Convergence of the iterative method based on the successive overrelaxation (SOR) method is investigated to solve the matrix equation in the moment analysis of array antennas. It is found this method can be applied to the sub domain method of moments with fast convergence if the grouping technique is applied and the over-relaxation parameter is properly selected, and the computation time for solving the matrix equation can be reduced to be almost proportional to the second power of the number of unknowns.

In this letter, a new blind anti-jammer pre-processor is proposed for GPS receivers to alleviate performance degradation due to strong jammers. Since strong jammers have been successfully removed before despreading, the proposed scheme can effectively extract the signals-of-interest, leading to significant performance enhancement as compared with conventional methods.

In this paper, we propose a global routing method for 2-layer BGA packages. In our routing model, the global routing for each net is uniquely determined by a via assignment of each net. Our global routing method starts from an initial monotonic via assignment and incrementally improves the via assignment to optimize the total wire length and the wire congestion. Experimental results show that our proposed method generates a better global routing efficiently.

As a blind linear-interference-canceller for DS-CDMA mobile communications, the orthogonal matched filter (OMF) minimizes the power of the output while maintaining constant power of the desired signal in the output. This paper studies the extension of OMF to an RAKE receiver (OMF-RAKE), which adaptively controls the steering vectors that determine the constraint. It also applies the QR-RLS algorithm to estimate the OMF-RAKE parameters and investigates a hardware implementation that employs a systolic array. Computer simulations show that OMF-RAKE with the QR-RLS algorithm and the systolic array structure can reduce the computational complexity to about a half that of the conventional RLS-type algorithm without degrading the BER.

In this paper, we present the condition for the effective wire addition in Look-Up-Table-based (LUT-based) field programmable gate array (FPGA) circuits, and an optimization procedure utilizing the effective wire addition. Each wire has different characteristics, such as delay and power dissipation. Therefore, the replacement of one critical wire for the circuit performance with many non-critical ones, i.e., many-addition-for-one-removal (m-for-1) is sufficiently useful. However, the conventional logic optimization methods based on sets of pairs of functions to be distinguished (SPFDs) for LUT-based FPGA circuits do not make use of the m-for-1 manipulation, and perform only simple replacement and removal, i.e., the one-addition-for-one-removal (1-for-1) manipulation and the no-addition-for-one-removal (0-for-1) manipulation, respectively. Since each LUT can realize an arbitrary internal function with respect to a specified number of input variables, there is no sufficient condition at the logic design level for simple wire addition. Moreover, in general, simple addition of a wire has no effects for removal of another wire, and it is important to derive the condition for non-simple and effective wire addition. We found the SPFD-based condition that wire addition is likely to make another wire redundant or replaceable, and developed an optimization procedure utilizing this effective wire addition. According to the experimental results, when we focused on the delay reduction of LUT-based FPGA circuits, our method reduced the delay by 24.2% from the initial circuits, while the conventional SPFD-based logic optimization and the enhanced global rewiring reduced it by 14.2% and 18.0%, respectively. Thus, our method presented in this paper is sufficiently practical, and is expected to improve the circuit performance.

In this paper, a new algorithm for MTMR adaptive array antenna (AAA) system combined with analog-type transmit power control (TPC) is proposed for DS-CDMA systems in order to employ high level modulation schemes like 64 QAM in wireless multimedia services. A conventional AAA system considering the strongest path as a target path cannot work effectively when angular dispersion between the strongest path and other delayed paths is large, that is, beam selectivity is so small due to severe frequency selective multipath fading. So, in order to solve such a beam selectivity problem, a beam directivity control scheme using a path manipulation technique is introduced for the BS and MS AAA combining in this paper, along with analog-type TPC. It utilizes virtual delay profiles which are modified from the measured complex delay profile and selects a desired path giving the maximum DUR with an optimized weight vector for BS and MS beamforming. We will show through computer simulation that the proposed scheme is very effective in enhancing the data throughput at the downlink of wideband DS-CDMA systems as compared with the conventional system.

In this paper, an adaptive microphone array system with a two-stage adaptation mode controller (AMC) is proposed for high-quality speech acquisition in real environments. The proposed system includes an adaptive array algorithm, a time-delay estimator and a newly proposed AMC. To ensure proper adaptation of the adaptive array algorithm, the proposed AMC uses not only temporal information, but also spatial information. The proposed AMC is constructed with two processing stages: an initialization stage and a running stage. In the initialization stage, a sound source localization technique is adopted, and a signal correlation characteristic is used in the running stage. For the adaptive array algorithm, a generalized sidelobe canceller with an adaptive blocking matrix is used. The proposed algorithm is implemented as a real-time man-machine interface module of a home-agent robot. Simulation results show 13 dB SINR improvement with the speaker sitting 2 m distance from the home-agent robot. The speech recognition rate is also enhanced by 32% when compared to the single channel acquisition system.

