An-Shyi Liu

Bio: An-Shyi Liu is an academic researcher from National Taiwan University. The author has contributed to research in topics: Waveguide filter & Antenna (radio). The author has an hindex of 7, co-authored 18 publications receiving 220 citations.

A Dual Wideband Filter Design Using Frequency Mapping and Stepped-Impedance Resonators

Abstract: A dual-wideband filter design implemented by stepped-impedance resonators, which involves the frequency mapping approach, is presented in this paper. The dual-band filter can be divided into two parts: the wideband virtual passband filter and the narrowband virtual stopband filter. Both filters are designed by conventional synthesis methods, under the assumption that the common connecting lines serve as J- and K-inverters simultaneously. The basic building resonators formed by paralleling open- and shorting-stubs are implemented by unbalanced stepped-impedance resonators, exhibiting the desired resonating frequencies and susceptance slope parameters at these two bands. Two filters are tested to validate this design.

Terahertz Microchip for Illicit Drug Detection

Abstract: To accurately detect minute amounts of substances without disturbing the surroundings of target molecules has been a major goal in bioanalytical technology. Here by integrating an optoelectronic terahertz (THz) microsource into a glass-substrated microchip within the near-field distance, we demonstrate a compact, label-free, noninvasive, and sensitive microbiosensing system with low-power consumption. The demonstrated THz microchip allows us to locally specify various illicit drug powders with weights of nanograms, with a promising future for rapid identification of the static status or even the dynamics of various biomolecules

Optimization for the Locations of Decoupling Capacitors in Suppressing the Ground Bounce by Genetic Algorithm

Abstract: In the high-speed digital printed circuit board, decoupling capacitors play an important role in lowering the power-ground planes impedance leading to the ground bounce noise in I/O ports while the logic is in transition. This paper investigates the optimal placement of decoupling capacitors in suppressing the input and transfer impedances of power-ground planes. The cavity model combines with genetic algorithm (GA) here to find the design specification and the optimal placement of the decoupling capacitors.

Bandwidth enhancement on waveguide transition to conductor backed CPW with high dielectric constant substrate

Abstract: This paper proposes a broadband transition design between conductor-backed coplanar waveguide (CB-CPW) and rectangular waveguide based on the concept of the multisection transformer. The genetic algorithm (GA) was adopted to efficiently optimize the multisection transformer for achieving wideband performance. Using a multisection of order 3, a V-band transition realized on an Al/sub 2/O/sub 3/ substrate could achieve 25% bandwidth with a return loss better than 20 dB. Two transitions connected back to back were realized to demonstrate the feasibility of the transition. Also, a tolerance analysis was performed via the simulation to verify the robustness of this transition design.

Ka-band 32-GHz planar integrated switched-beam smart antenna

Abstract: This paper presents an integrated planar switched-beam antenna based on rectangular waveguide antenna and Butler matrix network for beamforming, which is implemented by complementary-conducting-strip transmission line (CCS TL). The 32-GHz waveguide antenna with size of 71.5 mm by 4.1 mm, consisting of 20 slots in the broadside wall, is built on the Rogers RO4003 (/spl epsiv//sub r/ = 3.38) substrate. For a compact and reliable design of the Butler matrix beamformer, the branch-line coupler and the crossover of the Butler matrix are designed by CCS TLs with characteristic impedance of 60 and 85 /spl Omega/, respectively. The proposed 4-beam smart antenna shows the steered beams in orthogonal direction at 38/spl deg/, 76/spl deg/, 106/spl deg/, and 136/spl deg/, respectively, and demonstrates a great potential for planar integration of smart antenna for wireless communication application. Measured results agree well with theoretical predictions, validating the design concepts employed in the millimeter-wave smart antenna design.

