Seppo Saario

An assessment of cable radiation effects on mobile communications antenna measurements

Standard methods of antenna assessment require their connection via coaxial cable to a network analyser. For portable communications equipment, this situation is quite different from the standard operation because current in the outer conductor of coaxial cable feeds can significantly distort the impedance, gain and directional characteristics. The use of ferrite beads to minimise cable radiation effects is investigated for various configurations using FDTD modelling.

FDTD simulation of radiation characteristics of half-volume HEM- and TE-mode dielectric resonator antennas

Cylindrical and rectangular dielectric resonator antennas (DRAs) using HEM/sub 11/spl delta//, TE/sub 11/spl delta//, and TE/sub 01/spl delta// mode were examined to see the radiation pattern, impedance, field distribution and resonant frequency that were achieved when the DRAs were bisected through an image plane by a conducting sheet. The resultant half DRAs are smaller in volume and have a more directional radiation pattern. The elevation angle of maximum radiation was lowered in some cases. Finite-difference time-domain simulation techniques were used.

A Multi-Band Hybrid Balanced Antenna

The design of antennas for small user equipment has for many years relied on the use of unbalanced designs – usually ingenious variants of monopoles and inverted-L antennas. As the size of the equipment is reduced, unbalanced antennas become increasingly problematical because their input impedance and radiation properties become strongly dependent on the size of the groundplane and their position on it.

FDTD analysis of dielectric-embedded electronically switched multiple-beam (DE-ESMB) antenna array

The design procedure, finite-difference time-domain (FDTD) modeling, and experimental measurements for a novel dielectric-embedded electronically switched multiple-beam (DE-ESMB) antenna array are presented in this paper. Size reduction of a parasitic switched monopole antenna was accomplished by embedding the array in a cylindrical rod of L6G nylon with a relative permittivity /spl epsi//sub r/=4.4. Dielectric-embedded and free-space prototypes of a nine-element ESMB antenna array were modeled and experimentally characterized. Experimental measurements and numerical results are in good agreement. The measured return loss for the nine-element embedded antenna was less than -25 dB at 2.32 GHz. An overall volume reduction of 80% and footprint reduction of 50% was achieved. Adaptive simulated annealing with FDTD was used to optimize the 17-element DE-ESMB array, achieving a return loss of less than -10 dB across the 2.4 GHz to 2.5 GHz ISM band.

A novel wide band antenna for WLAN applications

With the emergence of WiMax and UWB for high-speed wireless applications and the existence of IEEE 802.11 a/b/g/n WLAN, antenna vendors are faced with the challenge of creating compact, wideband multiple-input multiple-output (MIMO) antennas for wireless applications. The wideband MIMO antenna presented in this paper is a novel antenna design based on pure dielectric antenna (PDA) technology. Pure dielectric antennas are like dielectric resonator antennas in that both typically use high /spl epsiv//sub r/ dielectric material, however we have found that the PDA does not follow the general design relations of a DRA (R.K Mongia and P. Bhartia (1994)).