This paper deals with the statistical modeling of a Time-Frequency Series of Speech (TFSS), obtained by Short-Time Fourier Transform (STFT) analysis of the speech signal picked up by a linear microphone array with two elements. We have attempted to find closer match between the distribution of the TFSS and theoretical distributions like Laplacian Distribution (LD), Gaussian Distribution (GD) and Generalized Gaussian Distribution (GGD) with parameters estimated from the TFSS data. It has been found that GGD provides the best models for real part, imaginary part and polar magnitudes of the time-series of the spectral components. The distribution of the polar magnitude is closer to LD than that of the real and imaginary parts. The distributions of the real and imaginary parts of TFSS correspond to strongly LD. The phase of the TFSS has been found uniformly distributed. The use of GGD based model as PDF in the fixed-point Frequency Domain Independent Component Analysis (FDICA) provides better separation performance and improves convergence speed significantly.

The descriptional complexity of iterative arrays (IAs) is studied. Iterative arrays are a parallel computational model with a sequential processing of the input. It is shown that IAs when compared to deterministic finite automata or pushdown automata may provide savings in size which are not bounded by any recursive function, so-called non-recursive trade-offs. Additional non-recursive trade-offs are proven to exist between IAs working in linear time and IAs working in real time. Furthermore, the descriptional complexity of IAs is compared with cellular automata (CAs) and non-recursive trade-offs are proven between two restricted classes. Finally, it is shown that many decidability questions for IAs are undecidable and not semidecidable.

In this paper, we propose a DOA (Direction Of Arrival) estimation method of speech signal using three microphones. The angular resolution of the method is almost uniform with respect to DOA. Our previous DOA estimation method using the frequency-domain array data for a pair of microphones achieves high precision estimation. However, its resolution degrades as the propagating direction being apart from the array broadside. In the method presented here, we utilize three microphones located at vertices of equilateral triangle and integrate the frequency-domain array data for three pairs of microphones. For the estimation scheme, the subspace analysis for the integrated frequency array data is proposed. Through both computer simulations and experiments in a real acoustical environment, we show the efficiency of the proposed method.

A mechanical phase shifter is designed for beam scanning in co-phase fed single-layer slotted waveguide arrays. The multiple-way power divider in this array consists of a series of π-junctions with one guide wavelength spacing in a feed waveguide. The movable narrow walls placed between the π-junctions perturb the guide wavelength as well as the phase of output ports. Method of Moment (MoM) analysis for one unit consisting of one movable plate and two junctions is conducted to estimate the available phase shift as well as the degradation of reflection. A phase shift of 86 degrees is predicted between two π-junctions under the condition of reflection below -20 dB; experiments at 4 GHz confirmed the design. The beam scanning capability of the arrays is also surveyed and the beam-scanning of about 10 degrees is predicted.

This paper presents a transmit diversity scheme that allocates space-time block codes (STBC) to beamspace and spreading codes for two-dimensional spreading orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) downlink transmission. In this scheme, the STBC output symbols are beam-steered using a pair of neighboring beams selected via closed-loop beam selection. The beam-steered symbols in two adjacent time slots are spread by two distinct spreading codes and multiplexed in the same spreading segment. User signals transmitted from different pairs of beams, but that share the same beam, interfere with each other when decoding STBC. Spreading codes are thus allocated to users according to beam pairs used. This is to suppress the interference in time-direction despreading that precedes decoding of STBC. Simulation results demonstrated that the proposed scheme provides beam gains or beam diversity gains or both and that it alleviates inter-code interference by spatially separating user signals by using transmit beam. The proposed scheme also provides high tolerance to large Doppler spread.

This paper describes an area-efficient dual-rail array logic architecture, a logic-cell-embedded PLA (LCPLA), which has 2-input logic cells in the structure. The 2-input logic cells composed of pass-transistors can realize any 2-input Boolean function and are embedded in a dual-rail PLA. The logic cells can be designed by connecting some local wires and do not require additional transistors over logic cells of the conventional dual-rail PLA. By using the logic cells, some classes of logic functions can be implemented efficiently, so that high-speed and low-power operations are also achieved. The advantages over the conventional PLAs and standard-cell-based designs were demonstrated by using benchmark circuits, and the LCPLA is shown to be effective to reduce the number of product terms. In a structure with a 64-bit input and a 1-bit output including 220 product terms, the LCPLA achieved an area reduction by 35% compared to the conventional high-speed dual-rail PLA, and the power-delay product was reduced by 74% and 46% compared to the conventional high-speed single-rail PLA and the conventional high-speed dual-rail PLA, respectively. A test chip of this configuration was fabricated using a 0.35-µm, 3-metal-layer CMOS technology, and was verified with a functional test using a logic tester and an electron-beam tester at frequencies of up to 100 MHz with a supply voltage of 3.3 V.

