Efficiency Of Noise Suppression Research Articles

Multi-Mode Excitation by Interleaved EBG Structure for Suppression of Power/Ground Noise in Multi-Layer PCBs

Signal line transition with layer transition via is inevitable in multi-layer PCB. The return current can generate voltage noise between the cavities due to the discontinuity of the return current path. Other layer transition vias passing through the cavity can pick up the voltage noise and result in problems of signal integrity. In this paper, an electromagnetic bandgap (EBG) structure is proposed for suppression of the broadband cavity noise. The impedance discontinuity between layers of interleaved EBG cell enhances the efficiency of noise suppression, and the slots embedded in the EBG cell excite multi-mode resonances for extending the bandwidth of noise suppression. The dispersion diagram is utilized to preliminarily analyze the characteristic of the proposed EBG cell, and a 5×5 cells EBG board is further analyzed for characterizing the efficiency of noise suppression. Both simulation and measurement results prove the proposed structure can effectively suppress the cavity noise under −35 dB over the frequency range from 0.56 GHz to the highest measurement frequency, 20 GHz.

METHOD FOR SPATIAL POLARIZATION COMPENSATION OF JAMMING

Context. To protect radars from active noise interference (jamming) acting along the side lobes of the antenna pattern, spatial signal filtering is used, which is realized by using diversity reception of the useful signal and interference. In this case, the difference in the directions of interference and signal makes it possible to compensate for interference and detect a useful signal. However, in the case where the source of interference is in the main lobe, the differences between the desired signal and the interference are reduced. This leads to significant distortion of the antenna main lobe pattern. As a result, the accuracy of angular coordinates measurement deteriorates, as well as the sensitivity of the receiving radar device. The article proposes a new method for spatial polarization processing of radar signals, which provides compensation for active noise interference both as from the directions of the side lobes and from the direction of the main beam of the antenna pattern. Objective. The goal is to develop a method for spatial polarization processing of radar signals under the influence of active noise interference both along the side lobes of the antenna pattern and along the main lobe. Method. The method is implemented by using structural adaptation of the noise protection device, depending on the direction of the interference. In this case, the control signal for structural adaptation is formed according to the magnitude of the current spatial filter weighting coefficient value. Results. A block diagram of a spatial polarizing filter which provides compensation for active noise interference acting both on the side lobes and on the main lobe of the radar antenna pattern. The mathematical model of the compensation unit that implements the structural adaptation of the spatial polarization filter has been developed. Under the conditions of the first special polarization basis, the efficiency of noise suppression acting along the main lobe of the antenna pattern is estimated. Conclusions. The scientific novelty of the research is the development of a new method of spatial polarization processing of radar signals under difficult conditions of radar operation under massive active noise interference. The practical significance of the research is in the development of a block diagram of a spatial polarizing filter that provides compensation for interference both from the direction of the side lobes and from the direction of the main lobe of the antenna pattern. The mathematical model of the filter has been developed. The efficiency of noise suppression under the conditions of the first special polarization basis is estimated.

INFLUENCE OF POWDER PARTICLE SIZES OF POROUS MATERIALS ON REDUCING THE AERODYNAMIC NOISE LEVEL

One of the main means of reducing aerodynamic noise is the use of silencers, which can be made of various porous materials, depending on the specific operating conditions. The aim of the work is to study the dependence of the noise reduction on the characteristics of porous permeable materials (PPM) obtained by vibration molding from metal powders. Such PPMs have a wide range of porosity, high permeability, mechanical strength, provide the ability to work in a wide temperature range, high corrosion resistance, and therefore find more and more widespread application in practice. When designing silencers, their pore size, permeability, mechanical strength, cost, and the chemical composition of the material are taken into account. Basic research methods – determination of noise level, powder particle size, permeability coefficient, pore size. Vibration molding of PPM samples for experimental studies was carried out on a ВЭДС 10-1А vibration bench with vibration parameters that ensured the maximum bulk density of the powder in the mold (acceleration 10 m/s2, frequency 500 Hz). Main results – the dependence of the noise reduction value on the PPM characteristics obtained by the method of vibration molding of metal powders of various grades of various particle size distribution was studied. It has been shown that the most effective damping is provided by PPM from spherical bronze powder of the БрОФ10-1 grade with particle sizes of 350–400 microns, which provides at the same time a combination of a high level of noise reduction and high permeability to air or gas. It was found that the thickness of the muff significantly affects the efficiency of noise suppression, while the minimum thickness of the muff, which provides a sufficiently high degree of noise reduction, is about 3.5 mm, therefore it is not practical to increase the thickness of the muffler material above this value.

