AM Signal Research Articles

Bidirectional Multi-Spectral Vibration Control: Insights from Automotive Engine Mounting Systems in Two-Dimensional Structures with a Damaged Vertical Active Element

Active mounting systems have become more prevalent in recent years to effectively mitigate structure-induced vibration across the automobile chassis. This trend is particularly evident in engine mounts. Considerable research has been dedicated to this approach owing to its potential to enhance the quietness and travel comfort of automobiles. However, prior research has concentrated on a limited spectrum of specific vibrations and noise control or has been restricted to vertical vibration control. This article describes the modeling, analysis, and control of a source structure employing a multidirectional active mounting system designed to closely simulate the position and direction of an actual automobile engine mount. A piezoelectric stack actuator is connected in series to an elastic (rubber) mount to form an active mount. The calculation of the secondary force required for each active mount is achieved through the application of harmonic excitation forces. The control signal can also reduce vibrations caused by destructive interference with the input signal. Furthermore, horizontal oscillations can be mitigated by manipulating the parameters via dynamic interconnections of the source structure. We specifically examined the level of vibration reduction performance in the absence of a vertical active element operation and determined whether the control is feasible. Simulation outcomes demonstrate that this active mount, which operates in both the vertical and horizontal directions, effectively mitigates excitation vibrations. Furthermore, a simulation was conducted to mitigate the vibrations caused by complex signals (AM and FM signals) and noise. This was achieved by monitoring the system response using an adaptive filter NLMS algorithm. Adaptive filter simulations demonstrate that the control efficacy degrades in response to complex signals and noise, although the overall relaxation trend remains unchanged.

Simulation and Research of Single Sideband AM Signal Demodulation Circuit Based on Simulink

Simulation and Research of Single Sideband AM Signal Demodulation Circuit Based on Simulink

Fabrication of a Novel GaAs Thermopile Sensor for RF Amplitude Demodulation

In this letter, a novel fabrication of straight-channel RF AM demodulator based on thermopile is presented. Its structure consists mainly of CPW line fed with AM signal, resistors and thermopiles to detect the demodulated signal. The structure is fabricated using GaAs Microwave Monolithic Integrated Circuit (MMIC) technology. Experiments are implemented and the results show that this thermopile-based demodulator is able to perform demodulation of AM signal with carrier frequency of 0.01-10 GHz and signal frequency of under 5 kHz. The influence of thermopile length on the performance is also studied and the result shows that when the thermopile length gets larger, the output amplitude of the demodulated signal gets larger, but its bandwidth gets smaller. In our scenario, the length of the thermopile can be set as 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m as a tradeoff between amplitude and bandwidth. 2022-0187

Research on STM32-Based Signal Conditioning System Measurement System

The measurement of the signal modulation system is a vital part of channel transmission signal technology, which has a very important position in the signal communication quality assurance system. With the development of radio communications in modern radio technology, the research of AM and FM signal modulation measurement methods has become an important element in this field of research. This research is a signal modulation system using an STM32F407 microcontroller as the control core. The hardware of the system is mainly composed of a coherent demodulation circuit system and a comparator judgment circuit system, and the coherent demodulation circuit system is divided into AM demodulation circuit system and an FM demodulation circuit system. The frequency of the input signal was measured by a comparator, and the frequency change was used to initially determine the signal type. In which the modulating signal of AM signal was obtained by DDS generating separate orthogonal sine and cosine signals with the input signal through a series of operations, while the FM signal was operated with the sine signal. Finally, the amplitude and frequency information of the FM signal was obtained through the comparator, and finally reduced to the modulating signal of the FM signal. Output demodulated signal, its signal waveform without obvious distortion apparent phenomenon. Promotes the prospect of using the calibration of AM and FM signal generators in the field of communication.

