Info

Kbps

internal ant

Table 2. The specifications of ETS-8.

Table 2. The specifications of ETS-8.

A custom antenna is needed for underwater vehicles because there is no commercial pressure-tight or water-resistant small antenna. A left-handed circularly polarized; double resonance antenna is matched to the ETS-VIII. Antenna minimum gain is 6.3 dBi. A four-element patch antenna, with a gain of about 14 dBi, and a single element patch antenna with phase difference feeding lines were made. The gain of the single element planar antenna is only 7 dBi. By decreasing the communication rate by 64 kbps, which gains 7 dB on power per bit compared with 384 kbps, antenna margin is kept.

The ocean-based system should be equipped with a satellite tracking system to lock on to the satellite, because of the vehicle oscillation. The tracker must also be water-resistant. For these reasons, a tracking system has developed using data on network design and the oscillating characteristics of the Urashima vehicle. Oscillation of the vehicle was measured with the high accuracy inertial navigation system installed in Urashima in a sea trial. An oscillation angle of 7 degrees and period of 0.15 Hz were estimated. We set the design target to pitching and rolling angles of less than 20 degrees and maximum frequency of 0.5 Hz, The tracking system consists of an attitude sensor and an attitude controller. To obtain the direction of the satellite, an inertial navigation system and a GPS are used as attitude sensors. The attitude controller has a three axis stepping motor driver. The system is currently undergoing tests with the first sea trial in November 2008.

Fig. 8. Picture of ELF wave transceiver tested in tap water and a received image.

Water-resistant case (Portable terminal)

Water-resistant case (Portable terminal)

Main pressure hull (Controller, etc.)

,Antenna + tracking system

Main pressure hull (Controller, etc.)

,Antenna + tracking system

Fig. 9. (left) An image of satellite communications with an underwater vehicle. (right) Photograph of the attitude controller with the 4-element planar antenna.

Was this article helpful?

0 0
Learn Photoshop Now

Learn Photoshop Now

This first volume will guide you through the basics of Photoshop. Well start at the beginning and slowly be working our way through to the more advanced stuff but dont worry its all aimed at the total newbie.

Get My Free Ebook


Post a comment