Shoichi Kitazawa

Loop Antenna Over Artificial Magnetic Conductor Surface and Its Application to Dual-Band RF Energy Harvesting

This paper studies loop antennas over artificial magnetic conductor (AMC) surfaces with the objective of designing a dual-band RF energy harvesting antenna. The AMC surface is well known to achieve low-profile and higher gain wire antennas. From a practical point of view, impedance matching is of paramount importance to achieve highly efficient reception of weak ambient RF energy. First, the driving-point impedance of a loop antenna over an AMC surface was studied, where a conventional method using image theory to estimate the impedance was found to be not always useful for loop antennas. As the AMC surface is within the reactive near field, mutual coupling between the antenna and the AMC unit cells is significant, which the conventional method does not take into account. Then, we proposed a novel use of a polarization-dependent AMC surface for dual-band RF energy harvesting. An AMC surface with a rectangular unit cell was adopted for two orthogonal polarizations with different frequencies. Finally, the AMC surface and the loop antennas were successfully implemented as a dual-band energy harvesting panel together with RF-to-dc conversion circuits and a power management circuit.

Feasibility study on millimetre wave multi-gigabit wireless LAN system

We are aiming at creating a millimetre wave wireless LAN system with a speed of multi-gigabits per second. This paper describes the preliminary system design, focusing on practical implementation, and its enabling technologies together with the selection of methods and parameters.

Demonstration experiment of millimeter wave multi-gigabit wireless LAN system

We have developed a new 60-GHz band millimeter wave multi-gigabit wireless local area network (WLAN) system that achieves a throughput of more than 1 Gbps. The developed system consists of high-gain eight-sector antenna, physical layer (PHY) for orthogonal frequency multiple access (OFDM) modulation/demodulation, and media access control (MAC) for time and space resource control on point to multi-point (P-MP) communication. The performance of the developed system was evaluated in a room environment. As a result, we confirmed that developed system achieves a high throughput, which exceeds considerably that of current microwave-band WLAN systems based on IEEE802.11.

Design of rectenna array panel taking into account mutual coupling for RF energy harvesting

A study of a rectenna (rectifying anntena) array on a 1×1-m substrate for RF energy harvesting is presented. Square loop antennas are laid out on the given substrate size assuming to harvest 500-MHz Digital TV radio waves. The optimum number of elements is determined from the obtainable DC power and its angle characteristics taking into account mutual coupling between antenna elements and the non-linear RF-to-DC conversion efficiency of the rectifier. Mutual coupling effects can be exploited to control the angle characteristics to some extent. In this particular consideration, a 4×3 rectenna array was optimum in the harvesting of 500-MHz radio waves from a broad angle range in the horizontal dimension.

A Dual-Band Comb-Line Filter Using a Half-Wavelength Stripline Nesting a Quarter-Wavelength Coplanar Waveguide Resonator

This paper presents a novel dual-band comb-line filter using a pair of hybrid resonators. The resonator consists of a half-wavelength stripline resonator short-circuited at both ends and a quarter-wavelength resonator of coplanar waveguide that is nested in the half-wavelength resonator. Numerical calculations by an electromagnetic simulator clarify the characteristics of dual-frequency resonance of the hybrid resonator when the structural parameters are changed. The surface current density on the resonator is also investigated at the resonant frequencies. A typical model of the resonator is fabricated and its resonance frequency characteristics are measured.

Microwave Propagation Channel Modeling in a Vehicle Engine Compartment

With the aim of providing an overview of the propagation channels in a vehicle engine compartment, narrow-band (1-2 MHz) and broadband (500 MHz) channels in the frequency range from 2 GHz to 7.75 GHz were analyzed. To secure as much generality of analysis as possible, more than 500 propagation channels of seven types of automobiles were measured. The path loss and delay spread were analyzed in terms of distance and frequency. Models that take into account the interdependence of distance and frequency were used, considering that the object sizes in an engine compartment are comparable to the measurement wavelengths. The path-loss exponent for distance was about one below a break point of 450 mm and about three above the break point. The exponent for frequency was around one. The root-mean-square (RMS) delay spread increased as distance increased. Based on the obtained delay spread model, the propagation channel model was finally provided, which is a function of frequency and distance. Then, the channel model was validated by comparing delay spreads calculated from the generated channels and the measured channels. It is also noted that the channel dependence on the types of vehicle was not significant.

Microwave radio propagation in automobile engine compartment

With the aim of achieving a wireless harness system in an automobile engine compartment (EC), radio propagation channels from 1.5 to 8 GHz in ECs were characterized with numerous measurements. Because there are many metal objects in EC, the channels frequency-distance interdependence was taken into account in the characterization. As a result, the path loss exponents for distance were found to be about 1 and 3 below and above 450 mm, respectively. The exponent for frequency was 0.5 to 1. The delay spread increased as distance increased at a rate of about 3 ns/m. It also exhibited a decreasing trend with increasing frequency at the far distance.

A Multilayer Single-Input/Single-Output Dual-Band Filter Fabricated in a High Permittivity LTCC Substrate

This paper presents a design procedure of multilayer single-input/single-output dual-band filters of small size fabricated in high-permittivity LTCC (Low Temperature Co-fired Ceramic) substrates. The present dual-band filter, with pass bands of 950 MHz and 1.9 GHz, consists of two single-band filters each one of which has a matching circuit for controlling the input impedance in the pass band of the counterpart. Discussed first in this paper is a dual-band filter that has the matching circuit connected to the single-band filters externally. Then, a dual-band filter with the matching circuit embedded in its body is investigated together with metallization patterns of the matching elements. Presented finally is a very small single-input/single-output dual-band filter suitable for dual-band wireless communication systems.

A study of switchable dual-frequency oscillator for 60 GHz FSK modulation

This paper reports on practical study of a switchable dual-frequency oscillator for 60-GHz binary FSK modulation, using a 0.15 mum commercial GaAs p-HEMT technology. The oscillator obtained an output power of 1.8 dBm at 61.43 GHz with a phase noise of -65dBc/Hz at 100 kHz offset and -87dBc/Hz at 1MHz offset to the carrier at the free-run state. A 500 Mbit/s FSK modulation was confirmed with the developed oscillator. This type of oscillator is feasible for of multi-gigabit data rate FSK modulation.

Control method of notch frequencies for coupled-resonator laminated band elimination filter

A control method of notch frequencies for coupled-resonator laminated band elimination filter (BEF) is studied. A transmission formula is derived from an equivalent circuit of the BEF. The effectiveness of the method is confirmed by circuit simulation and experiment. The BEF shows good performance of an elliptic function characteristic.