Total Noise Power Research Articles

Multi-Gb/s free-space laser communication at 4.6-μm wavelength using a high-speed, room-temperature, resonant-cavity infrared detector (RCID) and a quantum-cascade laser

Research has shown that free-space laser communication systems may experience fewer outages due to atmospheric impairments such as haze, fog, clouds, and turbulence by operating at a longer wavelength in the mid-wave or long-wave infrared, if disadvantages such as lower-performance transceiver components may be overcome. Here we report a resonant cavity infrared detector (RCID) with 4.6-µm resonance wavelength that enables 20-dB larger link budget than has been reported previously for ∼ 5 Gb/s operation. The device combines high responsivity, 1.97 A/W, with a low noise equivalent power (NEP) of 0.7 pW/Hz at room temperature, and a high bandwidth of 6.7 GHz at 3-dB. The relatively large surface-normal-incidence device with 30-µm diameter simplifies the coupling relative to intra-subband quantum cascade detectors. Although the RCID NEP is expected to increase with frequency to ∼ 1.5 pW/Hz, we estimate that the total equivalent noise power in a 2.5-GHz bandwidth is less than 200 nW. When combined with a relatively high power (∼100-mW) distributed-feedback quantum cascade laser, the difference of > 50 dB between modulated laser power and RCID noise significantly outpaces that of existing devices.

Noise reduction by bias cooling in gated Si/Six Ge1−x quantum dots

Silicon–germanium heterostructures are a promising quantum circuit platform, but crucial aspects, such as the long-term charge dynamics and cooldown-to-cooldown variations, are still widely unexplored quantitatively. In this Letter, we present the results of an extensive bias cooling study performed on gated silicon–germanium quantum dots with an Al2O3 dielectric. Over 80 cooldowns were performed in the course of our investigations. The performance of the devices is assessed by low-frequency charge noise measurements in the band of 200 μHz to 10 mHz. We measure the total noise power as a function of the applied voltage during cooldown in four different devices and find a minimum in noise at 0.7 V bias cooling voltage for all observed samples. We manage to decrease the total noise power median by a factor of 6 and compute a reduced tunneling current density using Schrödinger–Poisson simulations. Furthermore, we show the variation in noise from the same device in the course of eleven different cooldowns performed under the nominally same conditions.

Enhanced Detection Precision of the Taiji Program by Frequency Setting Strategy Based on a Hierarchical Optimization Algorithm

For space-based gravitational wave detection, a laser interferometric measurement system composed of a three-spacecraft formation offers the most rewarding bandwidth of astrophysical sources. There are no oscillators available that are stable enough so that each spacecraft could use its own reference frequency. The conversion between reference frequencies and their distribution between all spacecrafts for the synchronization of the different metrology systems is the job of the inter-spacecraft frequency setting strategy, which is important for continuously acquiring scientific data and suppressing measurement noise. We propose a hierarchical optimization algorithm to solve the frequency setting strategy. The optimization objectives are minimum total readout displacement noise and maximum beat-note frequency feasible range. Multiple feasible parameter combinations were obtained for the Taiji program. These optimized parameters include lower and upper bounds of the beat note, sampling frequency, pilot tone signal frequency, ultrastable clock frequencies, and modulation depth. Among the 20 Pareto optimal solutions, the minimum total readout displacement noise was 4.12 pm/Hz, and the maximum feasible beat-note frequency range was 23 MHz. By adjusting the upper bound of beat-note frequency and laser power transmitted by the telescope, we explored the effects of these parameters on the minimum total readout displacement noise and optimal local laser power in greater depth. Our results may serve as a reference for the optimal design of laser interferometry system instrument parameters and may ultimately improve the detection performance and continuous detection time of the Taiji program.

