Signal Generation Techniques Research Articles

Comparison of electronic and optoelectronic signal generation for (sub-)THz communications

Abstract In recent years, the significance of terahertz (THz) and (sub-)THz communications has grown substantially due to its promising trade-off between higher capacity compared to microwave-based communication and better resilience against weather dependent influences (e.g., fog and rain). While electronic and optoelectronic techniques have been extensively explored, each offering distinct advantages and limitations, they have predominantly been demonstrated and discussed as individual experiments, making performance comparison challenging. This paper addresses this gap by systematically benchmarking electronic and optoelectronic signal generation approaches under comparable conditions. Our experiments incorporate various receiver types, revealing that best performance is achieved by combining optoelectronic signal generation techniques at the transmitter in combination with an all-electric intradyne receiver. This results in a remarkable line rate of 200 Gbit/s over a distance of 52 m. To our knowledge, this represents the highest line rate achieved for technically relevant transmission distances for indoor access or outdoor small cell networks.

Direct comparison of colorimetric signal amplification techniques in lateral flow immunoassays.

The lateral flow immunoassay (LFIA) is widely adopted for point-of-care testing, but its limit of detection (LoD) falls short of that of laboratory-based immunoassays. Several techniques have been proposed to enhance the LoD of LFIAs using visual colorimetric readouts, yet a direct comparison of the LoDs achieved by these techniques has not been performed. In this work, we measure the LoDs of LFIAs designed for the detection of a malaria protein, PfHRP2, using four different colorimetric signal generation techniques: (i) AuNP(40 nm)-tagged detection antibodies (base case), (ii) AuNP-based enhancement of AuNP(40 nm) signal, (iii) oxidation of chloronaphthol/diaminobenzidine (CN/DAB) using HRP-tagged detection antibodies, and (iv) oxidation of CN/DAB using polyHRP(400)-tagged detection antibodies. The LoDs and the 95% confidence intervals of the LoDs achieved by the 4 techniques were 19.34 (13.37-27.62) ng mL-1, 9.57 (6.76-13.28) ng mL-1, 21.57 (14.26-32.18) ng mL-1, and 6.09 (2.23-13.47) ng mL-1, respectively. Contrary to popular perception, enzymatic signal generation using HRP-tagged detection antibodies did not improve the LoD compared to the base case of AuNP-based signal generation. Further studies revealed that the very high extinction coefficient of gold nanoparticles renders them an excellent choice for colorimetric detection, surpassing the performance of enzymatic signal generation using HRP-tagged antibodies. However, enzymatic signal generation using polyHRP-tagged antibodies improved the LoD compared to the base case. These results show that enzymatic signal amplification should not be a priori assumed to be superior to AuNP-based signal generation; and provide a reference point to LFIA developers to select an appropriate signal generation modality.

Microwave Photonics Based Millimeter-Wave Signal Generation Technique for 5G Systems

Microwave Photonics Based Millimeter-Wave Signal Generation Technique for 5G Systems

Epileptic EEG patterns recognition through machine learning techniques and relevant time-frequency features.

The present study is designed to explore the process of epileptic patterns' automatic detection, specifically, epileptic spikes and high-frequency oscillations (HFOs), via a selection of machine learning (ML) techniques. The primary motivation for conducting such a research lies mainly in the need to investigate the long-term electroencephalography (EEG) recordings' visual examination process, often considered as a time-consuming and potentially error-prone procedure, requiring a great deal of mental focus and highly experimented neurologists. On attempting to resolve such a challenge, a number of state-of-the-art ML algorithms have been evaluated and compare in terms of performance, to pinpoint the most effective algorithm fit for accurately extracting epileptic EEG patterns. Based on intracranial as well as simulated EEG data, the attained findings turn out to reveal that the randomforest (RF) method proved to be the most consistently effective approach, significantly outperforming the entirety of examined methods in terms of EEG recordings epileptic-pattern identification. Indeed, the RF classifier appeared to record an average balanced classification rate (BCR) of 92.38 % in regard to spikes recognition process, and 78.77 % in terms of HFOs detection. Compared to other approaches, our results provide valuable insights into the RF classifier's effectiveness as a powerful ML technique, fit for detecting EEG signals born epileptic bursts. As a potential future work, we envisage to further validate and sustain our major reached findings through incorporating a larger EEG dataset. We also aim to explore the generative adversarial networks (GANs) application so as to generate synthetic EEG signals or combine signal generation techniques with deep learning approaches. Through this new vein of thought, we actually preconize to enhance and boost the automated detection methods' performance even more, thereby, noticeably enhancing the epileptic EEG pattern recognition area.

