Amplitude Detection Research Articles

New Technique Based Peasant Multiplication for Effcient Signal Processing Applications

<p class="Standard"><span lang="EN-IN">The Direct Form FIR channel is utilized for DSP application where the channel request is settled. For the most part this channel devours more range and power. To defeat this issue Multiplier Control Signal Decision window (MCSD) plans is joined into Direct Form FIR channel to powerfully change the channel arrange. MCSD structures comprise of Control flag Generator (CG) and Amplitude Detection (AD) rationale circuits. Advertisement rationale is utilized to disavow the correct duplication process and screen the amplitudes of information tests. CG is utilized to control the channel operation through inside counter. Traditional reconfigurable FIR channel is planned utilizing Vedic Multiplier that devours more territory and deferral. In this paper, changed reconfigurable FIR filer is intended to additionally decrease the APT (Area, Power and Timing) item. The proposed Reconfigurable FIR filer, Vedic Multiplier is supplanted by Russian Peasant Multiplication procedure. Subsequently adjusted Reconfigurable FIR channel with Russian Peasant Multiplier expends less region, postponement and power than all analyzed techniques.</span></p>

Digital demodulation algorithm based on frequency correction for the near-infrared spectrometer.

For the scanning near-infrared spectrometer, the employments of traditional digital demodulation algorithms require that the sampling frequency is an integral multiple of the measured signal frequency. However, the measured signal frequency is unstable, and the sampling frequency is a fixed value in the spectrometer, which affects the accuracy of amplitude demodulation results. To improve the signal-to-noise ratio of spectra, this paper proposes an improved digital demodulation algorithm based on frequency correction. Through theoretical analysis, simulations, and experiments, the improved digital demodulation algorithm based on frequency correction was compared with a digital demodulation algorithm based on the average of the absolute value in a complete period. The results showed that the former algorithm decreased the noise caused by the fluctuation of the measured signal frequency. The signal-to-noise ratio of spectra increased from 626 to 1124, and the measurement time increased only 0.73%.

Fast two-snapshot structured illumination for temporal focusing microscopy with enhanced axial resolution

We present a new two-snapshot structured light illumination (SLI) reconstruction algorithm for fast image acquisition. The new algorithm, which only requires two mutually π phase-shifted raw structured images, is implemented on a custom-built temporal focusing fluorescence microscope (TFFM) to enhance its axial resolution via a digital micromirror device (DMD). First, the orientation of the modulated sinusoidal fringe patterns is automatically identified via spatial frequency vector detection. Subsequently, the modulated in-focal-plane images are obtained via rotation and subtraction. Lastly, a parallel amplitude demodulation method, derived based on Hilbert transform, is applied to complete the decoding processes. To demonstrate the new SLI algorithm, a TFFM is custom-constructed, where a DMD replaces the generic blazed grating in the system and simultaneously functions as a diffraction grating and a programmable binary mask, generating arbitrary fringe patterns. The experimental results show promising depth-discrimination capability with an axial resolution enhancement factor of 1.25, which matches well with the theoretical estimation, i.e, 1.27. Imaging experiments on pollen grain and mouse kidney samples have been performed. The results indicate that the two-snapshot algorithm presents comparable contrast reconstruction and optical cross-sectioning capability than those adopting the conventional root-mean-square (RMS) reconstruction method. The two-snapshot method can be readily applied to any sinusoidally modulated illumination systems to realize high-speed 3D imaging as less frames are required for each in-focal-plane image restoration, i.e., the image acquisition speed is improved by 2.5 times for any two-photon systems.

Application research on 4-pulsed amplitude modulation in 10 Gb/s passive optical access systems

A novel scheme which can realize high-speed bidirectional optical signals transmission and reception by using 4-pulsed amplitude modulation (4-PAM) and demodulation in 10Gb/s passive optical access systems, is introduced in this paper. In this scheme, a PAM sequence generator module, a M-ary pulse generator module and one Mach-Zehnder intensity Modulator (MZM) are employed for generating the 10Gb/s optical 4-PAM signals. The generated optical 4-PAM signal is achieved full-duplex transmission over 20km single mode fiber (SMF) for both downstream (DS) and upstream (US) access links application. The electrical spectrum diagrams, optical spectrum diagrams, and eye-diagrams are obtained, and the receiver sensitivities of 10Gb/s 4-PAM signals before and after bidirectional transmission are analyzed. The simulation results demonstrate that, while the 4-PAM signal is adopted in passive optical access systems as bidirectional transmission signal, it can be received effectively with the BER below the forward-error-correction (FEC) limit value.

