A broad-band U-slot rectangular patch antenna printed on a microwave substrate is investigated. The dielectric constant of the substrate is 2.33. The antenna is fed by a coaxial probe. The characteristics of the U-slot patch antenna are analyzed by the finite-difference time-domain (FDTD) method. Experimental results for the input impedance and radiation patterns are obtained and compared with numerical results. The maximum impedance bandwidth achieved is 27%, centered around 3.1 GHz, with good pattern characteristics.

A broad-band U-slot rectangular patch antenna on a microwave substrate

This paper presents a thorough investigation into the effects of several phone chassis-related parameters-length, width, thickness, and distance between the head and phone-on the bandwidth, efficiency, and specific absorption rate (SAR) characteristics of internal mobile phone antennas. The studied antenna-chassis combinations are located beside an anatomical head model in a position of actual handset use. The effect of the user's hand is also studied with two different hand models. The main part of the study is based on FDTD simulations, but also experimental results, which support the computationally obtained conclusions, are given. The presented analysis provides novel and useful information for future design of mobile handset antennas. The results show the general trends of bandwidth, SAR, and efficiency with different chassis parameters. The results also reveal a connection between these three performance parameters: an increase in SARs and a decrease in radiation efficiency occur compared to the general trend when the bandwidth reaches its maximum. This happens when the resonant frequency of the chassis equals that of the antenna.

Bandwidth, SAR, and efficiency of internal mobile phone antennas

Reduced-order modeling of an electromagnetic system is understood as the approximation of a continuous or discrete model of the system by one of substantially lower order, yet capable of capturing the electromagnetic behavior of the original one with sufficient engineering accuracy. Specific methodologies for model order reduction of distributed electromagnetic systems are discussed in this paper. It is shown that electromagnetic model order reduction enhances computational efficiency and, thus, facilitates system-level modeling and computer simulation of multifunctional systems. The proposed methodologies are demonstrated through applications to the reduced-order modeling of high-speed interconnects, electromagnetic waveguides, and microstrip antennas.

Electromagnetic model order reduction for system-level modeling

The penetration of high-intensity radiated fields (HIRF) into conducting enclosures via apertures is an EMI issue that is relevant to all aviation. The stories are numerous, of disrupted communications, disabled navigation equipment, etc., due to the effects of EM sources external to the aircraft. Here, the FDTD method is used to predict the shielding effectiveness of conducting enclosures with apertures, and the numerical results are compared with measurements. Several issues related to the FDTD analysis of highly resonant and high-quality factor (high-Q) structures, such as windowing and acceleration techniques, are examined and discussed.

HIRF penetration through apertures: FDTD versus measurements

We have investigated the application of two different types of novel shorted-patch antennas for mobile communications handsets at 1800 MHz. A single shorted-patch and a stacked shorted-patch antenna offering improved bandwidth are compared with data for a /spl lambda//4 monopole. The finite-difference time-domain (FDTD) technique was used to calculate antenna characteristics such as impedance and radiation patterns for two cases: on a handset and on a handset near a (2.5-mm voxel) heterogeneous head model in an actual position of phone use. We also obtained specific absorption rate (SAR) distributions and calculated the spatial peak 1-g SAR values. In addition, the effect on SAR and antenna characteristics of including a block model of the hand was assessed. Similar performance is achieved from the single or stacked shorted-patch antenna with the latter providing greater bandwidth, 8.2% versus 9.4% with the head and hand included. Both antennas reduce the l-g spatial peak SAR value in the head by 70% relative to the monopole. The presence of the hand reduces the efficiency of all three antenna types by approximately 10%.

Performance of shorted microstrip patch antennas for mobile communications handsets at 1800 MHz

The finite-difference time-domain (FDTD) method is being widely applied to antenna and microstrip calculations. One aspect of this application is accurately and efficiently modeling antenna and microstrip feeds within the constraints of the FDTD approximations. Several relatively straightforward approaches have been suggested, including gap and frill feeds. More complicated approaches, which involve including the coaxial feed cable in the FDTD calculation space, have also been suggested. A related aspect is the desirability of reducing the number of time steps required for the FDTD calculations to converge, especially for transient excitation. We illustrate that for many geometries a simple gap model with an internal source resistance provides accurate results while greatly reducing the number of time steps required for convergence.

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H.S. Langdon

Papers

A simple feed model that reduces time steps needed for FDTD antenna and microstrip calculations