Empowering 5G and Beyond: Advanced Multiband Signal Generation and High-Performance Signal Synthesis Techniques for Communications and Sensing Systems [From the Guest Editor’s Desk

Empowering 5G and Beyond: Advanced Multiband Signal Generation and High-Performance Signal Synthesis Techniques for Communications and Sensing Systems [From the Guest Editor’s Desk

A mm-Wave Signal Generation and Background Phase Alignment Technique for Scalable Arrays

This work presents a mm-wave signal generation method that provides background phase tuning and self-alignment between adjacent sources. This technique is based on direct monitoring of the mm-wave signal and provides phase tuning through a baseband feedback loop. We present the theory of the concept, provide the design methodology, and validate the proposed method with a two-element prototype in a 65-nm CMOS process. The prototype has a chip area of 1.3 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 mm and consumes a total dc power of 258 mW. Chip measurements demonstrate a phase tuning range of 140° at 35 GHz with 20°/step and 3.5° of rms phase error. The measured phase switching time is 20 ns. The measured phase noise at 1-MHz offset is below –117 dBc/Hz across phase settings, and the accumulated jitter is 86 fs. These results are consistent with theory and simulation. This work provides a phase alignment technique for large-scale mm-wave phased arrays.

Period-One Laser Dynamics for Photonic Microwave Signal Generation and Applications

Due to the advantages of rich dynamics, small size, and easy integration, semiconductor lasers have many applications in microwave photonics. With a proper perturbation to invoke period-one (P1) nonlinear laser dynamics, a widely tunable microwave signal can be generated. In this paper, we concentrate on the realization and application of photonic microwave signal generation based on the P1 oscillation state of semiconductor lasers. Recent developments in P1 dynamics-based tunable microwave signal generation techniques are reviewed with an emphasis on the optical injection system, which has a large frequency tuning range that is far beyond the intrinsic relaxation oscillation frequency. In order to improve the spectral purity and stability of the generated microwave signal, two typical approaches are introduced, i.e., microwave modulation stabilization, and delayed feedback stabilization. Various applications of the P1 dynamics-based microwave signal generator in diverse signal generation and photonic microwave signal processing are described. Development trends of the P1 dynamics-based photonic microwave signal generator are also discussed.

A review on signal generation techniques in radio over fiber systems

Abstract In this paper a review on different signal generation techniques for Radio over Fiber systems is presented. Radio over fiber has become a conspicuous contender in upcoming high data rate demands from household and enterprises users. Radio signals or waves can be generated back from optical signals at RAU (radio access unit) so that they may be transmitted to mobile stations. This generation is first assembled into different categories on the basis of some similar parameters, various aspects of each category are given and then a comparison between different aspect of each technique is summarized in table. Analysis of these techniques on the basis of ranges of radio frequencies that can be generated is also proposed in this paper.

Novel ripple reduction method using three-level inverters with unipolar PWM

This paper proposes a novel method to reduce voltage and current ripple for the inverters by using three-level inverters with unipolar pulse width modulation (PWM) (3LFB-2U). A simple technique of switching signal generation by using carrier-based dipolar modulation of three-phase three-level inverters is extended to single-phase inverters that can be done by generating all possible switching patterns of the single-phase three-level inverters. Moreover, the concept of carrier-based dipolar modulation and the construction of reference voltages from desired output voltage and added zero voltage to control unipolar switching is also shown. The research results reveal that the proposed method can reduce the voltage and current ripple. Furthermore, the voltage and current harmonics can reduce by 27.80% and 1.79%, respectively less than two-level inverters without a loss of a simple modulation to generate the switching signals.