Design Implementation and Performance Analysis of M-QAM and PAM-n Signalling Schemes

Abstract: Two circuits have been simulated in the Optisystem 20 software. One circuit has M-QAM and the other has PAM-n. Both the circuits have been compared on the basis of Bits per symbol, signal power,Noise power, etc. The total power and noise power havebeen calculated in the electrical power meter visualizer.In both the circuits, PRBS generator is used to generate the sequence of the bits. In M-QAM,return to zero pulse generator is used and in PAM-n notreturn to zero pulse generator is used. The full width pulse is also known as NRZ (not return to zero) and halfwidth pulse is also known as RZ (return to zero). The main objective of the simulation is to get perfect Eye diagram in the Eye Diagram Anaylzer. The parametriccomparison of different types of QAM have also be doneon the basis of number of samples, sequence length, samples per bit and output power in dBm andcomparison is done by state of art. In the final result, itwill be concluded that M-QAM performs much better than the PAM-n as it is capable of transferring higher data rates. The different types of M-QAM and PAM-n eye diagrams have been plotted like 16-QAM, 64-QAMand PAM-3.

Quantization noise analysis in FBMC receivers and its effect on the BER performance

This paper analyzes the fixed-point and floating-point roundoff errors in different Filter Bank MultiCarrier (FBMC) receiver implementations. Two different structures are considered: the polyphase network based and frequency spreading based. Theoretical closed-form formulas for the total Quantization Noise Power (QNP) are derived and verified through simulation. The results show the effects of each parameter and signal processing block on the overall QNP. Also, the results show that the total QNP for an arbitrary set of parameters can be determined using the derived results without performing exhaustive simulations. The effects of the chosen bit-resolution on the bit-error rate performance are also analyzed. Furthermore – based on the theoretical results – FBMC receivers can be designed with an optimal number of bits used in the arithmetic units without significantly affecting the receiver performance.

Intelligent-Reflecting-Surface-Assisted GFDM Communication Systems

Demands for higher data rates is an inevitable fact. Therefore, the effect of the frequency selectivity and time variation of communication channels will be more significant. One effective technique to combat the doubly dispersive channels is generalized frequency division multiplexing (GFDM) scheme. Nevertheless, nonorthogonality of the used prototype filter can deteriorate the GFDM performance. On the other hand, intelligent reflecting surface (IRS) is a new revolutionary technology for future wireless networks. IRS can smartly reconfigure the propagation environment in order to improve the efficiency of the communication systems. In this article, IRS is applied in a GFDM communication system to enhance the system's performance. In this way, an IRS-assisted GFDM communication system model is proposed. The goal is to design the reflecting coefficients of the IRS such that the total noise power at a GFDM block is minimized. In order to obtain an effective solution, the optimization problem is converted to a quadratically constrained quadratic program (QCQP). The developed QCQP problem is convex, which can be solved by using an iterative algorithm. An analytical derivation of the maximum achievable rate (MAR) and bit error rate (BER) of the proposed IRS-assisted GFDM system is provided. Also, in simulations, the performance of the proposed method is compared with the conventional GFDM system in terms of MAR and BER. Simulation results confirm that using IRS by employing the proposed method dramatically improves the performance of a GFDM system.

Fractional Spurs Reduction Technique Using Probability Density Shaping Sigma-Delta Modulator and Fractional Frequency Divider

A fractional spurs reduction technique using probability density shaping (PDS) sigma-delta modulator (SDM) and fractional frequency divider is presented. The PDS-SDM is utilized to reshape the quantization noise probability density. If a certain condition is obeyed, the loop nonlinearity would not induce fractional spurs. Moreover, in order to reduce the total quantization noise power, a fractional frequency divider, e.g., phase-interpolated (PI) frequency divider, is adopted to reduce the division ratio from 1 to 0.25, leading to 12 dB quantization noise suppression. By combining the PDS-SDM and fractional divider, the fractional spurs are greatly mitigated. A phase domain ADPLL Simulink model is proposed for verification and the simulation results demonstrate the proposed technique is effective for fractional spurs reduction.

Time-Division Multiarray Beamforming for UAV Communication

Recently, unmanned aerial vehicles (UAVs) have been widely used in various industries. However, the communication links of UAVs are also threatened by eavesdropping. To enhance physical layer security (PLS) for UAV communications, a time-division multiarray beamforming (TDMB) scheme is proposed. Multiple antenna arrays steer their beamforming vectors based on their position relative to the legitimate user (LU). Thus, angle-distance-dependent directional modulation (DM) can be achieved. Time-division means multiple antenna arrays take turns transmitting different symbols from a same packet. The receiver in undesired directions suffers from intersymbol interference (ISI) because of the path differences between the receiver and different antenna arrays. This paper shows the signal-to-interference-plus-noise ratio (SINR) distribution with the proposed method in a 2-dimensional plane. Also, the improvement of the secrecy rate with the proposed method under different total antennas and artificial noise power is studied. Overall, these results indicate that the security rate has improved more with the proposed method, where the numbers of antennas and the power of AN are limited. Therefore, this method is suitable for UAV security communication.

