- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Low Voltage Graphene-Based Amplitude Modulator for High Efficiency Terahertz Modulation
摘要： In this paper, a high-e?ciency terahertz amplitude modulation device based on a ?eld-e?ect transistor has been proposed. The polarization insensitive modulator is designed to achieve a maximum experimental modulation depth of about 53% within 5 V of gate voltages using monolayer graphene. Moreover, the manufacturing processes are inexpensive. Two methods are adopted to improve modulation performance. For one thing, the metal metamaterial designed can e?ectively enhance the electromagnetic ?eld near single-layer graphene and therefore greatly promote the graphene’s modulation ability in terahertz. For another, polyethylene oxide-based electrolytes (PEO:LiClO4) acts as a high-capacity donor, which makes it possible to dope single-layer graphene at a relatively low voltage.
关键词： solid electrolyte,terahertz,single-layer graphene,transmittance,metamaterial,amplitude modulation,?eld-e?ect transistor
更新于2025-09-23 15:21:01
-
High Speed Directly Modulated Fabry-Perot Lasers with an Ultra-Short Cavity Length
摘要： In this study, Fabry-Perot quantum well lasers with shortened cavity designs (25 and 50 μm) were fabricated. The devices had dry-etched and cleaved facets that exhibited an output power of up to 2.36 mW for a cavity length of 25 μm; good spectral performance was achieved. Single-optical-mode operation with better than 25dB of side mode suppression ratio can be achieved for the fabricated devices with 25- and 50-μm cavities. The short-cavity devices also exhibited high-speed modulation at elevated temperatures. Moreover, 25 Gb/s eye diagrams could be obtained at 65oC for the 25 μm device and 55oC for the 50 μm device. Due to their small area, ultra-short-cavity Fabry-Perot laser can be suitably used in next-generation light sources for optical communication.
关键词： Optical device fabrication,Semiconductor lasers,Laser cavity resonators,Amplitude modulation,Diode lasers,Quantum well lasers,Laser modes
更新于2025-09-23 15:21:01
-
Decoding of 10-G Optics-Based 50-Gb/s PAM-4 Signal Using Simplified MLSE
摘要： A simpli?ed maximum likelihood sequence estimation (MLSE) based on Viterbi algorithm has been proposed. Experimental results show that compared with the conventional MLSE, the proposed algorithm saves the multiplication by 25% with no sensitivity penalty when the memory length of MLSE is 2 both in the 25 Gb/s nonreturn to zero and 50 Gb/s four-level pulse-amplitude modulation (PAM-4) transmission systems. In order to further reduce the number of multiplications in the 50 Gb/s PAM-4 transmission system, we use 75 taps of feed-forward equalization to equalize the received PAM-4 signal into duo-binary PAM-4 (DB-PAM-4) signal and then use MLSE with the memory length of 1 to decode, which improves the sensitivity performance by 1.8 dB and reduces the computing complexity by ～98% compared with conventional MLSE (L = 4) method. As a result, a 10-km C-band transmission of 50 Gb/s PAM-4 signal is achieved using optical transceivers with a combined 3-dB bandwidth of ～8 GHz, and only 107 multiplications are required by using our proposed simpli?ed algorithm for equalization.
关键词： feed-forward equalization (FFE),four-level pulse-amplitude modulation (PAM-4),Viterbi algorithm,Maximum likelihood sequence estimation (MLSE)
更新于2025-09-23 15:21:01
-
Spectrophotometric and Chemometric Methods for Simultaneous Determination of Two Anti-Hypertensive Drugs in their Combined Dosage Form
摘要： In this study determination of Moexipril hydrochloride (MOX) and hydrochlorothiazide (HCT) were conducted by application of Spectrophotometric and Chemometric methods. Five different accurate, sensitive and reproducible methods were applied for the simultaneous determination of (MOX) and (HCT) in their bulk powder and pharmaceutical dosage form. The first method is the new absorbance subtraction (AS) method. The second method is the new amplitude modulation (AM) method. The third method is the new extended ratio subtraction (ERS) method coupled to ratio subtraction (RS) method. The fourth and fifth methods are multivariate calibration which includes Principal Component Regression (PCR) and Partial Least Squares (PLS). The suggested procedures were checked using laboratory prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparations. The validity of the proposed methods was further assessed by applying the standard addition technique. The results obtained by applying the proposed methods were statistically analyzed and compared with a reported method.
关键词： Absorbance subtraction,Hydrochlorothiazide,chemometric methods,Moexipril hydrochloride,Extended ratio subtraction,Amplitude modulation
更新于2025-09-23 15:21:01
-
[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Analytical Assessment of the Modulation Depth of Photoplethysmographic Signal Based on the Modified Beer-Lambert Law
摘要： The model for estimation of the amplitude modulation depth of photoplethysmographic (PPG) signal based on the modified Beer-Lambert law was developed. It was analytically confirmed that the modulation depth of PPG signal depends on the wavelength and illumination geometry. The modulation depth is directly proportional to the distance between the light source and the detector. The sensitivity of green light (525 nm) to blood volume changes is approximately 6-9 times greater than that for red (640 nm) and IR (805 nm) light. It was found that in case of green light, the main contribution to the modulation of PPG signal is made by absorption coefficient changes while in case of red and IR light, the modulation is mainly caused by scattering coefficient changes.
