scholarly journals A Novel MIMO–SAR Solution Based on Azimuth Phase Coding Waveforms and Digital Beamforming

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3374 ◽  
Author(s):  
Fang Zhou ◽  
Jiaqiu Ai ◽  
Zhangyu Dong ◽  
Jiajia Zhang ◽  
Mengdao Xing
Keyword(s):  
Multiple Input Multiple Output ◽  
Three Dimensional ◽  
Spatial Diversity ◽  
Reconstruction Method ◽  
Digital Beamforming ◽  
Phase Coding ◽  
Imaging Result ◽  
Multiple Input ◽  
Input Multiple Output ◽  
The Time Domain

In multiple-input multiple-output synthetic aperture radar (MIMO–SAR) signal processing, a reliable separation of multiple transmitted waveforms is one of the most important and challenging issues, for the unseparated signal will degrade the performance of most MIMO–SAR applications. As a solution to this problem, a novel APC–MIMO–SAR system is proposed based on the azimuth phase coding (APC) technique to transmit multiple waveforms simultaneously. Although the echo aliasing occurs in the time domain and Doppler domain, the echoes can be separated well without performance degradation by implementing the azimuth digital beamforming (DBF) technique, comparing to the performance of the orthogonal waveforms. The proposed MIMO–SAR solution based on the APC waveforms indicates the feasibility and the spatial diversity of the MIMO–SAR system. It forms a longer baseline in elevation, which gives the potential to expand the application of MIMO–SAR in elevation, such as improving the performance of multibaseline InSAR and three-dimensional SAR imaging. Simulated results on both a point target and distributed targets validate the effectiveness of the echo separation and reconstruction method with the azimuth DBF. The feasibility and advantage of the proposed MIMO–SAR solution based on the APC waveforms are demonstrated by comparing with the imaging result of the up- and down-chirp waveforms.

DESIGN AND MEASUREMENTS OF A MULTIPLE-OUTPUT TRANSMITTER FOR MIMO APPLICATIONS

2011 ◽  
Vol 20 (03) ◽  
pp. 515-529 ◽  
Author(s):  
CONSTANTINOS I. VOTIS ◽  
PANOS KOSTARAKIS ◽  
LEONIDAS P. IVRISSIMTZIS
Keyword(s):  
Antenna Array ◽  
Beam Steering ◽  
Multiple Input Multiple Output ◽  
Direct Digital Synthesis ◽  
Digital Beamforming ◽  
Channel Sounder ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Digital Synthesis ◽  
Array Performance

The design of a multiple-output transmitter for digital beamforming (DBF), Multiple-Input Multiple-Output (MIMO) and channel sounder applications, based on Direct Digital Synthesis (DDS) system is presented and investigated in terms of antenna array performance. DDS generates independently modulated signals on specific carrier frequencies and is employed as the first stage in the proposed implementation, furnishing output signal of configurable amplitude, phase and frequency. The resulting phase progression, amplitude and beamforming accuracy of a beam steering array are further investigated, showing that the proposed architecture can provide a steering beam with high accuracy. Experimental results of system performance indicate that this architecture can drive efficiently and accurately an antenna array with independent modulated RF signals, with programmable frequency, initial phase, and magnitude.

scholarly journals Downlink Multiuser Hybrid Beamforming for MmWave Massive MIMO-NOMA System with Imperfect CSI

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jing Jiang ◽  
Ming Lei ◽  
Huanhuan Hou
Keyword(s):  
Multiple Access ◽  
Multiple Input Multiple Output ◽  
Digital Beamforming ◽  
Cluster Set ◽  
Power Difference ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Hybrid Beamforming ◽  
Rate Requirement ◽  
Effective Channel

