An imperative problem in the field of vision-based aerial robotics is the ‘autonomous helicopter landing’. The complexity of this problem can be eliminated by dividing the problem into sets of independent and simple sub-problems and to solve each set individually, i.e. ‘divide and conquer’. Accordingly, we divide the pose parameters in different sets and estimate each set independently. We provide valid conditions to mask other sets of pose parameters while estimating a particular set. An H-shaped helipad made of a combination of three ellipses is used to estimate all sets of pose parameters. Thanks to simple computations, the system is much cheaper and faster than the current methods in practice. Real-time experiments indicate the effectiveness of the proposed method.
Biomedical micro-electromechanical systems (bioMEMS) and other biochips usually have exposed chip surfaces that interface with fluids containing biological elements. These chips require post-processing for fluidic encapsulation to confine the spreading of fluids during experiments. An effective fluidic encapsulation protocol is reported here that simplifies this encapsulation procedure. The protocol uses tools and components found in a typical fabrication laboratory setting. The procedure encapsulates each edge of the chip working area in one cycle and achieves sharply defined edges with thickness of 1 to 5mm with boundary tolerance less than 1mm. The protocol reduces time, complexity, cost and defects for biochip encapsulation with a working area having lengths between 3 to 100mm.
In this paper, a special complex-valued simplicial canonical piecewise linear (CSCPWL) function is presented for power amplifier and digital predistorter nonlinearity representation. The proposed function is derived from the simplicial canonical piecewise linear (SCPWL) function approximates to polynomial basis and can be easily applied for baseband modeling with complex-valued signal. Through the experiment simulation, the modeling capacity, algorithm complexity and numerical stability of the proposed function are discussed. Finally, the conclusion that the special CSCPWL function is a compromise between the system performance and hardware cost is given.
This letter proposes an easy-to-implement blindly weighted non-coherent receiver (BWNCR) for low data rate impulse radio ultra-wideband (IR-UWB) systems operating with pulse amplitude modulated (PAM) signals. We first derive the theoretically optimal weights for the likelihood ratio test based WNCR (LRT-WNCR) in closed-form. In order to refrain the LRT-WNCR from demanding a priori knowledge of the channel and the noise variance, we further develop a low complexity receiver to accomplish the optimal weight-setting and threshold-setting in an entirely blind manner. Simulations verify that the bit error rate (BER) of the BWNCR closely approaches that of the LRT-WNCR, which is achieved with ideally known channel state information and noise variance.
This paper presents a new approach for linearization of power Amplifier with memory effect using a digital pre-distorter system. This paper proposes a Multi-Level Two-Dimension LUT (ML-2D LUT) system for adaptive digital pre-distorter that compensates both nonlinear and memorial distortion of HPAs (High power Amplifier). The proposed system eliminates the trade-off between the adaption speed and the accuracy using multi-level scheme. An OFDM signal for DVB-T standard is used to validate this method. The convergence time of the propose system is 35 times faster than conventional 2D LUT with the same memory size and adaption step size.
Mathematical morphology techniques, such as white top-hat (WTH) and new white top-hat (NWTH) transformation have been researched for small target detection application in the infrared (IR) images. However, its target enhancement performance still depends on its SE size set by users. To solve this problem, we propose a recursive multi-structuring elements (multi-SEs) NWTH method with an automatic decision mechanism of the SE size. The proposed method based on the NWTH transformation updates the multi-SEs by calculating candidate target-to-clutter ratio gain (CTCRG) of the NWTH images by the multi-SEs. Through a recursive procedure, final multi-SEs is automatically selected, and then small targets can be detected in a summation image of NWTH images by the final multi-SEs.
Synchronization can be achieved by computing the correlation of a received signal using a locally stored synchronization sequence. The segment giving the maximum correlation is taken as the location of the sequence. In this letter, we present an ideal synchronization circuit using a sequence pair with bipolar correlation. When a sequence pair is inputted, the circuit outputs double maximum correlation values that are equal in magnitude and opposite in polarity at the zero and middle shifts, by using the sidelobe cancellation effect between the two sequences. Such a circuit is particularly useful for synchronization, since it can be used to double-check the synchronization timing.
