The MC-CDMA (multi-carrier code division multiple access) technique is known to be appropriate for high data-rate wireless communications such as mobile multimedia communication due to its robustness to multipath fading and its capability of handling high data rates with a simple one-tap equalizer. In this paper, the performance of an MC-CDMA system employing antenna array at the base station in a fading channel is presented. Following the discussion of optimal beamformer not requiring explicit DOA (direction of arrival) or training signals, it is shown that the interference from other users within a cell can be significantly reduced for both reverse link (mobile to base station) and forward link (base station to mobile) using an MC-CDMA with antenna array, thus increasing the system's user-capacity. Computer simulations that demonstrate user-capacity improvement of the proposed approach are discussed.

A method for locating underground pipes from a pulse radar image is presented. The method employs the Laplacian of Gaussian filter to extract edges and employs the Hough transform to determine the depth of the pipes. A preliminary experiment showed its ability to detect deeply buried pipes with weak signal echoes.

A 5-pole lumped element bandpass filter (BPF) of center frequency 264.05 MHz and fractional bandwidth (FBW) 0.76% is designed and fabricated using YBa2Cu3O7-d (YBCO) thin films deposited on both sides of a MgO substrate(40 mm 40 mm 0.5 mm). The return loss, minimum insertion loss and ripple were measured to be 20.0 dB, less than 0.1 dB and less than 0.1 dB at 70 K, respectively. These results verify both the compactness and low loss characteristics in the VHF band. The simulated frequency response, where the frequency dependences of inductance (L) and capacitance (C) elements and housing effect are taken into account, is in good agreement with the measured frequency response.

The paper shows some of benefits of multi-unitary decomposition in signal analysis applications. It is emphasized that decompositions of complex discrete-time signals onto a single basis provide an incomplete and in such way potentially misleading image of the signals in signal analysis applications. It is shown that the multi-unitary decimated filter banks which decompose the analyzed signal onto several bases of the given vector space can serve as a tool which provides a more complete information about the signal and at the same time the filter banks can enjoy efficient polyphase component implementation of maximally decimated, i. e. nonredundant, filter banks. An insight into the multi-unitary signal decomposition is provided. It is shown that the multiple-bases representation leads to an efficient computation of frequency domain representations of signals on a dense not necessarily uniform frequency grid. It is also shown that the multiple-bases representation can be useful in the detection of tones in digital implementations of multifrequency signaling, and in receivers of chirp systems. A proof is provided that there are possible benefits of the multiple-bases representations in de-noising applications.

High-temperature superconducting (HTS) films have low surface resistance in the microwave region. This indicates that HTS passive microwave devices, for example, filters and antennas, are promising for commercial use. For superconducting filters, low insertion loss, sharp skirt property and high attenuation value out of band are important, and for superconducting antennas, electrically small antennas and super-directive high-gain antennas are useful. It is known that the elliptic filter has a sharp skirt property compared with that of a Chebyshev filter. We examined a cross-coupled filter which is one type of elliptic filter. The insertion loss of the filter was approximately 0.3 dB. The skirt property of the four-resonator cross-coupled filter was almost equal to that of an eight-resonator hairpin filter. We also examined a cryocooler cooling system for superconducting antenna and measured the relative gain, directivity and power capability of an HTS antenna. The gain of the HTS patch antenna was approximately 10 dB larger than that of a normal conducting antenna. The large gain of the HTS antenna was caused by the low surface impedance and enhancement effect of the dielectric window of the cooling system.

The explicit formula for the coefficients of maximally linear digital differentiators is derived by the use of Taylor series. A modification in the formula is proposed to extend the effective passband of the differentiator with the same number of coefficients.