Multiple antenna systems are promising architectures for overcoming the effects of multi-path interference and increasing the spectrum efficiency. In order to be able to investigate these systems, in this article, we derive generalized spatial correlation equations of a circular antenna array for two typical angular energy distributions: a Gaussian angle distribution and uniform angular distribution. The generalized spatial correlation equations are investigated carefully by exact and approximate analyses.

This letter presents a novel two-dimensional (2-D) defected ground array (DGA) for planar circuits, which has horizontal and vertical periodicities of defect structure. The defect unit cell of DGA is composed of a Sierpinski carpet structure to improve the effective inductance. Measurements show that the proposed DGA provides steeper cutoff characteristics, lower cutoff frequency, and higher slow-wave factors than the conventional periodic defected ground structure in the same occupied surface.

This paper examines the Inter Carrier Interference (ICI) due to Doppler spread in OFDM mobile reception and proposes the use of Beam-Space Adaptive Array Antennas for moving receivers. In the proposed system, firstly we separate the multi-path signals into multi-beams according to their incident directions, then correct the frequency shift of each beam signal, considering the beam direction, and finally combine the corrected signals based on Maximal Ratio Combining (MRC). Further this paper clarifies the excellent performance of the proposed system in suppressing the influence of Doppler spread by carrying out computer simulation. Particularly, it was certified that it is possible to suppress the influence of the Doppler spread efficiently for all the receiving directions by using eight-element beam-space array antenna with element spacing of (3/8)λ, and referring three past symbol data when calculating the weight vector of MRC.

Many carriers are introducing multi-media services to satisfy customer demands for these services. In order to provide such services, carrier must increase their system capacity. It is well known that space division multiple access (SDMA) improves system capacity and is compatible with existing access systems. In order to evaluate the performance of SDMA, we developed an SDMA test bed. The test bed maintains the personal handy phone systems (PHS). The PHS adopts time division multiple access (TDMA). Aiming to compare the performance of SDMA and TDMA using the same analog hardware, the SDMA test bed employs a software-defined radio (SDR) technique. This paper shows the outline and performance of the test bed. The results of laboratory tests indicate that the bit error rate (BER) of the test bed operated in the SDMA mode at under 10-3 when the carrier-tointerference ratio (CIR) was larger than approximately -22 dB. Antenna patterns measured in an anechoic chamber show that the SDMA test bed produces correct antenna patterns when there are three desired signals and one interference signal. The results of the four field tests confirm that the test bed operated while two-multiplex SDMA mode doubled of the traffic and decreased the interference level as compared with the TDMA mode. Furthermore, the test bed operated while threemultiplex SDMA mode improves the traffic about 2.4 to 2.7 times. The SDMA test bed decreased the impact of the adjusted TDMA base station (BS). Therefore, we confirmed that the SDMA improves system capacity without any degradation.

Iterative Logic Arrays (ILAs) are widely used in many applications, e.g., general-purpose processors, digital signal processors, and embedded processors. Owing to the advanced VLSI technology, new defect mechanisms exist in the fabricated circuits. In order to ascertain the quality of manufactured products, the traditional single cell fault model is not sufficient. Therefore, more realistic fault models such as sequential fault models and delay fault models should also be adopted. A cell delay fault occurs if and only if an input transition cannot be propagated to the cell's output through a path in the cell in a specified clock period. It has been shown that all SIC (single input change) pairs of a circuit are sufficient to detect all robustly detectable path delay faults within the circuit. We extend the concept of SIC pairs for iterative logic arrays. We say that an ILA is C-testable for cell delay faults if it is possible to apply all SIC pairs of a cell to each cell of the array in such a way that the number of test pairs for the array is a constant. This is based on a novel fault model, called Realistic Sequential Cell Fault Model (RS-CFM). Necessary conditions for sending this test set to each cell in the array and propagating faulty effects to the primary outputs are derived. An efficient algorithm is also presented to obtain such a test sequence. We use the pipelined array multiplier as an example to illustrate our approach. The number of test pairs for completely testing of the array is only 84. Moreover, the hardware overhead to make it delay fault testable is about 5.66%.

In this paper, as an important technology for the software-defined radio, a novel scheme of adaptive array antenna utilizing bandpass sampling technique is proposed. For adaptive signal processing, it is necessary to convert the radio frequency signal received by the antenna that is given by real number into baseband region, i.e., complex number region. Then, the method for dividing the bandpass sampled signal to in-phase and quadrature components is analyzed. The sampling scheme is called the IQ-division bandpass sampling. An adaptive array antenna based on the IQ-division bandpass sampling is characterized by the signal processing at the bandpass sampled signal stage, namely, intermediate frequency stage, not baseband. Finally, we will confirm the validity of the proposed scheme through an experiment in a radio anechoic chamber.

The E-1-track switch torus array model and the "EAR" reconfiguration method are proposed for fault tolerance of mesh or torus-connected processor arrays, where the original idea of EAR is in EAM. The comparison among these and others is described in terms of the (run-time) array reliability, hardware overhead, and/or reconfiguration time. When a designer chooses one among fault tolerant methods, he should consider their features synthetically case by case, and we consider that the results given by this paper are useful for the choice.