An equivalent circuit of a single conductor line (Sommerfeld wave) is proposed. The circuit is based on physical quantities, such as the electric current and on the power of the traveling wave, while the line voltage is only indirectly obtained. The characteristic impedance and the per-unit-length parameters are calculated in closed form as functions of the complex wave numbers, which must be determined numerically. The circuit parameters are partly confirmed by literature results, and they differ only where the literature results have no physical meaning (e.g. negative conductance). Furthermore, circuit simulation solutions are used to determine the per-unit-length attenuation, and the results are confirmed by the well known analytical solution. The idea can be extended to other type of single conductor lines, having a more complex cross-sectional profile and inhomogeneous media.
The average bit BER performance of coded MIMO OFDM with maximum likelihood detection in multipath Nakagami-Rice fading channels is analyzed. The upper bound of the BER probability is derived by means of the union bound of the pairwise error probabilities. Asymptotic results for the high SNR region enable to consider the effect of fading correlations and the diversity advantage. Simulations are performed to verify the correctness of the mathematical analysis, and the analysis is validated to bound the actual BER probability tightly in the high SNR region.
This paper describes a novel high-precision bandgap reference with resistance variation compensated. Novel process-compensated emitter current generator allows a substantial reduction on VBE variation, resulting in an improved accuracy of the proposed bandgap reference. Comparison results in a 0.13µm CMOS technology indicated that the proposed voltage reference achieved up to 62% improvement in terms of accuracy, as compared to conventional bandgap reference. Process variation of reference voltage is shown to be ±3.67mV for all process corners without any post-process trimming.
A pulse diversity-based jammer cancellation processor is designed in this paper to cancel the deception electronic counter measures (ECM) signals repeated by a digital radio frequency memory (DRFM) for radar systems. In order to remove the conventional stationary hypotheses and the rigorous application conditions, an orthogonal transmission block code set is achieved in one pulse repetition interval by exploiting the orthogonal frequency division multiplexing (OFDM). The processor does not require parameter estimation and compensation across a period of a whole block code. It is applicable to rapidly varying conditions in the presence of deception jammers.
We performed a simulation of optical code generation and processing to determine the number of discriminable codes, which depends on the number of chips and the chip rate. Based on an actual optical binary phase shift keying (BPSK) code generation and processing system, the characteristics of devices in the code generation and processing with threshold processing were considered in this simulation. To handle variable BPSK codes, we used LiNbO3 (LN) modulators as an optical code generator and a transversal filter (TVF) as an optical code processor. We found that BPSK codes with 2-6 chips, 10, 20, 40Gchip/s had sufficient threshold margins for code discrimination in the simulation, and this result was in good agreement with experimental results. We performed experiments 4 chip, 10Gchip/s code generation and processing, and we experimentally confirmed the number of discriminable codes is 8.
In this paper, we propose a geometry histogram modification algorithm to increase the visibility of 3D point models. We define a weak feature as a group of neighboring points yielding the small deviations of normal directions. Geometry histogram is defined as the distribution of the signed distance between a feature point and the locally approximated plane. We equalize and stretch the geometry histogram and move the corresponding feature points accordingly. We also use the OpenGL API for simple and fast rendering of 3D point models. Experimental results show that the proposed algorithm efficiently enhances the geometry contrast of 3D point models by improving the appearance of the weak features.
In this paper, we propose a new IFFT design method for orthogonal frequency division multiplexing (OFDM) systems to reduce the memory size of IFFT based on a combined integer mapping of three IFFT input signals: modulated data, pilot and null signals. The proposed method focuses on reducing the size of memory cells in the first two stages of the pipelined architectures since the first two stages require 75% of the total memory cells. By simulations of 2048-point IFFT design for cognitive radio systems, it is shown that the proposed IFFT design method achieves more than about 35% reduction in gate count and about 34% reduction in power consumption compared with conventional IFFT design.
This letter proposes an adaptive all-pass filter (A2PF) based peak-to-average power ratio (PAPR) reduction scheme for signle input single output orthogonal frequency division multiplexing (OFDM) systems. A properly phase rotated OFDM symbol of reduced PAPR is generated by an A2PF with its filter coefficient found by the Newton-Raphson method. For the A2PF scheme, costly side information(SI) transmission is not needed unlike the selected mapping (SLM) scheme. The A2PF scheme achieves PAPR reduction performance comparable to the SLM scheme. Simulation results demonstrate that the A2PF scheme without SI leads to BER performance close to the SLM scheme with SI.