All-Optical Multilevel Amplitude Regeneration Based on Polarization-Orthogonal Continuous-Wave-Light-Assisted Nonlinear-Optical Loop Mirror (PC-NOLM) Subsystem

We demonstrate a multilevel amplitude regeneration experiment for non-return-to-zero 4-level pulse amplitude modulated (NRZ-PAM4) signals in the proposed polarization-orthogonal continuous-wave-light-assisted nonlinear-optical loop mirror (PC-NOLM) subsystem. A uniform regenerative behavior including the same noise-suppression efficiency and the noise-handling capability is observed across multiple amplitude levels. The pre-phase modulation is carried out for the input signal enabling the multilevel amplitude regeneration directly on highly-spectral-efficient modulated formats. An overall improvement of 2.33 dB is achieved by optimizing the launched optical power and the distortion strength in the all-optical NRZ-PAM4 regeneration experiment. The uniform regenerative performance for the proposed PC-NOLM regenerator is also analyzed numerically to reveal the regenerative mechanism and the influence from the operational parameters.

Homomorphic Two-Stage Image Sequence Filtering Algorithm in the Presence of Correlated Speckle Noise

Introduction. An images received from synthetic-aperture radar and ultrasonic medical coherent systems are distorted by speckle noise which can be spatially correlated. Sequence frame processing is applied due to poor quality of source images. The large number of filters for processing the images distorted by a multiplicative speckle noise were developed at the present time. Most of existing filters don’t take into account spatial correlation in the speckle noise which leads to lower efficiency of noise suppression. Image sequence processing leads to processed data volume increase. Thus, a problem of computing complexity and practical implementability of the filtering algorithms used for speckle noise suppression is even more relevant. Theoretical results. The task of filtering the sequence of images in the presence of correlated speckle noise becomes the task of filtering a signal component in the presence of the additive correlated noise as a result of homomorphic transformation. An expression for posteriori probability density of signal component pixel and the correlated noise pixel in each point of the sequence of images was created using property of the conditional independence. It’s used for combining received posterior distributions at the first stage as a result of executing one-dimensional non-linear filtering. The algorithm of computation of mathematical expectation and correlation matrix of joint posteriori probability density of a signal and correlated noise pixels in each point for a case of gaussian posterior distributions for non-causal intraframe and causal interframe processing is synthesized. Experimental results. The developed algorithm allows to receive a gain in signal-to-noise ratio in 5.8-1 dB for a model example by processing from one to five frames compared to interframe averaging algorithm. The number of segmentation errors for the images filtered by Otsu algorithm using three frames is 2 % for the developed algorithm and 18 % for interframe averaging. Conclusion. The homomorphic two-stage filtering algorithm of the sequence of images in the presence of correlated speckle noise was developed. It uses two-stage joint filtering of a signal component and the additive correlated noise with intraframe not causal and interframe causal processing after homomorphic transformation.

Speed of operation of equivalent time methods for conversion of noisy signals: A review

Based on the example of the conversion of noisy UWB radar signals, the speed of operation of comparator-type methods for equivalent time conversion of signals is compared. As a signal model, a sine monocycle is used. The obtained results are also compared with the efficiency of noise suppression in gated equivalent time converters. As a measure of the speed of operation of comparator-type converters, the minimal number of comparison operations of the signal and the threshold required for reaching the specified sensitivity and dynamic range is used. As a measure of the speed of operation, the number of averagings required for reaching the specified sensitivity is used for gated converters.

Experimental investigation of noise suppression using the modified up-and-down method

The noise suppression efficiency is experimentally investigated for discrete stroboscopic signal transformation providing 5–15 μV (RMS) sensitivity. A balanced comparator based on tunnel diodes is used as a clocked comparator. Ordinary and modified up-and-down methods are used to measure the instantaneous signal values. The experimental results are compared to the theoretical calculations.

An Efficient Noise Isolation Technique for SOC Application

A highly efficient CMOS process technique of suppressing the transmission of high-frequency noise induced by spiral inductors, ultrafast-switching MOS gates, or supply ringing through silicon substrate has been attained. The isolated n/sup +/-pocket structure formed by a promising process technique designed in this work has proven to be most effective in guarding vulnerable devices from remnant high-frequency noise roaming in the substrate among the structures we have used in the experiment: p/sup +/ guard ring, proton implant, and pocket structures. Excellent noise suppression efficiency of -75 dB with source and sense separated by only 21 /spl mu/m at 1 GHz has been achieved for the test keys with n/sup +/-pocket structure in contrast to -38 dB at 1GHz of unprotected devices. The isolated n/sup +/-pocket structure has manifested itself to possess the potential of becoming a key technology for mixed-mode circuits in future success of Si-based wireless communication system-on-chip (SOC) applications.

On the efficiency of synchronization of electronic clocks with reference time and frequency signals

A Markovian mathematical model is proposed for comparative analysis of noise suppression efficiency of systems for synchronization of electronic clocks with time codes transmitted as a part of standard time and frequency signals. Analytic expressions were derived for noise suppression efficiency as a function of probability of error in the received time code signal.