda, Steve Nagle, D. Orr, Ed Piekos, Martin Schmidt, Gregory Shirley, Mark Spearing, Choon Tan, Sheng-Yang Tzeng, Ian Waitz
José Oscar Mur-Miranda
MIT is developing a MEMS-based gas turbine generator. Based on high speed rotating machinery, this 1 cm diameter by 3 mm thick SiC heat engine is designed to produce 10-20 W of electric power while consuming 10 grams/hr of H2. Later versions may produce up to 100 W using hydrocarbon fuels. The combustor is now operating and an 80 W micro-turbine has been fabricated and is being tested. This engine can be considered the first of a new class of MEMS device, power MEMS, which are heat engines operating at power densities similar to those of the best large scale …
A Physical Model For The Kink Effect In Inalas/Ingaas Hemt’S, Mark Somerville, Alexander Ernst, Jesus Del Alamo
A Physical Model For The Kink Effect In Inalas/Ingaas Hemt’S, Mark Somerville, Alexander Ernst, Jesus Del Alamo
Mark Somerville
We present a new model for the the kink effect in InAlAs/InGaAs HEMTs. The model suggests that the kink is due to a threshold voltage shift which arises from a hole pile-up in the extrinsic source and an ensuing charging ofthe surface and/or the buffer-substrate interface. The model captures many of the observed behaviors of the kink, including the kink's dependence on bias, time, temperature, illumination, and device structure. Using the model, we have developed a simple equivalent circuit, which reproduced well the kink's dc characteristics, its time evolution in the nanosecond range, and its dependence on illumination.
Determining Dominant Breakdown Mechanisms In Inp Hemts, Mark Somerville, Chris Putnam, Jesus Del Alamo
Determining Dominant Breakdown Mechanisms In Inp Hemts, Mark Somerville, Chris Putnam, Jesus Del Alamo
Mark Somerville
We present a new technique for determining the dominant breakdown mechanism in InAlAs-InGaAs high-electron mobility transistors. By exploiting both the temperature dependence and the bias dependence of different physical mechanisms, we are able to discriminate impact ionization gate current from tunneling and thermionic field emission gate current in these devices. Our results suggest that the doping level of the supply layers plays a key role in determining the relative importance of these two effects.
Strained Si On Insulator Technology: From Materials To Devices, T. Langdo, M. Currie, Z.-Y. Cheng, J. Fiorenza, M. Erdtmann, G. Braithwaite, C. Leitz, C. Vineis, J. Carlin, A. Lochtefeld, M. Bulsara, Isaac Lauer, Dimitri Antoniadis, Mark Somerville
Strained Si On Insulator Technology: From Materials To Devices, T. Langdo, M. Currie, Z.-Y. Cheng, J. Fiorenza, M. Erdtmann, G. Braithwaite, C. Leitz, C. Vineis, J. Carlin, A. Lochtefeld, M. Bulsara, Isaac Lauer, Dimitri Antoniadis, Mark Somerville
Mark Somerville
SiGe-free strained Si on insulator (SSOI) is a new material system that combines the carrier transport advantages of strained Si with the reduced capacitance and improved scalability of thin film silicon on insulator (SOI). We demonstrate fabrication of 20% Ge equivalent strain level SSOI substrates with Si thicknesses of 100 and 400 Å by hydrogen-induced layer transfer of strained Si layers from high quality graded SiGe virtual substrates. The substrate properties are excellent: wafer scale strained Si film thickness uniformities are better than 8%, strained Si surface roughnesses are better than 0.5 nm RMS, and robust tensile strain levels are …
Floating-Gate Devices: They Are Not Just For Digital Memories Anymore, Paul Hasler, Bradley Minch, Chris Diorio
Floating-Gate Devices: They Are Not Just For Digital Memories Anymore, Paul Hasler, Bradley Minch, Chris Diorio
Bradley Minch
Since the first reported floating-gate structure in 1967, floating-gate transistors have been used widely to store digital information for long periods in structures such as EPROMs and EEPROMs. Recently floating-gate devices have found applications as analog memories, analog and digital circuit elements, and adaptive processing elements. Floating-gate devices have found commerical applications, e.g. ISD, for long-term non-volatile information storage devices for analog applications. The focus of floating-gate devices has been towards fabrication in standard CMOS processes, as opposed to the specialized processes for fabricating digital non-volatile memories. Floating-gate circuits can be designed at any or all of three levels: analog …
