Kikuo Wakino

Bi-directionally fed phased-array antenna downsized with variable impedance phase shifter for ISM band

A novel bi-directionally fed phased-array antenna (BiPA) is presented. A BiPA can operate at half the phase shift of the conventional antenna with the same performance, leading to smaller size and lower cost. Main components of a BiPA are antenna elements and variable impedance phase shifters (VIPSs). The VIPS consists of three resonant circuits that include variable capacitors, it is applicable for both functions as a power divider and as an impedance-matching device, since the input/output impedance and the phase shift can be independently varied. The BiPA with a VIPS is simulated and evaluated at a 2.45-GHz industrial-scientific-medical band. The measured results agree well with the simulated ones. The performances of the VIPSs are confirmed as 1.4 dB in insertion loss, and -17dB in return loss for a phase shift of 0/spl sim/80/spl deg/ with the control voltage from 0- to 3.5-V DC, and the measured radiation pattern of the BiPA is /spl plusmn/30/spl deg/ in the steering angle, 24/spl deg/ in beamwidth, and -9dB in the sidelobe. Furthermore, an enhancement of the sidelobe suppression can be expected by changing the power ratio of each antenna element.

Full-wave analysis for propagation characteristics of cylindrical coplanar waveguides with finite thickness of conductor

A full-wave analysis by the extended spectral-domain approach is successfully applied to solve the cylindrical coplanar-waveguide problem. The analysis incorporates the effects of the edge singularities properly and can afford the efficient and accurate calculation method for the characteristic impedances in addition to the phase constants of cylindrical coplanar waveguides (CCPWs) with zero- and finite-thickness conductor. The numerical results obtained by this method have revealed the effect of conductor thickness on the characteristics of higher order modes, as well as the odd and even dominant modes of CCPWs for the first time.

Full-Wave Analysis and Design of Circular Half-Width Microstrip Leaky-Wave Antennas

A half-width microstrip leaky-wave antenna on a circular substrate is proposed and investigated. A microstrip on a circular substrate has a broader bandwidth for free-space leaky-wave radiation than a planar microstrip. A half-width microstrip has similar radiation characteristics to a full-width microstrip, but it does not require complex feeding structures. Full-wave analysis based on the extended spectral domain approach (ESDA) is applied to analyze the propagation characteristics of the circular half-width microstrip. The ESDA accounts for field singularities near a conductor edge of finite thickness and it does not require a virtual boundary to obtain the finite extent of the analytical space. Consequently, the ESDA is more suitable for analyzing leaky-wave structures than other conventional analysis methods. Numerical calculations are performed to determine the characteristics of the leaky-wave radiation from half-width microstrips on circular and semicircular substrates. The leaky radiation elements can be efficiently designed based on these numerical results. Two practical antennas with leaky radiation elements and feeders are designed and implemented. The measured bandwidths of the free-space leaky-wave radiation indicate that these cylindrical antennas have better performances than planar ones and they are in reasonable agreement with theoretical results. The measured radiation patterns with frequency-scanning characteristics also agree well with the simulation results.

Simultaneous Determination of Complex Permittivity and Permeability of Columnar Materials With Arbitrarily Shaped Cross Section

An effective simultaneous evaluation method for the complex permittivity and permeability of lossy materials is proposed by applying it to an arbitrarily shaped cross-sectional post placed in a rectangular waveguide. We use one sample and only measure S 21 parameters for two different locations of the sample. The measurement of complex reflection parameter S 11 is not required in this evaluation method. The scheme of electromagnetic field analysis for the evaluation is based on the extended spectral-domain approach combined with the mode-matching method, which is accurate and efficient, and can be flexibly used for the iterative fitting operation for the estimation of material parameters. Sample preparation and setting is significantly easier in this method compared to conventional methods. The error caused by deviations in the setting of a sample is investigated. The estimated values for the sample material by this procedure show good agreement with the results obtained using the conventional method over the X-band.

