Improved Noise Performance Research Articles

Fully Digital Hysteretic Modulator for DC–DC Switching Converters

This paper presents an alternative modulation approach for digitally controlled DC-DC switching converters, which exploits the natural jittering activity of a digital hysteretic feedback loop in order to provide an effective increase in resolution. The proposed structure replaces conventional high-resolution digital pulse-width modulators (DPWM) or sigma-delta based (ΣΔ-DPWM) solutions with a single, fully-digital block featuring reduced complexity, high resolution, and improved noise performance and small-signal dynamic characteristics, enabling the design of accurate, high-bandwidth digital feedback loops with minimum hardware resources. A stochastic modeling approach is developed for the proposed structure, which allows the derivation of a simple and effective switching frequency control criterion. Analysis, simulation and experimental tests are shown to validate the properties of the proposed digital hysteretic modulator.

Flying start for biofuels

Air travel is something that modern travellers have taken for granted, but in the age of global warming it is coming under increasing pressure to clean up its act. The industry has been vehement in its defence of its environmental credentials, but despite that assertion it is Investing heavily in new technologies that will continue to reduce its carbon emissions. These improvements broadly fall within three areas fuel, engines and aircraft. Each new generation of aircraft and engine offers improved fuel efficiency, fewer emissions and Improved noise performance, but it is in the area fuels, or more accurately biofuels, that the chief breakthroughs are expected.

Towards ultrasensitive optical links enabled by low-noise phase-sensitive amplifiers

Optical phase-sensitive amplifiers (PSAs) are known to be capable, in principle, of realizing noiseless amplification and improving the signal-to-noise-ratio of optical links by 3 dB compared to conventional, phase-insensitively amplified links. However, current state-of-the-art PSAs are still far from being practical, lacking e.g. significant noise performance improvement, broadband gain and modulation-format transparency. Here we demonstrate experimentally, for the first time, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation-format independence, and nearly 6-dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links. The PSA has a record-low 1.1-dB NF, and can be extended to work with multiple wavelength channels with modest system complexity. This concept can also be realized in other materials with third-order nonlinearities, and is useful in any attenuation-limited optical link.

Improvement of Noise Performance in Phased-Array Receivers

This paper presents a new analytical approach and experimental verification for the improvement of noise performance in phased-array receivers. For analysis purposes, a multi-channel array system is converted into an equivalent single-channel system, such that the two presents the identical signal and noise powers at the output, respectively. We define an effective gain, noise figure, and signal-to-noise ratio in the equivalent system. Through the proposed approach, the noise performance of the array receiver is analyzed in a general and straightforward manner and then compared to that of each individual array channel. In addition, the phase noise of the array system is analyzed in a rigorous manner, showing its effective reduction by a factor of the array size. The predicted improvement of the noise performance is experimentally confirmed with a CMOS integrated phased-array receiver.

Low‐voltage bulk‐driven input stage with improved transconductance

AbstractA low‐voltage input stage constructed from bulk‐driven PMOS transistors is proposed in this paper. It is based on a partial positive feedback and offers significant improvement of both input transconductance and noise performance compared with those achieved by the corresponding already published bulk‐driven structures. The proposed input stage offers also extended input common‐mode range under low supply voltage in relevant to a gate‐driven differential pair. A differential amplifier based on the proposed input stage is also designed, which includes an auxiliary amplifier for the output common‐mode voltage stabilization and a latch‐up protection circuitry. Both input stage and amplifier circuits were implemented with 1 V supply voltage using standard 0.35µm CMOS process, and their performance evaluation gave very promising results. Copyright © 2010 John Wiley & Sons, Ltd.

Design Exploration of Helicopter Blades for HSI Noise and Aerodynamic Performance

In this study, the high-speed impulsive (HSI) noise and aerodynamic performance of helicopter blades were improved using multi-objective design exploration (MODE) comprised of multi-objective shape optimization and data mining. To broaden the design space of the problem, geometry definitions with a high degree of freedom were adopted. As a result, remarkable improvements in both HSI noise and aerodynamic performance were achieved. For data mining, analysis of variance (ANOVA) and self-organizing map (SOM) were used to extract design knowledge of the helicopter blades. The results indicated that tip chord length and blade twist are important factors for HSI noise and aerodynamic performance, respectively. Based on the design knowledge obtained from data mining, an additional design variable (twist) was introduced. The solutions obtained from the shape optimization using variable twist showed better blade loading performance than that from shape optimization using fixed twist.