In radio surveillance systems we consider the problem of identifying interferers or illegal radios in licensed communication channels. The systems considered are receivers using arrays of antennas for spatial processing. At the output of each antenna, we have a mixture of communication signals. The mixture will depend on the distance of the source radios and the propagation environment. These signals may or may not have the same modulation type. The main four tasks in the radio surveillance system are: Separation of the source signals contained in the data mixture at the array antenna, modulation recognition to identify the illegal radio, direction of arrival estimation to pinpoint the location of the illegal radios, and demodulation to intercept the information contained within the illegal transmission. In this paper we deal with the application of the Fast ICA algorithm to a uniform linear array. Our interest is to separate the independent source signals from the mixture of signals obtained at the sensors. Since the target system operates in the HF domain, where analog modulations dominate, the impinging signals are assumed analog modulated communication signals.

In speech enhancement with adaptive microphone array, the voice activity detection (VAD) is indispensable for the adaptation control. Even though many VAD methods have been proposed as a pre-processor for speech recognition and compression, they can hardly discriminate nonstationary interferences which frequently exist in real environment. In this research, we propose a novel VAD method with array signal processing in the wavelet domain. In that domain we can integrate the temporal, spectral and spatial information to achieve robust voice activity discriminability for a nonstationary interference arriving from close direction of speech. The signals acquired by microphone array are at first decomposed into appropriate subbands using wavelet packet to extract its temporal and spectral features. Then directionality check and direction estimation on each subbands are executed to do VAD with respect to the spatial information. Computer simulation results for sound data demonstrate that the proposed method keeps its discriminability even for the interference arriving from close direction of speech.

The performance enhancement technology for indoor-to-outdoor wireless communication systems is discussed in this study. In outdoor communication systems, transmitted signals may be severely degraded mainly by multipath fading effect of the channel and this problem can be overcome using conventional multiple antenna technology and array signal processing algorithms. But, since channel characteristics depend on both multipath fading and angle spread in indoor-to-outdoor communication systems, conventional algorithms which do not consider the effect caused by angle spread cannot give good results. In this letter, characteristics of indoor-to-outdoor channels are analyzed and a channel model suitable for this situation is proposed. And a new array antenna processing algorithm exploiting the concept of the mean steering vector is presented and the system performance is analyzed. It can be shown that the proposed algorithm outperforms conventional methods through computer simulations for the case in which signals sent from indoor transmitters arrive at outdoor receivers.

Beam-space time coding methods are being extensively investigated, since they provide levels of performance appropriate for the next and future generations of wireless communication systems. In this paper, we focus on beam-domain space-time coding, especially considering the case when transmit beams have inter-beam interference (IBI). A new beam-space time coding scheme that takes into account the overlap amount among beams is proposed. We observe that the overlap of beams introduces an amount of correlation to the channels in a similar way to the well-known Partial Response (PR) channel in magnetic recording. Based on that observation, the proposed system can make use of IBI to encode and decode the signals. We evaluate the proposed system both via theoretical upper bound and via computer simulations. The Bit Error Rate (BER) performance of the proposed system using IBI is better than that of the system with no-IBI because the proposed system delivers more coding gain. However, the overlap of beams decreases the diversity gain. The tradeoff relationship between diversity gain and coding gain is investigated.

In this paper, we propose the soft boundary concept achieved by dynamic tilted antenna to solve the issue of traffic congestion occurred in cellular wireless systems. The tilted antenna array can provide the merit of traffic balance and also achieve the optimization of the signal-to-interference ratio (SIR) at receivers by automatically tilting the antenna and implementing the soft boundary among cells, corresponding to the variation of traffic. According to our results, it is shown that power ratio control do not necessarily improved system performance when there is a large variation in traffic because it only control power levels. Also the properly chosen angle of tilt antenna can relieve the traffic congestion and perform the system performance optimization.

Employing a triangular dielectric phase shifter simplifies the beam forming network of an offset beam array antenna because this structure achieves phase control in a single configuration. This paper proposes a design method for a low loss offset beam planar antenna that incorporates a triangular dielectric plate phase shifter on parallel microstrip feedlines. Our design method reduces the loss of the phase shifter by optimizing the microstrip line width. By using the proposed design equation, the optimum low loss phase shifter configuration can be easily established. In addition, this paper presents the actual design of a triangular plate considering size reduction. The results of experiments of the offset beam antenna indicate that our design method is effective in obtaining a simple, low loss, and compact configuration.

The array-enhanced coherence resonance (AECR) in the diffusively coupled active rotators is investigated and its analysis with the nonlinear Fokker-Planck equation is presented. By considering the nonlinear Fokker-Planck equation of the rotators, it is found that the time-periodic solution exists in some parameter range. By solving the equation of a rotator and the Fokker-Planck equation simultaneously, the behavior of a rotator in the system with infinite number of rotators is considered, and it is found that AECR also takes place in this infinite system. Thus it is concluded that AECR is caused by the time-periodic solution of the probability density induced by noise.