A Novel Optimization Demodulation Method for Gear Fault Vibration Overmodulation Signal and Its Application to Fault Diagnosis

Many demodulation methods are devoted to obtain the gear fault modulation frequency as the fault diagnosis indicator instead of the precise amplitude and frequency demodulation. It is because the precise demodulation is a challenge especially for the over-modulation signal potentially caused by the gear fault, which further hinders the gear fault degree diagnosis. This paper proposes a novel optimization demodulation method for over-modulation signal. The Hilbert transform demodulation and Jacobi-Anger expansion form are respectively combined with the trust region reflection optimization algorithm to achieve the precise amplitude and frequency demodulation. The objective function about AM parameters considers the zero-crossing feature of the time domain AM in over-modulation signal. The iterated Hilbert transform demodulation is innovatively applied to remove the singularities effect in the residual signal caused by the over-modulation. The simulations and experiments demonstrate that the proposed method has the advantages of high accuracy and strong anti-noise performance in the demodulation of over-modulation signal. The quantitative FM and AM signals obtained by the proposed method can be applied to detect the gear fault degree, which provide an approach for establishing linkages between the modulation intensity and fault degree.

Signal modulation system measuring device

The design can measure and display other parameters such as the modulation system of the measured signal output by the signal source, identify and display the modulation mode of the measured signal, and output the demodulation signal. The measurement module is composed of an automatic gain amplifier circuit, a broadband amplifier, a low-pass filter circuit, a DDS signal generation circuit, an amplification circuit, and a display circuit. The working principle of the signal modulation measuring device is that the demodulated AM signal is obtained after the spectrum is transmitted by the multiplier, and the high-frequency signal is filtered out by the low-pass filter and amplified by the fixed gain amplifier. After the amplification circuit, the output waveform is sampled by the onboard ADC of MSP432E401Y, and then the fast Fourier transform is performed to obtain various parameters, which are finally displayed on the serial screen.

Modeling on RF Circuit and Thermal Conduction of a MEMS Amplitude Demodulator

An amplitude demodulator, using an on-line MEMS power sensor is studied in this paper. The model of the equivalent circuit of on-line structure is solved, and the heat transfer model related to the thermopile is proposed and also simulated to verify the feasibility of AM demodulation. Experiments are also performed to verify the proposed models. The microwave performance shows that the device has a return loss that is better than 20 dB, and an insertion loss of less than 0.5 dB up to 10 GHz. Both the model and the experimental results show that the MEMS device can perform demodulation of an AM signal with carrier frequency of 0.01–10 GHz and signal frequency of under 1kHz. [2021-0261]

Feature Extraction Using Parameterized Multisynchrosqueezing Transform

Parametrized time-frequency analysis (PTFA) can effectively improve time-frequency energy aggregation of non-stationary signal and immunity of cross term interference, but it exists the energy diffusion near the real instantaneous frequency. The improved multi-synchrosqueezing transform (IMSST) can improve the time-frequency energy aggregation, but it still has defects in processing strong FM and AM signals under noise interference. Therefore, in order to make use of their advantages and overcome their disadvantages, a novel parametrized multi-synchrosqueezing transform method based on weighted least square, IMSST and PTFA, namely PMSST is proposed in this paper. In the PMSST, the IMSST is designed to obtain the signal time-frequency representation with high energy aggregation. Then the ridge extraction algorithm is employed to extract the instantaneous frequency ridges of each mono-component signal. The weighted least square method is used to estimate the parameters of parameterized transform kernel. Finally, time-frequency spectrum is superimposed to obtain the time-frequency energy representation of the enhanced signal. The experiment results show that the PMSST can effectively process non-stationary signals with varying instantaneous frequency by the simulated signal and actual fault signals.

DRM DIGITAL BROADCASTING SYSTEM AUDIO PATH QUALITATIVE CHARACTERISTICS

The Digital Radio Mondiale (DRM) digital broadcasting system is the only ITU-approved digital broadcasting system for the LF, MF and HF bands. Numerous theoretical and field studies, as well as operating experience over the past 20 years, have allowed a good study of digital broadcasting networks organization according to this standard. However, some of the issues related to the audio path formal characteristics were not considered. The article discusses the audio coders used in the DRM system and the available data rates in various immunity modes. A set of test signals for instrumental measurements and listening has been developed. The results of experimental measurements for various data rates are presented. It is shown that the range of modulating frequencies in 7 modes of immunity is not narrower than for FM transmitters. In another 5 modes of noise immunity, the range of modulating frequencies is narrower than for FM transmitters, but wider than for AM transmitters. It is confirmed that at data rates of more than 16.5 kbps, the DRM transmitter signal quality becomes no worse than AM signal transmitter quality. Above 24 kbps, the DRM transmitter signal quality becomes comparable to that of an FM transmitter.

