Makoto Kijima

Low sidelobe and tilted beam base-station antennas for smaller-cell systems

A base-station antenna, which features both low sidelobe and variable beam tilt characteristics, is developed. A novel design objective pattern with many sidelobe ripples is proposed in synthesizing low sidelobe characteristics. A simple array group feed scheme is then proposed to realize a prescribed beam tilt angle, maintaining low sidelobe characteristics. The optimum group number is derived.<<ETX>>

A wide-band and slender base-station antenna for mobile radio

The authors propose a novel microstrip antenna which has broad bandwidth and small size. An excellent example of this microstrip antenna, a slender base station antenna, is shown. The double-layered broadband microstrip configuration yields a bandwidth of 17% at a voltage standing wave ratio of 1.5. The antenna width is extremely small at about 40 mm. The 120 degrees beamwidth in the horizontal plane is achieved by employing a 100-mm-width ground plane. A slender base station antenna covered with a 160-mm-diameter cylindrical radome has been constructed and tested. The measured radiation characteristics are satisfactory.<<ETX>>

Low sidelobe characteristics of a dual-frequency base station antenna in the case of electrical beam tilt use

To accommodate the remarkable increase in the numbers of mobile phone subscribers, plural systems and multi-frequency bands are being employed. In Japan, PDC (Personal Digital Cellular) systems use the frequency bands of 800 MHz and 1500 MHz. Typical electrical characteristics of base station antennas are low sidelobe levels and electrical beam tilt capabilities. In case of frequency sharing the 800 MHz and 1500 MHz bands, low sidelobe characteristics may be distorted. We discovered the suitable excitation coefficients to achieve low sidelobe characteristics. This paper showed the experimental results of sidelobe levels in the case of beam tilt use.

A slender two beam base-station antenna for mobile radio

Many cities around the world are seeing the introduction of multiple mobile radios systems. Operating at different frequencies, the base station antennas of different systems are often installed in the same buildings, so narrow antennas are required to make installation easier. This paper proposes a novel antenna configuration which produces two beams and yields antennas that are very slender. Beam designing techniques and antenna performance are also shown. Actual design examples for 6 sector zone use are also shown.<<ETX>>

Influence of VSWR of radiation elements on sidelobe degradation of low sidelobe array antennas

The influence of the VSWR (voltage standing wave ratio) of radiation elements on the sidelobe degradation of low-sidelobe array antennas is analyzed by deriving straightforward expressions. It is found that the relationship between VSWR and sidelobe level can be expressed with simple equations which depend only on reflection levels at elements and excitation phase differences. These equations can be used to determine the maximum VSWR that can be tolerated to achieve a specified level of sidelobe degradation. One result was that /spl Gamma//sub o/ must be smaller than -18dB if the sidelobes are to be suppressed to the level of -20dB.<<ETX>>