A metallic waveguide with dual in-line dielectric rods can propagate electromagnetic waves more than two times higher than the cutoff frequency region and without higher modes [1]. If the straight portion in the waveguide has even symmetry, then dielectric rods are only required in the bent portion. Connection losses between the portions are improved by adding other dielectric rods.

Optical wireless communications is a research topic of extreme interest since it offers high data rate (Gbps data rate), security, and RF interference immunity. However, optical wireless communications places severe restrictions on the communications paths; they must be direct beam connections. To increase the number of users and link robustness, optical wireless communications must be able to operate even when obstacles are placed between transmitters and receivers, so optical micro-cell (OMC) with autonomous beam control can overcome link robustness. In addition, OMC based optical wireless communication yields compact systems. This paper presents the design, an implementation, and a demonstration of a 114 Mbps autonomous beam control optical wireless communication system based on an OMC technique. The robust posture control results optimum downlink alignment and good eye diagram of data transmission.

We demonstrate a novel display structure for color electronic paper for the first time. Fully transparent amorphous oxide TFT array is directly deposited onto color filter array and combined with E Ink Imaging Film. Taking advantage of the transparent property of the oxide TFT, the color filter and TFT array are positioned at the viewing side of the display. This novel "Front Drive" display structure facilitates the alignment of the color filter and TFT dramatically.

This paper presents interference suppression using a subband adaptive array (SBAA) for uplink space-time block coding (STBC) code division multiple access (CDMA) under a frequency selective fading (FSF) channel. The proposed scheme utilizes CDMA with STBC and a receive array antenna with SBAA processing at the receiver. The received signal is converted into the frequency domain before despreading and adaptive processing is performed for each subband. A novel SBAA construction is introduced to process CDMA signals based on STBC. To improve the performance of the proposed scheme, we evaluate STBC-SBAA using spreading codes cyclic prefix (CP). Simulation results demonstrate an improved performance of the proposed system for single and multiuser environments compared to competing related techniques.

This letter presents an adaptive H∞ array beamforming scheme based on a generalized sidelobe canceller with lower computational load. It is shown that the adaptive H∞-based beamformer offers the advantages of faster convergence speed, insensitivity to dynamic estimation modeling error, and less sensitivity to pointing error over the conventional adaptive H∞ algorithm. Simulations confirm that the proposed technique achieves similar array performance of the adaptive H∞-based algorithm [4].

High-resolution Direction-of-Arrival (DOA) estimation techniques for antenna arrays have been widely desired in many applications such as smart antennas, RF position location, and RFID system. To realize high-resolution capability of the techniques, precise array calibration is necessary. For an array of single-mode elements, a calibration matrix derived by the open-circuit method is the simplest one. Unfortunately, calibration performance of the method is not enough for the high-reslution DOA estimation techniques. In this paper, we consider problems of the calibration matrix derived by the method, and show that errors in the matrix can be effectively removed by an optimal diagonal weight coefficient. In the proposed compensation technique, the number of newly introduced parameters, or unknowns, is only one for an array of the identical elements. Performance of the simple compensation technique is verified numerically and experimentally.

This paper presents design of an alternating-phase fed single-layer slotted waveguide array for a sector shaped beam in the E-plane radiation pattern. A sector beam pattern is very effective for radar applications for detecting obstacles in a certain angular range without mechanical or electronic scanning. The sector shaped beam with 13 degree beam width is synthesized by a cascade of T-junctions in the feed waveguide which excite the radiating waveguides with a longitudinal shunt slot array. In order to realize the required excitation distribution of the radiating waveguides for the sector shaped beam, 30 T-junctions with symmetrical arrangement are designed by tuning a width of the coupling window, an offset of the window, and a width of the feed waveguide cascaded to the subsequent T-junction, respectively. Design and measurement are performed in 60 GHz band. The prototype antenna assembles easily; the slotted plate is just tacked on the groove feed structure and is fixed by screws at the periphery, which is the key advantage of the alternating-phase fed arrays. The measured sector pattern with low sidelobe level agrees well with the predicted one. Validity of the sector beam design as well as the performance of the alternating-phase fed array is confirmed by the measurement.