Generation of faster-than-Nyquist coherent optical DFT-spread OFDM signals with high-baud and high-order modulations

In this paper, we successfully demonstrate the generation and reception of faster-than-Nyquist (FTN) orthogonal frequency-division multiplexing (OFDM) signals with coherent detection. We can improve the spectrum efficiency by using higher order QAMs. However, we believe that the realization of super-Nyquist channel has the following advantages to improve spectral efficiency: Firstly, when we use higher order modulation, the requirements for equipment will be increased, such as the linearity of the modulator. Secondly, flexibility. The signal compression ratio can be arbitrarily set within the maximum compression ratio in our experiment. However, if we increase the modulation order, it can only be an integral multiple of 2, such as 4QAM to 8QAM, which can’t fully and effectively use the channel resources. In the FTN OFDM transmission system, frequency shaping is realized by a delay-and-add filter (DAF) at the transmitter to ensure the energy of signal is concentrated at low frequencies, which will make the OFDM much more robust to strong filtering effect to some extent. We generate a quadrature phase-shift keying OFDM (QPSK-OFDM) signal with equivalent baud rate (In this paper, the generation of FTN signal is in the frequency domain since we used M-point DFT and N-point IDFT while M is greater than N. In other words, the high-frequency parts are discarded to increase spectrum efficiency. Hence, we use “equivalent baud rate” instead of a simple “baud rate”) of 100–120 Gbaud, which is much higher than the sampling rate (80 GSa/s) of digital-to-analog converter (DAC). With this FTN Discrete-Fourier transform spread (DFT-spread) OFDM signal generation technique, we achieve the highest equivalent baud rate (120 GBaud) QPSK-OFDM signal generation and transmission over 80 km single mode fiber (SMF) with bit error rate (BER) under soft-decision forward-error-correction (SD-FEC) limitation of 2.4 × 10−2. We also investigate the generation and reception of 32 Gbaud FTN 16-ary quadrature-amplitude modulation OFDM (16QAM-OFDM) with coherent detection to achieve higher spectrum efficiency in this paper. The experimental results show that there is negligible optical signal to noise ratio (OSNR) penalty when 32 Gbaud FTN DFT-spread 16QAM-OFDM is compressed and transmitted within 28 GHz bandwidth with the BER at 2.4 × 10−2 in optical back to back (OBTB).

One photon-per-bit receiver using near-noiseless phase-sensitive amplification

Space communication for deep-space missions, inter-satellite data transfer and Earth monitoring requires high-speed data connectivity. The reach is fundamentally dictated by the available transmission power, the aperture size, and the receiver sensitivity. A transition from radio-frequency links to optical links is now seriously being considered, as this greatly reduces the channel loss caused by diffraction. A widely studied approach uses power-efficient formats along with nanowire-based photon-counting receivers cooled to a few Kelvins operating at speeds below 1 Gb/s. However, to achieve the multi-Gb/s data rates that will be required in the future, systems relying on pre-amplified receivers together with advanced signal generation and processing techniques from fibre communications are also considered. The sensitivity of such systems is largely determined by the noise figure (NF) of the pre-amplifier, which is theoretically 3 dB for almost all amplifiers. Phase-sensitive optical amplifiers (PSAs) with their uniquely low NF of 0 dB promise to provide the best possible sensitivity for Gb/s-rate long-haul free-space links. Here, we demonstrate a novel approach using a PSA-based receiver in a free-space transmission experiment with an unprecedented bit-error-free, black-box sensitivity of 1 photon-per-information-bit (PPB) at an information rate of 10.5 Gb/s. The system adopts a simple modulation format (quadrature-phase-shift keying, QPSK), standard digital signal processing for signal recovery and forward-error correction and is straightforwardly scalable to higher data rates.

