Noise In Diodes Research Articles

Radiometer Calibration Using Colocated GPS Radio Occultation Measurements

We present a new high-fidelity method of calibrating a cross-track scanning microwave radiometer using Global Positioning System (GPS) radio occultation (GPSRO) measurements. The radiometer and GPSRO receiver periodically observe the same volume of atmosphere near the Earth's limb, and these overlapping measurements are used to calibrate the radiometer. Performance analyses show that absolute calibration accuracy better than 0.25 K is achievable for temperature sounding channels in the 50-60-GHz band for a total-power radiometer using a weakly coupled noise diode for frequent calibration and proximal GPSRO measurements for infrequent (approximately daily) calibration. The method requires GPSRO penetration depth only down to the stratosphere, thus permitting the use of a relatively small GPS antenna. Furthermore, only coarse spacecraft angular knowledge (approximately one degree rms) is required for the technique, as more precise angular knowledge can be retrieved directly from the combined radiometer and GPSRO data, assuming that the radiometer angular sampling is uniform. These features make the technique particularly well suited for implementation on a low-cost CubeSat hosting both radiometer and GPSRO receiver systems on the same spacecraft. We describe a validation platform for this calibration method, the Microwave Radiometer Technology Acceleration (MiRaTA) CubeSat, currently in development for the National Aeronautics and Space Administration (NASA) Earth Science Technology Office. MiRaTA will fly a multiband radiometer and the Compact TEC/Atmosphere GPS Sensor in 2015.

Observation of Shot Noise in Phosphorescent Organic Light-Emitting Diodes

We employed a cross correlation method to study current noise in phosphorescent organic light-emitting diodes. The noise spectra revealed two frequency-dependent components. The first component displays \({1/f}^{1.3}\) dependence and correlates with the light emission of the devices. The second component is dominant in low-bias regime and varies as \({1/f}^{2.8}\) . It is attributed to inhomogeneities of the barrier height at metal/organic interface. The extended bandwidth of the method allowed us to resolve frequency-independent term in the noise power, which was dominated by the shot noise. At bias voltages from 2.4 to 2.5 V, the Fano factor characterizing shot noise is close to one, confirming that the electron transport in this regime is limited by the carrier injection across metal/organic interface. At higher biases, in the regime where the transport is bulk-limited, the Fano factors drops to 0.5. Possible physical reasons for such behavior are discussed.

1/f noise in forward biased high voltage 4H-SiC Schottky diodes

The 1/f noise has been investigated for the first time at 300 and 77K in high-quality 4H-SiC Schottky diodes. It is shown that, at 77K, the dependence of the spectral noise density on current, SI(I), differs fundamentally between the cases of the current flowing through the main part of the diode with a comparatively high barrier and the current flowing through the nano-sized patches with a comparatively low barrier.

Microwave radiometer to retrieve temperature profiles from the surface to the stratopause

Abstract. TEMPERA (TEMPERature RAdiometer) is a new ground-based radiometer which measures in a frequency range from 51–57 GHz radiation emitted by the atmosphere. With this instrument it is possible to measure temperature profiles from ground to about 50 km. This is the first ground-based instrument with the capability to retrieve temperature profiles simultaneously for the troposphere and stratosphere. The measurement is done with a filterbank in combination with a digital fast Fourier transform spectrometer. A hot load and a noise diode are used as stable calibration sources. The optics consist of an off-axis parabolic mirror to collect the sky radiation. Due to the Zeeman effect on the emission lines used, the maximum height for the temperature retrieval is about 50 km. The effect is apparent in the measured spectra. The performance of TEMPERA is validated by comparison with nearby radiosonde and satellite data from the Microwave Limb Sounder on the Aura satellite. In this paper we present the design and measurement method of the instrument followed by a description of the retrieval method, together with a validation of TEMPERA data over its first year, 2012.

