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A compact microwave radiator is proposed for the treatment of a superficial tumor in a noninvasive hyperthermia application. The proposed radiator is designed to simplify treatment of relatively small tumors by reducing the physical size of the radiator. The proposed radiator is reduced to a size of 27.2 x 27.2 mm2 which corresponds to 0.038 λ x 0.038 λ at 433MHz, so as to induce the optimal heating area for approximately 30-mm tumors, and is studied using a phantom as a model to analyze the thermal characteristics for the human body. The concept of effective treatment area (ETA) is defined in this letter in order to evaluate the area that can be sufficiently heated. The specific absorption rate (SAR) and temperature are uniformly formed on the phantom surface with a symmetrical and circular-shaped distribution. An ETA ratio of 91.6% is achieved for the measurements, corresponding to a 30.4-mm diameter, and the temperature increase required for tumor necrosis is achieved. [ABSTRACT FROM AUTHOR]

A simple and exact closed-form equation to determine a penetrated ray path in a ray tracing is proposed for an accurate channel prediction in indoor environments. Whereas the penetrated ray path in a conventional ray tracing is treated as a straight line without refraction, the proposed method is able to consider refraction through the wall in the penetrated ray path. Hence, it improves the accuracy in ray tracing simulation. To verify the validation of the proposed method, the simulated results of conventional method, approximate method, and proposed method are compared with the measured results. The comparison shows that the proposed method is in better agreement with the measured results than the conventional method and approximate method, especially in high frequency bands. [ABSTRACT FROM AUTHOR]

Wafer-scale beamforming lenses for future IEEE802.15.3c 60 GHz WPAN applications are presented. An on-wafer fabrication is of particular interest because a beamforming lens can be fabricated with sub-circuits in a single process. It means that the beamforming lens system would be compact, reliable, and cost-effective. The Rotman lens and the Rotman lens with antenna arrays were fabricated on a high-resistivity silicon (HRS) wafer in a semiconductor process, which is a preliminary research to check the feasibility of a Rotman lens for a chip scale packaging. In the case of the Rotman lens only, the efficiency is in the range from 50% to 70% depending on which beam port is excited. Assuming that the lens is coupled with ideal isotropic antennas, the synthesized beam patterns from the S-parameters shows that the beam directions are -29.3°, -15.1°, 0.2°, 15.2° and 29.5°, and the beam widths are 15.37°, 15.62°, 15.46°, 15.51°, and 15.63°, respectively. In the case of the Rotman lens with antenna array, the patterns were measured by using on-wafer measurement setup. It shows that the beam directions are -26.6°, -21.8°, 0°, 21.8°, and 26.6°. These results are in good agreement with the calculated results from ray-optic. Thus, it is verified that the lens antenna implemented on a wafer can be feasible for the system-in-package (SiP) and wafer-level package technologies. [ABSTRACT FROM AUTHOR]

A concurrent dual-band class-E power amplifier using composite right/left-handed transmission lines (CRLH TLs) is proposed. Dual-mode operation is achieved by using the frequency offset and nonlinear phase slope of CRLH TLs for the matching network of power amplifiers. The frequency ratio of two operating frequencies is not necessarily an integer. Two operating frequencies are chosen as 836 MHz and 1.95 GHz for simulation. Three methods for designing a CRLH TL power amplifier are proposed. The measured results based on one method show that output powers of 22.4 and 22.2 dBm were obtained at 800 MHz and 1.70 GHz, respectively. In terms of maximum power-added efficiency, we obtained 42.5% and 42.6% at 800 MHz and 1.70 GHz, respectively. [ABSTRACT FROM AUTHOR]