Tunable THz Signal Generation and Radio-Over-Fiber Link Based on an Optoelectronic Oscillator-Driven Optical Frequency Comb

We propose and demonstrate experimentally a photonic THz signal generation technique based on a tunable optoelectronic oscillator (OEO), and its application in a radio over fiber (RoF) link. The OEO's frequency is tuned by varying the bandwidth of a tunable optical bandpass filter (TOBF) that is cascaded with a phase modulator (PM). The resulting tunable microwave photonic filter is used to generate OEO oscillations from 6.58 GHz up to 18.36 GHz (with a phase noise of ≤−103 dBc/Hz at 10 kHz offset from the carrier frequency). The OEO is subsequently used to drive an optical comb, generating 22 comb lines with a frequency spacing of 17.33 GHz covering a bandwidth of 360 GHz within a 20 dB envelope. By selecting two optical comb lines with a wavelength selective switch (WSS) and beating them in a uni-traveling carrier photodiode (UTC-PD), THz signals are generated at 101.5 GHz and 242.6 GHz with phase noise of −90 dBc/Hz and −78 dBc/Hz, respectively at 10 kHz offset from carrier frequency. Tunable mm-wave and THz signals can be generated either by changing the OEO oscillation frequency or the selected comb lines. Using the OEO driven OFCG, we implemented a RoF link at 242.6 GHz with a data rate of 24 Gbps over a wireless distance of 30 cm and with a bit error rate (BER) below the hard decision forward error correction (FEC) limit of 3.8 × 10−3. This method allows the creation of an all-photonic frequency reconfigurable THz signal generator and RoF system.

12 Gbit/s three‐tap FFE half‐rate transmitter with low jitter clock buffering scheme

A 12 Gbit/s feed-forward equalisation (FFE) transmitter has been designed in 65 nm CMOS process. The three-tap/half-rate highspeed tap signal generation technique for the segmented FFE driver is presented. A clock buffer scheme to make the equivalent signal transition for each segmented unit contributes to a low jitter performance. The measurement results show 9.31 ps RMS jitter at 12 Gbit/s after equalisation and the horizontal eye-opening is 0.204 UI at 10 -12 BER. The prototype transmitter occupies 0.042 mm 2 and consumes 1.58 pJ/bit.

W-Band 8QAM Vector Millimeter-Wave Signal Generation Based on Tripling of Frequency Without Phase Pre-Coding

In this paper, we propose a W-band 8-quadrature-amplitude-modulation (8QAM) frequency tripling photonic vector millimeter-wave (mm-wave) signal generation method by using a phase modulator (PM) with only amplitude pre-coding. The PM is driven by 2-Gbaud 8QAM-modulated amplitude precoded signal at 25 GHz. Instead of phase pre-coding, we only need to reverse the real part of the signal at the receiver after photo detector (PD). The structure of the transmitter and the structure of the receiver are simple. The frequency tripling scheme is completed by numerical simulation, the output optical spectrum is consistent with the theoretical analysis, and bit-error-ratio (BER) curves indicate that the put forward 75 GHz 8QAM vector signal generation technique has good performance. The BER of 6 Gbit/s 75 GHz 8QAM vector mm-wave signal is below $3.8 \times 10^{-3}$ after 12 km optical fiber transmission. For all we know, it is the first time to report on the generation of high-order QAM photonic mm-wave signal with odd times of RF frequency by using a single external modulator.

Enhanced orthogonal signal generator for a single‐phase grid‐connected converter

This study presents a new orthogonal signal generation (OSG) technique for the control system of a single-phase grid-connected voltage-source converter (VSC). The existing methods mostly suffer from delay, rely on the system parameters, or require multiple inputs. Among them, the second-order generalised integrator (SOGI) excludes the drawbacks of the other methods and shows better steady-state and dynamic response. The proposed OSG method here includes the advantages of the SOGI technique while demonstrating superior dynamic response and higher disturbance rejection capability. It is structurally simple without adding complexity to the control system. The proposed method is implemented in a DQ -frame current controller and its feasibility and reliability are verified through mathematical analysis, simulation, and experimental results.