A Low-Cost 60-GHz Switched-Beam Patch Antenna Array With Butler Matrix Network

Abstract: In this letter, a low-cost 60-GHz switched-beam patch antenna array with Butler matrix network is developed and experimentally demonstrated. In order to improve integration with the patch elements, a 4 times 4 planar Butler matrix is implemented in a low-dielectric substrate. The four rectangular patches fed by inset microstrip lines are connected to the outputs of the Butler matrix for the 60-GHz operation. Because of the fabrication tolerances, the operating frequency of the fabricated antenna shifts to 62 GHz. The radiation patterns measured at 62 GHz are in good agreement with the theoretical array factors. The antenna developed in this letter provides a cost-effective approach to implement an adaptive antenna for 60-GHz wireless communications.

Overview of Power Integrity Solutions on Package and PCB: Decoupling and EBG Isolation

Abstract: Mitigating power distribution network (PDN) noise is one of the main efforts for power integrity (PI) design in high-speed or mixed-signal circuits. Possible solutions, which are based on decoupling or isolation concept, for suppressing PDN noise on package or printed circuit board (PCB) levels are reviewed in this paper. Keeping the PDN impedance very low in a wide frequency range, except at dc, by employing a shunt capacitors, which can be in-chip, package, or PCB levels, is the first priority way for PI design. The decoupling techniques including the planes structure, surface-mounted technology decoupling capacitors, and embedded capacitors will be discussed. The isolation approach that keeps part of the PDN at high impedance is another way to reduce the PDN noise propagation. Besides the typical isolation approaches such as the etched slots and filter, the new isolation concept using electromagnetic bandgap structures will also be discussed.

A New Planar Artificial Transmission Line and Its Applications to a Miniaturized Butler Matrix

Abstract: A miniaturized quadrature hybrid coupler, a rat-race coupler, and a 4 times 4 Butler matrix based on a newly proposed planar artificial transmission line are presented in this paper for application in ultra-high-frequency (UHF) radio-frequency identification (RFID) systems. This planar artificial transmission line is composed of microstrip quasi-lumped elements and their discontinuities and is capable of synthesizing microstrip lines with various characteristic impedances and electrical lengths. At the center frequency of the UHF RFID system, the occupied sizes of the proposed quadrature hybrid and rat-race couplers are merely 27% and 9% of those of the conventional designs. The miniaturized couplers demonstrate well-behaved wideband responses with no spurious harmonics up to two octaves. The measured results reveal excellent agreement with the simulations. Additionally, a 4 times 4 Butler matrix, which may occupy a large amount of circuit area in conventional designs, has been successfully miniaturized with the help of the proposed artificial transmission line. The circuit size of the Butler matrix is merely 21% of that of a conventional design. The experimental results show that the proposed Butler matrix features good phase control, nearly equal power splitting, and compact size and is therefore applicable to the reader modules in various RFID systems.

A Multibeam Antenna Based on Substrate Integrated Waveguide Technology for MIMO Wireless Communications

Abstract: A 24-beams slot array antenna, which achieves 360-degrees coverage over azimuth direction, based on substrate integrated waveguide (SIW) technology is designed, fabricated and measured for supporting the concept of triangle cell, beam diversity and multiple input multiple output (MIMO) wireless communications. Constructed by six 4-beams single layer SIW antennas which integrate the 4times8 modified Butler matrix with a low side lobe level (SLL) amplitude distribution, measured SLLs are reduced as low as -14.5 dB for all beams in E-plane. The size of the SIW single layer multibeam antenna is 385 mm times 110 mm including feeding network. The usable bandwidth of the proposed antenna is 3.75% at 16 GHz.

THz Chemical Imaging for Biological Applications

Abstract: THz spectroscopy is advantageous in analytical chemistry because it can detect and identify intermolecular interactions in chemical compounds, such as hydrogen bonds and hydrations, and molecular networks. Recent advances in THz components, such as ultrashort pulsed lasers and photoconductive antennas, have improved the sensitivity of THz time-domain (TDS) spectroscopy and have made the THz chemical imaging possible. THz chemical imaging can reveal hydrogen bond distributions and will be a very powerful tool in biology, pharmacology, and life sciences. THz-TDS is also promising for the quantitative chemical analysis and detection of molecules and clusters in nanospace and ice.