Signal Generation Method Research Articles

A Low-Loss Broadband Quadrature Signal Generation Network for High Image Rejection at Millimeter-Wave Frequencies

This paper presents a broadband low-loss quadrature-hybrid-based network that enhances the phase and the amplitude matching of quadrature signals. The performance of this network is investigated, and a detailed theoretical analysis is provided. Several stages of this network can be cascaded to generate broadband balanced quadrature signals. Each stage has a loss of 0.5 dB and enhances the image rejection ratio (IRR) by approximately 8 dB. Compared with the conventional polyphase quadrature signal generation methods, the proposed network enables lower insertion loss, wider bandwidth, and reduced sensitivity to process variations. To verify the theoretical analyses, two proof-of-concept image-reject mixers are implemented in a 0.13- $\mu \text{m}$ SiGe BiCMOS technology. The first mixer achieves an average IRR of 37.5 dB across 40–76 GHz, whereas the second mixer achieves an average IRR of 33.5 dB across 40–102 GHz. The proposed network is a promising solution for broadband quadrature signal generation at millimeter-wave frequencies, as it eliminates the need for calibration and tuning.

Pre-distortion compensation for optical-based broadband LFM signal generation system

Abstract A high-quality broadband radio frequency linear frequency modulation (RF-LFM) signal generation method based on the optical frequency quadrupling and the direct digital waveform synthesize (DDWS) with time-domain pre-distortion compensation is theoretical analyzed and experimental demonstrated. In this method, the optical frequency quadrupling is realized by beating the higher-order sidebands using a dual-parallel Mach–Zehnder modulator (DPMZM) so as to achieve the RF-LFM signal output. Since this optical frequency quadrupling link will induce the amplitude and phase distortions for the LFM signal, a time-domain pre-distortion compensation technique is used based on polynomial fitting. The experimental result shows that a LFM signal with the bandwidth 12 GHz and pulse width 10 μ s at the central frequency 22 GHz can be obtained. With the pre-distortion compensation the output LFM spectrum flatness is improved from 6dB to 2dB, the phase error is reduced from 30°to 5°, and the peak side lobe ratio (PSLR) is improved from -10.12dB to -13.01dB, which is close to the theoretical value -13.26dB.

Improved Voltage Unbalance and Harmonics Compensation Control Strategy for an Isolated Microgrid

This paper suggests an enhanced control scheme for a four-leg battery energy storage systems (BESS) under unbalanced and nonlinear load conditions operating in the isolated microgrid. Simplicity, tiny steady-state error, fast transient response, and low total harmonic distortion (THD) are the main advantages of the method. Firstly, a new decoupled per-phase model for the three-phase four-leg inverter is presented. It can eliminate the effect of power stage coupling on control design; thus, the three-phase four-leg power inverter can be viewed as three single input single output (SISO) control systems. Then, using an improved orthogonal signal generation method, the per-phase model of the four-leg inverter in the stationary and synchronous frame is derived. As the second step, a per-phase multi-loop control scheme for the four-leg inverter under unbalanced load conditions is suggested. The proposed control strategy has the ability to provide balanced output voltages under unbalanced load conditions by avoiding the need to deal with the symmetrical components. Finally, a multi-resonant harmonic compensator is used to actively prevent low-order harmonic currents to distort the output voltages of the three-phase four-leg grid-forming power converter. Simulations results are also presented to verify the performance of the suggested control strategy.

A random signal generation method for microcontrollers with DACs

A random signal generation method for microcontrollers with DACs

Comparative analysis of interference, noise and losses in the mobile communication systems in millimeter wave range

The article analyzes the approaches to the mathematical modeling of mobile systems in the millimeter wave range. The architecture of a mobile network using Radio over Fiber (RoF) technology is considered which is proposed for forming and transmitting the millimeter-wave signals via fiber-optic communication lines. The noise of the optical heterodyne used for the formation of radio signals is analyzed. The mathematical analysis of the components of the energy budget of the radio link in the millimeter wave range is carried out on the basis of a study of the fundamental physical aspects that affect the value of noise, losses and signal gains. The comparative analysis of the signal-to-interference ratio and the signal-to-noise ratio, the probability of transmitting information radio signals through the reflected paths is carried out. A quasi-optical model of the narrow-beam antenna radiation is proposed for calculating noise interference and signal loss in multipath propagation models taking into account multiple reflections and diffractions, as well as absorption in various media. The analysis of the energy budget components of the radio link in the millimeter wave range shows that it is necessary to take into account both interference and noise associated with the method of signal generation and emission, for example, in phased antenna arrays, as well as the effects of molecular absorption (repeated radiation) in the atmosphere and the effects of the reflection of signals in urban scenario.