A waveguide crossed-slot linear array with a matching element is accurately analyzed and designed by the method of moments using numerical-eigenmode basis functions developed by the authors. The rounded ends of crossed-slots are accurately modeled in the analysis. The initial values of the slot parameters determined by a model with assumption of periodicity of field are modified and refined by the full-wave finite-array analysis for uniform excitation and small axial ratio. As an example, an 8-element linear array is designed at 11.85 GHz, which radiates a circularly polarized wave at a beam-tilting angle of 50 degrees. The radiation pattern, the frequency characteristics of the reflection and the axial ratio are compared between the analysis and the measurement and they agree very well. The calculated and measured axial ratio at the beam direction are 0.1 dB and 1.7 dB, respectively. This method provides a basic and powerful design tool for slotted waveguide arrays.

In this paper, single-input multiple-output (SIMO)-model-based blind source separation (BSS) is addressed, where unknown mixed source signals are detected at microphones, and can be separated, not into monaural source signals but into SIMO-model-based signals from independent sources as they are at the microphones. This technique is highly applicable to high-fidelity signal processing such as binaural signal processing. First, we provide an experimental comparison between two kinds of SIMO-model-based BSS methods, namely, conventional frequency-domain ICA with projection-back processing (FDICA-PB), and SIMO-ICA which was recently proposed by the authors. Secondly, we propose a new combination technique of the FDICA-PB and SIMO-ICA, which can achieve a higher separation performance than the two methods. The experimental results reveal that the accuracy of the separated SIMO signals in the simple SIMO-ICA is inferior to that of the signals obtained by FDICA-PB under low-quality initial value conditions, but the proposed combination technique can outperform both simple FDICA-PB and SIMO-ICA.

Transferring the image information in analog form between the focal plane array (FPA) and the external electronics causes the disturbance of the outside noise. On-chip analog-to-digital (A/D) converter into the readout integrated circuit (ROIC) can eliminate the possibilities of the cross-talk of noise. Also, the information can be transported more efficiently in power in the digital domain compared to the analog domain. In designing on-chip A/D converter for cooled type high density infrared detector array, the most stringent requirements are power dissipation, number of bits, die area and throughput. In this study, pipelined type A/D converter was adopted because it has high operation speed characteristics with medium power consumption. Capacitor averaging technique and digital error correction for high resolution was used to eliminate the error which is brought out from the device mismatch. The readout circuit was fabricated using 0.6 µm CMOS process for 128 128 mid-wavelength infrared (MWIR) HgCdTe detector array. Fabricated circuit used direct injection type for input stage, and then S/N ratio could be maximized with increasing the integration capacitor. The measured performance of the 14 b A/D converter exhibited 0.2 LSB differential non-linearity (DNL) and 4 LSB integral non-linearity (INL). A/D converter had a 1 MHz operation speed with 75 mW power dissipation at 5 V. It took the die area of 5.6 mm2. It showed the good performance that can apply for cooled type high density infrared detector array.

In this paper, we propose a spatio-temporal equalizer for the space-time block coded transmission over the frequency selective fading channels with the presence of co-channel interference (CCI). The proposed equalizer, based on the tapped delay line adaptive array (TDLAA), performs signal equalization and CCI suppression simultaneously using the minimum mean square error (MMSE) method. It is to show that our scheme outperforms the previous two-stage combined adaptive antenna and delayed decision feedback sequence estimator (DDFSE) approach. We also show that performance can be further improved if the synchronization between the preceding and delayed paths is achieved.

In this report, we propose a tracking algorithm of speaker direction using microphones located at vertices of an equilateral triangle. The method realizes tracking by minimizing a performance index that consists of the cross spectra at three different microphone pairs in the triangular array. We adopt the steepest descent method to minimize it, and for guaranteeing global convergence to the correct direction with high accuracy, we alter the performance index during the adaptation depending on the convergence state. Through some computer simulation and experiments in a real acoustic environment, we show the effectiveness of the proposed method.

This paper describes a new multi-channel method of noisy speech recognition, which estimates the log spectrum of speech at a close-talking microphone based on the multiple regression of the log spectra (MRLS) of noisy signals captured by distributed microphones. The advantages of the proposed method are as follows: 1) The method does not require a sensitive geometric layout, calibration of the sensors nor additional pre-processing for tracking the speech source; 2) System works in very small computation amounts; and 3) Regression weights can be statistically optimized over the given training data. Once the optimal regression weights are obtained by regression learning, they can be utilized to generate the estimated log spectrum in the recognition phase, where the speech of close-talking is no longer required. The performance of the proposed method is illustrated by speech recognition of real in-car dialogue data. In comparison to the nearest distant microphone and multi-microphone adaptive beamformer, the proposed approach obtains relative word error rate (WER) reductions of 9.8% and 3.6%, respectively.