Conversion of amplitude modulation to phase modulation in the human cochlea

When an amplitude modulated signal with a constant-frequency carrier is fed into a generic nonlinear amplifier, the phase of the carrier of the output signal is also modulated. This phenomenon is referred to as amplitude-modulation-to-phase-modulation (AM-to-PM) conversion and regarded as an unwanted signal distortion in the field of electro-communication engineering. Herein, we offer evidence that AM-to-PM conversion also occurs in the human cochlea and that listeners can use the PM information effectively to process the AM of sounds. We recorded otoacoustic emissions (OAEs) evoked by AM signals. The results showed that the OAE phase was modulated at the same rate as the stimulus modulation. The magnitude of the AM-induced PM of the OAE peaked generally around the stimulus level corresponding to the compression point of individual cochlear input–output functions, as estimated using a psychoacoustic method. A computational cochlear model incorporating a nonlinear active process replicates the abovementioned key features of the AM-induced PM observed in OAEs. These results indicate that AM-induced PM occurring at the cochlear partition can be estimated by measuring OAEs. Psychophysical experiments further revealed that, for individuals with higher sensitivity to PM, the PM magnitude is correlated with AM-detection performance. This result implies that the AM-induced PM information cannot be a dominant cue for AM detection, but listeners with higher sensitivity may partly rely on the AM-induced PM cue.

A High Conversion Gain Envelope Detector with Wide Input Range for Simultaneous Wireless Information and Power Transfer System

Wireless sensors networks (WSN) have been gradually facilitating the pervasive connectivity of wireless sensor nodes. A greater number of wireless sensors have been used in different aspects of our life. However, limited device battery life restricts the applications of large-scale WSN. This paper presents a batteryless envelope detector with radio frequency energy harvesting (RFEH) for wireless sensor nodes, which enables simultaneous wireless information and power transfer (SWIPT). The envelope detector is designed for small modulation index AM signals with large amplitude variations. Therefore, the envelope detector is supposed to have wide input range while achieving a high conversion gain. We proposed an adaptive biasing technique in order to extend the input range of envelope detector. The input differential pair is adaptively biased through a feedback loop to overcome the variation of bias point when the amplitude of input signal changes. The cross coupled rectifier and DC-DC boost converter with maximum power point tracking (MPPT) are presented against power conversion efficiency (PCE) degradation of RF rectifier with the input power varying. The adaptive biased envelope detector is theoretically analyzed by square law MOSFET model. Designed with 0.18 μm complementary-metal-oxide-semiconductor (CMOS) standard process, the power consumption of proposed envelope detector is 9 μW. Simulated with a 915 MHz AM input signal with 2 Mbps data rate and 0.05 modulation index, the proposed envelope detector achieves 20.37 dB maximum conversion gain when the amplitude of input signal is 0.5 V, and the PCE of energy harvesting circuits achieves 55.2% when input power is –12.5 dBm.

Преобразование спектра амплитудно-модулированного сигнала на омическом нелинейном элементе

Introduction. In many physical processes, the spectrum of the modulated signal is transferred to the low-frequency region, which also manifests itself in active dielectrics in radio sound. In the general case, the analysis of the spectrum transformation process is a very difficult task related with solving a system of nonlinear differential equations. And in the accepted form, the principle of superposition is not applicable here, since the parameters of the output signal cannot be determined by algebraic summation of the signals received separately from each source. The spectrum of an input amplitude-modulated signal is nonlinearly related to the spectrum at the output. Aim. The conversion of the current spectrum under supplying an amplitude-modulated voltage to an active non-linear element with a non-linear current-voltage characteristic is considered. Materials and methods. In the analysis of the spectral transformation, a power approximation of the current-voltage characteristic in the form of a polynomial of the third degree with trigonometric functions is used. In the examples, spectrum transformations for a mono signal, amplitude-modulated signal, and beats are considered. Application of amplitude modulation methods is essential for transferring the spectrum of the signal to the low frequency region. Results. A graphical representation of the dependence of the current function on time for an AM signal and beats, as well as their spectral representation, is given. Conclusion. The paper analyzes the transformation of the signal spectrum for the current when applying any, but amplitude-modulated voltage on the ohmic nonlinear element. The carrier signal is represented as a harmonic trigonometric function of the cosine of the current time. However, signal spectrum conversion has not related with detection.

