Signal Transmission Path Research Articles

A 1.15-ps Bin Size and 3.5-ps Single-Shot Precision Time-to-Digital Converter With On-Board Offset Correction in an FPGA

This paper presents the implementation of a high-resolution time-to-digital converter (TDC), which is adapted to varying environmental conditions. The TDC is implemented in field-programmable gate arrays (FPGA), using carry chains to achieve fine time measurement. Multiple carry chains are integrated in a single TDC channel for resolution enhancement. The TDC performance would suffer greatly without temperature compensation due to its sensitivity to the operating temperature. In order to improve the TDC adaptability, we analyzed the temperature-dependent delay variation function, and designed a powerful offset canceler to ensure stable performance of our TDC over a wide temperature range. The offset canceler can effectively correct the delay offset over temperature for the carry chain as well as for the signal transmission path. The TDC channels are tested to be fully functional with the operating temperature continuously varying from −20 °C to 60 °C. The averaged TDC bin size is 1.15 ps, and the single-shot precision is 3.5 ps. The duplications of the TDCs in three FPGA chips show good performance reproducibility according to the tests in a temperature chamber.

Global Variations of Ionospheric Total Electron Content (TEC) Derived from GPS Global Ionospheric Maps

This paper is aimed to investigate diurnal, monthly and seasonal variation of ionospheric total electronic content (TEC) obtained from two GPS satellites IGS and COD and to inspect mean VTEC Correlation between the two satellites by the year of 2008. TEC is defined by the integral of electron density in a 1 m2 column along the signal transmission path. It is an important parameter to monitor possible space weather impacts. The processed and archived data taken from IGS and COD satellites has been imported in to a MATLAB code which gave us the results of the value of VTEC. Results of the two satellites revealed that, Out of the selected equinox and solstice day’s maximum value of TEC is recorded on March 20/2008 over North and South west equator due to the maximum solar radiation reaching to the ionosphere of the Earth. On the contrary, the Minimum peak ionospheric TEC value is recorded on June 21/2008 over south Asia particularly Srilanka and Bangladesh due to emission of low solar radiation. As regards to monthly variations of ionospheric TEC, results of IGS and COD satellites show that highest mean TEC value is recorded on March and July recorded the least peak TEC value. Results regarding to seasonal variation also revealed that E-Season recorded maximum TEC value and least TEC value is recorded on J-Season. The observations of the two satellites also show that the mean TEC value presents stronger solar activity sensitivity at lower-latitude bands than the middle and high latitudes. In general, there was a very high correlation between Mean TEC value recorded by IGS and COD satellites by the year of 2008 in all low, middle and high latitudes.Keywords: IGS and COD satellites, GPS, Ionosphere, Low, middle and high-latitudes, TEC.

Compact dual-band bandpass filter based on signal-interference techniques

To realize good isolation between two signal passbands, a dual-band bandpass filter (BPF) in this article was presented using signal-interference techniques, in which five open loop resonators are adopted. The proposed filter topology is made up of two signal transmission paths in parallel, under signal-interference principles, overlap section of two original passbands, decided respectively by two different transmission paths, is selectively removed from the combined passband, as a result, two aim passbands are realized. In addition, good isolation between two aim passbands is established due to two new transmission zeros, produced by adopted signal-interference techniques. At last, good agreement can be observed between simulation and measurement.

Compact and Broadband Variable True-Time Delay Line with DLL-Based Delay-Time Control