A Floating-Gate Technology For Digital Cmos Processes, Bradley Minch, Paul Hasler
A Floating-Gate Technology For Digital Cmos Processes, Bradley Minch, Paul Hasler
Bradley Minch
We discuss the possibility of developing high-quality floating-gate memories and circuits in digital CMOS technologies that have only one layer of polysilicon. Here, the primary concern is whether or not we can get adequate control-gate linearity from MOS capacitors. We employ two experimental procedures to address this issue and find acceptable floating-gate circuit behaviour with MOS capacitors. First, we simultaneously characterize an MOS capacitor and a linear capacitor; the experimental data show that MOS capacitors behave similarly to linear capacitors over a finite, but usable range. Second, we characterize two typical floating-gateMOS circuit primitives, a floating-gate amplifier and a multiple-input …
Adaptive Circuits Using Pfet Floating-Gate Devices, Paul Hasler, Bradley Minch, Chris Diorio
Adaptive Circuits Using Pfet Floating-Gate Devices, Paul Hasler, Bradley Minch, Chris Diorio
Bradley Minch
In this paper, we describe our floating-gate pFET device, with its many circuit applications and supporting experimental measurements. We developed these devices in standard double-poly CMOS technologies by utilizing many effects inherent in these processes. We add floating-gate charge by electron tunneling, and we remove floating-gate charge by hot-electron injection. With this floating-gate technology, we cannot only build analog EEPROMs, we can also implement adaptation and learning when we consider floating-gate devices to be circuit elements with important time-domain dynamics. We start by discussing non-adaptive properties of floating-gate devices and we present two representative non-adaptive applications. First, we discuss using …
Medic: A Legged Millirobot Utilizing Novel Obstacle Traversal, Nicholas Kohut, Aaron Hoover, Kevin Ma, Stanley Baek, Ronald Fearing
Medic: A Legged Millirobot Utilizing Novel Obstacle Traversal, Nicholas Kohut, Aaron Hoover, Kevin Ma, Stanley Baek, Ronald Fearing
Aaron M. Hoover
This work presents the design, fabrication, capabilities, and obstacle traversal mechanics of MEDIC (MillirobotEnabled Diagnostic of Integrated Circuits), a small legged robot able to overcome a varied array of obstacles. MEDIC features a hull that keeps its body in contact with the ground at all times, and uses only four actuators to move forward, turn, mount obstacles, and move in reverse. The chassis is fabricated using a Smart Composite Microstructures (SCM) approach and the robot is actuated by coiled Shape Memory Alloy (SMA). MEDIC also features a camera which will be useful for navigation in the future.
An Autozeroing Floating-Gate Amplifier, Paul Hasler, Bradley Minch, Chris Diorio
An Autozeroing Floating-Gate Amplifier, Paul Hasler, Bradley Minch, Chris Diorio
Bradley Minch
We have developed a bandpass floating-gate amplifier that uses tunneling and pFET hot-electron injection to set its dc operating point adaptively. Because the hot-electron injection is an inherent part of the pFET's behavior, we obtain this adaptation with no additional circuitry. Because the gate currents are small, the circuit exhibits a high-pass characteristic with a cutoff frequency less than 1 Hz. The high-frequency cutoff is controlled electronically, as is done in continuous-time filters. We have derived analytical models that completely characterize the amplifier and that are in good agreement with experimental data for a wide range of operating conditions and …
Multiple-Input Translinear Element Networks, Bradley Minch, Paul Hasler, Chris Diorio
Multiple-Input Translinear Element Networks, Bradley Minch, Paul Hasler, Chris Diorio
Bradley Minch
We describe a new class of translinear circuits that accurately embody product-of-power-law relationships in the current signal domain. We call such circuits multiple-input translinear element (MITE) networks. A MITE is a circuit element, which we defined recently that produces an output current that is exponential in a weighted sum of its input voltages. We describe intuitively the basic operation of MITE networks and provide a systematic matrix technique for analyzing the nonlinear relationships implemented by any given circuit. We also show experimental data from three MITE networks that were fabricated in a 1.2-μm double-poly CMOS process.
