Nobuhiro Kuga

A notch-wire composite antenna for polarization diversity reception

This paper presents a notch-wire composite antenna for polarization diversity reception in an indoor base-station system. A three-notched disk antenna and a wire antenna are proposed as component antennas for the horizontal and the vertical polarization, respectively. These component antennas are unified as a single composite diversity antenna by mounting the wire antenna on the notched disk. Antenna characteristics are calculated using the method of moments (MoM), with wire grid models and examined in terms of component arrangement, and terminal isolation. It is found that maximum isolation is obtained when the current path of the wire antenna is where the current exciting the H-pol element is cancelled. Consequently, both component antennas may work independently even in the composite form. The quasi-monopole pattern is also confirmed for each polarization.

Short-Circuit Transmission Line Method for PIM Evaluation of Metallic Materials

A short-circuit transmission line method for PIM evaluation of metallic materials is proposed in this paper. This method has no restriction of impedance matching at all, and is advantageously free from the low noise termination problem. This enables to treat arbitrarily-shaped samples as a point PIM source, and evaluate them in appropriate current density condition. In addition, the current anti-node of a standing wave located on a sample magnifies observed PIM property. These features improve the resolution and stability in low-level PIM measurement compared for the conventional method using terminated transmission line. Validity of the proposed method is confirmed by the experiments using wires and copper foils in 2 GHz. The sample is evaluated in the form of a shorting wire so that the current density on sample is estimated exactly. PIM characteristics of copper foils are also investigated, which indicates that small differences among the foils are detected clearly.

A flat four-beam switched array antenna

A low-profile four-beam switched array antenna for mobile terminals is proposed in this paper. A flat antenna concept modeled as a square magnetic line current array is realized by thin trapezoidal cavity elements. A unidirectional beam is obtained which can be redirected by alternating input terminals of the hybrid coupler. Element characteristics are calculated approximately using a cavity model with the two-dimensional finite-element method. Input characteristics and radiation pattern of the array antenna are evaluated by experiments.

Non-Contact PIM Evaluation Method using a Standing-Wave Coaxial-Tube

A non-contact PIM measurement method is introduced into the standing wave transmission line method. DUT is tested inside the inner conductor of an opened-coaxial line which is excited in standing wave field. The electromagnetic excitation of DUT realizes non-contact measurement and eliminates electrical contacts such as soldering connection. Employment of wire with the resonant length enables low-power testing. It is also shown that PIM has a relation with its source size and position, and is less produced in small sample compared with operating wavelength.

PIM characteristics of resistive loads

Passive intermodulation (PIM) characteristics of resistive components are experimentally investigated. Resistive dummy loads and attenuator are employed as DUTs, and they are evaluated by the 2-tone test in 2GHz band. It is shown that the PIM has saturation characteristics for high power excitation such as 43dBm /spl times/ 2-tone although it obeys to the ideal theory in low power excitation. The saturation in the high power excitation is also evaluated with the slope factor introduced in this paper, which shows a difference in PIM saturation characteristics between resistive load and nonresistive element. By circuit simulation, the influence of resistance value on PIM level is investigated. PIM reduction technique by using attenuators is also proposed and its validity is confirmed by experiment.

PIM-linearity improvement by the size of a diode mounting hole

A new method for the dynamic range enhancement of the PIM-producing patch antenna with diode is proposed, and its effectiveness is verified by experiment. In 2GHz-band experiment, we shows that the size reduction of the diode-mounted hole has an equivalent effect of the diode-rotation in the previous work, and contributes to the linearity improvement in the high power excitation. Through the testing result of 800MHz-band antenna, it is demonstrated that good linearity is obtained up to 43dBm excitation in swept-power test when Dh=4.6mm. The frequency characteristics of the employed diode are also verified through a frequency-swept test. The resultant PIM-level variation is less than 2dB, which is negligibly small in comparison with the difference between 800MHz- and 2GHz-antennas.

Non-Contact PIM Measurement Method for Electrical Connection Inspection

A non-contact inspection method using electromagnetic intermodulation is proposed for electrical connections. It uses heavy intermodulation, which occurs at the connection with high current density. In the proposed method, a small probe at the tip of semi-rigid coaxial line excites the DUT and detects the intermodulation signal via the near field, which is effective to achieve high spatial resolution. In this paper, a small monopole and a small loop are used as the probes and their capability are examined through the experiments. The evaluation result of a packaged substrate is also shown as an application. To evaluate the capability of the proposed technique, an electrical contact is used as a defected connection. As a sample of other kinds of noise sources, the sample containing a ferromagnetic material in part is also evaluated. The results show that the loop-probe wrapping around the DUT is effective to detect the PIM source even in a continuous material, and the monopole-probe is effective to evaluate electrical-connection failures.

A four beam-switched planar array antenna for mobile terminals

Low-profile beam-switched antennas are effective for mobile terminals to reduce the interference such as multipath fading, co-channel interference or near-far problem. A four beam-switched antenna consisting of four monopoles and corner reflectors was proposed for antenna pattern diversity by Ikegami et al. (1986); however, it was not suitable for practical usage. For the flat four-beam switched antenna, we require a cardioid pattern in the vertical plane with 90/spl deg/ of the half power beam width in the horizontal plane. A flat array antenna concept using four magnetic line currents and hybrid couplers proposed by Arai et al. (1990) was realized by a low profile trapezoidal cavity antenna element. However, this element had narrow band width due to the element configuration, and was not suitable for practical use. Therefore we need to develop a wide band beam-switched flat antenna. In this paper, we propose a modified flat array concept and a low profile element for wide band four-beam switched array antenna. The characteristics of the antenna element are evaluated by a cavity resonator model and finite element method (FEM), which are verified by experiments.

BEAM-SWITCHED PLANAR ARRAY ANTENNA FOR MOBILE COMMUNICATIONS

Reduction or elimination of interfering waves is important for preventing degradation of communication quality in mobile communications. A directivity switched antenna, based on the concept of four antennas beam-switched by four linear magnetic currents and using 90° phase-lag hybrid junctions, has been proposed as a means to eliminate interfering waves. In this paper, a wide-band planar antenna element suitable for a magnetic current antenna and improved placement of array antennas are proposed. It is confirmed that directivity of four-directional type is achieved by the four-element array antennae. The eigenvalue of the antenna is obtained by the finite element method in the two-dimensional approximation and the unloaded quality factor Q is examined. The antenna directivity was evaluated and tested by the magnetic current model, neglecting the mutual coupling of elements, and good agreement was obtained. Correlations between directional branches and the directivity of antennas loaded by dielectric materials are studied.

Dual notched annular ring PIM-generator

In this paper, dual notched annular ring PIM-generator is proposed. It is confirmed that effective excitation of short steel wire is achieved by using notch structure. By PIM measurement using printed dipole antenna, where PIM-generator is positioned about 4/3 λ from antenna, it is also confirmed that PIM-level generated from proposed PIM-generator can be controlled from -84 dBm to -100 dBm by rotating PIM-generator mounting angle.