In multiple-input multiple-output (MIMO) wireless relay networks, simultaneously using multiple relay nodes can improve the capacity of source-to-destination communications. Recent information theories have shown that passing the same message across multiple relay nodes can improve the capacity of source-to-destination communications. We have previously proposed three relay schemes that use jointly QR decomposition and the phase control matrix; computer simulations have confirmed the superiority of these schemes over conventional ones such as amplify-and-forward and zero-forcing schemes. In this paper, we analyze the capacity and achievable gains (distributed array gain, intra-node array gain and spatial multiplexing gain) of the previously proposed relay schemes (QR-P-QR, QR-P-ZF, and ZF-P-QR) and thus provide an insight into what contributes to their superiority over conventional schemes. The analyses show that the location of the relay nodes used has a significant impact on capacity. On the basis of this observation, we further propose a method that enables each relay node to individually select its relay scheme according to its channel conditions so as to maximize the capacity. A computer simulation confirms the capacity improvement achieved by the proposed selection method.

In this paper, small sized arrays with a few elements are investigated. The antenna diameter is assumed to be less than 3λo. The focus of this paper is to compare the gain characteristics of a triangle arrangement with these of a uniform arrangement. The method of moments is used to calculating the gain characteristics. It is shown that the triangle arrangement is not always sufficient to obtain maximum gain for a small-sized antenna with only a few elements. Also, the type of antenna element used greatly influences the required number of elements and the element configuration.

To create a next-generation mobile satellite communication system that offers large communication capacity, the onboard antenna system must be a multi-beam system consisting of a light weight 20-m class reflector and a light weight 100-beam class antenna feed system. We clarify that the antenna gain decrease created by the reflector surface distortion expected in orbit is relatively large. This paper presents a deformed antenna pattern compensation method that minimizes circuit scale. Validity of the proposed method is confirmed by antenna pattern calculations and experiments on a fabricated array-fed reflector antenna.

The size-dependent array problem is a problem with systolic arrays such that the size of systolic arrays limits the size of calculations, which in a do-loop structure controls how many times it is repeated and how deep the nesting loops are. A systolic array cannot deal with larger calculations. For the size-dependent array problem, a spiral systolic array has been studied so far. It has non-adjacent connections between PEs, such as loop paths for sending data back so that data flows over the array independently of its own size. This paper takes an approach to the problem without non-adjacent connections. This paper discusses systolic messy arrays for infinite iterative algorithms so that they are independent from the size of calculations. First a systolic messy array called two-square shape is introduced then the properties of two-square shape are summarized: memory function, cyclic addition, and cyclic multiplication. Finally a way of building systolic messy arrays that calculate infinite iterative algorithms is illustrated with concrete examples such as an arithmetic progression, a geometric progression, N factorial, and Fibonacci numbers.

This paper deals with adaptive array beamforming based on stochastic gradient descent independent component analysis (ICA) for suppressing interference with robust capabilities. The approach first uses estimates of the interested source directions to construct the multiple regularized constraints, which form an efficient ICA-based beamformer to achieve fast convergence and more robust capabilities than existing MCMV and ESB beamformers. In conjunction with the regularization parameters of the high-order derivative constraints, the width of the main beam for remaining the desired signal and the depth of nulls for suppressing interferers can be adjusted. Several computer simulation examples are provided for illustration and comparison.

The peak SAR values of two-element array antennas for mobile handsets in the vicinity of a spherical phantom of a human head are evaluated numerically as a function of the distance between the array antenna and the head phantom when the two elements of a two-element array antenna are either co-phase voltage-fed or reverse-phase voltage-fed. It is found that relation between the worst case of the SAR and the phase difference of array elements strongly depends on the distance. When part of the head phantom is located in the reactive near-field region of the array antenna, although the co-phase feed SAR value is slightly smaller than the reverse-phase feed SAR value, the SAR value is practically independent of the phase difference, but when the head is completely outside the reactive near-field region, the co-phase feed SAR value is larger than the reverse-phase feed SAR value.

