Naoki Inagaki

Classification and characterization of wireless power transfer systems of resonance method based on equivalent circuit derived from even- and odd mode reactance functions

Wireless connections by resonance method are promising for mobile and contactless power transfer, but the essential properties remain to be completely elucidated. This paper treats basic systems consisting of two equal lossless antennas of closed path type or open path type. Resonance and anti-resonance frequencies for even- and odd mode excitations are used to formulate the reactance functions and the image impedance of the system, from which a simple but accurate equivalent circuit with five different LC elements is derived. High image impedance frequency band is found to exist, which would broaden the possible applications.

Correlation-constrained CMA adaptive array using cyclostationary signal properties

We have proposed the constant modulus algorithm (CMA) adaptive array under the cyclic correlation constraint suitable for mobile communications. Via computer simulation, we have shown that the correlation constrained CMA (CC-CMA) gives a better signal capture performance even at the low input signal to interference ratio. In particular, it is verified that the CC-CMA in which the control vector is optimized by the CR-SCORE algorithm (Agee et al. 1990) provides the best performance in our simulation.

Rapid and stable optimization of CMA adaptive array by Marquardt method

The authors present a rapidly converging and well-conditioned algorithm based on the nonlinear least squares method referred to as the Marquardt method for the CMA (constant modulus algorithm) adaptive array. Computer simulation with a pi /4-shifted QPSK (quadrature phase-shift keying) signal verified its rapid and stable convergence characteristics for any radio environment. Taking into consideration the increase of computation for one weight update, the Marquardt method can reduce the convergence time by a factor of 10 to 100 compared to the steepest descent method.<<ETX>>

Numerical analysis of a cylindrical antenna with finite gap excitation based on realistic modeling

The delta gap model and the frill magnetic current model are often used as models for the feed point in numerical calculations for cylindrical antennas. When the delta gap model with finite gap width is used, the electrical field produced by the magnetic current of the feed point may be included in the excitation function of the integral equation so that a solution separated into the external and internal surface currents of a hollow cylindrical antenna can be derived. Such an analytic solution, however, has been obtained only for the case in which the cylindrical antenna has infinite length or is placed between two parallel conductive plates. This paper considers a cylindrical antenna of finite length using the same integral equation. As the first step, a numerical calculation of the excitation function for the feed point is considered. The excitation function is derived numerically by a method based on mode expansion in cylindrical coordinates and by a method based on the electric vector potential of the magnetic current ring. The properties of the excitation function are examined. As the next step, the cylindrical antenna is numerically analyzed by the method of moments. In all of these analytical procedures, the current is represented by piecewise sinusoidal functions on the surface of the cylinder, and the Galerkin method is applied. The convergence of the input admittance thus obtained is compared to the results of various other methods, such as point matching without considering the magnetic current at the gap (approximation by the two-dimensional surface current and the one-dimensional axial current), and approximation of the axial current by the frill magnetic current feed model.

Design of circularly polarized dielectric resonator antenna using modal polarization current model method

Circularly polarized dielectric resonator antenna (CP-DRA), especially the CP-DRA of cuboidal shape, is most easily manufactured with simple feeding systems. However, the design of the cuboidal CP-DRA has not been fully studied. This paper investigates a design method of the CP-DRA made of a cuboidal dielectric and a single feeding probe located outside. At the first step of the design, we apply the conventional design method of circularly polarized microstrip patch antenna to the CP-DRA, and at the second step of the design we analyze the structure including the feeding probe by the modal polarization current model method repeatedly to find the optimum structural parameters for axial ratio and impedance matching. The frequency of wireless LAN (5 GHz) has been chosen throughout the investigation.

Microstrip line to waveguide transition connecting antenna and backed RF circuits

A novel thin and planar waveguide circuit is proposed to connect an antenna and backed RF circuits in millimeter-wave module. A microstrip, line to waveguide transition and waveguide E-plane corner are designed and fabricated in 70 GHz band. Low loss characteristics are confirmed by the experiments. Future study is to realize wide frequency bandwidth.

Consideration on performance of the CMA adaptive array antenna for 16 QAM signals

The CMA adaptive array was developed for capture of constant modulus signals. As is well known, the CMA adaptive array can suppress interferences successfully under multipath environments. In order to investigate the availability of CMA adaptive array for other non-constant modulus signals, this paper deals with performance of the CMA adaptive array for 16 QAM signals which have high bandwidth efficiency. Several CMA-based cost functions modified for the QAM signals are introduced and also an algorithm of switching those cost functions in the process of adaptation is proposed. Via computer simulation, it is shown that the CMA adaptive array with the cost functions changed in adaptation has significantly better convergence characteristics for the 16 QAM signals. In addition, the BER performance of the cost functions is clarified.

3-D corner reflector antenna and its analysis using UTD

A 3-D corner reflector antenna consists of three planar reflectors and a 3/4/spl lambda/(/spl lambda/ is the wavelength) monopole located on one of the reflectors as shown. The idea of this antenna was first proposed by Inagaki (1974) in which it was reported that the gain is about 5 dB greater than that of the conventional 2-D corner reflector antenna, and that the input impedance is between 50 /spl Omega/ and 75 /spl Omega/ which is adequate for direct feed by coaxial cables. But this analysis was based on image theory and EMF method, and sidelobe suppression was evaluated in only an approximate manner. This paper calculates the radiation pattern accurately with diffracted fields evaluated by the UTD. Moreover it is demonstrated through a detailed analysis that a higher order mode structure using a 5/4/spl lambda/ or a longer monopole instead of a 3/4/spl lambda/ monopole exhibits higher directivity while the sidelobe level being kept lower than -20 dB.<<ETX>>

On improving the CR-SCORE adaptive array by using multiple cyclic correlation properties

Many array signal processing techniques have been proposed for application in mobile cellular and mobile satellite communication systems. Particularly, much attention is focused on adaptive antenna arrays operating in the spatial domain (i.e., smart antennas), which enable spatial reuse of allocated frequency slots in those communication systems. Blind adaptive arrays are increasingly being used in a number of signal processing applications because they can reduce cost and outage time in radio communication systems. SCORE (spectral self-coherence restoral) is a blind adaptive algorithm which exploits the cyclostationary nature of many communication signals and merely requires knowledge of a cycle frequency which is determined by the carrier frequency and/or symbol rate of the desired signal. We improve the cross-SCORE (CR-SCORE) algorithm, which is one of the SCORE algorithms, by using the multiple cyclostationary properties of the desired signal. Via computer simulation, we show the effectiveness and advantage of the improved CR-SCORE adaptive array.

CMA Adaptive Array Antenna Using Transversal Filters for Spatial and Temporal Adaptability in Mobile Communications

The CMA (Constant Modulus Algorithm) was developed for the adaptive receiving systems to capture the desired signal having the constant modulus property such as FM, PSK and FSK signals. The CMA is an algorithm suitable for mobile communications because it has the great advantage of not requiring a reference signal as the LMS aluorithm does.