A Dual-Channel MEMS Amplitude Demodulator for On-Line Detection in Radio Relay Station

A dual-channel amplitude demodulator based on a micro-electromechanical systems (MEMS) approach for radio relay station on-line detection is proposed in this letter. This MEMS demodulator adopts a clamped-clamped beam to couple part of the signal from the main line to dual channels for on-line amplitude demodulation. The MEMS-based demodulation applies the square law of the thermal converter. The fabrication of the device is compatible with GaAs monolithic microwave integrated circuit process. Experiments show that the on-line MEMS demodulator has a return loss that is better than 20 dB, and an insertion loss of less than 0.5 dB up to 10 GHz. This design can realize direct demodulation of an amplitude modulation signal with a carrier frequency of 0.01-10 GHz.

Planetary Gearbox Fault diagnosis via Joint Amplitude and Frequency Demodulation Analysis Based on Variational Mode Decomposition

Planetary gearbox vibration signals have strong modulation features due to the amplitude modulation and frequency modulation (AM-FM) effect of gear faults, as well as the amplitude modulation (AM) effect of time-varying vibration transfer paths, on gear meshing vibrations. This results in an involute sidebands structure in Fourier spectrum, possibly misleading fault diagnosis. The modulating frequency of both amplitude modulation (AM) and frequency modulation (FM) parts is closely related to the gear fault characteristic frequency. This inspires the idea of joint amplitude and frequency demodulation analysis, thus addressing the complex sidebands issue inherent in Fourier spectrum. Demodulation analysis requires mono-component signals for accurate estimation of instantaneous frequency, and proper selection of an AM-FM component sensitive to gear fault. To this end, we firstly decompose the complex signal into intrinsic mode functions (IMFs) via variational mode decomposition (VMD), by exploiting its capability in decomposing complex modulated signal into constituent AM-FM components. For effective application of VMD in complex planetary gearbox signal analysis, we propose a method to determine a key parameter in VMD, i.e. the number of IMFs to be separated. For accurate instantaneous frequency estimation, we decompose IMFs via empirical AM-FM decomposition, to remove the influence of AM on instantaneous frequency estimation. Then, we select the sensitive IMF that contains the main gear fault information for further demodulation analysis. In order to properly select the sensitive IMF, we propose a criterion based on the gear vibration characteristics and the VMD properties. Finally, we obtain the amplitude and frequency demodulated spectra by applying Fourier transform to the amplitude envelope and instantaneous frequency of the selected sensitive IMF. According to the characteristics exhibited in the demodulated spectra, we can detect planetary gearbox fault. The proposed method is illustrated via a numerical simulated planetary gearbox vibration signal, and is further validated using lab experimental vibration signals of a planetary gearbox. Faults on all the three types of gear (sun, planet and ring) are successfully identified.

Effect of unitary sample shifted Laplacian and rectangular distributions in bearing fault identifications of induction motor

Fault identifications of bearings are complex process and require non-stationary signal processing methods along with the envelope and cepstral analysis techniques to demodulate the amplitude modulated signals. In this study, the fault signals from the drive end induction motor bearings are detected using proposed unitary sample shifted rectangular and Laplacian probability density functions (pdf). These functions are used to generate recursive frame-based crest factor (FCF), frame-based kurtosis (FKS) and frame-based energy (FE) time series. These time series substantially detect the impulses that depict the fault and shaft rotating frequencies effectively. Apart from detection of fault, the proposed method significantly suppresses the higher order modulated resonating frequencies without the use of non-coherent amplitude demodulation technique. Similarly, the spectral analyses are found to be observable in fault and shaft rotating frequencies identification using rectangular pdf. However, it is observed that the Laplacian pdf is more sensitive in detecting faults and the spectral leakages are lower than rectangular pdf for variable defect sizes. It is also found that the FCF and FKS time series are more probable in detecting fault, whereas FE is significant in depicting shaft rotation.

Amplitude Estimation Technique for Intermittent Contact Atomic Force Microscopy

This article describes how one of the biggest challenges in designing of high-speed intermittent contact atomic force microscope (AFM) is the construction of a fast amplitude detector. The measurement techniques commonly used in commercial microscopes, such as RMS to DC converters or lock-in amplifiers often do not provide sufficient bandwidth to perform high speed imaging. On the other hand, many techniques developed especially for high-speed AFM are characterized by poor signal-to-noise ratio. In this paper, a novel amplitude estimation method based on the generalized Goertzel algorithm is presented. The detection system, composed of 16-bit 100 mega-samples per second analog-to-digital converter and field-programmable gate array device, allows to measure the signal amplitude within the time comparable to one oscillation cycle of the AFM cantilever. The effectiveness and validity of the designed detector were investigated by computer simulation. High spatial resolution of the presented method implemented in the actual atomic force microscopy system is also demonstrated.