Investigating the Performance of SCM/MMW/RoF Optical-Wireless Access System for Next Generation Communications

In this paper, we propose a model of subcarrier multiplexing millimeter wave radio-over-fiber SCM/MMW/RoF optical-wireless access system for next generation mobile communications using QPSK modulation. We then calculate signal and total noise power at the end of optical fiber link and at mobile subscribers through wireless medium. Next, system performance showed by SNR, BER at the end of system is determined. They are investigated, compared, evaluated by Matlab in many different scenarios including BER performance versus EDFA’s Gain, optical transmitter power at central office (CO), optical oscillator power in coherent receiver, wireless frequencies, wireless link distance corresponding to two wireless cases of Line of Sight (LoS) and Non Line of Sight (NLoS). Numerical results show that when number of SCM channels increase system performance becomes worse due to nonlinear effect in SCM modulation.

Model Implementation of Lorentzian Spectra for Circuit Noise Simulations in the Frequency Domain

This work presents a new method for the Verilog-A implementation of Lorentzian noise models, in a module called VERILOR, which can automatically generate either Lorentzian or 1/f-like noise spectra depending on the trap density and gate oxide area, for all bias conditions, in a one-step simulation. Based on statistical experimental data, we demonstrate the importance of Lorentzian noise modeling in contrast to classic frequency domain 1/f or time domain Random Telegraph Noise (RTN) modeling, in terms of PSD, total noise power, and device-to-device noise variability reproduction. Moreover, we validate the applicability of VERILOR in circuit simulators in both frequency and time domain, and how it can enable precise noise variability studies at a circuit level. Finally, fundamental digital and analog circuits such as the Ring Oscillator are used to showcase the usefulness and applicability of the VERILOR model in circuit noise simulations.

Sensor Selection for Relative Acoustic Transfer Function Steered Linearly-Constrained Beamformers

For multi-microphone speech enhancement, different microphones might have different contributions, assome are even marginal. This is more likely to happen in wireless acoustic sensor networks (WASNs), where somesensors might be distant. In this work, we therefore consider sensor selection for linearly-constrained beamformers. Theproposed sensor selection approach is formulated by minimizing the total output noise power and constraining thenumber of selected sensors. As the considered sensor selection problem requires the relative acoustic transfer function(RTF), the covariance whitening based RTF estimation or a direct-path RTF approximation is exploited. For a singletarget source, we can thus substitute the estimated RTF or the assumed RTF to the original problem formulation in orderto design a minimum variance distortionless response (MVDR) beamformer. Alternatively, we can integrate the two RTFsto design a linearly constrained minimum variance (LCMV) beamformer in order to alleviate the effects of RTFestimation/approximation errors. By leveraging the superiority of LCMV beamformers, the proposed approach can beapplied to the multi-source case. An evaluation using a simulated large-scale WASN demonstrates that the integration ofRTFs for the sensor selection based LCMV beamformer can be beneficial as opposed to relying on either of theindividual RTF steered sensor selection based MVDR beamformers. We conclude that the sensors that are close to thetarget source(s) and also some around the coherent interferers are more informative.

Gain-forming effect on optical signal-to-noise ratio in Raman fiber amplifier

Abstract We have introduced the comprehensive optical-to-noise ratio (OSNR) to investigate simultaneously the effects of all three major linear noise sources in distributed Raman fiber amplifier (DRFA). The total noise power contains double Rayleigh backscattering (DRB) noise, amplified spontaneous emission (ASE) noise, and relative intensity noise (RIN). Also, we have introduced an approximated gain profile approach, which helps in evaluating the OSNR for higher-order pumping (HOP) configuration for backward, forward, and bidirectional DRFA schemes. Finally, by applying the dynamic and static full-numerical computations on a system of eight wavelength division multiplexing (WDM) channels (for amplifier lengths of 70, 140, and 210 km), we demonstrated that for RIN frequencies greater than 100 kHz, the higher-order bidirectional pumping scheme exceeds the backward schemes by 12 dB.