Fuzzy Sliding Mode Based Series Hybrid Active Power Filter for Power Quality Enhancement

This paper contributes an innovative gating signal generation technique based on fuzzy sliding mode pulse width modulation (FSMPWM) with a Series Hybrid Active Power Filter (SEHAPF) for reducing the total harmonic distortion (THD). Hybrid filters are used for compensating reactive power on the load side and mitigate harmonics for the growth of power quality under variable source and load conditions in the utility system. The objective of the paper is to eradicate the various power quality (PQ) problems with development in power factor and reducing distortion in transmission and distribution line due to harmonics. With the implementation of FSMPWM of the proposed filter, the gating pulses are generated by implementing a Mamdani fuzzy rule with sliding surfaces. For producing a fixed pulse the presented method reduces the chattering reaction by controlling the narrow boundary coating on the sliding surface. The results of the projected technique are analyzed and compared with the traditional hysteresis band current controller (HCC). The overall proficiency and results are examined with the help of MATLAB/SIMULINK environment.

Design of less-detectable RADAR waveforms using stepped frequency modulation and coding

Radar signal generation and processing techniques are developing with an aim of reducing interference and signal interception. Signal jamming and signal detection have become emerging areas of interest in the field of radar engineering. So there is a need for design and development of new waveforms which are less detectable by the hostile receiver and less susceptible to jamming. In the work mentioned here, Stepped Frequency Waveform (SFW) is modulated with phase modulation techniques such as Barker codes and polyphase codes to improve the complexity and to reduce the detectability of waveform thus increasing the bandwidth of waveform and limiting the transmitted power of the waveform by using pulse compression techniques. The SFW considered here is generated having varying step size. Pulse compression technique is employed here in order to generate a pulse having a range resolution of shorter pulse and transmitted power of longer pulse. The modulated waveform characteristics have been studied and analyzed using ambiguity functions of the waveform.

Fast and Robust Single-Phase &lt;inline-formula&gt;&lt;tex-math&gt;$DQ$&lt;/tex-math&gt;&lt;/inline-formula&gt; Current Controller for Smart Inverter Applications

This paper presents a fast and robust $DQ$ current controller to regulate the output power of single-phase grid-connected inverters. The proposed method generates the grid current orthogonal component without introducing any additional dynamics or distortions to the control loop. Moreover, its operation does not depend on the system parameters. The proposed method exhibits improved steady-state and dynamic performances in comparison with the inverters equipped with the conventional orthogonal signal generation techniques. Its improved characteristics make the proposed controller suitable for smart inverter applications, to provide advanced grid functionalities as demanded by recently revised standards. Simulation and experimental results show the feasibility and performance of this control structure.

Comparison of Various Levels of Parallel Multilevel Active Filter Using NPC Multilevel Inverter

&lt;p&gt;This paper puts forward the technique of reference signal generation of the reactive instantaneous power and the technique of the SPWM control signal generation of the multilevel active filter. A comparison between the source currents before and after filtering is made. Then a comparison between the different source currents of different multilevel active filters. The subjects of comparison are the total harmonic distortions (THD) of the source current. The obtained simulation results have proved that the filtering quality is improved when increasing the active filter levels. Simulations are carried out by PSIM program.&lt;/p&gt;

New Three-Dimensional Space Vector-Based Switching Signal Generation Technique Without Null Vectors and With Reduced Switching Losses for a Grid-Connected Four-Leg Inverter

In this paper, the performance of the new three-dimensional space vector-based switching signal generation technique for a grid-connected four-leg voltage source inverter used as a shunt compensator is proposed. The shunt compensator can be used for reactive power compensation, harmonic elimination, load balancing, and neutral current elimination in a three-phase four-wire grid-connected system. It is shown through experimental studies that switching losses in the four-leg voltage source inverter are appreciably reduced to a maximum of 33% in three-dimensional space vector modulation without NULL vector as the number of switches controlled at any instant of time is six out of eight. The new proposed technique is compared with three-dimensional space vector modulation with null vector. Experimental results are given to show the validity of the proposed switching control strategy.