We propose a wavelength-dispersion equalizing scheme that counteracts the signal degradation caused by residual dispersion in Nyquist optical time-division multiplexing. To counteract the signal degradation, this scheme uses optical correlation receivers and a distorted reference signal. At a Q factor of 6.4 dB, the permissible values of the residual dispersion increased from 14.5 ps/nm to 99.5 ps/nm at a baud rate of 160 GBd.
A new radar system using a radio over fiber (RoF) is proposed. The proposed system is optical-fiber-connected passive primary surveillance radar (OFC-PPSR), which is based on a passive bistatic radar approach and uses RoF technology. A separate receiver unit uses the waves scattered from aircraft and the radar reference data transmitted by the RoF. The reference data include the radio frequency signals of the transmitter unit and the processing data of the controller unit, such as radar rotation angle. We first present the principles of OFC-PPSR and the experimental system, which was deployed at the Sendai airport in Japan. Moreover, we present some preliminary experimental results obtained with the proposed system. The proposed system is capable of detecting moving aircraft, as demonstrated by a comparison of the experimental results with real surveillance data.
Our research group reported successful observation of “co-faulting” Earth’s magnetic field changes because of piezomagnetic effects caused by earthquake tremors during the 2008 Iwate-Miyagi Nairiku earthquake of M7.2 using a geomagnetic observation system with flux-gate magnetometers. This is an important finding: electromagnetic fields propagate from a source to an observation site at the light speed in the crustal materials. Further earthquake detection efforts can lead us to a new system for super-early warning of earthquake detection with the geomagnetic signal. However, the observed result with the earthquake was suggested that the geomagnetic field change accompanying fault movement, whose sources are the piezomagnetic effects, is very small and short term. Therefore, to develop an extremely important high-resolution magnetometer system, we first conducted long-term precise geomagnetic observations using a high-temperature superconductor based superconducting quantum-interference device (HTS-SQUID) magnetometer system. The HTS-SQUID magnetometer system had never been used for high-resolution geomagnetic observations outdoors. Since March 2012, we have observed geomagnetic field using the HTS-SQUID magnetometer at Iwaki observation site (IWK) in Fukushima, Japan. Comparison between the introduced HTS-SQUID magnetometer and conventional flux-gate clarified that the HTS-SQUID magnetometer in our system has higher resolution of magnetic field observation.
Typically, typing character strings on a keyboard is used for personal authentication for PC login and unlocking. Although some graphical and biometric-based methods have been developed, most of them have weak authentication strength, weak shoulder surfing resistance, or other drawbacks. In this paper, we propose a personal authentication method that employs mouse operations in which the mouse itself does not need to be moved. Thus, the user can hide the mouse during authentication, so the method has shoulder surfing resistance and can be used in public places. We performed user testing to validate the proposed method.
With the potential use of wireless implanted devices for transplanted liver monitoring applications, it is important to investigate the in-body propagation channel at liver area and to demonstrate the feasibility of the applications. Experimental measurements were performed using our developed multilayer human equivalent phantoms. Subsequently, path loss data were recorded and analyzed for various distances between the implanted and on-body antennas at lower range of ultra-wideband to assess the in-body propagation channel. Finally, our preliminary results indicate a possibility for liver implanted wireless communications using UWB technology in the example case scenario.
A multi-slot and multi-user detection scheme is presented for the contention resolution diversity slotted ALOHA (CRDSA) in satellite networks. The scheme can effectively resolve the deadlock loop of the collided packets of J users in J slots, and can be applied to DVB-RCS2 directly with a little change on receiver. The simulation results show the throughput of the CRDSA with the proposed scheme can improve greatly when the PLR is at 0.001, and has less latency compared with the conventional CRDSA.
This paper presents conditions of a laminated sheet composed of copper and magnetic sheets for obtaining wideband shielding effectiveness below 10 MHz. The following two conditions are clarified: (1) the optimum thickness ratio of the copper sheet to the laminated sheet is 0.5–0.7, (2) the loss factor (tan δ) of the relative permeability of the magnetic sheet is above 1 for increasing reflection losses of the laminated sheet. These conditions are validated by measuring the shielding effectiveness of the laminated sheet. The shielding effectiveness of the laminated sheet is higher than that of the copper sheet in the frequency from 0.1 MHz to 10 MHz.
In this letter, a rotationally-symmetrical array (RSA) arrangement of a receiving dipole array antenna is optimized to maximize the performance of the null-beamforming method for the suppression of self-interference. The optimum RSA for a receiving dipole array with four elements is clarified. Through numerical simulations, we found that the optimized RSA arrangement suppressed the self-interference significantly.