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A compact wideband high gain directional antenna is proposed in this paper for marine communications. The antenna consists of a back plane (reflector), a slot-loop antenna (driven element), and a director of rod. Based on the current distribution, the slot-loop antenna is equivalent to an array of three linear current dipoles. The dipole acts as an element of the director, which provides a high efficient director for slot-loop antenna according to theoretical analysis. Both the impedance bandwidth and the 1 dB gain bandwidth are 45% covering 1.7–2.7 GHz in this design. A gain of 11.2 to 12.2 dBi is obtained in the working band with only one set of directors. The directors have a dimension less than the antenna aperture in the H-plane, which can be seen as one director in the end-fire direction. Compared with the classic Yagi antenna with the same gain level, the newly proposed antenna is only half of the size in radiation direction, which is a breakthrough for the Yagi antenna design. This size reduction can significantly minimize the interference between ship-borne antennas. The antenna is fabricated using only metal of low cost, which is useful for the ship-to-shore/ship communicating applications and desirable for the large-scale deployment.

Diagnosis and troubleshooting are critical to efficiently detecting the imperfections and improving the radio frequency designs for wireless systems in the research and development stage. For achieving these, this paper proposes a decomposition method for the measurement of multi-input multi-output (MIMO) devices’ over-the-air (OTA) performance. By using the proposed method, the antenna active envelope correlation coefficient, the radiated sensitivity of each receiver, the total isotropic sensitivity, the self-interference, and the desensitization can all be achieved separately, and in the OTA working mode. In consideration of the MIMO system's complex array antennas and radio frequency receivers, the parameters obtained by this decomposition method are significant for discovering the imperfections, for debugging, and for improving the design of the devices. It is a valuable tool to raise the debugging efficiency of MIMO systems.

Wireless geolocation in a multipath environment is of particular interest for wideband communications and fast-developing ultrawideband (UWB) technologies. Conventional methods are solely based on first arriving signals. In this paper, it is investigated whether and under what conditions processing delay estimates of multipath components in addition to first arrivals can enhance the positioning accuracy. It is shown that the enhancement depends on two principal factors: strength of multipath components and variance of nonline-of-sight (NLOS) delays. Analytical results, which are derived as an extension of a single-path propagation case (IEEE Trans. Wireless Commun., Feb. 2006), are presented first. Their practical implications are then discussed by examining several numerical examples. Finally, modified schemes of practical interest in a multipath environment are proposed