MIMO systems using a space division multiplexing (SDM) technique in which each transmit antenna sends an independent signal substream have been studied as one of the successful applications to increase data rates in wireless communications. The throughput of a MIMO channel can be maximized by using an eigenbeam-SDM (E-SDM) technique, and this paper investigates the practical performance of 22 and 44 MIMO E-SDM based on indoor measurements. The channel capacity and bit error rate obtained in various uniform linear array configurations are evaluated and are compared with the corresponding values for conventional SDM. Analysis results show that the bit error rate performance of E-SDM is better than that of SDM and that E-SDM gives better performance in line-of-sight (LOS) conditions than in non-LOS ones. They also show that the performance of E-SDM in LOS conditions depends very much on the array configuration.

An adaptive array code acquisition for direct-sequence/code-division multiple access (DS/CDMA) systems was recently proposed to enhance the performance of the conventional correlator-based method. The scheme consists of an adaptive spatial and an adaptive temporal filter, and can simultaneously perform beamforming and code-delay estimation. Unfortunately, the scheme uses a least-mean-square (LMS) adaptive algorithm, and its convergence is slow. Although the recursive-least-squares (RLS) algorithm can be applied, the computational complexity will greatly increase. In this paper, we solve the dilemma with a low-complexity conjugate gradient (LCG) algorithm, which can be considered as a special case of a modified conjugate gradient (MCG) algorithm. Unlike the original conjugate gradient (CG) algorithm developed for adaptive applications, the proposed method, exploiting the special structure inherent in the input correlation matrix, requires a low computational-complexity. It can be shown that the computational complexity of the proposed method is on the same order of the LMS algorithm. However, the convergence rate is improved significantly. Simulation results show that the performance of adaptive array code acquisition with the proposed CG algorithm is comparable to that with the original CG algorithm.

The quantization error of phase delay in an ultrasonic annular arrays imaging system is analyzed which impairs image resolution, and proper sampling rate is considered to reduce system complexity.

Monolithically integrated four-channel distributed feedback (DFB) laser array has been fabricated by metal organic vapor phase epitaxy (MOVPE) selective area growth for 1.55 µm coarse-wavelength division multiplexing (CWDM) systems. Wide-stripe MOVPE selective area growth and electron-beam lithography are used to obtain wide CWDM channel spacing of 20 nm. Compared to hybrid integration of discrete lasers, monolithic integration of laser array on a single substrate greatly simplifies device alignment and packaging process.

We propose a dipole array antenna assisted Doppler spread compensator with maximum ratio combining (MRC) diversity for mobile reception by a digital television terrestrial broadcasting receiver. Although OFDM (Orthogonal Frequency Division Multiplexing), used for the physical layer standard of digital terrestrial television broadcasting (DTTB), is robust to multi-path delay spreading thanks to its long symbol interval, it is sensitive to Doppler spread. OFDM itself cannot mitigate the performance degradation due to fading unless error correction coding is also used. Furthermore, although a Doppler spread compensator based on a linear array antenna has already been proposed, it has problems concerning the mutual coupling effect and polarization mismatch between the transmitter and receiver antennas. The proposed dipole antenna array assisted Doppler spread compensator is not only capable of mitigating both Doppler and fading phenomena, but also of efficiently receiving horizontally polarized radio waves. Computer simulation results showed that the proposed scheme outperforms the conventional monopole array assisted Doppler spread compensator.

For the uplink of a radio-on-fiber system or an electromagnetic field sensor, a resonant type optical modulator array connected with antennas can effectively convert a micro/millimeter-wave to a light wave. We designed and fabricated 10 GHz band resonant modulators and micro-strip antennas. And we demonstrated the simultaneous operation of four modulators using power received by micro strip antennas connected to each modulator. We confirmed that the optical phase change induced by the received power could be proportionally increased with the number of arrays.

This paper deals with the scattering of transverse magnetic (TM) plane wave by a perfectly conductive surface made up of a periodic array of finite number of rectangular grooves. By the modal expansion method, the total scattering cross section pc is numerically calculated for several different numbers of grooves. It is then found that, when the groove depth is less than wavelenght, the total scattering cross section pc increases linearly proportional to the corrugation width W. But an exception takes place at a low grazing angle of incidence, where pc is proportional to Wα and the exponent α is less than 1. From these facts, it is concluded that the total scattering cross section pc must diverge but pc/W the total scattering cross section per unit surface must vanish at a low grazing limit when the number of grooves goes to infinity.