Synchronous radio-frequency FM signal generator using direct digital synthesizers.

A novel Radio-Frequency Frequency-Modulated (RF-FM) signal generation method is introduced and a prototype circuit developed to evaluate its functionality and performance. The RF-FM signal generator uses a modulated, voltage-controlled time delay to correspondingly modulate the phase of a 10 MHz sinusoidal reference signal. This modulated reference signal is, in turn, used to clock a Direct Digital Synthesizer (DDS) circuit resulting in an FM signal at its output. The modulating signal that is input to the voltage-controlled time delay circuit is generated by another DDS that is synchronously clocked by the same 10 MHz sine wave signal before modulation. As a consequence, all of the digital components are timed from a single sine wave oscillator that forms the basis of all timing. The resultant output signal comprises a center, or carrier, frequency plus a series of phase-synchronized sidebands having exact integer harmonic frequency separation. In this study, carrier frequencies ranging from 10 MHz to 70 MHz are generated with modulation frequencies ranging from 10 kHz to 300 kHz. The captured spectra show that the FM signal characteristics, amplitude and phase, of the sidebands and the modulation depth are consistent with the Jacobi-Anger expansion for modulated harmonic signals.

A Discrete Fourier Transform Based Dithering Signal Generation Method for Reduced Quantization Error

Addressing the impact of quantization error in analog-to-digital converter (ADC) for signal processing, a Discrete Fourier Transform (DFT) based method for the generation of dithering signals is presented. Effective in reducing quantization error, the dithering signal generated using the method is not only independent of the input signal but also can improve the performance of the ADC. To illustrate the advantages of the dithering signal reconstructed using the method, three kinds of typical dithering effects, namely, Triangular Distribution Dithering, Gaussian Distribution Dithering and Uniform Distribution Dithering on the quantization error in an ADC are considered. The properties of three practical dithering signals are investigated. It is shown that while these typical dithering may be useful they are some potential problems. The dithering signals reconstructed using the DFT based generation scheme is shown to contribute significantly to reducing quantization error. Numerical experiments and theoretical analyses demonstrate that the DFT based dithering reconstruction can obtain prominent performance for ADC in comparison to typical dithering signals.

Phase-aligned Dual-frequency Constant Envelope Multiplexing Technique for GNSS Signals

In the new generation of Global Navigation Satellite Systems (GNSS), dual-frequency constant envelope multiplexing is widely desired and is becoming an important subject in signal design. Considerable work has been devoted to multiplexing for the Alternative Binary Offset Carrier (AltBOC)-like signal model, for which each sideband consists of two or fewer signal components. In this paper, a phase-aligned dual-frequency constant envelope multiplexing technique is proposed for a general dual-frequency signal model. This multiplexing technique can be used to combine two constant-envelope-modulated signals in two sidebands into a composite signal with a constant envelope, where the constant-envelope-modulated signal in each sideband consists of an arbitrary number of signal components with an arbitrary power ratio and phase relationship among the signal components. A Lookup Table (LUT)-based signal generation method is also proposed, for which the required driving clock rate of the signal generator can be flexibly adjusted to meet the requirements of the satellite payload. Applications for the AltBOC-like signal model and a general dual-frequency signal model in the Beidou B1 band validate the flexibility and high multiplexing efficiency of our method. Specifically, AltBOC is a special case of the proposed method.

Method for pseudo-noise signal generation based on M-sequences with non-multiple recurring periods

Method for pseudo-noise signal generation based on M-sequences with non-multiple recurring periods

Development and performance test of dynamic simulation system for X-ray pulsar navigation