Synthesis Of Dynamic Multiple-Input Translinear Element Networks, Bradley Minch
Synthesis Of Dynamic Multiple-Input Translinear Element Networks, Bradley Minch
Bradley Minch
In this paper, the author discusses an approach to the synthesis of dynamic translinear circuits built from multiple-input translation elements (MITEs). In this method, we realize separately the basic static nonlinearities and dynamic signal-processing functions that when cascaded together, form the system that one wishes to construct. The circuit is then simplified systematically through local transformations that do not alter the behavior of the system. The author illustrates the method by synthesizing a simple nonlinear dynamical system, an RMS-DC converter.
Synthesis Of A Translinear Analog Adaptive Filter, Eric Mcdonald, Bradley Minch
Synthesis Of A Translinear Analog Adaptive Filter, Eric Mcdonald, Bradley Minch
Bradley Minch
In this paper, we present a methodology for synthesizing analog systems using a class of circuits called dynamic translinear circuits. We illustrate this method by synthesizing part of a Least-Mean-Squares (LMS) adaptation algorithm used in an analog adaptive filter. We present preliminary experimental results from a chip fabricated ina 0.5-μm double-poly CMOS process.
Inverting The Bipolar Differential Pair For Low-Voltage Applications, Bradley Minch
Inverting The Bipolar Differential Pair For Low-Voltage Applications, Bradley Minch
Bradley Minch
In this paper, the author presents a new bipolar differential transconductor that functions just like an emitter-degenerated differential pair, except for the following: it operates on a low power supply; it has a rail-to-rail common-mode input-voltage range; permits a wide output-voltage swing; has a transconductance gain that is nearly constant with the common-mode input voltage; and requires only n-p-n transistors in the signal path. We describe intuitively how the circuit functions and provide DC measurements from a prototype circuit, breadboarded from a quad TPQ3904 and a thick-film resistor array demonstrating proper operation on a single-ended 1.2-V power supply.
Synthesis Of Multiple-Input Translinear Element Log-Domain Filters, Bradley Minch
Synthesis Of Multiple-Input Translinear Element Log-Domain Filters, Bradley Minch
Bradley Minch
I present a simple procedure for synthesizing multiple-input translinear element (MITE) log-domain filters from state-space descriptions. We can obtain such state-space descriptions from a variety of sources, and the procedure that I describe can be utilized regardless of the source of the description. We can often derive such descriptions conveniently from already extant filters that have been previously implemented using a different class of filters. I shall illustrate the synthesis procedure by deriving two simple MITE log-domain filters from single-ended voltage-mode OTA-C filter prototypes-I synthesize both a first-order lowpass filter and a fully tunable second-order lowpass filter.
A Second-Order Section Built From Autozeroing Floating-Gate Amplifiers, Paul Hasler, Theron Stanford, Bradley Minch
A Second-Order Section Built From Autozeroing Floating-Gate Amplifiers, Paul Hasler, Theron Stanford, Bradley Minch
Bradley Minch
We introduce the autozeroing floating-gate (AFGA) secondorder section. We built this second-order filter where the corner frequency and Q are electronically tunable based on a classic filter topology and principles of operational transconductance amplifiers. We built this second order filter using three AFGAs—our floating-gate amplifier that sets its operating point by the interaction of hot-electron injection and electron tunneling.
A Low-Voltage Mos Cascode Bias Circuit For All Current Levels, Bradley Minch
A Low-Voltage Mos Cascode Bias Circuit For All Current Levels, Bradley Minch
Bradley Minch
In this paper, the author describes a simple low-voltage MOS cascode bias circuit that functions well at all current levels, ranging from weak inversion to strong inversion. He describes an approach to defining the onset of saturation that is generally useful from a bias-circuit design viewpoint and explains specifically how it was used in designing the low-voltage cascode bias circuit. The author discusses an efficient strategy for laying out the cell in the full-stacked style. He also presents experimental results from a version of the bias circuit that was fabricated in a 1.2-μm CMOS process.
