低損失樹脂多層プリント基板に内蔵した超広帯域マイクロ波回路の研究

摘要

In Chapter 1, background of this research, a proposal of microwave circuitsembedded in printed circuit boards (PCBs), and a proposal of accurate design methodfor ultra-wideband microwave circuits are described. Various wireless communicationsystems play increasingly important roles in highly-sophisticated information society.To connect these wireless systems seamlessly, methods to integrate wireless microwavecircuits compactly, are eagerly demanded. In parallel, increased data transmission ratesusing wider bandwidth are targeted in many systems. To satisfy these demands,excellent fabrication platforms to realize design accuracy, excellent performance,miniaturized size, and low cost for microwave circuits, are also eagerly demanded. Forthe demands, the PCB platform is proposed, and is shown viable by comparing withother platforms, such as that with Low Temperature Co-fired Ceramics (LTCC). Inaddition, the total system design method for designing and integrating widebandcircuits is proposed, where return loss of the integrated circuit is minimized byoptimizing both the magnitude and the phase of the reflection coefficient between unitcircuits over the ultra-wide bandwidth.In Chapter 2, for relatively narrow communication systems such as Bluetooth andwireless LAN systems, the PCB platform is verified to be valuable. Firstly, whereasinsertion loss of microwave circuits in the conventional PCBs was too large forpractical applications, satisfactory insertion loss is shown to be obtained using recentlow-loss resin materials. Secondly, characteristics for unit circuits of filters, baluns,and switches fabricated on the material are described, which demonstrates high designaccuracy and excellent characteristics. In addition, both of design accuracy andexcellent performance are also confirmed for integrated circuits of the unit circuits.Finally, temperature characteristics and reliability of the microwave circuits areverified to be practical for wireless applications.In chapter 3, broadband filters applicable for the Ultra-Wideband (UWB) radiosystems are demonstrated. Differential-mode filters using broadside coupled lines areanalyzed to be advantageous to obtain ultra-wideband characteristics. To realize theconstitution, innovative 4-coupled line differential-mode band-pass filters (BPFs) areproposed. The filters exhibit up to 170 % fractional bandwidth. Thus, the fractionalbandwidth exceeds the broadest US’s UWB band (109%: 3.1 GHz - 10.6 GHz) to alarge extent. In addition, filter systems, where a band-elimination filter for 5GHz bandwireless LAN, a semi-lumped low-pass filter, and an abrupt rejection semi-lumpedBPF are integrated with the 4-coupled line BPFs, are designed and fabricatedsuccessfully to comply the radiation mask of the UWB system. Whereas designing theintegration of the ultra-wideband circuits is usually quite difficult, total system designmethod is verified to be very effective for the integration of the wideband circuits.In Chapter 4, practical realization of ultra-wideband antennas for UWB applicationsand their miniaturization limit are explained. Firstly, design and measured results of thefabricated self-complementary antennas are described. The antennas exhibitultra-wideband characteristics covering fully the US’s UWB band (3.1 GHz 10.6GHz). Secondly, after the theoretical limits of the antenna’s characteristics analyzed byChu are referred, the analysis is shown to leave room for improvement especiallyregarding broadband antennas. Based on the speculation, theoretical limits forbroadband antennas are rigorously analyzed. With the analysis, it is shown theoreticallythat the minimum size of the broadband antenna derived by Chu, can be brokenthrough with the optimized matching circuit. Thirdly, with the total system designmethod, the optimized matching circuit for the self-complementary antenna fabricatedon high permittivity (10.2) material is described. The fabricated broadband antenna isverified to be smaller than the minimum sized antenna derived by Chu. Finally,broadband antennas fabricated on the low-cost FR-4 material of lower permittivity(4.6), are shown to be miniaturized equivalently utilizing loop conductors betweenantenna conductors. Measured results for the integrated circuits of ultra-widebandfilters and ultra-wideband antennas are also described.In Chapter 5, achieved findings are summarized. Utilizing these achievement, betterperformance, miniaturization, larger integration, and diversification will be promotedfor the microwave wireless equipment.