Delay Device Research Articles

Information Theory and Coding Techniques for 5G Wireless Communication Systems: Towards Efficient Spectrum Utilization

The introduction of 5G wireless communication networks has initiated a new period of connectivity, offering extremely high data rates, minimal delay, and extensive device compatibility. However, in order to fully use the capabilities of 5G, it is crucial to prioritize the effective exploitation of spectrum. Efficiency in data transmission is achieved by the optimization of data transmission, error minimization, and maximization of throughput, which are facilitated by information theory and coding techniques. This work examines the convergence of information theory and coding methods in the context of 5G wireless communication systems, with an emphasis on improving the efficiency of spectrum usage. The core of information theory is centered around the notion of entropy, which measures the level of uncertainty linked to a random variable. Information theory offers valuable insights into the underlying constraints of communication networks by utilizing concepts like channel capacity and error-correcting codes. When it comes to 5G, it is crucial to comprehend these limitations in order to develop transmission strategies that effectively utilize the spectrum resources at hand. Coding techniques, such as forward error correction (FEC) and channel coding, are essential for reducing the impact of noise, interference, and fading in wireless channels. Forward Error Correction (FEC) is a technique that enhances the reliability of transmitted data by introducing redundancy. This allows receivers to repair errors without requiring retransmissions, thus increasing the efficiency of the available spectrum. Advanced coding techniques such as low-density parity-check (LDPC) codes and polar codes are crucial for delivering high data transfer rates and reliability in 5G networks. By combining various access strategies, such as orthogonal frequency-division multiple access (OFDMA) and non-orthogonal multiple access (NOMA), along with advanced coding schemes, we can achieve higher spectral efficiency and increase the capacity for users. These strategies facilitate the optimal distribution of resources, enabling multiple users to efficiently share the same spectrum while satisfying their quality-of-service demands. Information theory and coding.

Modal group refractive index measurement of few-mode fibers based on time-domain cross-correlation

We propose a measurement method based on the time-domain cross-correlation technique, combined with the cut-back method, enabling the measurement of group refractive indices (n g ) in few-mode fibers (FMF). A Mach–Zehnder interferometric system, equipped with high-precision and extensive range delay devices, is established. The system records off-axis holograms of spatial reference light at various delays interfering with the emitted light from the fiber under test. The interference energy is extracted from these holograms, and a time-domain mode energy curve is developed utilizing the principle of cross correlation. Optimal holograms at each of the curve peaks are used to reconstruct the modal field distribution, effectively separating and accurately identifying each mode within the FMF. By integrating the cut-back method, the n g corresponding to each mode is calculated based on the changes in group delay before and after fiber cutting. The n g of modes in the two-mode fibers was measured and the differential group delay calculated from the measurement agrees with the manufacturer’s specifications. The measured n g of a standard single-mode fiber aligns with the manufacturer’s specifications. Furthermore, the n g of the higher-order modes in four-mode fibers were measured by exciting them at different angles and validating the wave optics theory that the n g of the fiber modes is independent of the excitation angle. This method can simultaneously measure the n g of several modes in a fiber, providing support for the development and application of FMFs.

Assessment of the increase in the proportion of pulses received by an RF spectrum management system in a complex signal environment when using delay devices

Assessment of the increase in the proportion of pulses received by an RF spectrum management system in a complex signal environment when using delay devices

Integrated multi-operand optical neurons for scalable and hardware-efficient deep learning

Abstract Optical neural networks (ONNs) are promising hardware platforms for next-generation neuromorphic computing due to their high parallelism, low latency, and low energy consumption. However, previous integrated photonic tensor cores (PTCs) consume numerous single-operand optical modulators for signal and weight encoding, leading to large area costs and high propagation loss to implement large tensor operations. This work proposes a scalable and efficient optical dot-product engine based on customized multi-operand photonic devices, namely multi-operand optical neuron (MOON). We experimentally demonstrate the utility of a MOON using a multi-operand-Mach–Zehnder-interferometer (MOMZI) in image recognition tasks. Specifically, our MOMZI-based ONN achieves a measured accuracy of 85.89 % in the street view house number (SVHN) recognition dataset with 4-bit voltage control precision. Furthermore, our performance analysis reveals that a 128 × 128 MOMZI-based PTCs outperform their counterparts based on single-operand MZIs by one to two order-of-magnitudes in propagation loss, optical delay, and total device footprint, with comparable matrix expressivity.

