This letter presents novel resonant elements with four axial symmetry constructing a reflectarray for dual-polarization and wideband use. These elements have low cross-polarization property because the current flows on the strip elements cancel out cross polarized fields. To verify usefulness of the proposed elements, a reflectaray with offset feed is designed in Ku-band, and also the radiation pattern is investigated numerically and experimentally.

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Wireless communication systems using Tomlinson-Harashima precoding (THP) suffer from modulo operation error in noisy environments. The error causes fatal performance degradation when soft-input forward error correction is applied because the conventional soft demappers provide unreliable log-likelihood ratio (LLR) values. In this paper, we propose an efficient low complexity soft demapper with reliable LLR values for expanded M-QAM constellations of the THP systems. Computer simulations are given to show the effectiveness of the proposed demapper.

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Most existing authentication methods have a common problem, referred to as shoulder-surfing, in which authentication information is covertly obtained by peeking over the shoulder of a user as he/she completes the authentication sequence. In this paper, we propose a puzzle authentication method that is very simple and sufficiently secure, even when the authentication sequence is being leaked. We also implemented the proposed method on a mobile terminal and is evaluated through experiments and questionnaire surveys.

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The measurements of the characteristics of an artificial mains network (AMN) are always affected by an AC-coaxial adapter connecting an impedance measuring equipment to the AMN. The present paper theoretically investigates the influences of the adapter on the measured AMN S-parameters in terms of the mode S-parameters. As a result, it proposes a correction method for eliminating the adapter influences in order to reveal the true AMN characteristics. The experimental measurements using two adapters of considerably different characteristics prove that the proposed method can yield almost the same estimates of the AMN impedance.

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