Jen-Chun Yeh

SYNTHESIS OF TRIPLE-BAND AND QUAD-BAND BANDPASS FILTERS USING LUMPED-ELEMENT COPLANAR WAVEGUIDE RESONATORS

This paper develops a novel design method for synthesizing the multi-passband filter with high flexibility in various passband location and fractional bandwidth. Using the proposed compensation technology in the equivalent circuit of multi-passband resonator, the cutoff frequencies and matching property in passband regions can be improved. Tripleand quad-band bandpass filters operating in both wireless local area network (WLAN) 802.11 a/b/g and worldwide interoperability for microwave access (WiMAX) systems are presented to verify the design method. The lumped-element coplanar waveguide stub fabricated by the split-ring resonator is established to realize filter with compact size. All the measured, full-wave simulated and equivalent-circuit modeled results illustrate a good agreement among them, which validates the multi-passband design methodology and shows the advantages of DC elimination and deep rejection between each passband.

A Novel Triple-Band Microstrip Branch-Line Coupler With Arbitrary Operating Frequencies

This letter presents a novel microstrip branch-line coupler operating in three frequency bands. The design methodology of the triple-band branch-line coupler is established by using a compensation technique to improve the matching property within each passband region. The proposed coupler with compact size is realized by folded microstrip open-circuited and short-circuited stubs. The measured, full-wave simulated and equivalent-circuit modeled results illustrate good agreement among them, which validates the design method and shows the advantages of deep rejection between each operating frequency, and the dc grounded input and output ports.

A novel wideband circularly polarized dual-fed slot antenna with microstrip feeding network

This study presents the design of novel dual-fed circularly polarized (CP) antenna. This antenna consists of a tapered slot, a backside metal plate and a microstrip-fed delay line phase shifter. Based on the analysis of the radiation mechanism of antenna ground plane, the edge shape is optimized as a half-circle type to enhance the bandwidth of antenna gain and CP purity. The proposed antenna possesses a wideband return loss better than 10 dB in the range of 4.18–7.57 GHz, covering the bandwidth of axial ratio lower than 3 dB from 4.25 to 6.75 GHz. The measured antenna gain is approximately 9–10.5 dBic and the radiation patterns are broadside and consistent within the CP operating bandwidth.

Broadband and strong coupling metamaterial-based cavity resonator using artificial magnetic surfaces

This study proposes a novel metamaterial-based cavity with a strong coupling effect between the transmitting and receiving devices. It is compact in size and the field distribution is uniform inside the cavity, which is realized by combining four artificial magnetic conductor surfaces at the four sidewalls and two metal palates at the top and bottom walls. The AMC consisting of a periodic array of square patches printed on the metal-backed double-layer dielectric substrate without connecting vias to enhance its operating bandwidth. Two monopole-type antennas are used as the transmitting and receiving terminals to examine the transmission property. The measured insertion loss of the metamaterial-based with different receiving positions are 1.06 dB, 2.26 dB, 2.02 dB, and 0.6 dB for position A, B, C, and D, respectively. The fabrication and measurement of the metamaterial-based cavity are demonstrated to validate its broad bandwidth and compact size.

Novel compact metamaterial-based cavity resonator with broad bandwidth

Metamaterials have attracted considerable interest among scientists and engineers owing to their interesting electromagnetic properties not observed in naturally occurring materials [1]. As a kind of metamaterial, the artificial magnetic conductor (AMC) [2]-[4] is composed of the periodic metal arrays on a metal-backed dielectric substrate. Such a structure functions as a perfect magnetic conductor (PMC) with the capability of presenting a near-zero reflection phase for a wave normally incident to the surface. Among the numerous applications that these AMC structures can be found, they include ground plane of antennas [2], cavity antennas [3], and quasi-TEM waveguides [4].