关键词： blood volume,modulation depth,photoplethysmography,amplitude modulation,modified Beer-Lambert law
更新于2025-09-23 15:19:57
-
Improvement of optical fiber channel capacity using compressed non-orthogonal frequency quadrature amplitude modulation
摘要： A new modulation scheme, that can increase the channel capacity of optical ?ber link, is proposed in this paper. It is implemented by using a non-orthogonal frequency shift keying (FSK), quadrature amplitude modulation (QAM), and sparse sinusoidal sampling based on a compressed sensing. The proposed technique can allow us to have the improved transmission capacity because frequency spacing among digitally sample RF subcarriers becomes much narrower than the channel bandwidth by the non-orthogonality and the total signal length can be reduced by using the sparse sinusoidal sampling. For experimental veri?cation, a 64-non-orthogonal frequency quadrature amplitude modulation (NoFQAM) signal is generated using non-orthogonal 4-FSK and 16-QAM. The total length of 64-NoFQAM signal is reduced up to 60% at the bit error rate (BER) of 4 × 10?5 by the sparse sinusoidal sampling. The BER of 2 × 10?5 was measured at a frequency spacing between digitally sampled RF subcarriers corresponding to 10% of channel bandwidth (500 MHz). The 7.5-Gb/s transmission of 64-NoFQAM signal with the channel bandwidth of 500 MHz was demonstrated successfully by using 50-km and 300-km optical ?ber link.
关键词： Non-orthogonal frequency quadrature amplitude modulation,Sparse sinusoidal sampling,Channel capacity,L1-minimization,Compressed sensing
更新于2025-09-23 15:19:57
-
Analytic and simulative comparison of turbulent FSO system with different modulation techniques
摘要： In this paper, we characterize the performance of Intensity Modulation/Direct Detection (IM/DD) and coherent detection modulation techniques in free-space optical (FSO) communication system in terms of bit error rate (BER). The system of interest includes M-ary Pulse Position Modulation (M-PPM) in correspondence to IM/DD and M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) with respect to coherent detection. The system is subjected to weak turbulence regime of log-normal channel with scintillation index less than 0.75. Coherent techniques involve the amount of signal pulses transmitted in a particular time as the major component of their generation, except IM/DD which is a result of photon intensity, i.e. the number of photons forming a pulse. It is worth mentioning that in previous studies, the performance of IM/DD techniques had been evaluated in terms of photon-count fluctuation statistics and thus the impact of fading strength of channel on signal intensity was not discussed anywhere. In this work, an objective equivalence has been achieved between these two kinds of detection by deriving the BER expression of M-PPM in terms of probability density function of signal intensity, while considering fading strength, scintillation index, thermal noise and outage probability as system parameters for numerical analysis.
关键词： M-ary Pulse Position Modulation (MPPM),M-ary Phase Shift Keying (MPSK),M-ary Quadrature Amplitude Modulation (M-QAM),Intensity Modulation/Direct Detection (IM/DD),Scintillation index,Coherent detection
更新于2025-09-19 17:15:36
-
Symbol Error Probability Performance of Rectangular QAM with MRC Reception over Generalized <i>α</i>-<i>μ</i> Fading Channels
摘要： In this paper, a new and an accurate symbol error probability’s analytical model of Rectangular Quadrature Amplitude Modulation in α-μ fading channel is presented for single-user single-input multi-output environment, which can be easily extended to generalized fading channels. The maximal-ratio combining technique is utilized at the receiving end and unified moment generating functions are used to derivate the results. The fading mediums considered are independent and non-identical. The mathematical model presented is applicable for slow and frequency non-selective fading channels only. The final expression is presented in terms of Meijer G-function; it contains single integrals with finite limits to evaluate the mathematical expressions with numerical techniques. The beauty of the model will help evaluate symbol error probability of rectangular quadrature amplitude modulation with spatial diversity over various fading mediums not addressed in this article. To check for the validity of derived analytical expressions, comparison is made between theoretical and simulation results at the end.
关键词： α-μ fading channel,maximal-ratio combining,symbol error probability,SIMO,rectangular quadrature amplitude modulation
更新于2025-09-19 17:15:36
-
Open Innovation Using Satellite Imagery for Initial Site Assessment of Solar Photovoltaic Projects
摘要： Two novel blind equalization techniques for odd bit rectangular quadrature amplitude modulation (RQAM) signaling are proposed in this paper, namely, rectangular contour algorithm (RRECT CA) and improved rectangular contour algorithm (IRCA). The proposed RRECT CA algorithm minimizes the dispersion of constant with respect to a rectangular-shaped zero error contour. The algorithm exploits the geometry of the RQAM to correct phase error within 180?, thus enhancing the convergence rate while minimizing the equalizer mis-adjustments. On the other hand, the proposed IRCA algorithm employs the estimated output from the decision device into the cost function, thus guiding the equalizer output to reside on multiple zero error rectangular shaped moduli. This method of feeding back the slicer output further reduces the mis-adjustment between the transmitted constellation and the new cost function in an ef?cient manner, which leads to faster convergence and better intersymbol interference suppression. The proposed algorithms can also work for the square QAM by mere change of only two constellation dependent constants, thus facilitating the implementation in hardware to enable transmission of both even and odd number of bits per symbol based constellations. Steady-state error analysis, MSE, and residual ISI comparison through the simulation results con?rm the good performance of the proposed algorithms. Furthermore, the convergence characteristics of the proposed IRCA scheme establish the supremacy of IRCA over RRECTCA, which is its parent algorithm.
关键词： rectangular QAM,quadrature amplitude modulation (QAM),Blind equalization,cross QAM,inter symbol interference (ISI),mean square error (MSE)
更新于2025-09-19 17:13:59
-
[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Physical Encryption Based on Chaotic Sequence-assisted Pseudo QAM Systems
摘要： In this work, we proposed a physical encryption scheme based on chaotic sequence-assisted pseudo quadrature amplitude modulation (QAM) systems. We simulated the proposed scheme and verified its feasibility by plotting BER curves and constellation diagrams.
关键词： physical encryption,quadrature amplitude modulation,chaotic sequence-assisted
更新于2025-09-16 10:30:52