Evaluation of adaptively enhanced two-shot fringe pattern phase and amplitude demodulation methods.

Phase-shifting interferometry is a standard tool in optical metrology. Most frequently, it needs three or more interferograms to solve the system of fringe equations for phase or amplitude retrieval, which limits its time resolution. Recently, the topic of two-shot, arbitrary-phase-step fringe pattern phase and amplitude demodulation has been flourishing and attracting attention with several novel and interesting methods being proposed. In this work, we evaluate six up-to-date two-shot phase-shifting methods analyzing their main error sources and proposing efficient ways to minimize their influence by adaptive filtering using the Hilbert-Huang transform.

Adaptive Clutter Demodulation for Non-Contrast Ultrasound Perfusion Imaging.

Conventional Doppler ultrasound is useful for visualizing fast blood flow in large resolvable vessels. However, frame rate and tissue clutter caused by movement of the patient or sonographer make visualizing slow flow with ultrasound difficult. Patient and sonographer motion causes spectral broadening of the clutter signal, which limits ultrasound's sensitivity to velocities greater than 5-10 mm/s for typical clinical imaging frequencies. To address this, we propose a clutter filtering technique that may increase the sensitivity of Doppler measurements to at least as low as 0.52 mm/s. The proposed technique uses plane wave imaging and an adaptive frequency and amplitude demodulation scheme to decrease the bandwidth of tissue clutter. To test the performance of the adaptive demodulation method at suppressing tissue clutter bandwidths due to sonographer hand motion alone, six volunteer subjects acquired data from a stationary phantom. Additionally, to test in vivo feasibility, arterial occlusion and muscle contraction studies were performed to assess the efficiency of the proposed filter at preserving signals from blood velocities 2 mm/s or greater at a 7.8 MHz center frequency. The hand motion study resulted in initial average bandwidths of 175 Hz (8.60mm/s), which were decreased to 10.5 Hz (0.52 mm/s) at -60 dB using our approach. The in vivo power Doppler studies resulted in 4.73 dB and 4.80 dB dynamic ranges of the blood flow with the proposed filter and 0.15 dB and 0.16 dB dynamic ranges of the blood flow with a conventional 50 Hz high-pass filter for the occlusion and contraction studies, respectively.

Performance Evaluation of an Automatic GPS Ionospheric Phase Scintillation Detector Using a Machine‐Learning Algorithm

Ionospheric phase scintillation can cause errors or outage in GNSS navigation solutions. Timely detection of phase scintillation will enable adaptive processing to mitigate its effects on navigation solutions. This paper presents a machine-learning algorithm to autonomously detect phase scintillation based on frequency domain features. Validation using data from Gakona shows phase scintillation detection accuracy around 92 percent. Test results using data from Poker Flat, Jicamarca, Singapore, and Hong Kong demonstrate the capability of the trained detector to be applied more generally. Performance evaluation reveals that the values of phase scintillation index σϕ may be poor indications of scintillation activities. Concurrent phase and amplitude scintillation detection using similar machine-learning algorithms is further investigated with low-latitude data. Results suggest that at low latitudes an amplitude detector alone is sufficient to capture scintillation in general, while at high latitudes, a phase scintillation detector is necessary to capture the dominating phase scintillation events. Copyright © 2017 Institute of Navigation

Demodulation Techniques for Self-Oscillating Eddy-Current Displacement Sensor Interfaces: A Review

This paper presents a comprehensive study of demodulation techniques for high-frequency self-oscillating eddy-current displacement sensor (ECDS) interfaces. Increasing the excitation frequency is essential for lowering the skin depth in many demanding industrial applications, that require better resolution. However, a high excitation frequency poses design challenges in the readout electronics, and particularly in the demodulation functional block. We analyze noise, linearity, and stability design considerations in amplitude demodulators for nanometer and sub-nanometer ECDSs. A number of state-of-the-art amplitude demodulation techniques employed in high-frequency ECDSs are reviewed, and their pros and cons are evaluated.

Amplitude modulation and demodulation of an electromagnetic wave in magnetized ion-implanted semiconductor plasmas having SDDC

In communication processes, amplitude modulation is very helpful to save power using a single band transmission. Using the hydrodynamical description of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave in magnetized ion implanted semiconductor plasmas having strain dependent dielectric constants. Analysis is made under different wave number regimes over a wide range of cyclotron frequencies without and with colloids. Numerical estimations are made for n-doped BaTiO3 crystal irradiated by pump wave frequency 1.78 × 1013s−1. It has been found that ion implantation of negatively charged colloids modifies nearly ≈ 105 of magnitude of amplitude modulation and demodulation processes. Ion implantation plays a key role in development of optoelectronics.