Constraining the initial phase in water–fat separation

An algorithm is described for use in chemical shift-based water–fat separation to constrain the phase of both species to be equal at an echo time of zero. This constraint is physically reasonable since the initial phase should be a property of the excitation pulse and receiver coil only. The advantages of phase constrained water–fat separation, namely, improved noise performance and/or reduced data requirements (fewer echos), are demonstrated in simulations and experiments.

A Bandwidth Enhanced Transimpedance Amplifier with Improved Noise Performance

A new TIA topology with enhanced bandwidth is presented in this paper. By adding an extra capacitive feedback loop to the resistive feedback TIA, bandwidth and sensitivity are increased without sacrificing the low power consumption. It is shown that this topology is superior to the self-compensated TIA when the photodiode is integrated on the same die as the TIA. An implementation is presented that boosts the bandwidth by a factor of 9 and reduces the noise by a factor of 4.2 for a photodiode capacitance of 106 pF, the parasitic capacitance of a POF-compliant 1 mm integrated photodiode in 130 nm CMOS.

A new method to combine 3D reconstruction volumes for multiple parallel circular cone beam orbits

This article presents a new reconstruction method for 3D imaging using a multiple 360 degrees circular orbit cone beam CT system, specifically a way to combine 3D volumes reconstructed with each orbit. The main goal is to improve the noise performance in the combined image while avoiding cone beam artifacts. The cone beam projection data of each orbit are reconstructed using the FDK algorithm. When at least a portion of the total volume can be reconstructed by more than one source, the proposed combination method combines these overlap regions using weighted averaging in frequency space. The local exactness and the noise performance of the combination method were tested with computer simulations of a Defrise phantom, a FORBILD head phantom, and uniform noise in the raw data. A noiseless simulation showed that the local exactness of the reconstructed volume from the source with the smallest tilt angle was preserved in the combined image. A noise simulation demonstrated that the combination method improved the noise performance compared to a single orbit reconstruction. In CT systems which have overlap volumes that can be reconstructed with data from more than one orbit and in which the spatial frequency content of each reconstruction can be calculated, the proposed method offers improved noise performance while keeping the local exactness of data from the source with the smallest tilt angle.

One-chip electronic detection of DNA hybridization using precision impedance-based CMOS array sensor

This paper describes a label-free and fully electronic detection method of DNA hybridization, which is achieved through the use of a 16 × 8 microarray sensor in conjunction with a new type of impedance spectroscopy constructed with standard complementary metal-oxide-semiconductor (CMOS) technology. The impedance-based method is based on changes in the reactive capacitance and the charge-transfer resistance after hybridization with complementary DNA targets. In previously published label-free techniques, the measured capacitance presented unstable capacitive properties due to the parallel resistance that is not infinite and can cause a leakage by discharging the charge on the capacitor. This paper presents an impedance extraction method that uses excitation by triangular wave voltage, which enables a reliable measurement of both C and R producing a highly sensitive sensor with a stable operation independent of external variables. The system was fabricated in an industrial 0.35-μm 4-metal 2-poly CMOS process, integrating working electrodes and readout electronics into one chip. The integrated readout, which uses a parasitic insensitive integrator, achieves an enlarged detection range and improved noise performance. The maximum average relative variations of C and R are 31.5% and 68.6%, respectively, after hybridization with a 1 μM target DNA. The proposed sensor allows quantitative evaluation of the molecule densities on the chip with distinguishable variation in the impedance. This fully electronic microsystem has great potential for use with bioanalytical tools and point-of-care diagnosis.