This study presents the design and implementation of a compact and wideband active variable true-time delay line for timed array applications. Using a combination of coarse delay cells and fine delay cells, the proposed delay line achieves a large delay range and a high delay tuning resolution. Instead of LC delay lines or transmission lines, the delay can be approximated by compact active filters using transconductors and capacitors. The coarse delay cell adopts inductive peaking to broaden the bandwidth, and the fine delay cell employs a novel differential active inductor to improve the delay resolution and integration level. The group delays of the coarse delay cells and fine delay cells are analyzed and optimized. The signal transmission path is controlled by path-selection amplifiers and V---I conversion switches to achieve delay variability. The delay time is calibrated by the delay-locked loop (DLL) to mitigate the process, voltage and temperature variations. The complementary metal-oxide-semiconductor (CMOS) variable true-time delay line is fabricated in a 0.18-$$\upmu \hbox {m}$$μm CMOS process. Experiments indicate that the maximal relative delay is 95?ps and that the delay resolution is 5?ps within a 10% delay variation over a frequency range of 0.6---4.2?GHz. The chip dissipates 88?mW under a 1.8-V supply, and the core area including the DLL circuit is only 0.05?$$\hbox { mm}^{2}$$mm2.

GPS differential code biases considering the second-order ionospheric term

Differential code biases (DCBs) of the global positioning system (GPS) are generally estimated together with total electron content (TEC) along the signal transmission path through the ionosphere. However, better accuracy can be obtained theoretically by also considering the second-order ionospheric term, which is related to the magnetic field of the earth and TEC along the signal path. Using data from the international GNSS service tracking network stations, we built a regional TEC model by considering the second-order ionospheric term and estimated the DCBs of both GPS satellites and receivers. The geomagnetic field was calculated by IGRF-12 model. The results show that the second-order ionospheric term causes a 10−3 ns level effect to the estimated DCBs of GPS satellites and receivers and a 10−2 TECU (TEC unit) level change of modeled TEC. As higher accuracy is achieved, more input data such as magnetic field data of the earth are also needed. When the second-order ionospheric term is considered, the processing gets more complicated and needs more time. However, the effect of the second-order ionospheric term on DCB estimate also shows an obvious diurnal variation and showing the same monotonicity over time as local VTEC.

An Investigation on Ground Electrodes of Capacitive Coupling Human Body Communication.

Utilizing the body surface as the signal transmission medium, capacitive coupling human body communication (CC-HBC) can achieve a much higher energy efficiency than conventional wireless communications in future wireless body area network (WBAN) applications. Under the CC-HBC scheme, the body surface serves as the forward signal path, whereas the backward path is formed by the capacitive coupling between the ground electrodes (GEs) of transmitter (TX) and receiver (RX). So the type of communication benefits from a low forward loss, while the backward loss depending on the GE coupling strength dominates the total transmission loss. However, none of the previous works have shown a complete research on the effects of GEs. In this paper, all kinds of GE effects on CC-HBC are investigated by both finite element method (FEM) analysis and human body measurement. We set the TX GE and RX GE at different heights, separation distances, and dimensions to study the corresponding influence on the overall signal transmission path loss. In addition, we also investigate the effects of GEs with different shapes and different TX-to-RX relative angles. Based on all the investigations, an analytical model is derived to evaluate the GE related variations of channel loss in CC-HBC.

A novel fault diagnosis approach of gearbox using an embedded sensor fixed gear body

The vibration signals measured from the surface of a gearbox are complex, nonlinear and non-stationary. This paper presents a novel test approach for tooth root crack fault diagnosis of a spur gearbox using an embedded piezoelectric accelerometer. This enhances the ability to extract useful fault information and provide early fault detection in gear transmission systems. The proposed method uses two piezoelectric accelerometers embedded symmetrically on the gear body, which effectively shortens the transmission path of the vibration signals stimulated by a gear fault. The proposed approach is tested by analyzing experimental data from a healthy gear system and systems with cracked gear faults. In order to extract the weak fault information from the experimental data, minimum entropy deconvolution (MED) is first used to eliminate noise from the vibration signals, and then the cyclic autocorrelation function is used to extract the frequency components. The results suggest that the proposed approach can effectively detect 2 mm and 4 mm crack faults, while traditional methods can only detect 4 mm crack faults.