A novel low density parity check coded differential amplitude and pulse position modulation free-space optical system for turbulent channel

Based on the proposed partly equidifferent mapping and its specific Differential Amplitude and Pulse Position Modulation (DAPPM) demodulation, a modified FSO scheme for turbulent channel is designed and analyzed. The novel Low Density Parity Check (LDPC) coded 4×4 and 4×8 DAPPM Free-Space Optical communication (FSO) system is constructed. The Monte Carlo simulation results show approximately 2dB transmit power reduction against classical LD-PC-DAPPM at the identical Bit-Error-Rate in strong turbulent channel. The proposed partly equidifferent mapping is compatible with other modulations, so it enables widespread adoption in other coded FSO systems.

Planetary Gearbox Fault Diagnosis via Torsional Vibration Signal Analysis in Resonance Region

Planetary gearbox torsional vibration signals are free from the extra amplitude modulation effect due to time-varying transmission paths and have simpler frequency structure than translational ones. Gear faults result in modulation on the torsional resonance vibration and are manifested by the modulation feature. These merits are exploited for planetary gearbox fault diagnosis in this paper. Gear fault induced torsional vibrations in resonance region are modelled as amplitude modulation and frequency modulation (AM-FM) processes, the explicit equation of Fourier spectrum is derived, and the sideband characteristics are summarized. To avoid complex sideband analysis, amplitude and frequency demodulation analysis methods are exploited. The equations of amplitude and frequency demodulated spectra are derived in closed form, and their frequency structures are revealed. For fault diagnosis based on above theoretical derivations, a resonance frequency identification approach is proposed through time-frequency analysis of torsional vibrations during variable speed processes, according to the independence nature of resonance frequency on running conditions. The theoretical derivations and proposed approach are illustrated by numerical simulated signal analysis and are further validated through dynamics modelling and lab experimental tests. Localized faults on the sun, planet, and ring gears are successfully diagnosed.

Mechanical demodulation of aircraft antenna signal

Presented paper concentrates on accidentally identified, specific method of mechanical vibration demodulation, radiated high-frequency signal of aircraft communication antenna, located directly on the aircraft. It describes the structure and solution of the designed laboratory workplace at which it is possible to evoke mechanical vibration demodulation as a specific phenomenon. The aim is to analyze possible physical electric characteristics of antenna as a source of mechanical vibration on “Monopole“ type of antenna. Next, transfer amplitude frequency characteristics of the antenna, as a mechanical vibration demodulator, are analyzed. As this is a basic research of this accidentally identified phenomenon, an observation method of experiment results is used to find out the analogies by the form of their comparison with a classical amplitude demodulator. The results show that if the mechanic influence of artificial ground is suppressed, the transfer amplitude frequency characteristics of such demodulated signal has minimal distortion in frequency range 200Hz to 3.5kHz. The paper presents brief summary of measured basic values on the base of which obtained results are analyzed and brief conclusions of observed phenomenon are defined. They are the first outputs of the phenomenon observations on the base of which it can be concluded that it is reasonable to deal with this problem. At the same time this is not just the antenna characteristics analysis but also the analysis of mechanical oscillations of the antenna from the viewpoint of its more secure fixing at the aircraft fuselage. Because the concurrent influence of two kinds of vibrations, primary – as a result of aerodynamic circumfluence of antenna during the flight in collaboration with the secondary – as a result of its radiation, places higher requirements on its mechanical fixation. Presented facts mean the increase of air traffic operation.

A soft decoding algorithm and hardware implementation for the visual prosthesis based on high order soft demodulation.