Rapid and sensitive determination of Se and heavy metals in foods using electrothermal vaporization inductively coupled plasma mass spectrometry with a novel transportation system.

Rapid, sensitive and simultaneous determination of trace multi-elements in various plant food samples such as grain, oilseed, vegetable and tea is always a challenge thus far. In this work, a rapid determination method for Se, Cd, As and Pb in food samples by inductively coupled plasma mass spectrometry (ICP-MS) using slurry sampling electrothermal vaporization (SS-ETV) was developed. To improve the analytical sensitivity and precision as well as eliminate the memory effect, a gas turbulator line and signal delay device (SDD) were for the first time designed for the graphite furnace (GF) ETV coupled with ICP-MS. The signal acquisition parameters of ICP-MS, ashing and vaporization conditions, and the flow rates of carrier gas and gas turbulator were investigated for Se, Cd, As and Pb in food samples. Under the optimized conditions, the limits of determination (LODs) for Se, Cd, As and Pb were 0.5 ng g-1, 0.3 ng g-1, 0.3 ng g-1 and 0.6 ng g-1, respectively; the limits of quantification (LOQs) for Se, Cd, As and Pb were 1.7 ng g-1, 1.0 ng g-1, 1.0 ng g-1 and 1.9 ng g-1, respectively; linearity (R2) in the range of 1 to 4,000 ng g-1 was >0.999 using the standard addition method. This method was used to analyze 5 CRMs including rice, tea and soybeans, and the concentrations detected by this method were within the range of the certified values. The recoveries of Se, Cd, As and Pb in plant food matrices including grain, oilseed, celery, spinach, carrot and tea samples were 86-118% compared to the microwave digestion ICP-MS method; and the relative standard deviations (RSDs) were 1.2-8.9% for real food sample analysis, proving a good precision and accuracy for the simultaneous determination of multi-elements. The analysis time was less than 3 min, slurry preparation time < 5 min without sample digestion process. The proposed direct slurry sampling ICP-MS method is thus suitable for rapid and sensitive determination of Se, Cd, As and Pb in food samples with advantages such as simplicity, green and safety, as well as with a promising application potential in detecting more elements to protect food safety and human health.

More Than a Device: Function Implementation in a Multi-Gate Junctionless FET Structure

The miniaturization of the transistor sizes to keep up with Moore's Law in Integrated Circuits (ICs) is rapidly approaching the physical limits. To push the horizons of Moore's Law, among the various approaches available in the literature, single device-based computing shows promise by achieving more functionality in a smaller footprint. However, a single device-based computing approach either mainly embeds only the primitive logic hence inefficient in performance, or requires exotic devices like spin logic devices, and memristor which involve non-conventional costly manufacturing steps. Previously, we introduced the concept of embedding logic in a single device based on Crosstalk Computing, where deterministic signal interference between nano-metal lines is leveraged for logic computation. This paper elaborates upon the methodology of realizing complex Boolean functions through TCAD-based modeling and simulations, quantifying results, and compares against existing approaches. Core to our approach is a multi-gate Junctionless FET-based device, methodical placement of the independent gates, manipulation of device parameters, and dimension. This paper shows the implementation of various complex logic functions along with the primitive gates in the proposed device. Our benchmark results show 8x density benefits and 8x less power consumption on average than CMOS-based implementation. For the case of delay, elementary and complex logic devices show comparable characteristics with 14 nm PTM counterparts. Such realization of complex functions in a stand-alone device is compatible with the existing fabrication process.

