Takashi Amano

Frequency tunable antennas for mobile phone for terrestrial digital TV broadcasting reception

In this paper, two types of loop antenna and a broadband T-shaped antenna with a switch mounted on one end of its conductor are proposed. A RF switch such as single port multi throw (SPMT) is chosen rather than variable capacitors for these proposed antennas. Variable capacitors such as a diode, however, are influenced by the radiation power of cellular phones. Moreover, a bias voltage should be controlled continuously to change its resonance frequency. Tunable antennas can be designed as a built-in antenna with the full frequency coverage. Simulations and experiments are conducted to clarify its operation

Improvements of impedance and radiation performances with a parasitic element for mobile phone

In this paper, novel usage of a parasitic element is proposed. This approach creates a kind of 3lambda/4 length antenna. Proposed antenna improves input impedance with wider bandwidth as well as its radiation patterns in both free space and handhold environment. A parasitic lambda /4 element is attached at an opposite side of corner which is roughly lambda /4 away from the feeding point. By this layout, its input impedance improves and influence from user hand is minimized at holding position. Through various analyses, overall performance of the proposed antenna shows better than that of conventional antenna without a parasitic element since leakage current on its ground plane is reduced and dominant radiating part is set away from user hand.

A study on loop antenna with uniform current distribution

A new antenna concept is proposed to improve and stabilize performance at the talk position of cellular telephones. Constant vertical average gain which is independent of its tilting angle and suppressed radiation toward an operator side can be realized by loop type antennas with uniform current distribution. The proposed square antenna of 0.54 /spl lambda/ circumference length with distributed capacitances is measured. Predictable results are obtained.

Improvement of the radiation pattern by reducing the leakage current on the ground plane for antennas of PC terminals

In order to reduce the leakage current on the ground plane and improve the radiation pattern, we have proposed an antenna structure with parasitic elements. The validity of the simulated result is shown by comparison with the measurement. The proposed antenna is satisfied with the required bandwidth of IEEE 802.11b/g. Since the leakage current on the ground plane is reduced with the proposed antenna in comparison with the inverted-F antenna, the radiation pattern of vertical polarization in the horizontal plane is improved.

A study on modified planar dipole antenna with broadband radiation patterns

In this paper, a modified planar dipole antenna is proposed. Design methodology and mechanism of the proposed antenna with wideband input impedance characteristics and radiation patterns from 3 GHz to 8 GHz are introduced