Multi-Level Simulation Of A Translinear Analog Adaptive Filter, Eric Mcdonald, Bradley Minch
Multi-Level Simulation Of A Translinear Analog Adaptive Filter, Eric Mcdonald, Bradley Minch
Bradley Minch
In this paper, we briefly discuss a methodology for synthesizing analog systems from a high-level behavioral specification using a class of circuits called dynamic translinear circuits. We illustrate this method by synthesizing a Least-Mean-Square (LMS) adaptation algorithm used in an analog adaptive filter. The resulting systems can be simulated at various levels of abstraction during the design phase. As an example, we presentsimulation results from a four-tap analog adaptive filter simulated using Matlab and SPICE.
A Folded Floating-Gate Differential Pair For Low-Voltage Applications, Bradley Minch
A Folded Floating-Gate Differential Pair For Low-Voltage Applications, Bradley Minch
Bradley Minch
The author presents a new folded differential pair topology that is suitable for low-voltage applications. The new differential pair is made from floating-gate MOS (FGMOS) transistors and simultaneously provides a rail-to-rail common-mode input voltage range with a high rejection of the common-mode input voltage by keeping the sum of the two output currents fixed. Moreover, when biased in weak or moderate inversion, the allowable output voltage swing is also almost from rail-to-rail. The author discusses the operation of the circuit and some of the trade-offs involved in its design. He also shows experimental measurements from a version of the circuit, …
A Transistor-Only Circuit Model Of The Autozeroing Floating-Gate Amplifier, Paul Hasler, Matt Kucic, Bradley Minch
A Transistor-Only Circuit Model Of The Autozeroing Floating-Gate Amplifier, Paul Hasler, Matt Kucic, Bradley Minch
Bradley Minch
We developed an transistor-only version of our autozeroing floating-gate amplifier (AFGA). We use a subthreshold transistor to model the behavior of an electron-tunneling device, and we use another subthreshold transistor to model the behavior of pFET hot-electron injection. We have derived analytical models that completely characterize the amplifier and that are in good agreement with experimental data. This circuit is a bandpass filter, and behaves similarly to the AFGA with different operating parameters. Both the low-frequency and high-frequency cutoffs are controlled electronically, as is done in continuous-time filters. This circuit has a low-frequency cutoff at frequencies above 1 Hz, and …
A Simple Way To Extend The Common-Mode Input-Voltage Range Of The Mos Differential Pair, Bradley Minch
A Simple Way To Extend The Common-Mode Input-Voltage Range Of The Mos Differential Pair, Bradley Minch
Bradley Minch
In this paper, we describe a simple technique involving indirect negative feedback that extends the useable common-mode input-voltage range of the MOS differential pair by a saturation voltage. In this method, we use a replica differential pair to sense when the bias transistor supplying the tail current falls out of saturation. We then set the bias voltage so that the sum of the two differential-pair output currents is equal to the bias current. We present experimental results from a version of the differential pair that was fabricated in a 0.5 μm CMOS process along with a comparison with an identical …
Synthesis Of Mite Log-Domain Filters With Unique Operating Points, Shyam Subramanian, David Anderson, Paul Hasler, Bradley Minch
Synthesis Of Mite Log-Domain Filters With Unique Operating Points, Shyam Subramanian, David Anderson, Paul Hasler, Bradley Minch
Bradley Minch
Practical log-domain filter circuits might have multiple operating points in regions in which the translinear element does not obey the exponential law. In this paper, a method is proposed to implement any filter by a log-domain circuit that necessarily has a unique operating point. Any state-space description of the filter is shown to have an equivalent description that can be implemented by such a circuit. This methodology is applied to the synthesis of multiple-input translinear element (MITE) filters. As an example, shifted-companion-form (SCF) filters are synthesized. Further, it is proved that the resulting filters have a unique operating point.
