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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • Schottky diodes
  • frequency multipliers
  • submillimeter-wave technology
  • terahertz technology.
  • Submillimeter-wave sources
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • California Institute of Technology
201 条数据
?? 中文（中国） ▾

  • Space-Time Block Coding Based Beamforming for Beam Squint Compensation

    摘要： In this paper, the beam squint problem, which causes significant variations in radiated beam gain over frequencies in millimeter wave communication system, is investigated. A constant modulus beamformer design, which is formulated to maximize the expected average beam gain within the bandwidth with limited variation over frequencies within the bandwidth, is proposed. A semidefinite relaxation (SDR) method is developed to solve the optimization problem under the constant modulus constraints. Depending on the eigenvalues of the optimal solution, either direct beamforming or transmit diversity based beamforming is employed for data transmissions. Through numerical results, the proposed transmission scheme can compensate for beam squint effectively and improve system throughput. Overall, a transmission scheme for beam squint compensation in wideband wireless communication systems is provided.

    关键词： Throughput,beam squint,Space-time Block Coding,Beamforming,Millimeter Wave

    更新于2025-09-10 09:29:36

  • Line-Of-Sight Massive MIMO Channel Characteristics in an Indoor Scenario at 94 GHz

    摘要： The fading and correlation characteristics of virtual, yet realistic, line-of-sight (LOS) 4 × 2500 millimetric (mmW) massive MIMO channels are investigated at 94 GHz in an indoor office environment for three different Tx–Rx distance scenarios. The capability of the mmW massive MIMO channel to spatially decorrelate the users is evaluated with the computation of the channel correlation and other channel metrics, such as power-to-interference ratio and condition number. In particular, the correlation between channel vectors for a given user and its influence on receiving correlation is discussed. The results clearly demonstrate the capability of mmW massive MIMO systems to reach orthogonal Tx–Rx streams even for a small 7 × 7 antenna array subset with correlation between users <0.2. Moreover, strong phase variations at Tx side at this frequency range are highlighted through channel phase correlation studies and were shown to contribute to the decorrelation at Rx side between close users, paving the way for further massive MIMO system enhancements.

    关键词： massive MIMO,Millimeter wave,indoor propagation

    更新于2025-09-10 09:29:36

  • Robust Hybrid Transceiver Design for AF Relaying in Millimeter Wave Systems Under Imperfect CSI

    摘要： In this paper, we present a robust hybrid transceiver design for millimeter-wave communication systems operating in amplify-and-forward multiple-input multiple-output relay channels. Unlike most of current works that assume the perfect or partial channel state information (CSI) at the transceivers in the design, the CSI uncertainty is taken into consideration to design a robust transceiver. To achieve that end, the average received signal-to-noise ratio (SNR) is adopted as the objective function. To produce a tractable expression, an accurate approximation of the average received SNR is derived and used as the design criterion. An alternating maximization algorithm is proposed to optimize the design criterion, in which an orthogonal matching pursuit-based algorithm is utilized to design the transceiver at the relay. Simulations show that the algorithm takes a few iterations to produce converged transceivers for the source, relay, and destination nodes. Numerical results demonstrate the substantial performance gains of the proposed scheme, compared with the existing non-robust designs.

    关键词： MIMO,cooperative communication,Millimeter wave communication

    更新于2025-09-09 09:28:46

  • [IEEE 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Portland, OR, USA (2018.11.13-2018.11.14)] 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Frequency Agile Photonic Front-End for Wideband Transmission and Reception

    摘要： We have developed and tested a 0-45 GHz frequency agile photonic front-end for up- and down-conversion of signals with >800 MHz instantaneous bandwidth, <1 us switching speed, and low end-to-end latency. The 3U OpenVPX system has been tested in a TRL6 demonstration.

    关键词： millimeter-wave photonics,photonic front-ends,pulsed photonic links,microwave photonics

    更新于2025-09-09 09:28:46

  • Design of Bias-Free Operational Uni-traveling-Carrier Photodiodes by Transient Simulation for High-power Pulsed Millimeter-Wave Signal Generation in the Sub-THz Regime

    摘要： In this paper, bias-free operational uni-traveling-carrier photodiodes (UTC-PDs) for high-power pulsed millimeter-wave signal generation in the sub-terahertz regime are designed and investigated. The reliability of the physics-based transient simulation is first demonstrated by comparing with reported experimental results. Then, the epitaxial layers are analyzed and optimized through transient simulation for bias-free operation and high-power pulsed millimeter-wave signal generation. The performance between original and optimal structure is compared under excitation of pulse train and sinusoidal optical signals. The results show that the peak output power of the modified UTC-PD under 100-GHz, 200-GHz, and 312.5-GHz pulse train excitation is 4.685 dBm, 1.128 dBm, and ? 4.653 dBm, improved by 2.05 dB, 5.15 dB, and 9.36 dB, respectively.