Improvement on the noise performance of InAs-based HEMTs with gate sinking technology

Improvement on the RF and noise performance for 80 nm InAs/In 0.7Ga 0.3As high-electron mobility transistor (HEMT) through gate sinking technology is presented. After gate sinking at 250 °C for 3 min, the device exhibited a high transconductance of 1900 mS/mm at a drain bias of 0.5 V with 1066 mA/mm drain–source saturation current. A current-gain cutoff frequency ( f T ) of 113 GHz and a maximum oscillation frequency ( f max) of 110 GHz were achieved at extremely low drain bias of 0.1 V. The 0.08 × 40 μm 2 device with gate sinking demonstrated 0.82 dB minimum noise figure and 14 dB associated gain at 17 GHz with only 1.14 mW DC power consumption. Significant improvement in RF and noise performance was mainly attributed to the reduction of gate-to-channel distance together with the parasitic source resistance through gate sinking technology.

하나의 원형 편파 안테나와 PLL을 이용하여 소형이면서도 개선된 잡음 성능을 갖는 2.4 GHz 바이오 레이더 시스템

In this paper, we design a 2.4 GHz bio-radar system that can detect human heartbeat and respiration signals with small size and improved noise performance using single circular-polarized antenna and phase-locked loop. The demonstrated bio-radar system consists of single circular-polarized antenna with hybrid, low-noise amplifier, power amplifier, voltage-controlled oscillator with phase-locked loop circuits, quadrature demodulator and analog circuits. To realize compact size, the printed annular ring stacked microstrip antenna is integrated on the transceiver circuits, so its dimension is just . Also, to improve signal-to-noise-ratio performance by phase noise due to transmitter leakage signal, the phase-locked loop circuit is used. The measured results show that the heart rate and respiration accuracy was found to be very high for the distance of 50 cm without the additional digital signal processing.

A Chopper Current-Feedback Instrumentation Amplifier With a 1 mHz <formula formulatype="inline"><tex Notation="TeX">$1/f$</tex> </formula> Noise Corner and an AC-Coupled Ripple Reduction Loop

This paper presents a chopper instrumentation amplifier for interfacing precision thermistor bridges. For high CMRR and DC gain, the amplifier employs a three-stage current-feedback topology with nested-Miller compensation. By chopping both the input and intermediate stages of the amplifier, a 1 mHz 1/f noise corner was achieved at an input-referred noise power spectral density (PSD) of 15 nV/?Hz. To reduce chopper ripple, the amplifier employs a continuous-time AC-coupled ripple reduction loop. Due to its continuous-time nature, the loop causes no noise folding to DC and hence offers improved noise performance over auto-zeroed amplifiers. The loop reduces chopper ripple by more than 60 dB, to levels below the amplifier's own input-referred noise. Furthermore, a maximum input referred offset of 5 ? V and a CMRR greater than 120 dB were measured at a supply current of 230 ?A at 5 V.

Comprehensive Study of InAlAs/InGaAs Metamorphic High Electron Mobility Transistor with Oxidized InAlAs Gate

A comprehensive study of an InAlAs/InGaAs metal-oxide-semiconductor metamorphic high electron mobility transistor (MOS-MHEMT) with liquid-phase-oxidized InAlAs as gate insulators has been demonstrated. The MOS-MHEMT exhibits a lower leakage current density with suppressed impact ionization effect, better microwave characteristics, and improved noise performance in comparison with the conventional Schottky gate metamorphic high electron mobility transistor. The unity current gain cutoff and maximum oscillation frequencies are 29.7 and 58.8 GHz, respectively, for MOS-MHEMT. Also, the large-signal power gain, saturated output power, and maximum power-added efficiency at 2.4 GHz are 18.66 dB, 14.32 dBm, and 34%, respectively. The introduced liquid phase oxidation does not degrade the device radio-frequency performance, which is a good candidate for high speed applications.

