Kenji Saegusa

Analysis of a large phased array antenna in assembly of sub-arrays attached with phase shifters

Power Satellite System needs a huge on-board antenna called a spacetenna. This antenna may be realized by a phased array antenna (PAA) which adopts elements of a half-wavelength in scale. In this case, the number of elements is quite large so that the simplification of feeding system is inevitable. This paper deals with a large-scale phased array antenna that is divided into sub-arrays, and equipped with a phase shifter to each sib-array. The effectiveness of the phase shifter reduction and the radiation characteristics in beam scanning are clarified.

The radiation characteristics and current distribution of a full wavelength dipole

This paper presents the radiation characteristics of a full-wavelength dipole obtained by simulation. It will be shown that a full-wavelength dipole changes the radiation pattern from a single lobe to split lobes according to the offset of a feed point. With a reflector in proximity to a dipole, the radiation pattern is split and has a null at the boresight for even small offset of 0.02λ.

Proposal of a multiple folding phased array antenna and phase compensation for panel steps

Satellite users tend to require a larger antenna so that the antenna should be folded small to be installed in a cargo room of a rocket in launch phase. This paper proposes a novel multiple folding scheme in order to realize efficient folding better than a folded parabola or a single fold array antenna. In the case of a multiple fold, however, the mechanical steps between panels cause significant phase deterioration. Then we propose a phase compensation method with deduced equations. The availability of the proposed schemes is shown by simulation.

Array antenna with uniformly excited elements to realize an equivalent arbitrary field distribution: A key technology for mass-production antenna engineering

A large array antenna is composed of a large number of radiating elements so that the cost should be reduced by mass-production. We propose a novel technology for mass-production adding to previously proposed ones. Each element is driven with uniform excitation to cut complicated operation. Instead, the element separation is adjusted in the proposed algorism. The validity of the theory is confirmed by simulation.

Generation of a beamed wave using a phased array antenna

This paper presents a novel method to generates a beamed wave by a phased array antenna. Each radiating element of the antenna is fed with a phase correspondent to a spherical wave front of a Gaussian beam. Simulation results reveal that the convergence characteristics are strongly dependent on the transmitting antenna size, distance, and frequency. This work could be used in wireless power transmission through a long distance.

A large-scale phased array antenna

This paper describes a solar power satellite system as an application of a large-scaled phased array antenna. Key technologies are extracted, and their solutions are presented. Consequently, a paradigm shift from a-la-carte production to mass-production is pointed out.

Instantaneous expansion of a collimated beam to a wider pattern to cope with system emergencies

It is required to change a collimated beam in a normal state to another pattern in order to cope with system emergencies. This paper proposes an instantaneous expansion of the beam for a phased array antenna. The design principle of the antenna is described on the basis of the phase distribution of a spherical wave. The simulation results are presented.

Radio wave emission from 1 MHz to 18 GHz due to rock fracture and the estimation of the emitted energy

Radio wave emission due to rock fracture was measured at four frequency bands. Though the antenna gain is difficult to measure at the lowest frequency of 1MHz, the measuring system was successfully calibrated, and the emitted energy was estimated. The obtained results at 1MHz to 18GHz suggest the wave source to be quite narrow electrical signals, and show a possible application to the detection of an earthquake or volcanic activity.

Partial drive techniques to simplify a spacetenna by reducing the driven elements of an array

Partial drive is a novel technique to replace driven elements with parasites on the basis of positive utilization of element coupling, and are effective to simplify an array antenna. This paper comprehensively describes three kinds of array antennas in partial drive schemes and corresponding coupling methods. Finally, the practical uses of each antenna are discussed.

A basic examination of estimating the magnitude of TSUNAMI by T-wave

Paying attention to the sound of breaking sea bottom depending on the magnitude of TSUNAMI, we examined the acquisition of a sea sound wave at Japan waters. We considered the traveling route of the sea sound wave radiated from the hypocenter of the Tohoku-Pacific Ocean Earthquake, and estimated the propagation loss, which has a characteristic that the diffusion loss depending on distance is dominant. Thus, the sound pressure level of the hypocenter was presumed being at least 252 dB. (0 dB = 1u Pa). A sea sound wave radiation from the earthquake with the tsunami in Japanese waters is expected to attenuate the receiving about 55 dB at an area along the shore.