Study on the Signal Transmission Characteristics of 2.4GHz Wireless Network in Dorms

In accordance with the deployment requirements of WLAN node in college student dorms and its features of application environment, this paper studies the relevance among factors like radio-frequency signal transmission characteristics, communication distance, AP height and transmission path, etc., with a case study of AP radio frequency 2.4GHz. Experiments show that the attenuation of wireless network signal in student dorms conforms to Keenan-Motley model. When AP is fixed, the signal strength received by laptop generally reduces with the increase of communication distance, yet just opposite with packet loss rate. When deploying AP, 1.25-1.75 height is ideal, and one-side coverage of 3 dorm rooms optimal. Based on the above researches, a relational model of AP height, communication distance and received signal strength is established. In it, model parameter and AP height display a cubic polynomial relationship, and attenuation coefficient and AP height show a quadratic polynomial relationship. Experiment results demonstrate that this model can satisfactorily predict the received signal strength of different AP heights and communication distances, providing technical support for wireless network deployment in student dorms.

Compact inline substrate integrated waveguide filter with enhanced selectivity using new non‐resonating node

A high selective inline substrate integrated waveguide (SIW) filter based on novel stepped-impedance non-resonating node (NRN) is presented. The stepped-impedance NRN is realised by inserting a stepped-impedance substrate integrated coaxial line resonator into the volume of a third-order SIW filter. It introduces extra signal transmission path between source and load. Thus, one more transmission zero (TZ) is produced compared with conventional NRN that further improves the selectivity of the filter. Also, the proposed filter achieves a compact circuit size as the stepped-impedance NRN is embedded in the SIW cavity without occupying extra layout. To validate the proposed concept, a prototype filter with two TZs locating at both the lower and upper stop-bands, is designed, fabricated and measured. The measured results are well consistent with the simulation ones.

The solution of linear mechanical systems in terms of path superposition

We prove that the solution of any linear mechanical system can be expressed as a linear combination of signal transmission paths. This is done in the framework of the Global Transfer Direct Transfer (GTDT) formulation for vibroacoustic problems. Transmission paths are expressed as powers of the transfer matrix. The key idea of the proof is to generalise the Neumann series of the transfer matrix – which is convergent only if its spectral radius is smaller than one – into a modified Neumann series that is convergent regardless of the eigenvalues of the transfer matrix. The modification consists in choosing the appropriate combination coefficients for the powers of the transfer matrix in the series. A recursive formula for the computation of these factors is derived. The theoretical results are illustrated by means of numerical examples. Finally, we show that the generalised Neumann series can be understood as an acceleration (i.e. convergence speedup) of the Jacobi iterative method.

Compensated, nonlinear weighted exponential average filtering for digital holography on rough surfaces

The concept of exponential averaging of a reconstructed wavefront is extended by considering the full process of image formation in digital holographic microscopy (DHM), including object illumination, optical imaging, reference wave, and hologram sampling. Phase filtering by exponential averaging uses the whole capability of DHM to retrieve both the amplitude and phase of a wavefront. The aim is to apply the exponential filtering to the spatial distribution of the complex reflection coefficient of the object surface rather than to the whole orthoscopically reconstructed wavefront. To identify possible contributions to errors in the weighting of the exponential averaging, the phase measurement process of DHM is described as a signal transmission path. Accordingly, the orthoscopic wavefront needs to be compensated for both amplitude and phase of the illuminating wave and of the reference wave as closely as possible. As hologram sampling can introduce spectral amplitude attenuation, its numerical compensation is also proposed. Finally, nonlinear amplitude weighting is proposed in exponential averaging. For a better understanding of the physical meaning of weighting and its particular importance for measuring rough object surfaces, the effect of object roughness on an imaged object wavefront is presented by the concept of optical convolution.