Highly compact digital pixel structures developed for the CEPC vertex detector

The Circular Electron Positron Collider (CEPC) has been proposed to measure the Higgs properties with a new level of precision. The stringent physics requirements drive a vertex detector constructed with pixel sensors featuring high granularity, fast processing speed and low power dissipation. To explore in-pixel signal processing structures with compact layout size, while maintaining processing speed and low power, a second prototype CMOS pixel sensor, named JadePix-2, has been designed and fabricated in a 0.18μm CMOS image sensor (CIS) process. The prototype contains two versions of digital pixels, both of which have been realized within 22μm pitch size. It operates in the rolling-shutter mode, with processing speed of 100 ns/row and 80 ns/row, respectively, for the two pixel structures. Experimental results show that the total equivalent noise charge (ENC) and power dissipation of the two structures are about 29.5 e− with 6.5 μA/pixel, and 31 e− with 3.7 μA/pixel respectively.

Noise in NC-AFM measurements with significant tip-sample interaction.

The frequency shift noise in non-contact atomic force microscopy (NC-AFM) imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip–sample interactions. The total noise power spectral density DΔf(fm) is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip–sample interaction, by the coupling between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure DΔf(fm) for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip–sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops.

Cost efficient amplifier placement and gain adjustment in all-Optical networks: A noise-minimizing approach

Erbium doped fiber amplifiers (EDFA) are known to be well suited for transparent optical networks due to their proper relative properties. Link amplifiers are responsible for adequately compensating fiber loss in optical links. However, amplified spontaneous emission (ASE) noise would degrade the optical signal to noise ratio (OSNR) which leads to degradation in quality of service (QoS). This paper aims at optimally determining the location and relative gain settings of the employed line amplifiers in order to minimize the total ASE noise power on each link. A non-linear optimization approach is developed. Then, two amplifier placement and gain adjustment algorithms called optimal EDFA placement (OEP) and Incremented-OEP are proposed. Numerical results in addition to simulations indicate the fact that the proposed schemes outperform the existing conventional EDFA placement (CEP) solution in terms of average ASE noise power and blocking rate.

Noise-induced resonance-like phenomena in InP crystals embedded in fluctuating electric fields

We explore and discuss the complex electron dynamics inside a low-doped n-type InP bulk embedded in a sub-THz electric field, fluctuating for the superimposition of an external source of Gaussian correlated noise. The results presented in this study derive from numerical simulations obtained by means of a multi-valley Monte Carlo approach to simulate the nonlinear transport of electrons inside the semiconductor crystal. The electronic noise characteristics are statistically investigated by calculating the correlation function of the velocity fluctuations, its spectral density and the integrated spectral density, i.e. the total noise power, for different values of both amplitude and frequency of the driving oscillating electric field and for different correlation times of the field fluctuations. Our results show that the nonlinear response of electrons is strongly affected by the field fluctuations. In particular, crucially depending on the relationship between the correlation times of the external Gaussian noise and the timescales of complex phenomena involved in the electron dynamical behavior: (i) electrons self-organize among different valleys, giving rise to intrinsic noise suppression; (ii) this cooperative behavior causes the appearance of a resonance-like phenomenon in the noise spectra.

Electron dynamical response in InP semiconductors driven by fluctuating electric fields

The complexity of electron dynamics in low-doped n-type InP crystals operating under fluctuating electric fields is deeply explored and discussed. In this study, we employ a multi-particle Monte Carlo approach to simulate the non-linear transport of electrons inside the semiconductor bulk. All possible scattering events of hot electrons in the medium, the main details of the band structure, as well as the heating effects, are taken into account. The results presented in this study derive from numerical simulations of the electron dynamical response to the application of a sub-Thz electric field, fluctuating for the superimposition of an external source of Gaussian correlated noise. The electronic noise features are statistically investigated by computing the correlation function of the velocity fluctuations, its spectral density and the variance, i.e. the total noise power, for different values of amplitude and frequency of the driving field. Our results show the presence of a cooperative non-linear behavior of electrons, whose dynamics is strongly affected by the field fluctuations. Moreover, the electrons self-organize among different valleys, giving rise to the reduction of the intrinsic noise. This counterintuitive effect critically depends on the relationship among the characteristic times of the external fluctuations and the temporal scales of complex phenomena involved in the electron dynamical response. In particular, the correlation time of the electric field fluctuations appears to be crucial both for the noise reduction effect and the appearance of an anomalous diffusion effect.

