Ken-ichiro MAKI

The use of phased array antenna (PAA) with a power taper in a space solar power systems requires a configuration that can be mass-produced. However, there was no conventional method of constructing a PAA with power taper, which suitable for mass production. Therefore, this paper proposes a method of constructing a PAA with a single type of amplifier and uniform spacing between antenna elements, which gradually increases the number of elements in the subarray. As a result of applying the proposed method to a 10-dB truncated Gaussian taper, the power transmission efficiency is equal to or higher than that conventional methods. In addition, the proposed method was demonstrated in experiments using a one-dimensional patch antenna array.

Electromagnetic emissions observed in a series of rock fracture tests are described. Four kinds of rocks, basalt, gabbro, granite and quartzite were pressed by uniaxial compression to fracture, for all of which many signals were detected at two microwave bands (2GHz and 300MHz). These detected signals consist of intermittent pulses of a short duration. Comparing the microwave records and the observation with a high-speed digital video camera, we found that the pulse signals were generated after the decrease of the axial load, and even after the macroscopic fracture (deformation) was completed. This differs from the occurrence of lower frequency emissions (0.3-300kHz) monitored as well, which became active and was strongest during the load decrease. The occurrence of signals at the two microwave bands did not always coincide, but a signal at 300MHz often followed a signal at 2GHz with a short interval of 50-100ns. An additional detector at 22GHz picked up emissions only for quartzite, which occurred exclusively during the decrease of axial load.