RELATIVE EXPLOSIVE FORCE OF Al/MoO3 NANOCOMPOSITE/POLYMERIC BINDER

We briefly overview the common and most studied nanothermite composites of different formulations. The paper primarily deals with systems whose main representatives are nanothermite composites for pyroautomatic delay and special devices and initiator primers. The problem of the development of gas-free (low-gas), fast-burning pyrotechnic compositions based on nanothermites is considered herein. The experimental part discusses an understudied issue of explosive transformation mechanisms, including the identification of governing chemical reactions. A study on the effect of fluoropolymer F-42L on the relative explosive force of a pyrotechnic composition based on a thermite reaction between nanopowdered aluminum as the fuel and molybdenum oxide as the basic oxidizer is also reported. The fluoropolymer was shown to reduce the explosive force of the nanocomposite, in which case the governing chemical reaction of explosive transformation was found to be the reaction of Al with the fluoropolymer.

Enhanced and controllable reflected group delay based on Tamm surface plasmons with Dirac semimetals

The reflected group delay from a multilayer structure comprising a one-dimensional photonic crystal coated with a bulk Dirac semimetal (BDS) separated by a spacer layer is investigated theoretically. It is shown that the group delay of the reflected beam in this structure can be significantly negatively enhanced and switched from negative to positive. The enhanced group delay originates from the steep phase change caused by the excitation of the optical Tamm state at the interface between the BDS and spacer layer. Moreover, positive and negative group delays can be actively tuned through the Fermi energy and the relaxation time of the BDS. We believe that this enhanced and tunable delay scheme has important research significance for the fabrication of optical delay devices.

Tunable Superluminal and Subluminal Reflected Group Delay in an Air-Weyl Semimetal Film-Weyl Semimetal Substrate Layered System

In this work, we theoretically investigate the superluminal and subluminal reflected group delay from an air-Weyl semimetal film-Weyl semimetal substrate layered structure by using 4*4 magneto-optical matrix. We show a tunable transition between positive and negative group delays of reflection pulse in such a layered structure controlled by the properties of the Weyl Semimetal layer and reveal its mechanism to control the propagation properties of the light pulse reflected from such structure. It is demonstrated that the reflected group delays are tunable from positive to negative values and vice versa, which are adjusted by tuning the incident angle, thickness of Weyl semimetal film, tilt parameter, and Fermi energy. The control of the magnitude and the sign of the reflected group delay of light propagation represent a key point in slow and fast light technologies. Our results are helpful to control the pulse propagations and are useful for design of Weyl semimetal-based delay devices.

Slow Light Mode at the Degenerate Band Edge for True Time Delay Applications

Tuneable true time delay device is designed at the degenerate band edge (DBE) by using two coupled periodic silicon ridge waveguides. The holes of the two ridge waveguides are well-tuned to let four modes couple and degenerate at the bandgap providing a slow light mode (the DBE mode). Transfer matrix method is utilized to trace and verify the slow light mode in the device. A 25-unit cell device ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10~ \boldsymbol {\mu m}$ </tex-math></inline-formula> length device) is constructed to realize the slow mode at the DBE with 70% transmission and 42.5 ps signal delay over 130 GHz dispersion free bandwidth. Liquid crystal cladding layer is incorporated to provide continuous control of the slow mode velocity around the DBE resonance for UWB antenna array beamforming applications.

Impact of Work Function Tunability on Thermal and RF Performance of P-type Window based Junctionless Transistor

