Journals >Laser & Optoelectronics Progress
ing at the asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) systems with direct current (DC) offset, a diversity combining receiver using single fast Fourier transform (FFT) is proposed. In a visible light communication (VLC) system, the background light source will inevitably cause a DC offset at the receiving end. Through the symmetric recovery operation, the odd and even signals of the ACO-OFDM system can be reconstructed in the time domain to estimate the DC offset of the system. The results show that the proposed diversity combining receiver has lower complexity, is insensitive to DC components, and has the same diversity gain as that of the conventional diversity combining receiver.
.ing at the interference problem introduced by satellite multipath signals, a blind source separation model of satellite multipath interference signals is established. The joint approximate diagonalization of eigenmatrix (JADE) algorithm based on dimensionality reduction Householder transformation is used to perform the joint approximate diagonalization of the fourth-order cumulants of received mixed signals, so as to extract multipath signals. Experimental results show that the algorithm can well separate the multipath signals with spectrum completely overlapped and the interference signals with spectrum partially overlapped. In terms of extracting multipath signals, the performance of this algorithm is superior to fast independent component analysis (FastICA) algorithm . In terms of running time, the average time of FastICA algorithm running 1000 times is about 6 times that of the Cardoso Givens-JADE(CG-JADE) algorithm, and the average running time of this algorithm is 0.0024 s less than that of GG-JADE algorithm, which proves its effectiveness and rapidity.
.ing at the technical challenge that it is difficult to realize the on-site detection of the particle size of the underground injection water for the water-drive oilfield development, we present a design concept of an optical system based on the optical scattering principle for the on-site injection water particle size detection. Using a laser beam with a wavelength of 640 nm and a 4× collimated beam expander system, we obtain an 8 mm illumination aperture. Using pupil matching and aberration balance, we achieve the optimal design of a compact optical system with a diameter of 42 mm, which meets the particle size detection requirements in the 1--100 μm range and has the ability to realize the real time underground on-site detection. The focal length of the optical system is 50 mm, the field of view is 17°, the aperture is 8 mm, and the spot radius within the field of view is less than 6 μm, which can effectively avoid the interference of non-scattered light on the energy of the photosensitive ring. The detection of standard particle samples via prototype shows that the test accuracy is less than 5%, which meets the design requirements and thus verifies the feasibility and rationality of the designed system.
.ing at the large error problem of distance vector-hop (DV-Hop) algorithm in multilateral positioning, the cause of positioning error is analyzed in detail, and an improved artificial bee colony optimization DV-Hop localization algorithm is proposed in this work. The algorithm introduces a mathematical optimization model, uses an improved area-limited artificial bee colony algorithm to optimize the model, and optimizes the execution process of multilateral positioning. Experimental results demonstrate that the modified artificial bee colony algorithm can reduce the error and the amount of calculation in the multilateral positioning stage, and the positioning effect is good.
.