BackgroundHigh order modulation and demodulation technology can solve the frequency requirement between the wireless energy transmission and data communication. In order to achieve reliable wireless data communication based on high order modulation technology for visual prosthesis, this work proposed a Reed–Solomon (RS) error correcting code (ECC) circuit on the basis of differential amplitude and phase shift keying (DAPSK) soft demodulation. Firstly, recognizing the weakness of the traditional DAPSK soft demodulation algorithm based on division that is complex for hardware implementation, an improved phase soft demodulation algorithm for visual prosthesis to reduce the hardware complexity is put forward. Based on this new algorithm, an improved RS soft decoding method is hence proposed. In this new decoding method, the combination of Chase algorithm and hard decoding algorithms is used to achieve soft decoding. In order to meet the requirements of implantable visual prosthesis, the method to calculate reliability of symbol-level based on multiplication of bit reliability is derived, which reduces the testing vectors number of Chase algorithm. The proposed algorithms are verified by MATLAB simulation and FPGA experimental results. During MATLAB simulation, the biological channel attenuation property model is added into the ECC circuit.ResultsThe data rate is 8 Mbps in the MATLAB simulation and FPGA experiments. MATLAB simulation results show that the improved phase soft demodulation algorithm proposed in this paper saves hardware resources without losing bit error rate (BER) performance. Compared with the traditional demodulation circuit, the coding gain of the ECC circuit has been improved by about 3 dB under the same BER of 10^{-6}. The FPGA experimental results show that under the condition of data demodulation error with wireless coils 3 cm away, the system can correct it. The greater the distance, the higher the BER. Then we use a bit error rate analyzer to measure BER of the demodulation circuit and the RS ECC circuit with different distance of two coils. And the experimental results show that the RS ECC circuit has about an order of magnitude lower BER than the demodulation circuit when under the same coils distance. Therefore, the RS ECC circuit has more higher reliability of the communication in the system.ConclusionsThe improved phase soft demodulation algorithm and soft decoding algorithm proposed in this paper enables data communication that is more reliable than other demodulation system, which also provide a significant reference for further study to the visual prosthesis system.

Low power RF amplifier circuit for ion trap applications

A low power RF amplifier circuit for ion trap applications is presented and described. The amplifier is based on a class-D half-bridge amplifier with a voltage mirror driver. The RF amplifier is composed of an RF class-D amplifier, an envelope modulator to ramp up the RF voltage during the ion analysis stage, a detector or amplitude demodulation circuit for sensing the output signal amplitude, and a feedback amplifier that linearizes the steady state output of the amplifier. The RF frequency is set by a crystal oscillator and the series resonant circuit is tuned to the oscillator frequency. The resonant circuit components have been chosen, in this case, to operate at 1 MHz. In testings, the class-D stage operated at a maximum of 78 mW at 1.1356 MHz producing 225 V peak.

Fast demodulation of pattern images by spiral phase transform in structured-illumination reflectance imaging for detection of bruises in apples

A structured-illumination reflectance imaging (SIRI) system was recently developed in our laboratory for enhanced quality evaluation of horticultural products. It was implemented using a digital camera to acquire reflectance images from food products subjected to sinusoidal patterns of illumination, instead of conventional diffuse or uniform illumination. The reconstruction of amplitude images is a key step in implementing SIRI technique. Conventional methods require acquisition and subsequent demodulation of three phase-shifted pattern images, which limits the speed of image acquisition. This study proposed the use of spiral phase transform (SPT) for demodulation of pattern images acquired by SIRI. Three SPT-based methods involving only one or two images were investigated through numerical simulation, followed with experiments on the detection of fresh bruises in apples. Compared to conventional three-phase based and two-phase based Gram-Schmidt (GS) orthonormalization demodulation methods, the two-phase SPT method achieved the same or even higher demodulation accuracy, which applies to two pattern images that can be arbitrarily phase-shifted. SPT also allowed single-image based demodulation, although its performance still needs to be improved. This study demonstrated that SPT for amplitude demodulation can increase the imaging speed of SIRI by using one or two pattern images, which is a significant step towards real-time implementation of the technique.

Amplitude and frequency demodulation analysis for fault diagnosis of planet bearings

The vibration signals of planet bearings feature more complex amplitude modulation and frequency modulation (AM-FM) than those of fixed-axis bearings, due to the effects of time-varying vibration transfer path, load zone passing and time-varying angles between gear pair mesh lines of action and impact force vector, in addition to that of bearing fault. Their Fourier spectra have a complex sideband structure, leading to difficulty in feature extraction and fault diagnosis. In order to address this issue, a joint amplitude and frequency demodulation analysis method is proposed to reveal the fault features, by considering the modulation characteristics. To thoroughly understand planet bearing vibration characteristics, the explicit equations for amplitude and frequency demodulated spectra of outer race, rolling element and inner race fault cases are derived, and the fault symptoms are summarized respectively. The signal is firstly decomposed into intrinsic mode functions (IMFs) by empirical mode decomposition (EMD), thus meeting the mono-component requirement by instantaneous frequency calculation. Then a sensitive component with the instantaneous frequency fluctuating around the resonance frequency is chosen for further frequency demodulation analysis. Finally, planet bearing fault can be diagnosed by matching the peaks identified in amplitude and frequency demodulated spectra with the theoretical fault characteristic frequencies. The proposed method is validated with both numerical simulated and lab experimental signal analyses.