This paper proposes a simple adaptive channel estimation scheme for orthogonal frequency division multiplexing (OFDM) in order to realize high-rate wireless local area networks (LANs). The proposed estimator consists of simple frequency-domain FIR filters, which are adaptively selected according to the difference vector between adjacent subcarriers and channel amplitude of the subcarrier. No precomputation or matrix signal processing is required in the derivation of these characteristics. Computer simulations show that the packet error rate performance of the proposed scheme is superior to that of the least-squares scheme by 1.1 dB in terms of required Eb/N0 at PER=0.1 in AWGN channels. They also show, for the same criterion, a 0.7 dB improvement in a frequency selective fading channel with delay spread values of 100 ns.

A new class of nonlinear filters called Vector Median Rational Hybrid Filters (VMRHF) for multispectral image processing is introduced and applied to color image filtering problems. These filters are based on Rational Functions (RF). The VMRHF filter is a two-stage filter, which exploits the features of the vector median filter and those of the rational operator. The filter output is a result of vector rational function operating on the output of three sub-functions. Two vector median (VMF) sub-filters and one center weighted vector median filter (CWVMF) are proposed to be used here due to their desirable properties, such as, edge and details preservation and accurate chromaticity estimation. Experimental results show that the new VMRHF outperforms a number of widely known nonlinear filters for multispectral image processing such as the Vector Median ilter (VMF) and Distance Directional Filters (DDf) with respect to all criteria used.

In this paper, the Linear Exponential Quadratic Gaussian with Loop Transfer Recovery (LEQG/LTR) methodology is employed for the design of high performance induction motor servo systems. In addition, we design a speed sensorless induction motor vector controlled driver with both the extended Kalman filter and the LEQG/LTR algorithm. The experimental realization of an induction servo system is given. Compared with the traditional PI and LQG/LTR methods, it can be seen that the system output sensitivity for parameter variations and the rising time for larger command input of the proposed method can be significantly reduced.

This paper presents two types of two-variable analog filters with maximally flat magnitude-squared attenuation response in the two-dimensional pass region. These are applied in order to obtain five types for the distribution of two-dimensional pass regions with respect to the design of microwave band pass filters consisting of a cascade of commensurate-line filter and lumped LC filter or a cascade of two commensurate-line filters in different propagation times.

Weighted summation (W-SUM) operation of multi-input signals plays an important role in signal processing, image compression and communication systems. Conventional digital LSI implementation for the massive high-speed W-SUM operations usually consumes a lot of power, and the power dissipation linearly increases with the operational frequencies. Analog or digital-analog mixed technology may provide a solution to this problem, but the large scale integration for analog circuits especially for digital-analog mixed circuits faces some difficulties in terms of circuit design, mixed-simulation, physical layout and anti-noises. To practically integrate large scale analog or digital-analog mixed circuits, the simplicity of the analog circuits are usually required. In this paper, we present a solution to realize the parallel W-SUM operations of multi-input analog signals based on our developed digital-controlled analog operational circuits. The major features of the proposed circuits include the simplicity in the circuitry architecture and the advantage in the dissipation power, which make it easy to be designed and to be integrated in large scale. To improve the design efficiency, a Top-Down design approach for mixed LSI implementation is proposed. The proposed W-SUM circuits and the Top-Down design approach have been practically used in the LSI implementation for a series of programmable finite impulse response (FIR) filters and matched filters applied in adaptive signal processing and the mobile communication systems based on the wideband code division multiple access (W-CDMA) technology.

Millimeter-wave systems increasingly are entering into commercial systems, both for communication and sensors for traffic or industrial applications. In many cases, circuit technology of the involved front-ends includes monolithic and hybrid integrated circuits and even waveguide components like filters or antenna feeds. In addition to the standard technical and environmental requirements, these front-ends have to be fabricated in large quantities at very low cost. After a short review of the problems and some general interconnect and packaging techniques for mm-wave front-ends, achievements of a research program will be presented at the example of components for a 28 GHz communication front-end. Emphasis is put on a novel feed-through structure using multilayer carrier substrates for mm-wave circuits, some advances in electromagnetic field coupling for interconnects to mm-wave MMICs, and the realization of packages including waveguide components by plastic injection molding and electroplating. Results of filters and a diplexer produced in this way are shown, including pretuning of the filters to compensate the shrinking of the plastic parts during cooling.