Noise characteristics of InAs/GaSb superlattice infrared photodiodes

AbstractA sophisticated noise measurement setup employing a switching unit to measure statistically relevant numbers of InAs/GaSb superlattice photodiodes has been developed. The noise current resolution limit of 20 fA Hz‐1/2 enables the characterization of focal plane array‐sized InAs/GaSb superlattice homojunction photodiodes for the long‐wavelength infrared at 77 K. To resolve midwavelength infrared photodiodes a junction area of about (400 µm)2 is required. Without switching unit and by using a dedicated low noise amplifier, noise currents down to 2 fA Hz‐1/2 can be achieved, allowing the noise characterization of mid‐wavelength photodiodes with smaller junction areas. With this setup long‐wavelength and mid‐wavelength InAs/GaSb superlattice photodiodes, with generation‐recombination limited dark current behavior, are investigated at 77 K. The measured diode noise follows the theoretically predicted shot noise level within the white noise part of the spectra. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Noise Source Module for In-Situ Noise Figure Measurements From DC to 50 GHz at Cryogenic Temperatures

This letter presents the design and performance of a noise source module for in-situ noise temperature measurements at cryogenic temperatures. The noise source module operates from DC up to 50 GHz and is suitable for measurements of noise temperatures as low as a few Kelvin, achieving a measurement accuracy of about $\pm {1.2}~{\rm K}$ . The GaAs MMIC used in the module includes a well matched 50 $\Omega$ termination with better than 20 dB return loss, a heating element and an on-chip temperature sensor, hence the noise source module can directly be connected to the device under test (DUT) with no additional elements or transitions needed. The measurement can then be taken with standard noise measurement equipment. Noise temperatures as low as 13 K have been measured in Ka-band with this device. Due to the ease of use, the good matching, the extraordinary bandwidth and the less involved calibration technique, the noise source module outperforms the conventional measurement setup using a noise diode in conjunction with a cooled attenuator.

Transmission Analysis of OFDM-Based Services Over Line-of-Sight Indoor Infrared Laser Wireless Links

Radio-on-free space optical (RoFSO) communication systems are gaining popularity because of their ability to transmit simultaneously multiple radio frequency signals comprised of various wireless services over FSO links using wavelength division multiplexing technology. We propose a new approach of use of the RoFSO technology for high-speed indoor communication systems and introduce an analytical model for the transmission of orthogonal frequency-division multiplexing-based signals over a line-of-sight link with diverged Gaussian beam. We have analyzed the laser safety restrictions for the proposed system and derived a closed-form bit-error probability, taking into account the ambient noise and laser diode nonlinear distortion. Simulation results are shown and the system performance is discussed.

Theoretical analysis of mode-competition noise in modulated laser diodes and its influence on the noise performance of fibre links

We analyse mode-competition (MC) noise in sinusoidally modulated laser diodes and assess its contribution to the noise performance of directly modulated fibre links. The noise figure (NF) is used to evaluate the noise performance of the link. The present analyses are based on a multimode rate equation model that takes into account both symmetric and asymmetric suppressions of the cross-modal gain. Variations of the MC relative intensity noise of both the total output and the oscillating modes with modulation conditions are investigated. The obtained results show that regardless of the fact that the non-modulated laser oscillates nearly in single-mode or in two-mode hopping, the modulated laser oscillates in single mode when the signal is continuous, and converts into multimode when the signal is pulsing. The contribution of MC noise to the NF of the link increases with an increase in the modulation depth and with a decrease in the modulation frequency, except when the signal has period doubling. This contribution is negligible under high modulation frequencies when the laser signal is continuous and uniform, and is most enhanced (∼53 dB) under low modulation frequencies when the signal is pulsing and superposed with non-uniform relaxation oscillations.

밀리미터파 복사계의 제작

Abstract We have manufactured a close range Dicke type radiometer which consists of two stage low noise amplifier and diode detector. Frequency range of this system is 35 GHz. And this is used for studying temperature calibration on specific objects. We have present millimeter-wave radiometer's thermal calibration method and its characteristics. From absolute temperature 299K to 309K, in proportion to increase temperature, output voltages are linearly increased. In this case, undefined objects can be measured thermal noise temperature relatively. Overall from absolute temperature 214K to 309K, we have obtained relation of temperature and output voltage;V= 0.03601K - 10.70517. Key Words : Dicke type radiometer, Millimeter-wave radiometer, Thermal noise, Calibration * 정회원, 상지대학교 이공대학 응용물리전자학과접수일자 2010.9.4, 수정완료 2012.5.15게재확정일자 2012.6.8.Received: 4 September, 2010, Revised: 15 May, 2012Accepted: 8 June, 2012 * Corresponding Author:kookim@dongguk.eduDept. of Applied Physics & Electronics, Sangji University, Korea

Shot noise of a high-speed resonance-tunneling diode based on the GaAs/AlAs heterosystem

