Kyouichi Iigusa

Reactance-domain MUSIC for ESPAR antennas (experiment)

The electronically steerable parasitic array radiator (ESPAR) antenna offers low cost and low complexity relative to conventional array antennas. Because of the low complexity of the antenna there is only a single-port output for processing the signals impinging on the antenna elements. Since a reactance-domain MUSIC algorithm for ESPAR antennas has been proposed, the practical problem of estimating the direction of arrival of signals impinging toward an ESPAR antenna can be tackled. In this paper, two experimental methods of estimating the arrival signal angles are proposed. A method of solving the practical problem of calibrating the ESPAR antenna output signal model is also shown. The experimental results show that for one impinging signal the direction of arrival can be estimated with precision of 3 degrees.

Sector-mode beamforming of a 2.4-GHz electronically steerable passive array radiator antenna for a wireless ad hoc network

An electronically steerable passive array radiator (ESPAR) antenna features a simple hardware structure, which enables the use of adaptive array techniques in user terminals, especially in an ad hoc network. We propose the sector-mode beamforming of a 2.4-GHz ESPAR antenna. A single source power maximization technique is presented to find a control voltage vector of the antenna that provides a sector-pattern toward the source direction. Experiments in a radio anechoic chamber give 12 bias voltage vectors and, correspondingly, 12 sector-patterns at every 30/spl deg/.

A simple and accurate mathematical model of electronically steerable parasitic array radiator antennas

A new mathematical model of electronically steerable parasitic array radiator (ESPAR) antennas is proposed. The ESPAR antenna is a kind of adaptive array antenna expected to spread as a terminal antenna for home LANs or wireless ad-hoc networks. Parasitic elements loaded with variable-reactance terminations are excited by mutual-coupling, so the current distributions along each wire element are not in the ideal sinusoidal function. To consider the current distributions, an equivalent weight vector (EWV) model is modified by introducing a vector effective length (VEL) for each wire element. The vector effective length of a parasitic dipole can be calculated by the reactance value of the variable reactor loading the dipole. The directivity of ESPAR antennas can be calculated simply and accurately by the EWV-VEL model.

A slot-array antenna on a coaxial cylinder

In mobile communication, omnidirectional directivity and circular polarization are convenient properties because when they are used, acquisition and track operations for direction and polarization are not needed. As an antenna which has such properties, we developed a slot-array antenna on an oversize coaxial cylinder. This array antenna has less loss than microstrip arrays because energy is transported to each slot in the oversize coaxial waveguide. Also we can shape the beam in the vertical plane by controlling the size and position of slots. We developed cosecant and conical beam antennas. They are scale model antennas for respectively indoor communication by millimeter waves and mobile satellite communications. We show the performance of these antennas.

A slot‐array antenna on a coaxial cylinder with a circularly polarized conical beam

In mobile communication, omnidirectional directivity and circular polarization are convenient properties because when they are used, acquisition and track operations for direction and polarization are not needed. As an antenna which has such properties, we developed a slot-array antenna on an oversize coaxial cylinder. This array antenna has less loss than microstrip arrays because energy is transported to each slot in the oversize coaxial waveguide. Also we can shape the beam in the vertical plane by controlling the size and position of slots. We developed cosecant and conical beam antennas. They are scale model antennas for respectively indoor communication by millimeter waves and mobile satellite communications. We show the performance of these antennas.

RF- and DC- line share ring frequency controllable antenna

An RF- and DC-line share ring frequency controllable (shriquen) antenna is proposed, where an anti-series-connected variable-capacitance (varactor) diode pair is loaded in a conductor ring. Reactance diversity is achieved by exchanging DC-bias voltage from positive to negative, or negative to positive. Because the ring serves as a DC voltage feeding line and not only as an RF radiating antenna, neither additional devices for DC of the circuit nor a cable for the DC supply are needed. It is shown that the shriquen antenna can achieve both input impedance matching and diversity effects over the UHF band.

A Stepwise Recursive Search Algorithm for Adaptive Control of the Electronically Steerable Parasitic Array Radiator Antenna

A stepwise recursive search algorithm (SRSA) is proposed for adaptively controlling the electronically steerable parasitic array radiator (ESPAR) antenna. By calculating the cumulative distribution function (CDF), the algorithm is shown to obtain a higher gain for output SINR than the normalized steepest gradient method (SGM) when the iteration number is small and the objective function is calculated precisely.