The choice of gate metal technology for junctionless transistors needs to have diverse characteristics as metals have distinct work functions and hence, they show incompatibility while tailoring threshold of the device. In such a scenario, bimetallic stacked gate can be a promising candidate to present wide range of tunable work functions required for nano-regime junctionless transistors. This paper explores the electronic phenomena occurring at metal-metal interface and the impact of Platinum (Pt)/Titanium (Ti) bimetallic stacked gate-based work function tunability on the RF and thermal performances of p-type window-based Silicon on Insulator Junctionless Transistor (SOI JLT) using numerical simulator SILVACO ATLAS. The parameters considered for performance evaluation are ON-state current (I_{ON}), OFF-state current (I_{OFF}), I_{ON}/I_{OFF} ratio, transconductance (g_m),\linebreak cutoff frequency (f_T), Transconductance Frequency Product (TFP), Intrinsic Gate Delay (IGD), intrinsic gain (A_V), and Global Device Temperature (GDT). The g_m, f_T, TFP, A_V and GDT improve for modified over conventional in the ON state at higher work function, while IGD improves at lower work function. The improvements of 11.7% and 2.21% are obtained in maximum g_m and f_T, respectively, for modified transistor over conventional. The findings suggest that bimetallic stacked gate modified SOIJLT is a better option than conventional for low-power RF application.

The operating algorithm of the delay device processing time overlapped pulses in a matrix receiver

Matrix receiver from about the 1960s is used for wideband analysis of the signal environment (SE). Its use provides simultaneously a wide instantaneous analysis bandwidth, relatively high sensitivity, no signal gaps and the possibility of narrow-band processing of the output signal. However, there is a high probability of time-overlapping for pulses from pulse streams created by various radio emission sources in modern SE. When processing time-overlapped pulses in a classical matrix receiver, measurement ambiguities and abnormal errors occur. Therefore, multiple approaches are used to improve its efficiency in a complex SE. One such approach is based on installing a delay device to the wideband receiver's input. The principle of operation of the delay device consists of multiple signal transfers from the microwave range to the optical one and vice versa with the passage through fiber segments of various lengths. However, the operation algorithm of such a device has not been developed in detail. That's why our purpose is to substantiate and develop the algorithm for operating the delay device installed at the input of the matrix receiver to ensure the processing of time-overlapped pulses. In addition to the main algorithm for adapting the delay value to the pulse duration, we developed a nested algorithm for choosing a segment of the adjustable delay line. To store the pulse for the duration of processing by the receiver of previously received pulses, we developed a nested algorithm for executing the delay cycle. The use of the delay device operating following the proposed algorithm makes it possible to reduce the likelihood of measurement ambiguity and abnormal errors during the operation of the matrix receiver in the complex SE.

Photonic Beamforming for 5G and Beyond: A Review of True Time Delay Devices Enabling Ultra-Wideband Beamforming for mmWave Communications

The next generations of wireless communications are promising high capacity, low latency, and high throughput, enabled by millimeter wave spectrum. Beamforming and beam steering are key requirements for millimeter wave systems due to the fundamental limitations of such high frequencies. Traditional phased array antennas are narrow band and conventional beamforming techniques are too bulky, energy hungry, and expensive to integrate into consumer electronics. Therefore, new approaches of beamforming and beamsteering are required for 5G and beyond due to shortcomings of existing technologies. Here we present a comprehensive review of the photonic true time delay units for application in beamforming of next generations of wireless communications. The prospects and progress of several photonic techniques are discussed here along with their challenges. The fundamental focus of this endeavor will be on the on-chip Silicon-on-Insulator based approaches which enable utilizing conventional CMOS fabrication process for integration with other optical components for compact photonic integrated circuit.