Noise performance in AlGaN/GaN HEMTs under high drain bias

The advent of fully integrated GaN PA-LNA circuits makes it meaningful to investigate the noise performance under high drain bias. However, noise performance of AlGaN/GaN HEMTs under high bias has not received worldwide attention in theoretical studies due to its complicated mechanisms. The noise value is moderately higher and its rate of increase is fast with increasing high voltage. In this paper, several possible mechanisms are proposed to be responsible for it. Impact ionization under high electric field incurs great fluctuation of carrier density, which increases the drain diffusion noise. Besides, higher gate leakage current related shot noise and a more severe self-heating effect are also contributors to the noise increase at high bias. Analysis from macroscopic and microscopic perspectives can help us to design new device structures to improve noise performance of AlGaN/GaN HEMTs under high bias.

A new class of floating-point data formats with applications to 16-bit digital-signal processing systems

Sixteen-bit, programmable, digital-signal processors suffer from inadequate dynamic range and noise performance due in part to the use of standard data formats with few bits available for numeric precision. A solution to this problem is developed that involves the use of irregular data formats. A new class of irregular floating-point formats is developed. A specific format is derived from this class that provides greater dynamic range and improved noise performance for 16-bit DSP applications. An experiment with one of the new formats is conducted and analyzed, and improved performance is verified. The importance of our work and its potential applications are discussed.

Experimental Investigation of RF Noise Performance Improvement in Graded-Channel MOSFETs

In this paper, measured RF noise performance of graded-channel metal-oxide-semiconductor (MOS) transistors (GCMOS - also named laterally asymmetric channel transistors) shows impressive reduction in minimum noise figure ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NF</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) as compared to classical MOSFET transistors (with the same gate length <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Lg</i> = 0.5 mum). The reason is proven to be because of the higher noise correlation coefficient ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> ). GCMOS also shows lower sensitivity to extrinsic thermal noise as compared to classical MOSFET. Moreover, it is demonstrated that the use of 0.5- mum-gate-length GCMOS gives a competitive RF noise performance as compared to 0.25-mum-gate-length classical nMOS transistors.

P‐44: Adaptive Threshold Overdriving Scheme for Improved LCD‐TV Noise Performance

AbstractThis paper proposes an adaptive threshold overdriving algorithm to avoid exacerbating noise problems in LCD‐TVs. In conventional LCD‐TVs, video image noise is boosted by the timing controller's overdrive function, resulting in harsh noise as perceived by the human visual system. Various gray data and noise levels have been analyzed, and the conditions which generate the boosted noise have been extracted and applied to a new algorithm to adjust overdrive threshold criteria according to the input images. The new overdriving scheme shows greatly improved noise performance compared to conventional fixed threshold schemes.

A 70 dB MTPR Integrated Programmable Gain/Bandwidth Fourth-Order Chebyshev High-Pass Filter for ADSL/VDSL Receivers in 65 nm CMOS

This paper presents a fourth-order Chebyshev high-pass filter (HPF) in 65 nm CMOS process with programmable gain and corner frequency to support ADSL and 5/6 band VDSL applications. The HPF improves noise performance by reducing the number of cascaded stages in the receive path and using capacitive feedback to minimize the total number of resistors in the filter. The choice of filter architecture and the optimization of the feedback structure reduce noise for a given total filter capacitance. It achieves a 70 dB MTPR and -161 dBm/Hz (2.8 nV/radicHz ) input-referred noise for ADSL mode. An IM3 of -80 dBc at 10 MHz is measured for VDSL mode. The HPF consumes 236 mW from 2.5 V power supply with active area of 3 mm2.

Cryogenic SiGe ASICs for readout and multiplexing of superconducting detector arrays

This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuits (ASICs: Application Specific Integrated Circuits). We have designed successively two ASICs in standard BiCMOS SiGe 0.35 μm technology that have proved to be operating at cryogenic temperatures. The main functions of these circuits are the readout and the multiplexing of TES/SQUID arrays. We report the cryogenic operation of a first ASIC version dedicated to the readout of a 2 × 4 pixel demonstrator array. We particularly emphasize on the development and the test phases of an ultra low white noise (0.2 nV/sqrtHz) cryogenic amplifier designed with two multiplexed inputs. The cryogenic SiGe amplifier coupled to a SQUID in a FLL operating at 4.2 K is also presented. We finally report on the development of a second version of this circuit to readout a 3 × 8 detectors array with improved noise performances and upgraded functionalities.