Ring resonators have been widely used for various applications. Dual-mode ring resonators have also been investigated due to their applicability to multifrequency mode requirement. In this paper, dual-mode ring resonators using a branch line are designed along with a systematic approach. Triple-mode branch-line ring resonators are also designed adding two branch lines to the ring resonator. Adding more branch lines, multimode resonators can be realized based on the design procedure developed here. The location of the branch lines determines the additional resonant frequencies other than the fundamental resonant frequency generated by the enclosing ring. Furthermore, half-ring resonators working at 2.5 GHz are proposed for suppressing multiple harmonics (second and third harmonics) and providing size reduction with employment of various physical configurations. Equalizing the even- and odd-mode phase delays, harmonics are suppressed effectively in the design of half-ring resonators. Double half-ring resonators with a long opening gap are investigated to continuously decrease the resonant frequency. An open-loop structure provides flexible design and lowers the resonant frequency. Two dual-mode ring resonators and one triple-mode ring resonator are simulated and fabricated along with three different half-ring resonators. [ABSTRACT FROM AUTHOR]

A new form of a Rotman lens is proposed for microwave/millimeter-wave applications such as a collision-avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses fabricated with conducting plates at millimeter-wave frequency. Taking the field distribution inside the dielectric slab into account, the TE0 mode was chosen to excite the dielectric slab lens. The dielectric Rotman lens consists of a dielectric slab, tapered slot structure, and the transitions between the antipodal slots and microstrip lines for subminiature A connectors. The conventional design equations have been modified for use in designing the dielectric slab Rotman lens with a high dielectric material. A prototype was implemented with nine beam ports and nine array ports. Measurements from 10 to 20 GHz show that mutual coupling can be lowered at higher frequency. The obtained efficiency of the dielectric slab lens system is approximately 30%. The efficiency of the lens is comparable to that of the conducting plate lenses even though there is a spillover loss from the dielectric slab. [ABSTRACT FROM AUTHOR]

This letter presents a novel dual-band balun using the branch-line configuration. We establish design equations for dual-band balun based on the even-odd mode method. The proposed circuit operates at 2.45 GHz and 5.25 GHz. The single-ended power is divided differentially at the balanced ports. The insertion losses (S21 and S31) show around -2.7 dB to -4.3 dB at the two different frequencies. The phase difference between the balanced ports shows maximum 3° deviation from 180°. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 642–644, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24996 [ABSTRACT FROM AUTHOR]

In this letter, the design procedure and electrical performance of a dual band (2.4/5.8GHz) printed dipole antenna using spiral structure are proposed and investigated. For the first time, a dual band printed dipole antenna with spiral configuration is proposed. In addition, a matching method by adjusting the transmission line width, and a new bandwidth broadening method varying the distance between the top and bottom spirals are reported. The operating frequencies of the proposed antenna are 2.4GHz and 5.8GHz which cover WLAN system. The proposed antenna achieves a good matching using tapered transmission lines for the top and bottom spirals. The desired resonant frequencies are obtained by adjusting the number of turns of the spirals. The bandwidth is optimized by varying the distance between the top and bottom spirals. A relative position of the bottom spiral plays an important role in achieving a bandwidth in terms of 10-dB return loss. [ABSTRACT FROM PUBLISHER]

A new form of a Rotman lens has been proposed for applications above 10 GHz, such as a collision avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses at higher frequency than 10 GHz. The prototype was implemented with nine beam ports and nine array ports. The measurements show that the mutual coupling can be lowered at higher frequency, and that the efficiency of the dielectric slab lens of about 30% can be obtained. We conclude that the dielectric lens is comparable to the conducting plate lens even though a spillover loss is presumed at frequency of the implementation. [ABSTRACT FROM PUBLISHER]

The article presents the latest method for suppressing surface waves on a millimetre-wave microstrip array antenna designed at 77 gigahertz (GHz) for W-band radar applications. Topics covered include the design of the complementary split ring resonator (CSRR), a comparison of the simulation and experimental results with regards to the gain and the side lobe level with and without CSRR, and the ability of the CSRR between series patch antenna array to suppress surface waves.

In the above letter [1], Wang, Wang, and Wang presented a coupled resonator bandpass filter with wide stop-band. Before [1] was published, the authors proposed various novel ring resonators among which a coupled double half-ring resonator had been realized by placing two identical open half-ring configuration, leading to suppression of multiple harmonics [2], [3]. Even though the above letter [1] designed a filter using only one element composed of a single ring resonator, the resonator used is conceptually the same as the single element filter in terms of the layout and resulting performance. [ABSTRACT FROM PUBLISHER]