Stitching and Geometric Modeling Approach Based on Multi-Slice Satellite Images

Time delay and integration (TDI) charge-coupled device (CCD) is an image sensor for capturing images of moving objects at low light levels. This study examines the model construction of stitched TDI CCD original multi-slice images. The traditional approaches, for example, include the image-space-oriented algorithm and the object-space-oriented algorithm. The former indicates concise principles and high efficiency, whereas the panoramic stitching images lack the clear geometric relationships generated from the image-space-oriented algorithm. Similarly, even though the object-space-oriented algorithm generates an image with a clear geometric relationship, it is time-consuming due to the complicated and intensive computational demands. In this study, we developed a multi-slice satellite images stitching and geometric model construction method. The method consists of three major steps. First, the high-precision reference data assist in block adjustment and obtain the original slice image bias-corrected RFM to perform multi-slice image block adjustment. The second process generates the panoramic stitching image by establishing the image coordinate conversion relationship from the panoramic stitching image to the original multi-slice images. The final step is dividing the panoramic stitching image uniformly into image grids and employing the established image coordinate conversion relationship and the original multi-slice image bias-corrected RFM to generate a virtual control grid to construct the panoramic stitching image RFM. To evaluate the performance, we conducted experiments using the Tianhui-1(TH-1) high-resolution image and the Ziyuan-3(ZY-3) triple liner-array image data. The experimental results show that, compared with the object-space-oriented algorithm, the stitching accuracy loss of the generated panoramic stitching image was only 0.2 pixels and that the mean value was 0.799798 pixels, achieving the sub-pixel stitching requirements. Compared with the object-space-oriented algorithm, the RFM positioning difference of the panoramic stitching image was within 0.3 m, which achieves equal positioning accuracy.

Modeling Kelvin wake imaging mechanism of visible spectral remote sensing

Kelvin wake is an important detection target of ocean visible spectral remote sensing. In the case of slow ship speed and low atmospheric transmissivity, the wake signal is weak and the SNR (Signal-Noise Ratio) is low. Therefore, the image obtained by the visible spectral remote sensing imaging system is often “unclear”. In order to solve the problems above, this paper carries out the modeling of Kelvin wake imaging mechanism of visible spectral remote sensing. The Kelvin wake reflection distribution characteristics of rough sea surface are simulated based on the hydrodynamic model of Kelvin wake and the probability density distribution of rough sea surface, and a method to quantify the reflectance resolution for Kelvin wake imaging of rough sea surface is proposed. The changes in reflectance resolution caused by different wind speeds, ship parameters, source angle, receiver angle are also analyzed. Then the imaging link model of TDI-CCD (Time Delay and Integration Charge Coupled Devices) imaging system was established. The imaging results of a Kelvin wake reflected on the rough sea surface are simulated, and the impact of the changes of main imaging parameters (optical system F number, quantization bits, integration stages) on the imaging results of a Kelvin wake at different reflectance resolutions are analyzed. The research has clarified the mechanism of the visible spectral remote sensing system to clearly imaging the Kelvin wake, which can provide guidance on parameters design and attitude planning for the ocean visible spectral remote sensing system, and improve the ability of the imaging system to detect weak wake signals.

High Resolution Imaging Camera (HiRIC) on China’s First Mars Exploration Tianwen-1 Mission

The High-Resolution Imaging Camera (HiRIC) is one major payload of China’s first Mars exploration mission, and its main objective is to obtain the detailed observation images of the key areas on the Martian surface. In this paper, the leading group of HiRIC shows a full blueprint of the HiRIC. The HiRIC can achieve a high resolution (0.5 m at an altitude of 265 km) with a wide swath width of 9 km. The HiRIC adopts an Off-Axis Three-Mirror Astigmatic (TMA) optical system with a focal length of 4640 mm, an F-number of 12 and a Field of View (FOV) of 2° × 0.693°. In order to reduce the instrument weight, carbon-based material is widely used in the opto-mechanical structure which is in ultra-lightweight design, thus, a light-weight camera with a total mass of 42 kg is obtained. The Time Delay and Integration (TDI) Charge Coupled Devices (CCDs) and Complementary Metal-Oxide-Semiconductor Transistor (CMOS) detectors are all set on the imaging plane to achieve the push-broom imaging and frame imaging, respectively. And the high Signal-to-Noise Ratio (SNR) >100:1 can achieve in multi observation types for various scientific imaging tasks. After 4-year design and fabricate, the HiRIC has been assembly. The testing results show that the instrument is in good condition, and the Modulation Transfer Function (MTF) can achieve 0.18 at Nyquist frequency. The HiRIC can achieve a well image on China first Mars exploration mission.