The uplink of a space-time block coded multicarrier modulation code division multiple access (MC-CDMA) system equipped with a uniform linear array (ULA) at the base station is studied. A blind decoder that provides closed-form solutions of both transmitted symbol sequences and directions of arrival (DOAs) for all active users in one macrocell is derived without the uplink space-time vector channel estimation. The decoder uses an ESPRIT-like method to separate multiple co-channel users with different impinging DOAs. As a result, the DOAs of multiple users are obtained. In particular, a set of signal spaces, every one of which is spanned by the coded symbol sequences of an individual user, are also obtained. From these signal spaces, the original symbol sequences of multiple users are estimated by exploiting the special structure of space-time block coding (STBC) in combination with the finite alphabet property of transmitted symbols. Performance of the proposed scheme is evaluated by extensive computer simulations.

In this paper, we propose an adaptive algorithm based on accumulated signal processing, which could be applicable to Post-FFT-type OFDM adaptive array antennas. Proposed scheme calculates the weight of each element at a particular instant t, by considering both post- and pre-received symbols. Because of the use of additional forthcoming information on channel behavior in the weight calculation scheme, one can expect an improved performance in fast fading conditions by using the proposed adaptive algorithm. This paper also discusses the application of the proposed adaptive algorithm to OFDM adaptive array. In OFDM application, a few subchannels are being used to transmit pilot symbols, and at the receiver, the proposed adaptive algorithm is applied to those pilot subchannels, and interpolates the weights for the data subchannels which are allocated between the pilot subchannels. Finally, the system performance improvement with the application of the proposed adaptive algorithm is verified by computer simulation.

This paper describes the choke-loaded patch array antenna for use in the IMT-2000 repeater systems. The choke structure of the 4-element array is designed by means of an electromagnetic analysis. A high front-to-back (FB) ratio is required for suppressing mutual coupling in order to stop the oscillation caused by the interference waves between a transmitting and receiving antenna. The suppression of the FB ratio by a choke is limited in the case of the 16-element array because its side lobe level is large. In this paper, we examine the effect of suppressing the mutual coupling using a binomial array.

In this paper, we present a noble pattern synthesis method of linear and planar array antennas, with non-uniform spacing, for simultaneous reduction of their side-lobe level and pattern distortion during beam steering. In the case of linear array, the Gauss-Newton method is applied to adjust the positions of elements, providing an optimal linear array in the sense of side-lobe level and pattern distortion. In the case of planar array, the concept of thinned array combined with non-uniformly spaced array is applied to obtain an optimal two dimensional (2-D) planar array structure under some constraints. The optimized non-uniformly spaced linear array is extended to the 2-D planar array structure, and it is used as an initial planar array geometry. Next, we further modify the initial 2-D planar array geometry with the aid of thinned array theory in order to reduce the maximum side-lobe level. This is implemented by a genetic algorithm under some constraints, minimizing the maximum side-lobe level of the 2-D planar array. It is shown that the proposed method can significantly reduce the pattern distortion as well as the side-lobe level, although the beam direction is scanned.

The design, manufacture, and test results are presented for a 90polarization-rotating Van Atta array reflector with suppressed scattered field for the 1.27-GHz band. The reflector consists of 48 element antennas, half for horizontal polarization and half for vertical polarization. It receives a horizontally or vertically polarized wave and retransmits a vertically or horizontally polarized wave, respectively. The measured cross-polarized radar cross section of the reflector was 15.8 dBm2 on average, which agreed well with a theoretical prediction. Although the suppression of the scattered field was limited to about -20 dB relative to the retransmitted field, we could suppress more the scattered field by accurate positioning and careful characteristics adjustment of element antennas. Theoretical calculations showed that total phase errors of the element antennas including positioning errors and impedance characteristics errors have to be within 7.5to suppress the scattered field by less than -30 dB.

In cellular systems, a code division multiple access (CDMA) technology with array antennas can significantly reduce interferences by taking advantage of the combination of spreading spectrum and spatial filtering. We investigate performance of cellular CDMA systems through adopting two types of array antennas, switched beam forming (SBF) and tracking beam forming (TBF) in the base station. Through Monte-Carlo simulations, we evaluate average bit-error-rate (BER) and outage probability of the systems under log-normal shadowing channels with multi-cell environment. When we consider 2 beams and 4 beams per sector for the SBF method, it is observed that the TBF method gives at least 10% and 30% capacity improvement over the SBF method in aspects of 10-3 BER and 1% outage probability, respectively.

We fabricate the organic light-emitting devices (OLEDs), which have dot array structures with organic layer, and discuss the improvement of coupling-out efficiency.