Variational method of coupled strip lines with an inclined dielectric substrate

A variational method is presented for the analysis of coupled strip lines with an inclined dielectric substrate for the first time. The stationary expressions of the line capacitance matrix elements are derived based on extended spectral domain approach combined with mode-matching method (ESDMM). Numerical computations are based on Galerkins procedure and the basis functions for the unknown aperture fields take the edge singularities into consideration. The accurate numerical values can be obtained by using a small number of basis functions.

An accurate measurement method of high permittivity materials by numerical analysis of coplanar waveguide

An accurate and simple technique for evaluation of high permittivity materials, (Bs,Sr) TiO/sub 3/ (BST) ceramics, in the microwave region is developed with assistance of full-wave analysis of a coplanar waveguide (CPW). S-parameters of the CPW are measured from 0.5 to 40 GHz, and effective permittivity and attenuation constants at each frequency are obtained from the S-parameter data. Relative permittivity (/spl epsiv//sub r/) and tan/spl delta/ are evaluated by numerical calculations using the extended spectral domain approach taking the conductor thickness effect into consideration. The estimated /spl epsiv//sub r/s of Ba/sub 0.7/Sr/sub 0.3/TiO/sub 3/, Ba/sub 0.5/Sr/sub 0.5/TiO/sub 3/, and Ba/sub 0.3/Sr/sub 0.7/TiO/sub 3/ are 660, 1650, and 4450, respectively. The /spl epsiv//sub r/ decreases slightly as frequency increased due to dielectric dispersion. This technique enables the evaluation of even a small deviation in high permittivity materials.

Determination of complex permittivity and permeability of materials in rectangular waveguide using accurate hybrid numerical calculation

An effective simultaneous evaluation method for the complex permittivity and permeability of the specimen filling partially the rectangular waveguide is proposed. Electromagnetic field analysis for the evaluation is based on the extended spectral domain approach combined with the mode-matching method (ESDMM). ESDMM is accurate and more efficient than FEM and suitable for the iterative fitting to estimate the material characteristics. Microwave absorbing rubber sheet was measured over the X-band by the present method. The sample preparation and setting are far easy compared with conventional method, because it is not necessary to fill exactly the cross section of waveguide. The evaluated results by ESDMM for the several samples have showed good agreement with ones measured by conventional method.

An efficient analysis on discontinuities of lossy obstacle in axially symmetrical transmission lines using hybrid numerical method

A novel efficient numerical method, which is based on the extended spectral domain approach combined with the mode-matching method, is applied to evaluating the transmission characteristics for a axial symmetric lossy obstacle placed in a coaxial line or a circular waveguide. Since the formulation procedure utilizes the biorthogonal relation and it does not utilize any approximate perturbational scheme, the method is capable to analyze a variety of obstacles, thinner and/or thicker and wide range of conductivity in short computation time. The present method provides not only the precise analysis and design of coaxial devices including conductive and/or dielectric discontinuities, but also provides the useful tools for the accurate frequency-dependent measurement of the materials properties. The results are compared with FEM where FEM computations are feasible, although the FEM computations cannot cover the whole performances of the present method. The good agreement is observed in the correspondent range.

Space-Wave Leakage of Strip Lines on Circular Substrate

The space-wave leakage of strip lines on circular substrate is analyzed for the first time. The circular curved single-conductor strip structure has the broader bandwidth of the space-wave radiation than planar structure and is less affected by the surface wave leakage. This structure is suitable for the leaky-wave antennas for wireless broad-band communication applications

Broadband Leaky-Wave Antenna Fed With Composite Right/Left-Handed Transmission Line

The broadband feeder line is investigated to exploit the broadband nature of leaky-wave antenna. The feeding structure is realized by inserting the composite right/left-handed transmission line (CRLH-TL) into the feeder. Microstrip CRLH-TL feeder line is designed for the microstrip leaky-wave antenna. The microstrip leaky-wave antenna system shows a return loss of less than 9.5 dB (VSWR < 2.0) from 6.2 GHz to 9.3 GHz in the measured result, and exhibits the beam-steering nature as frequency is varied.