A method for the measurement of the shot noise of semiconductor diodes at low temperatures and frequencies of no less than 100 MHz is proposed. The technique is based on the Y-factor method that is modified for the measurement in which the device under study is not matched with the measurement circuit. The shot noise of high-speed resonance-tunneling diodes (RTDs) based on the GaAs/AlAs heterosystem is analyzed. It is demonstrated that an increase in the bias voltage leads to an increase in the Fano factor from about 0.5 at low bias to values of greater than unity in the range of the negative differential conductance of the RTD. When the bias voltage further increases, the Fano factor decreases and becomes close to 0.5. At all of the temperatures and bias voltages, a reliable decrease in the Fano factor to a level of less than 0.5 is not observed. We assume the sequential rather than coherent electron transport for the RTD based on the GaAs/AlAs heterosystem.

Cryogenic Self-Calibrating Noise Parameter Measurement System

A system for measuring the noise parameters of a device at cryogenic temperatures is described. The method includes the thermal calibration of a module consisting of a noise diode, a dispersive coupling network, a temperature sensor, heater, and a bias-tee. The magnitude and phase of the reflection coefficient presented by the module vary rapidly with frequency and the noise output of the module can be thermally calibrated by changing the temperature of the module with an internal heater. The resulting variable impedance-calibrated noise source can be used to measure noise parameters of transistors or amplifiers over a frequency range of 0.4 to 12 GHz via the wideband frequency-variation method. The calibration scheme is not unique to the module and may be applied in general to any noise source. Calibration and noise parameter measurements are made at cryogenic temperatures on a discrete transistor and two different low-noise amplifiers. The results are compared against theoretical values and those obtained using independent measurements. To the best of the authors' knowledge, this is the first measurement of a transistor's noise parameters at cryogenic temperatures using such techniques.

Unbiased flux calibration methods for spectral-line radio observations

Position and frequency switching techniques used for the removal of the bandpass dependence of radio astronomical spectra are presented and discussed in detail. Both methods are widely used, although the frequency dependence of the system temperature and/or noise diode is often neglected. This leads to systematic errors in the calibration that potentially have a significant impact on scientific results, especially when using large-bandwidth receivers or performing statistical analyses. We present methods to derive an unbiased calibration using a noise diode, which is part of many heterodyne receivers. We compare the proposed methods and describe the advantages and bottlenecks of the various approaches. Monte Carlo simulations are used to qualitatively investigate both systematics and the error distribution of the reconstructed flux estimates about the correct flux values for the new methods but also the 'classical' case. Finally, the determination of the frequency-dependent noise temperature of the calibration diode using hot-cold measurements or observations of well-known continuum sources is also briefly discussed.

Formulas of 1/f noise in Schottky barrier diodes under reverse bias

This paper presents the formulas of 1/f noise in Schottky barrier diodes under reverse bias condition. The derived formulas show that the electron density near the metal–semiconductor interface plays an important role in determining the power spectral density of 1/f noise current in Schottky diodes under reverse bias. The formulas give information on how to calculate the low-frequency noise in metal–semiconductor (or oxide)–metal devices such as resistive switching devices or memristors which have structures of two back-to-back Schottky barrier diodes as well as in the reverse-biased Schottky diodes.The formulas show that the power spectral density of the flicker noise in reverse-biased Schottky barrier diodes increases proportional to the square of the dc current in thermionic emission-limited condition.

Probability characteristics of electrical noise in heterojunction light-emitting diodes

A hardware-software complex for measurements of the characteristics of electrical and optical noise in light-emitting diodes (LEDs) in the frequency range from 1 to 40 kHz is described. The electrical noise of several types of heterojunction-based LEDs are studied; these types include red-emission LEDs with AlInGaP/GaAs quantum wells and the green- and blue-emission LEDs with AlInGaN/SiC quantum wells are studied by the method of discrete samples. The spectra of all studied LEDs in the frequency range from 1 to 10 kHz have the form 1/f γ. It is noteworthy that, for red-emission LEDs, the exponent γ is significantly smaller than unity; this index is close to unity for the green- and blue-emission LEDs. The characteristic time of correlation of the noise of red-emission LEDs by several times exceeds the correlation times for the blue- and green-emission LEDs. It is shown that reduced functions of the amplitude distribution of the noise voltage are close to Gaussian functions with almost the same dispersion for all LED types.