X-ray pulsar navigation is a complete autonomous navigation system, which has broad application prospects. Because of the huge cost of the navigation system, the implementation of ground simulation system is essential to the application of X-ray pulsar navigation. At present, most of researches on the semi physical experiment system are static. The aim of this article is to develop the dynamic simulation experiment system as well as its performance test. Specifically, this system consists of the dynamic signal database, X-ray simulation source, vacuum system and detection system designed for different science purposes. The core component of the X-ray source is the gate controlled X-ray tube, which can simulate the pulse profile of arbitrary waveform. The detecting system is based on the silicon drift detector with high time response capability. It uses trapezoidal shape for signal processing, and the timing resolution of the detection system is better than 2 s. In addition, the dynamic signal generation method is given by analyzing the time transformation model while the SINC interpolation method is provided to generate the dynamic pulse profile. Finally, the spacecraft revolving around the earth for a circle and receiving a pulse signal of Crab is simulated. In the simulation, the orbital radius of satellite is 6578 km and the orbital period is 5400 s. The Crab pulsar is selected, and the pulse period is 33.4 ms, the number of photons received by the detector is 200 per second. As a contrast, a set of static experiments is also performed. The correlation coefficient between the cumulative pulse profile and the standard pulse profile is 0.9953. However, the correlation coefficient decreases gradually, from 0.9094 at 300 s to 0.4080 at 5400 s, in the dynamic experiment. Then, the pulse period is searched from the arrival time of photons. The periodicity of the pulse signal is sinusoidal when the search period is 60 s. The change rate of photon flux is less than 2\%, and the influence on the period search is negligible. The variation of pulse period is consistent with the motion law of spacecraft, which indicates that spacecraft motion is the dominant factor in time conversion. Finally, the arrival time of photons is transformed into the time at the solar system barycenter, indicating that the correlation coefficient between cumulative pulse profile and standard pulse profile is 0.9882. The result shows that the simulation system can simulate the X-ray pulse signal received by the spacecraft in orbit, which can provide the experimental basis for verifying the navigation algorithm and calibrating the detector performance.

A Novel Fast Open-loop Phase Locking Scheme Based on Synchronous Reference Frame for Three-phase Non-ideal Power Grids

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

OFDM Multitone Signal Generation Technique for Analog Circuitry Test Characterization

Multitone test is an effective technique in many wideband circuit test applications. However, the traditional multitone test signal generation methods are complex and/or time consuming. In this brief, a new approach utilizing orthogonal frequency-division multiplexing technique is developed, which can effectively produce multiple frequency tones concurrently with fine resolution and low design overhead. For validation, filter test characterizations are performed and demonstrated.

Efficient Raw Signal Generation Based on Equivalent Scatterer and Subaperture Processing for One-Stationary Bistatic SAR Including Motion Errors

This paper presents an efficient raw signal generation method based on equivalent scatterer and subaperture processing for the one-stationary bistatic synthetic aperture radar (SAR). It considers the moving platform's motion error to generate the precise raw signal for real SAR systems. First, the imaging geometry in elliptical polar coordinates is built, and then, the scene is divided into several equidistant elliptical rings. Based on the equivalent scatterer model, the approximate SAR system transfer function is derived; thus, each pulse's raw signal is calculated by the convolution of the transmitted signal and transfer function, via the fast Fourier transform (FFT). To further improve the simulation speed, the subaperture and subscene processing is used. The transfer function for the same subaperture's pluses is calculated simultaneously by the weighted sum of all subscenes' equivalent scattering coefficient in the same equidistant elliptical ring, which is performed by the nonuniform FFT (NUFFT). This method only involves the FFT, NUFFT, and complex multiplication, which means the easier operation and higher efficiency. The implementation, limitation, and evaluation of the proposed method are discussed. Simulation results are given to prove the correctness and validity of the proposed method.

Beam propagation method for wide-field nonlinear wave mixing microscope**Project supported by the National Natural Science Foundation of China (Grant Nos. 11174019, 61322509 and 11121091) and the National Basic Research Program of China (Grant No. 2013CB921904).

We develop a nonlinear beam propagation method for signal generation in inhomogeneous medium for wide-field nonlinear wave mixing microscope. Experimental results performed in wide-field coherent anti-Stokes Raman imaging have shown good agreement with the developed theory.

Infrared sensor signal generation method for direct signal injection simulation

Direct signal injection (DSI) simulation has been widely used in the performance testing and evaluation of an infrared imaging system (IRIS). A method to generate a high realism infrared sensor signal (HRIRSS) for DSI simulation is proposed. The IR sensor signal generation system hardware is based on a computer and field-programmable gate array processor. Mathematical models are adopted to quantitatively characterize the imaging physical effects (IPES) of the IRIS. Spatial template convolution and pixel processing approaches are used to realize high-speed real-time computation of the IPES. Taking advantages from low-noise circuit design methodologies, we designed a low-noise digital–analog converter to convert digital images generated by the system to analog signals for DSI simulation. The noise voltage of the converter within the passband is less than 244 μV, which ensures the system a 14-bit precision. For simulation of IR sensors with a resolution of 320×256 pixels, the processing speed is up to 240 frames per second (fps) and that for the 128×128 pixel sensor is 480 fps. The test results also show that the generated IR sensor signals have high confidence. In addition, the system has the advantages of simple structure, strong expansibility, low cost, and it has been used in practical applications.