A Highly Linear Wideband Polar Class-E CMOS Digital Doherty Power Amplifier

This article presents the first application of a digital-intensive intrinsically linear digitally controlled class-E technique in a Doherty configuration. By careful nonlinear segmentation and multiphase RF-clocking along with overdrive-voltage control and automatic duty-cycle correction, it is shown that even the nonlinearities related to Doherty operation can be fully handled by the underlying design such that digital predistorion (DPD) can be, in principle, omitted. The nonlinearity behavior of the whole digital Doherty power amplifier (PA) is analyzed, and closed-form equations are given to predict the AM-AM and AM-phase modulation (PM) curves. In addition, time/phase mismatch between the peak and main branches and the AM and PM signals is accurately compensated. In order to achieve the maximum intrinsic linearity, two separate chips with the same architecture, but different design parameters, are fabricated as the main and peak amplifiers in 40-nm bulk CMOS. To achieve a large RF bandwidth and high passive combiner efficiency, a differential low-loss, wideband Marchand balun-based Doherty power combiner, implemented using reentrant coupled lines with independent second-harmonic control is proposed, and together with the matching network is fabricated on a two-layer PCB. The measured peak/6-dB power backoff P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</sub> , drain efficiency/power-added efficiency at 2.4 GHz are 17.5 dBm/12.2 dBm, 57%/52% and 36%/25% with VDD main/peak = 0.6 V/0.7 V. Measured results without using DPD show -41-dBc adjacent channel power ratio (ACPR) and -36-dB error vector magnitude (EVM) for a 16-MHz OFDM signal at 2.5 GHz. By using DPD, the measured ACPR and EVM of a 16-MHz /32-MHz OFDM signals are -52 dBc/-48 dBc and -50 dB/-48 dB, respectively.

Pembangkit Sinyal ELT pada Frekuensi 121,5 MHz

An ELT is a beacon indicating the location of distress or crash of aircraft on land or sea. The ELT is placed in an airplane, which is a transmitter with low transmit power and an antenna. The ELT transmitter has been widely used for flights at the frequency of 121.5 MHz (civilian) and 243 MHz (military). The purpose of this study is to produce ELT signal generators at the 121.5 MHz frequency, with low-cost devices that meet specifications for civil aviation. In this research has been produced a design of an ELT signal generator at the frequency of 121.5 MHz, consist of a crystal oscillator, a sawtooth generator, a VCO, and an amplitude modulator. Based on the measurement and test results, the sawtooth generator generated a sawtooth signal at the frequency of 1.8 to 3.6 Hz, the VCO generated a sinusoidal signal at the frequency of 316 to 366 Hz, the RF generator generated a sinusoidal at the frequency of 121.505 MHz. The ELT signal generator was able to generate AM signals at the minimum amplitude deviation of 100 mVpp to maximum one of 156 mVpp, the modulation index (m) of 21.875%, and the frequency of 121.505 MHz. The results of this study are ELT signal generators at the frequencies of 121.5 MHz that are in accordance with specifications for civil aviation.

Medium and Short Wave RF Energy Harvester for Powering Wireless Sensor Networks.