Closed-Form Relations for Resonance Detection Error Using Statistical Analysis of Amplitude Noise

The optimization of resonance-tracking sensors relies critically on proper estimation of resonance detection error. We study this error in two common resonance detection algorithms: the absolute minimum method and the linear regression method. Closed-form relations for the error originating from additive noise are presented. The formulation accommodates the majority of lineshapes of practical interest and a wide variety of noise statistics. Lorentzian and Fano line shapes are studied here with further detail for their practical importance. It is discussed that while the performance of the absolute minimum method depends on the tail of the noise probability distribution function, for the linear regression method the total noise power is the determining characteristic of the noise. This fact is explained for the specific case of quantization noise. The results of this study enable a quantitative comparison of the performance of resonance-based sensors, which is a center piece in the optimization of their limit of detection.

Identification of noise generation and flow kinematics in the air gap for two different blade tip designs of an axial fan

Importance of the role of axial fans in our everyday life as well as in industrial sphere is crucial. Their presence dictates indispensable reduction of the emitted noise level. The aerodynamically born noise due to the kinematics of the air-flow in the gap between rotor and stator is one predominant source of emitted noise by most fans and is the most intensive within the human audible spectrum. Two different rotor blade tip shapes A and B were analysed in details and the results presented in this paper. Their influence on the emitted noise was determined by measurements of the integral aerodynamic characteristic and by the level of the sound pressure level of the fan. It was confirmed that the kinematics of the air-flow within the blade tip gap is significantly different for both observed blade tip designs and plays a crucial role when generation and size of the total emitted noise power is concerned. Frequency spectra of the measured noise pressure level for both observed blade designs was also essentially different and served to confirm the well-known fact that intensity of the sound pressure level decreases with the frequency, which helps to assess and identify mechanisms of the noise generation. A typical measured amplitude decrease of the sound pressure level was observed and explained in details for both blade tip versions for the frequency range f>1000 Hz: appropriate scaling for the blade tip A and for the blade tip B was determined as \(\omega^{-2.8}\) and \(\omega^{-4/3}\) respectively. Distinctive differences between the two observed frequency spectra were established. Identification of locations, sources and specificity of the generated noise together with their detailed explanation was made possible by measurements of local pressure, velocity and their variances and is supported by simultaneous experimental flow visualization.

Dynamic response of Antarctic ice shelves to bedrock uncertainty

Abstract. Accurate and extensive bedrock geometry data is essential in ice sheet modelling. The shape of the bedrock on fine scales can influence ice sheet evolution, for example through the formation of pinning points that alter grounding line dynamics. Here we test the sensitivity of the BISICLES adaptive mesh ice sheet model to small-amplitude height fluctuations on different spatial scales in the bedrock topography provided by Bedmap2 in the catchments of Pine Island Glacier, the Amery Ice shelf and a region of East Antarctica including the Aurora Basin, Law Dome and Totten Glacier. We generate an ensemble of bedrock topographies by adding random noise to the Bedmap2 data with amplitude determined by the accompanying estimates of bedrock uncertainty. We find that the small-amplitude fluctuations result in only minor changes in the way these glaciers evolve. However, lower-frequency noise, with a broad spatial scale (over tens of kilometres) is more important than higher-frequency noise even when the features have the same height amplitudes and the total noise power is maintained. This is cause for optimism regarding credible sea level rise estimates with presently achievable density of thickness measurements. Pine Island Glacier and the region around Totten Glacier and Law Dome undergo substantial retreat and appear to be more sensitive to errors in bed topography than the Amery Ice shelf region which remains stable under the present-day observational data uncertainty.