Investigation of flicker noise in silicon diodes under reverse bias

This article analyses some connections between the reverse properties of silicon power diodes and their flicker noise under reverse bias conditions. It is shown that the presence of defects in the silicon surface near the pn-junction termination has a significant influence on both the reverse VA characteristics (RVAC) and the low-frequency power noise of diodes under reverse bias conditions. However, the inherent relationship between both effects becomes apparent only under special conditions and by the use of sophisticated measurements.The article presents a simple physical model, describing the behaviour and effect of surface structural defects on the silicon surfaces in connection with the reverse and noise properties of the tested diodes. The model identifies and consequently performs the mutual relationships with respect to the physical nature of the investigated defects.The most important practical contribution of this article is to identify a simple way to reveal latent defects of chip reverse properties undetected by the standard in-process inspection, and to rectify these defects by a simple operation process (e.g. chemical etching). This information has great importance for reasonable prognosis of devices’ reliability and lifetime, especially before encapsulation and introduction on the market.

Defect Characterization Using Random Telegraph Noise in GaN-Based Light-Emitting Diodes

In order to investigate the influence of the traps which exist in the multi-quantum-well (MQW) of GaN-based light-emitting diodes (LEDs), we analyzed the output current fluctuation known as random telegraph noise (RTN) at reverse-biased region. We could find the two-level current fluctuations at two samples (S1, S2) and the low-level average time (τlow) is larger than the high-level average time (τhigh) at both samples, which means that the energy level of the trap is located below the mid-gap of used material. With increasing a reverse bias voltage, in case of S1, τhigh becomes higher and τlow becomes lower as the energy level of the trap becomes relatively higher in reference to quasi Fermi level, EFn. On the contrary, the τhigh becomes lower and the τlow becomes higher at S2 as the energy level of the trap becomes relatively lower in reference to quasi Fermi level, EFp.

A Cryogenic Integrated Noise Calibration and Coupler Module Using a MMIC LNA

A new cryogenic noise calibration source for radio astronomy receivers is presented. Dissipated power is only 4.2 mW, allowing it to be integrated with the cold part of the receiver. Measured long-term stability, sensitivity to bias voltages, and noise power output versus frequency are presented. The measured noise output versus frequency is compared to a warm noise diode injected into cryogenic K-band receiver and shows the integrated noise module to have less frequency structure, which will result in more accurate astronomical flux calibrations. It is currently in operation on the new 7-element K-band focal plane array receiver on the NRAO Robert C. Byrd Green Bank Telescope (GBT).

Characterization of White and Flicker Frequency Modulation Noise in Narrow-Linewidth Laser Diodes

Frequency modulation noise of narrow-linewidth external cavity laser diodes is characterized in terms of power spectral density (PSD) using the recirculating delayed self-heterodyne method. The measured PSD is consistent with the oscillator noise model consisting of white and flicker noise. Based on this model, beat signal spectra observed in heterodyne measurements are derived, which explain well the delay- or observation time-dependent lineshape obtained in the experiments.

Uncertainty analysis of a commercial microwave noise temperature measurement system using Monte Carlo simulations

AbstractA Monte Carlo simulation, a non‐linear fitting routine, and an uncertainty extraction routine are used to analyze the uncertainty of a commercial microwave noise temperature measurement system. Measured data for an S/C band synthetic FET‐based cold load, two microwave solid‐state noise diode hot loads, and an ambient load is obtained, and the measurement system uncertainties are subsequently assessed using different DUTs. An estimation of the measurement system uncertainties is determined for a range of DUT temperatures, and the results are consistent with the noise temperature uncertainties calculated from the measured data at the same frequency. Copyright © 2010 John Wiley & Sons, Ltd.

Impact Ionization in InAs Electron Avalanche Photodiodes

A systematic study of impact ionization, avalanche multiplication, and excess noise in InAs diodes has been carried out, confirming that avalanche multiplication is dominated by the impact ionization of electrons. This results in highly desirable “electron avalanche photodiode” characteristics previously only demonstrated in HgCdTe diodes, which are discussed in detail. The suppression of excess noise by nonlocal effects, to levels below the local model minimum of F = 2, is explained. An electron ionization coefficient is calculated and shown to be capable of modeling the electron impact ionization, which differs characteristically from that in wider bandgap III-V materials.