This paper aims to provide a comprehensive scheme with limited feedback for downlink millimeter wave (mmWave) multiuser multiple-input multiple-output (MIMO) nonorthogonal multiple access (NOMA) system. Based on the feedback of the best beam and the channel quality information (CQI) on this beam, the users are grouped into a cluster having the same or coherent best beam and the maximal CQI-difference. To further reduce the intercluster interference, only the candidate cluster can join the cluster set whose intercluster correlation with the existing clusters is lower than threshold. Based on the results of clustering, mmWave hybrid beamforming is designed. To improve the user experience, each cluster selects the best beam of the user with the higher guaranteed rate requirement as the analog beamforming vector. For digital beamforming, the weak user applies the block diagonalization algorithm based on the strong user’s effective channel to reduce its intracluster interference. Finally, an intracluster power allocation algorithm is developed to maximize the power difference in each cluster which is beneficial to improve the successive interference cancelation (SIC) performance of the strong user. Finally, simulation results show that the proposed MIMO-NOMA scheme offers a higher sum rate than the traditional orthogonal multiple access (OMA) scheme under practical conditions.

Thermoacoustic Modeling of a Gas Turbine Combustor Equipped With Acoustic Dampers

2005 ◽  
Vol 127 (2) ◽  
pp. 372-379 ◽  
Author(s):  
Valter Bellucci ◽  
Bruno Schuermans ◽  
Dariusz Nowak ◽  
Peter Flohr ◽  
Christian Oliver Paschereit
Keyword(s):  
Transfer Function ◽  
Gas Turbine ◽  
Mixture Fraction ◽  
Time Lag ◽  
Multiple Input Multiple Output ◽  
Three Dimensional ◽  
Analytical Models ◽  
Gas Turbine Combustor ◽  
Input Multiple Output ◽  
The Time Domain

In this work, the TA3 thermoacoustic network is presented and used to simulate acoustic pulsations occurring in a heavy-duty ALSTOM gas turbine. In our approach, the combustion system is represented as a network of acoustic elements corresponding to hood, burners, flames and combustor. The multi-burner arrangement is modeled by describing the hood and combustor as Multiple Input Multiple Output (MIMO) acoustic elements. The MIMO transfer function (linking acoustic pressures and acoustic velocities at burner locations) is obtained by a three-dimensional modal analysis performed with a Finite Element Method. Burner and flame analytical models are fitted to transfer function measurements. In particular, the flame transfer function model is based on the time-lag concept, where the phase shift between heat release and acoustic pressure depends on the time necessary for the mixture fraction (formed at the injector location) to be convected to the flame. By using a state-space approach, the time domain solution of the acoustic field is obtained. The nonlinearity limiting the pulsation amplitude growth is provided by a fuel saturation term. Furthermore, Helmholtz dampers applied to the gas turbine combustor are acoustically modeled and included in the TA3 model. Finally, the predicted noise reduction is compared to that achieved in the engine.

scholarly journals Watchstrap-Embedded Four-Element Multiple-Input–Multiple-Output Antenna Design for a Smartwatch in 5.2–5.8 GHz Wireless Applications

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Chia-Hao Wu ◽  
Jwo-Shiun Sun ◽  
Bo-Shiun Lu
Keyword(s):  
Ground Plane ◽  
Multiple Input Multiple Output ◽  
Three Dimensional ◽  
Antenna Design ◽  
Mimo Antenna ◽  
Wireless Applications ◽  
Plastic Materials ◽  
Monopole Antennas ◽  
Multiple Input ◽  
Input Multiple Output

This paper presents a compact four-element multiple-input–multiple-output (MIMO) antenna design operating within the WiFi 802.11 ac bands (5.2–5.84 GHz) for a smartwatch. The antenna is fabricated using a polyamide substrate and embedded into the strap of a smartwatch model; the strap is created using three-dimensional etching of plastic materials. The four-element MIMO antenna is formed by four monopole antennas, has a simple structure, and is connected to the system ground plane of the smartwatch. Due to the stub and notched block between two antennas and the slit in the system ground, the four-element MIMO antenna exhibits favorable isolation. Moreover, the envelope correlation coefficient of the antennas is considerably lower than 0.005 in the operating band. The measured −6 dB impedance bandwidths of the four elements of the antenna (Ant1–Ant4) with the human wrist encompass the WiFi 802.11 ac range of 5.2–5.84 GHz; moreover, an isolation of more than 20 dB is achieved. The measured antenna efficiency with and without a phantom hand are 45%–55% and 93%–97%, respectively.