Investigation of aging induced processes on thermo-kinetic and combustion characteristics of tungsten pyrotechnic delay composition

A degradation in performance parameters related to thermal decomposition and combustion behaviour of tungsten based pyrotechnic delay composition can occur when subjected to accelerated aging conditions in a controlled environment. The present study utilizes various methods to quantify the extent of degradation in thermo-kinetic and burning characteristics as well as to postulate a fundamental aging mechanism for traditional tungsten (W) pyrotechnic delay material, which has not been attempted in the past. The delay composition based on metallic fuel (W) and perchlorate oxidizer is subjected to aging at constant temperature of 71 °C and 95% relative humidity, for 2 and 12 weeks, respectively. Experiments including thermal analysis, combustion temperature profile and burning rate measurements are conducted together with numerical simulation of an actual pyrotechnic delay device. Moreover, the reaction mechanism, chemical kinetics, and combustion behaviour between pristine and aged cases are examined. Results illustrate that there exist two aging induced processes, which increases the presence of large agglomerated particles, high metal oxide content by thickening the outer oxide layer of metallic fuel, and more unreacted oxygen to instigate incomplete combustion in aged samples. This alters the reaction pathway of combustion process, lowers average thermal conductivity, and reduces diffusion of reactants in aged samples, thus causing significant decrement in the heat of reaction (31%), combustion zone temperature (10%), reactivity (12%), and burning rates (10%), such that the overall pyrotechnic delay device experiences misfiring during operation or a failure in accomplishing its actual intended task.

MmW Rotman Lens-Based Sensing: An Investigation Study.

A Rotman lens is a wideband true-time delay device. Due to its simplistic structure with wave/signal routing capabilities, it has been widely utilized as a beamforming device in numerous communication systems. Since the basic Rotman lens design incorporates multiple input, output, and dummy ports, in this study, and for the first time, we utilized a Rotman lens as a sensor. The main idea was to gather abundant information from available Rotman lens ports to obtain better sensing performance. The realized lens is optimized to work in the millimeter wave (mmW) band from 27 to 29 GHz with a focus on a central frequency of 28 GHz. The design has a footprint of 140 × 103 × 0.8 mm3. The polarity correlator was used to characterize the material under investigation.

Slow light in rod type 2D photonic crystal waveguide comprising of cavity: Optimization and analysis

Structure comprising of 2D photonic crystal waveguide and cavity (PhCWC) is designed in this paper and propagation of slow light through it is investigated for its potential application as optical delay device. Rod type 2D photonic crystal structure has been considered here. Two-dimensional finite difference time domain (2DFDTD) method has been used in the present investigations. The proposed PhCWC structure is optimized in two steps. In the first step, Q factor is optimized by varying the number of rods of the cavity. In the second step, number of rods are kept fixed (as optimized for Q in the first step), and the delay is maximized by varying radius of the cavity rods. The resultant structure thus obtained is further investigated for (i) dispersion and group velocity, (ii) variation of optical delay with input pulse width, (iii) variation of optical delay with wavelength and (iv) variation of optical transmission with wavelength.The present paper proposes optical delay in the one cavity structure that could be manipulated by manipulating the number of cavity rods in the waveguide and radius of the central rod of the cavity. Further, the structure can be designed to operate at a desired wavelength.

Ultrafast control of slow light in THz electromagnetically induced transparency metasurfaces

In this paper, we experimentally demonstrate ultrafast optical control of slow light in the terahertz (THz) range by combining the electromagnetically induced transparency (EIT) metasurfaces with the cut wire made of P+-implanted silicon with short carrier lifetime. Employing the optical-pump THz-probe spectroscopy, we observed that the device transited from a state with a slow light effect to a state without a slow light effect in an ultrafast time of 5 ps and recovered within 200 ps. A coupled oscillator model is utilized to explain the origin of controllability. The experimental results agree very well with the simulated and theoretical results. These EIT metasurfaces have the potential to be used as an ultrafast THz optical delay device.