    关键词： Bias-free,Optical communication,Millimeter-wave,Transient simulation,Terahertz communications,Sub-terahertz,Uni-traveling-carrier photodiodes (UTC-PD)

    更新于2025-09-09 09:28:46

  • [IEEE 2017 IEEE Global Communications Conference (GLOBECOM 2017) - Singapore (2017.12.4-2017.12.8)] GLOBECOM 2017 - 2017 IEEE Global Communications Conference - Polar Decomposition Based Hybrid Beamforming Design for mmWave Massive MIMO Systems

    摘要： This paper considers hybrid beamforming (HBF) for the point-to-point (P2P) millimeter wave (mmWave) massive MIMO systems. The optimal hybrid precoding and combining matrices that maximizes the system capacity can be obtained based on the singular value decomposition (SVD) of the channel matrix. Then, the optimal unconstrained hybrid digital and analog precoders (combiners) are designed according to the polar decomposition of the optimal hybrid precoding (combining) matrix. Considering the actual hardware constraints, we propose a joint transmitter and receiver HBF algorithm based upon polar decomposition. In this algorithm, the hybrid analog constrained precoding and combining matrices can be derived without having to incur an excessive computational complexity of an iterative approach. Simulation results show that the proposed algorithm can approach the performance of optimal unconstrained precoding, and is insensitive to the accuracy of the channel state information (CSI).

    关键词： spectral efficiency,polar decomposition,massive MIMO,Hybrid beamforming,millimeter wave

    更新于2025-09-09 09:28:46

  • New W-band Scattering Measurement System: Proof of Concept and Results for 2D Objects

    摘要： The paper deals with a detailed study of an original system dedicated to scattering measurements of millimeter waves in the W-band. The system’s main innovations lie in its high-precision swivel arm, semi-anechoic environment, flexibility for positioning the object on the measurement tower, as well as the post-processing developed to correct measurement errors. We use canonical objects, i.e. cylinders, for tests and evaluate measurement errors and system performance by comparisons with the theoretical scattered field, which has an analytical expression. For the sake of generality, we work with both VV and HH-polarizations. We propose a complete workflow that performs noise suppression and positioning error correction, relying on two quantities: 1) the cut-off frequency of a low pass filter and 2) the pre-determination of the position of the device under test (DUT). The originality of our approach is that both quantities are fully-defined by the measurement data without a priori knowledge of the DUT. Since the different steps of the workflow are generic, it can easily be transposed to any scattering measurement system. Finally, once corrected, measurements at 75, 95, and 110 GHz exhibit signal-to-noise ratios (SNR) of close to 15 dB for dielectric cylinders and up to 25 dB for metallic ones. To the best of our knowledge, this is the first time that such values have been exhibited in the W-band.

    关键词： Millimeter wave measurements,Measurement errors,Electromagnetic diffraction

    更新于2025-09-09 09:28:46

  • DoA and DoD Estimation and Hybrid Beamforming for Radar-Aided mmWave MIMO Vehicular Communication Systems

    摘要： In millimeter wave (mmWave) communications, the feature of relatively large signal absorption and directional transmission render new challenges for wireless communications and signal processing. To further improve the performance of mmWave communications, a novel radar-aided mmWave communication (RAMC) approach is proposed, which can be used in vehicular communications. There are two parts in the proposed RAMC system, including the radar subsystem and the mmWave communication subsystem. In the radar subsystem, the bistatic co-prime multi-input and multi-output (MIMO) arrays are considered. With the radar antenna arrays, both the directions of departure (DoD) and the directions of arrival (DoA) are estimated. Additionally, the compressed sensing (CS)-based method is proposed to obtain the target positions. Using the estimated angle and position information, the channel estimation and feedback link of the mmWave communication subsystem can be eliminated. Moreover, a hybrid beamforming algorithm is proposed in the mmWave communication subsystem, which can overcome the shortage of the analog-only beamforming. Simulation results show that the better estimation performance can be achieved by the bistatic co-prime MIMO arrays than that by the traditional uniform linear arrays (ULA), and with the radar aided, the mmWave communication subsystem can reduce the beam search time, and the cell discovery time is improved significantly.

    关键词： compressed sensing,millimeter wave,hybrid beamforming,DoA estimation,radar

    更新于2025-09-09 09:28:46

  • [IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - An On-Board Differential Patch Array for 79 GHz Single-Channel Radar Applications

    摘要： This paper demonstrates the design and characterization of an on-board 4x2 corporate-fed differential patch array at 79 GHz band to equip a fully differential millimeter-wave radar transceiver. The array is based on two single-ended 4x1 arrays and it has a measured peak gain of more than 14 dBi over the 77-81 GHz band with a simulated efficiency of more than 60%.

    关键词： differential,antenna,array,radar,millimeter-wave

    更新于2025-09-09 09:28:46

  • [IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - A Stand Alone Millimetre Wave Imaging Scanner: System Design and Image Analysis Setup

    摘要： Millimetre wave sensors are capable of measuring the structure and composition as well as detecting small variations thereof in a wide range of dielectric materials, such as plastics, dry goods and foodstuffs. To produce an image that modern image recognition algorithms can be applied on, a resolution, i.e. pixel density, comparable to those of optical cameras has to be realized. In this paper, we present a rotating scanner system that operates in a CW mode at 90 GHz and allows for a high pixel density for medium measurement object velocities using only a single measurement channel. Additionally, we present an image exploitation setup for the detection of defects in scanned goods and the fusion of amplitude and phase data as well as images acquired from an optical camera for fast and easy goods inspection.

    关键词： image matching,object segmentation,microwave imaging,manufacturing industries,radar imaging,image recognition,millimeter wave radar,product safety,image fusion

    更新于2025-09-09 09:28:46