Low-Voltage Wilson Current Mirrors In Cmos, Bradley Minch
Low-Voltage Wilson Current Mirrors In Cmos, Bradley Minch
Bradley Minch
In this paper, we describe three simple low-voltage CMOS analogs of the Wilson current mirror that function well at all current levels, ranging from weak inversion to strong inversion. Each of these current mirrors can operate on a low power-supply voltage of a diode drop plus two saturation voltages and features a wide output-voltage swing with a cascode-type incremental output impedance. Two of the circuits requires an input voltage of a diode drop plus a saturation voltage while the third one features a low input voltage of a saturation voltage. We present experimental results from versions of these three current …
Floating-Gate Techniques For Assessing Mismatch, Bradley Minch
Floating-Gate Techniques For Assessing Mismatch, Bradley Minch
Bradley Minch
I discuss the importance of capacitor matching in the context of using charge stored on floating-gate MOS (FGMOS) transistors to compensate for transistor mismatch in analog circuits. I describe a simple technique that only involves static measurements for assessing the relative mismatch between capacitors. I also show experimental measurements of capacitor mismatch for small capacitors fabricated in 1.2-μm and 0.35-μm double-poly it n-well CMOS process that are commonly available.
A Simple Class-Ab Transconductor In Cmos, Bradley Minch
A Simple Class-Ab Transconductor In Cmos, Bradley Minch
Bradley Minch
In this paper, we present a simple class-AB CMOS transconductor, which is based on Delbriick's bump/antibump circuit, whose differential output current is an expansive nonlinear function of its differential-mode input voltage. We describe the operation of the new transconductor qualitatively and derive an analytical model of its output currents from the Enz-Krummenacher-Vittoz (EKV) model of the MOS transistor. We also provide experimental measurements of the DC transfer characteristics of a version of the circuit that was fabricated in a 0.5-mumCMOS process through MOSIS.
Evolution Of A Folded Floating-Gate Differential Pair, Bradley Minch
Evolution Of A Folded Floating-Gate Differential Pair, Bradley Minch
Bradley Minch
The author presents a folded floating-gate MOS (FGMOS) differential pair circuit that is capable of simultaneously providing a rail-to-rail common-mode input voltage range and a rail-to-rail output voltage swing with a low power-supply voltage. In this configuration, the voltage drop across the bias current source is folded up into the same range over which the output voltages swing, facilitating low-voltage operation. The floating-gate charge can be used to trim out the offset voltage of the differential pair and to reduce the required power-supply voltage for a given bias current level. The author provides both a qualitative description of how the …
Single-Event Charge Enhancement In Soi Devices, David Kerns, Sherra Kerns, L Massengill, M Alles
Single-Event Charge Enhancement In Soi Devices, David Kerns, Sherra Kerns, L Massengill, M Alles
Sherra E. Kerns
Studies are presented of single-particle ion effects in body-tied CMOS/silicon-on-insulator (SOI) devices. It is shown that two mechanisms can contribute to SOI soft-error rates: a direct ion-induced photocurrent and a local lateral bipolar current. The total amount of charge collected is sensitive to the relative locations of the ion strike and the body-to-source tie.
Single-Event Charge Enhancement In Soi Devices, David Kerns, Sherra Kerns, L Massengill, M Alles
Single-Event Charge Enhancement In Soi Devices, David Kerns, Sherra Kerns, L Massengill, M Alles
David V. Kerns
Studies are presented of single-particle ion effects in body-tied CMOS/silicon-on-insulator (SOI) devices. It is shown that two mechanisms can contribute to SOI soft-error rates: a direct ion-induced photocurrent and a local lateral bipolar current. The total amount of charge collected is sensitive to the relative locations of the ion strike and the body-to-source tie.
A Parallel Circuit Model For Multi-State Resistive-Switching Random Access Memory, Albert Chen
A Parallel Circuit Model For Multi-State Resistive-Switching Random Access Memory, Albert Chen
Albert B Chen
Large, rapidly growing literature is available on bipolar resistive-switching random access memories (RRAM) made of myriad of simple and advanced materials. Many of them exhibit similar resistance switching behavior but, until now, no unifying model can allow quantification of their voltage and time responses. Using a simple parallel circuit model, these responses of a newly discovered RRAM made of a thin-film random material are successfully analyzed. The analysis clearly reveals a large population of intermediate states with remarkably similar switching characteristics. Such modeling framework based on simple circuit constructs also appears applicable to several RRAM made of other materials. This …