Improving of the Generation Method of Repeated PWM Based on the Signals Combinations Applied to a PV Pumping System

In this paper, we present a new method of the PWM signal generation with repetition of data segments, based on the round robin segment of different amplitudes converters, applied to the photovoltaic water pumping system and the variable frequency variable voltage systems, in order to use the data stored signals to generate other signal amplitudes intermediate to optimize memory usage and reduce the cost of the control board.

An Algorithm for the Automatic Analysis of Signals From an Oyster Heart Rate Sensor

An in situ optical oyster heart rate sensor generates signals requiring frequency estimation with properties different to human ECG and speech signals. We discuss the method of signal generation and highlight a number of these signal properties. An optimal heart rate estimation approach was identified by application of a variety of frequency estimation techniques and comparing results to manually acquired values. Although a machine learning approach achieved the best performance, accurately estimating 96.8% of the heart rates correctly, a median filtered autocorrelation approach achieved 93.7% with significantly less computational requirement. A method for estimating heart rate variation is also presented.

Benefits of large healthcare databases for drug risk research

Large electronic healthcare databases have become an important worldwide data resource for drug safety research after approval. Signal generation methods and drug safety studies based on these data facilitate the prospective monitoring of drug safety after approval, as has been recently required by EU law and the German Medicines Act. Despite its large size, a single healthcare database may include insufficient patients for the study of a very small number of drug-exposed patients or the investigation of very rare drug risks. For that reason, in the United States, efforts have been made to work on models that provide the linkage of data from different electronic healthcare databases for monitoring the safety of medicines after authorization in (i) the Sentinel Initiative and (ii) the Observational Medical Outcomes Partnership (OMOP). In July 2014, the pilot project Mini-Sentinel included a total of 178million people from 18 different US databases. The merging of the data is based on a distributed data network with a common data model. In the European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (ENCEPP) there has been no comparable merging of data from different databases; however, first experiences have been gained in various EU drug safety projects. In Germany, the data of the statutory health insurance providers constitute the most important resource for establishing a large healthcare database. Their use for this purpose has so far been severely restricted by the Code of Social Law (Section 75, Book 10). Therefore, a reform of this section is absolutely necessary.

Alcohol Dehydrogenase-Catalyzed Gold Nanoparticle Seed-Mediated Growth Allows Reliable Detection of Disease Biomarkers with the Naked Eye.

Here, we reported a strategy-based plasmonic enzyme-linked immunosorbent assay (ELISA) using alcohol dehydrogenase-catalyzed gold nanoparticle seed-mediated growth to serve as a colorimetric signal generation method for detecting disease biomarkers with the naked eye. This system possesses the advantages of outstanding robustness, sensitivity, and universality. By using this strategy, we investigated the hepatitis B surface antigen (HBsAg) and α-fetoprotein (AFP) with the lowest concentration of naked-eye detection down to 1.0 × 10(-12) g mL(-1). Experiments with real serum samples from HBsAg-infected patients are presented, demonstrating the potential for clinical analysis. Our method eliminates the need for sophisticated instruments and high detection expenses, making it possible to be a reliable alternative in resource-constrained regions.

An Alternative Method for PM Signal Generation and Detection

ABSTRACTThis paper presents a novel scheme for generating a phase modulated (PM) continuous wave carrier of constant envelope and the corresponding demodulation scheme. The modulator is based on the principle of the quadrature carrier multiplexing (QCM) wherein the sine wave carrier is multiplied by the message signal, m(t), and the cosine wave carrier is multiplied by the modified signal, √ (1–m2(t)), with the constraint that │m(t)│<1. The demodulator includes an amplitude limiter, a bandpass filter, and a coherent detector. The proposed scheme introduces a maximum linear phase shift of about ±20° when the message signal amplitude is 0.9 V. The phase shift introduced into the carrier is linear to the tune of ±360° as the message signal amplitude is reduced. The proposed scheme allows for the use of high-frequency stable quadrature oscillators in the modulator and offers better noise immunity like the conventional PM carrier. Furthermore, this paper presents a view point that the existing analogue modulation schemes can be viewed as special cases of the QCM principle.