In this paper, fast algorithms for the CMA (constant modulus algorithm), which is one of the widely used algorithms for blind equalizationi are presented. We propose the FBCMA (frequency domain block CMA) which takes advantage of fast linear convolution in the DFT domain by using the overlap save method. For the FBCMA, a nonlinear error function in the frequency domain is derived using Parseval's relation. Also, an adaptive algorithm in the DFT domain is introduced to adjust the frequency domain filter coefficients. For a block size and filter length of N, the multiplications required for the conventional CMA and proposed FBCMA are on the order of O(N2) and O(N log N), respectively.

This paper proposes a fully balanced circuit structure with a zero common-mode gain. The common-mode gain of the proposed structure becomes theoretically zero with a perfect device matching. Even if a perfect device matching is not achieved, the common-mode signal can be sufficiently suppressed by the feedback loops provided with the structure. Based on this concept, an integrator is composed. Furthermore the concept can be directly applied to a filter design. The application results in reduced chip area. A design example of a second-order filter and simulation results verify the theoretical expectation.

A novel multipath diversity scheme used in TDD-CDMA systems is presented. A FIR filter is added in the transmitter, while a RAKE combiner is used in the receiver. The optimum FIR filter problem may be viewed as an eigenvalue problem. The multiple antennas system is also analyzed. Results show that this new scheme can greatly improve the output Signal to Noise Ratio (SNR) compared with conventional RAKE receiver or Pre-RAKE diversity system.

This paper deals with a method of estimating the parameters and the order of a linear system using differential digital filters and the resultant. From the observed signals of the input and output of an objective system, we extract the differential signals from the zero order to an appropriate high order with the same phase characteristics, using several digital filters. On the assumption that the system order is known, we estimate the parameters of the transfer function and evaluate the estimation error bounds. We propose a criterion function generated by the product of the highest order coefficients and the resultant of the numerator and denominator of the estimated transfer function. Applying this criterion function, we can estimate the order of the objective system. The threshold corresponding to this criterion function is evaluated from the deviation in the frequency characteristics of the used differential filters and the error bound of the estimated parameters. In order to demonstrate the propriety of the proposed method, some numerical simulations are presented.

This paper presents a new number representation called the Signed-Weight (SW) number system, which is useful for designing configurable counter-tree architectures for digital signal processing applications. The SW number system allows the unified manipulation of positive and negative numbers in arithmetic circuits by adjusting the signs assigned to individual digit positions. This makes possible the construction of highly regular arithmetic circuits without introducing irregular arithmetic operations, such as negation and sign extension in the two's complement representation. This paper also presents the design of a Field-Programmable Digital Filter (FPDF) architecture--a special-purpose FPGA architecture for high-speed FIR filtering--using the proposed SW arithmetic system.

In this paper we propose a new pipelined architecture for the LMS adaptive filter which can be implemented with less than half the amount of calculation needed for the conventional architectures. Even though the proposed architecture reduces the required calculation, it can simultaneously produce good convergence characteristics, a short latency and high throughput characteristics.

We have developed an InP-based monolithic optical frequency discriminator consisting of a temperature-insensitive optical filter and dual photodiodes. This integrated device detects the optical frequency deviation of the input light as differential photocurrent from the dual photodiodes, and the photocurrent is fedback to the light source for frequency stabilization through a differential amplifier. The FSR and extinction ratio of the filter are 50 GHz and 20 dB. The total opto-electronic conversion efficiency is 40%. In a frequency stabilization experiment using the developed discriminator, the frequency fluctuation of a DFB laser was reduced to less than 10 MHz.

In this paper, comparison of various orthogonal transforms in Wiener filtering is discussed. The study involves the family of discrete orthogonal transforms called Complex Hadamard Transform, which has been recently introduced by the same authors. Basic definitions, properties and transformation kernel of Complex Hadamard Transform are also shown.