Investigating Vibration Properties of a Planetary Gear Set with a Cracked Tooth in a Planet Gear


 
 
 Comparing with fixed shaft gearbox, vibration properties of planetary gearbox are much more complicated. In a planetary gearbox, there are multiple vibration sources as several pairs of sun-planet gears and several pairs of ring- planet gears mesh simultaneously. In addition, the signal transmission path changes due to the rotation of the carrier. To facilitate fault detection of a planetary gearbox and avoid catastrophic consequences caused by gear failures, it is essential to understand the vibration properties of a planetary gearbox. This paper aims to simulate vibration signals and investigate vibration properties of a planetary gear set when there is a cracked tooth in a planet gear. Displacement signals of the sun gear and the planet gear, and resultant acceleration signals of the whole planetary gear set will be simulated and investigated. Previous work mainly focuses on the vibration properties of a single component, like the sun gear, the planet gear or the carrier. This paper simulated the vibration signal of a whole planetary gear set when there is a cracked tooth in a planet gear. In addition, fault symptoms will be revealed, which can be utilized to detect the crack in the planet gear. Finally, the proposed approach is experimentally validated.
 
 

Application of Continuous and Structural ARMA modeling for noise analysis of a BWR coupled core and plant instability event

This paper presents a first application of a novel Continuous and Structural Autoregressive Moving Average (CSARMA) modeling approach to BWR noise analysis. The CSARMA approach derives a unique representation of the system dynamics by more robust and reliable canonical models as basis for signal analysis in general and for reactor diagnostics in particular. In this paper, a stability event that occurred in a Swiss BWR plant during power ascension phase is analyzed as well as the time periods that preceded and followed the event. Focusing only on qualitative trends at this stage, the obtained results clearly indicate a different dynamical state during the unstable event compared to the two other stable periods. Also, they could be interpreted as pointing out a disturbance in the pressure control system as primary cause for the event. To benchmark these findings, the frequency-domain based signal transmission-path (STP) method is also applied. And with the STP method, we obtained similar relationships as mentioned above. This consistency between both methods can be considered as being a confirmation that the event was caused by a pressure control system disturbance and not induced by the core. Also, it is worth noting that the STP analysis failed to catch the relations among the processes during the stable periods, that were clearly indicated by the CSARMA method, since the last uses more precise models as basis.

Design and implementation of a 700–2,600 MHz RF SiP module for micro base station

In this paper, we present a complete 700---2,600 MHz RF SiP module for micro base station. This RF SiP design integrates transmitter, receiver, feedback module, ADC/DAC and CLK module. The module consists of two multi-layer organic substrates that are vertically stacked using BGA interconnections. With the integration of 33 chips and about 600 passive components, this RF SiP module retains small form factor and measures 5.25 cm × 5.25 cm × 0.7 cm. The RF input signal transmission path insertion loss is less than 0.34 dB and the return loss is less than ?14 dB at 2.6 GHz. Full load thermal simulation result indicates that each chip junction temperature is below 100 °C. We summarize the RF SiP module design, assembly and simulated thermal characteristics. The proposed RF SiP can generally be characterized by small size, low cost and short development cycle.

Research on the Transmission Characteristics of Mechanical Vibration Signals in Optical Axis with Different Diameters

In view of the phenomenon that the complex transmission path of signals in the gear box and the lack of analysis and test methods for appropriate vibration source signals, the paper takes different-diameter optical axis as the research object, and firstly establishes the propagation model to analyze how the source signal changes and decays in the optical axis of different diameters from the perspective of wave equation. Then this paper builds proper text platforms to conduct experiment, and verify the correctness and validity of the theory. Besides, through the experiments, the paper analyzes the stress change of the optical axis transverse, the lowing trend of transmission speed of the stress wave in the axis, and the relationship between displacement and scope. At last, the paper aims to verity the rationality and generalization performance of the experimental system, which will support the future study on the transmission characteristics of mechanical vibration signals in optical axis theoretically and experimentally.