Internet of Things (IoT) is an emerging platform in which every day physical objects provided with unique identifiers are connected to the Internet without requiring human interaction. The possibilities of such a connected world enables new forms of automation to make our lives easier and safer. Evidently, in order to keep billions of these communicating devices powered long-term, a self-sustainable operation is a key point for realization of such a complex network. In this sense, energy-harvesting technologies combined with low power consumption ICs eliminate the need for batteries, removing an obstacle to the success of the IoT. In this work, a Radio Frequency (RF) energy harvester tuned at AM broadcast has been developed for low consumption power devices. The AM signals from ambient are detected via a high-performance antenna-free LC circuit with an efficiency of 3.2%. To maximize energy scavenging, the RF-DC conversion stage is based on a full-wave Cockcroft–Walton voltage multiplier (CWVM) with efficiency up to 90%. System performance is evaluated by rating the maximum power delivered into the load via its output impedance, which is around 62 μW, although power level seems to be low, it is able to power up low consumption devices such as Leds, portable calculators and weather monitoring stations.

A 5-mW 750-kb/s Noninvasive Transceiver for Around-the-Head Audio Applications

This brief presents a noninvasive energy-efficient frequency-modulated ultra-wideband (FM-UWB) transceiver. 8-frequency-shift-keying (FSK) subcarrier modulation is utilized to enhance the data rate with a slight increment of hardware complexity compared to the conventional 2-FSK FM-UWB system. The transmitter employs a fast settling PLL with a pretuned relaxation VCO for 8-FSK subcarrier modulation. The transmitted signal by an FLL-assisted ring VCO followed by a single-stage class AB power amplifier meets the FCC spectrum mask. The regenerative receiver employs a wideband LNA with a stacked structure to save power. Two 4th-order Butterworth bandpass filters and envelope detectors convert the FM signal to an AM signal with good linearity. The 3.5-4 GHz 750-kb/s transceiver implemented in 65-nm CMOS consumes 5 mW from a 1-V supply, achieving an energy efficiency of 6.7 nJ/bit.

Measurements of Medium Wave HD Radio Reception in a Dense Urban Region

This paper presents the results of measurements of medium wave received field strength, HD Radio audio quality and maximum coverage distances in a dense urban region. Analog AM and digital HD Radio signals broadcasting the same content were simultaneously transmitted in Sao Paulo, the largest city in Brazil. The received signal intensity and the reception quality were recorded along radial routes of up to 45 km from the transmitter under both mobile and static conditions, enabling the comparative assessment of the digital and analog system performances

Detection and Demodulation of AM Signals Using Two Dimensional Spectral Surface

This paper is designed to detect AM signals, evaluate its parameters and consequently provides demodulation procedure using the methods of Short Time Fourier Transform (STFT) and Discrete Fourier Transform (DFT) combined with two Dimensional Spectral Surface (2DSS). The proposed technique is noise robust since the energies of modulated signal and noise located in different position on 2DSS which could be discarded during the analysis. Comparing with the Hilbert Transform the proposed method can extract envelopes of different carriers transmitted in the same channel.

Automated Demodulation of Amplitude Modulated Multichannel Signals with Unknown Parameters Using 3D Spectrum Representation

In current research, new method of automated demodulation of amplitude modulated multichannel signals transmitted with unknown parameters has been proposed and tested. The method is perspective and actual because demodulation is an ill-posed problem when both the carrier and envelope signals are broadband and unknown. The innovative point of this study is the elaboration of the method that enables the evaluation of unknown parameters of the AM signal. The method is based on a new approach called the 3D spectrum representation of AM signals, where the first dimension indicates the allocation of carrier frequencies, the second indicates the band of message signal and the third is related to time. In this study, we report that the 3D representation enables to track unknown AM signal parameters, such as the carrier frequency, frequency of message signal and number of channels and apply demodulation techniques even for time-varying parameters of the signal. The results of the performed experiments indicate that the proposed method effectively performs the envelope detection and automated demodulation of multichannel AM signals.

Estimating Parameters of Combined AM and PM Signals Using Prior Information

A method for estimating parameters of combined amplitude and phase modulation signals from digital sampling data is proposed. It can be employed with advantage to analyze combined modulation functions of commercial function generators. Though this problem of inference has applications in communication technology, it has also become a concern to the power industry in issues related to phasor measurement unit tests. Prior information available to metrologists about the signal components allows the reduction of the dimensionality of the search algorithm with consequent time savings.