scholarly journals A MIMO-SAR Tomography Algorithm Based on Fully-Polarimetric Data

Sensors ◽  
2019 ◽  
Vol 19 (22) ◽  
pp. 4839
Author(s):  
Kong ◽  
Xu
Keyword(s):  
Synthetic Aperture Radar ◽  
Covariance Matrix ◽  
Multiple Input Multiple Output ◽  
Three Dimensional ◽  
Synthetic Aperture ◽  
Estimation Accuracy ◽  
Sample Covariance ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Aperture Radar

A fully-polarimetric unitary multiple signal classification (UMUSIC) tomography algorithm is proposed, which can be used for acquiring high-resolution three-dimensional (3D) imagery, in a polarimetric multiple-input multiple-output synthetic aperture radar (MIMO-SAR) with a small number of baselines. In terms of the elevation resolution, UMUSIC provides an improvement over standard MUSIC by utilizing the conjugate of the complex sample data and converting the complex covariance matrix into a real matrix. The combination of UMUSIC and fully-polarimetric data permits a further reduction of the noise of the sample covariance matrix, which is obtained through pixel averaging of multiple two-dimensional (2D) images. Considering the consistency of four polarizations, this algorithm not only makes scattering centers have the same estimated height in four polarizations, but it also improves the estimation accuracy. Simulation results show that this algorithm outperforms the popular distributed compressed sensing (DCS). Image processing of measured data of an aircraft model using a multiple-input multiple-output synthetic aperture radar (MIMO-SAR) with six baselines is presented to validate the proposed algorithm.

scholarly journals DBF Processing in Range-Doppler Domain for MWE SAR Waveform Separation Based on Digital Array-Fed Reflector Antenna

2020 ◽  
Vol 12 (19) ◽  
pp. 3161
Author(s):  
Shenjing Wang ◽  
Yifan Sun ◽  
Feng He ◽  
Zaoyu Sun ◽  
Pengcheng Li ◽  
...  
Keyword(s):  
Rapid Development ◽  
Multiple Input Multiple Output ◽  
High Gain ◽  
Reflector Antenna ◽  
Time Shift ◽  
Planar Antenna ◽  
Digital Beamforming ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Short Time

With the rapid development of the multiple-input multiple-output synthetic aperture radar (MIMO SAR) system, the demands for miniaturization and high gain of antenna are increasing. The digital array-fed reflector antenna has such virtues so that it can play an important role in such system. However, the geometric models and signal models based on a reflector antenna are considerably different from the directly radiating planar antenna. The signal processing for the reflector antenna is more complex and difficult. As a result, the applications of the reflector antenna in SAR system are not as mature as those of the planar antenna. A combination of multidimensional waveform encoding (MWE) technique and digital beamforming (DBF) technology at the receiving end can greatly improve the MIMO SAR system performance, especially ambiguity suppression and waveform separation. This configuration can realize different radar functions and meet multidimensional observation requirements, such as the polarized SAR. Thus, this study combines digital array-fed reflector antenna and the DBF technique in the elevation direction for MWE SAR waveform separation. The echo models for the array-fed reflector antenna and the planar antenna are established based on short-time shift-orthogonal waveforms. In the models, a mismatch in steering vectors is inevitable if DBF processing is continuously performed traditionally in the azimuth-elevation two-dimensional time domain. This mismatch will worsen the waveform separation effect and the image quality. Therefore, we propose a DBF method which is processed in range-Doppler domain. The method enables waveform separation without ambiguity at the receiver. Then, the conventional SAR imaging methods are enabled, and we acquire an ideal SAR image. The simulation results for both point targets and distributed targets prove the effect and feasibility of the proposed DBF method.

Sign in / Sign up

Export Citation Format

Share Document