Galvanic Coupling Transmission in Intrabody Communication: A Finite Element Approach

Galvanic coupling in intrabody communication (IBC) is a technique that couples low-power and low-frequency voltages and currents into the human body, which acts as a transmission medium, and thus constitutes a promising approach in the design of personal health devices. Despite important advances being made during recent years, the investigation of relevant galvanic IBC parameters, including the influence of human tissues and different electrode configurations, still requires further research efforts. The objective of this work is to disclose knowledge into IBC galvanic coupling transmission mechanisms by using a realistic 3-D finite element model of the human arm. Unlike other computational models for IBC, we have modeled the differential configuration of the galvanic coupling as a four-port network in order to analyze the electric field distribution and current density through different tissues. This has allowed us to provide an insight into signal transmission paths through the human body, showing them to be considerably dependent on variables such as frequency and inter-electrode distance. In addition, other important variables, for example bioimpedance and pathloss, have also been analyzed. Finally, experimental measurements were also carried out for the sake of validation, demonstrating the reliability of the model to emulate in general forms some of the behaviors observed in practice.

The Finite-Element Simulation of the Intra-Body Communication Used in Wireless Body Area Networks

The finite-element simulation of the intra-body communication used in wireless body area networks has been introduced. Firstly, a novel finite-element method for modeling the whole human body is proposed, while a FE model of the whole human body used for IBC simulation was developed. Secondly, the simulations of the galvanic coupling IBC with the different signal transmission paths were implemented. Finally, the feasibility of the proposed method was verified by using the in vivo measurements. Our results indicate that the proposed method will offer the significant advantages in theoretical analysis and the application of the intra-body communication used in wireless body area networks.

A Survey on Weighted Network Measurement and Modeling

Real networks have complex topological structure characteristics such as pares of nodes have different strength and capacity connection. There are many instances in our real life. Every person has strong or weak relationship with others in social network and different reaction paths have non-uniform flow in metabolic network. In the food chain predator and prey have diverse relation and in the neural network electrical signal transmission paths have different capacity. All these systems could be described well by the concept of weighted network and weight of each edge in weighted network stand for the connection strength among individuals. This paper aims to provide an overview of recent advances in such study area. We first introduce a series of weighted network statistical characteristic parameter and concepts .Then in particular, we also discuss some practical network application examples. Empirical results show that pure topological model is not sufficient to explain the abundant and complex characteristics observed in real systems and it is necessary to improve such model. So we finally focus on some latest optimized weighted network models and give comparisons.

An energy kurtosis demodulation technique for signal denoising and bearing fault detection

Rolling element bearings are commonly used in rotary machinery. Reliable bearing fault detection techniques are very useful in industries for predictive maintenance operations. Bearing fault detection still remains a very challenging task especially when defects occur on rotating bearing components because the fault-related features are non-stationary in nature. In this work, an energy kurtosis demodulation (EKD) technique is proposed for bearing fault detection especially for non-stationary signature analysis. The proposed EKD technique firstly denoises the signal by using a maximum kurtosis deconvolution filter to counteract the effect of signal transmission path so as to highlight defect-associated impulses. Next, the denoised signal is modulated over several frequency bands; a novel signature integration strategy is proposed to enhance feature characteristics. The effectiveness of the proposed EKD fault detection technique is verified by a series of experimental tests corresponding to different bearing conditions.

Modeling of IEEE1588 on OPNET and Analysis of Asymmetric Synchronizing Error in Smart Substation

The IEEE1588 network time synchronization, matched with smart substation information network transmission, is becoming the next generation advanced data synchronization of the smart substation. It is known that the inherent asymmetry error of the network synchronization approach in the smart substation is highlighted, which is concerned particularly. This paper models the synchronization process of the IEEE1588 based on the communication simulation software of OPNET Modeler. Firstly, it builds the models of master-slave clock, IEEE1588 protocol and network synchroniza- tion model, and analyzes the composition and influencing factors of the asymmetry error. Secondly, it quantitatively analyzes the influence of the synchronous asymmetric error of the IEEE1588 affected by the network status differences and the clock synchronization signal transmission path differences. Then its correction method is analyzed, in order to improve the IEEE1588 synchronization reliability and gives the solutions to its application in smart substation.