Author : Khair Ayman Al Shamaileh
Publisher :
ISBN 13 :
Total Pages : 109 pages
Book Rating : 4.:/5 (953 download)
Book Synopsis Realization of Miniaturized Multi-/wideband Microwave Front-ends by : Khair Ayman Al Shamaileh
Download or read book Realization of Miniaturized Multi-/wideband Microwave Front-ends written by Khair Ayman Al Shamaileh and published by . This book was released on 2015 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ever-growing demand toward designing microwave front-end components with enhanced access to the radio spectrum (e.g., multi-/wideband functionality) and improved physical features (e.g., miniaturized circuitry, ease and cost of fabrication) is becoming more paramount than ever before. This dissertation proposes new design methodologies, simulations, and experimental validations of passive front-ends (i.e., antennas, couplers, dividers) at microwave frequencies. The presented design concepts optimize both electrical and physical characteristics without degrading the intended performance. The developed designs are essential to the upcoming wireless technologies. The first proposed component is a compact ultra-wideband (UWB) Wilkinson power divider (WPD). The design procedure is accomplished by replacing the uniform transmission lines in each arm of the conventional single-frequency divider with impedance-varying profiles governed by a truncated Fourier series. While such non-uniform transmission lines (NTLs) are obtained through the even-mode analysis, three isolation resistors are optimized in the odd-mode circuit to achieve proper isolation and output ports matching over the frequency range of interest. The proposed design methodology is systematic, and results in single-layered and compact structures. For verification purposes, an equal split WPD is designed, simulated, and measured. The obtained results show that the input and output ports matching as well as the isolation between the output ports are below –10 dB; whereas the transmission parameters vary between –3.2 dB and –5 dB across the 3.1–10.6 GHz band. The designed divider is expected to find applications in UWB antenna diversity, multiple-input-multiple-output (MIMO) schemes, and antenna arrays feeding networks. The second proposed component is a wideband multi-way Bagley power divider (BPD). Wideband functionality is achieved by replacing the single-frequency matching uniform microstrip lines in the conventional design with NTLs of wideband matching nature. To bring this concept into practice, the equivalent transmission line model is used for profiling impedance variations. The proposed technique leads to flexible spectrum allocation and matching level. Moreover, the resulting structures are compact and planar. First, the analytical results of three 3-way BPDs of different fractional bandwidths are presented and discussed to validate the proposed approach. Then, two examples of 3- and 5-way BPDs with bandwidths of 4–10 GHz and 5–9 GHz, respectively, are simulated, fabricated, and measured. Simulated and measured results show an acceptable input port matching of below –15 dB and –12.5 dB for the 3- and 5-way dividers, respectively, over the bands of interest. The resulting transmission parameters of the 3- and 5-way dividers are –4.77±1 dB and –7±1 dB, respectively, over the design bands; which are in close proximity to their theoretical values. The proposed wideband BPD dividers find many applications in microwave front-end circuitry, especially in only-transmitting antenna subsystems, such as multi-/broad-cast communications, where neither output ports matching nor isolation is a necessity. The third proposed component is a 90° hybrid branch-line coupler (BLC) with multi-/wideband frequency matching. To obtain a multi-frequency operation, NTLs of lengths equal to those in the conventional design are incorporated through the even- and odd-mode analysis. The proposed structure is relatively simple and is fabricated on a single-layered substrate. Two design examples of dual-/triple-frequency BLCs suitable for GSM, WLAN, and Wi-Fi applications are designed, fabricated and evaluated experimentally to validate the proposed methodology. The same concept is extended to realize a broadband BLC with arbitrary coupling levels. Based on how impedances are profiled, the fractional bandwidth of a single-section 90° 3-dB BLC is extended to 57%, and the realization of broadband BLCs with predefined coupling levels is also achieved. Furthermore, higher-order harmonics are suppressed by enforcing BLC S-parameters to match design requirements only at a given frequency range. Three examples of 3-dB, 6-dB, and 9-dB BLCs are demonstrated at 3 GHz center frequency. The obtained analytical response, EM simulations, and measurements justify the design concept. The fourth proposed component is an UWB antipodal Vivaldi antenna (AVA) with high-Q stopband characteristics based on compact electromagnetic bandgap (EBG) structures. First, an AVA is designed and optimized to operate over an UWB spectrum. Then, two pairs of EBG cells are introduced along the antenna feed-line to suppress the frequency components at 3.6–3.9 and 5.6–5.8 GHz (i.e., WiMAX and ISM bands, respectively). Simulated and measured voltage standing wave ratio (VSWR) are below 2 for the entire 3.1–10.6 GHz band with high attenuation at the two selected sub-bands. This simple yet effective approach eliminates the need to deform the antenna radiators with slots/parasitic elements or comprise multilayer substrates.
