Siang-Wen Lan

A Tri-Band Bandpass Filter With Wide Stopband Using Asymmetric Stub-Loaded Resonators

This letter presents a tri-band bandpass filter (BPF) with a wide stopband using asymmetric stub-loaded resonators (ASLR). A tri-band filter sample was fabricated by using two ASLRs with coupled I/O ports. By properly tuning the electrical length ratios of the ASLRs ( α and γ), three passbands can be designed at 1.4, 2.4, and 3.5 GHz. The harmonic responses are suppressed effectively by forming an uncoupled section at the end of the ASLRs, and the stopband region is formed from 3.7 to 7 GHz with a rejection level of 30 dB. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

Design of a high band-isolation diplexer based on asymmetric stepped-impedance resonators with side-coupling structure

In this paper, a high band-isolation diplexer based on two bandpass filters (BPFs) formed using asymmetric stepped-impedance resonators is presented. The passbands of the diplexer are operated at 1.8 GHz for global system for mobile communications (GSM) and 2.4 GHz for wireless local area network (WLAN). Side-coupling structure is adopted in BPFs to create two additional transmission zeros, thus enhancing the band isolation and stopband region. The measured results of the proposed diplexer show the passband at 1.8 GHz with a low insertion loss of 1.09 dB, a 3 dB fractional bandwidth (FBW) of 9.4% in the first channel and a passband at 2.4 GHz with an insertion loss of 2.6 dB, a 3 dB FBW of 6.2% in the second channel. The measured results of the fabricated diplexer also show a good agreement with the simulated ones.

Preparation of a Carbon Doped Tissue-Mimicking Material with High Dielectric Properties for Microwave Imaging Application

In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs) doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were 2 wt %, 4 wt %, and 6 wt %. The effect of doping material and amount on the microwave dielectric properties including dielectric constant and conductivity were investigated over an ultra-wide frequency range from 2 GHz to 20 GHz. The coaxial open-ended reflection technology was used to evaluate the microwave dielectric properties. Six measured values in different locations of each sample were averaged and the standard deviations of all the measured dielectric properties, including dielectric constant and conductivity, were less than one, indicating a good uniformity of the prepared samples. Without doping, the dielectric constant was equal to 23 ± 2 approximately. Results showed with doping of carbon based materials that the dielectric constant and conductivity both increased about 5% to 20%, and the increment was dependent on the doping amount. By proper selection of doping amount of the carbon based materials, the prepared material could map the required dielectric properties of special tissues. The proposed materials were suitable for the phantom used in the microwave medical imaging system.

Compact quad-band bandpass filter based on uniform impedance stub-loaded resonators

A new quad-band bandpass filter for Global System for Mobile Communications, Wireless Local Area Network, and Worldwide Interoperability for Microwave Access is designed and fabricated using the stub-loaded resonator (SLR) technology without complex fabrication process, such as via-hole or multi-layer substrate. Owing to the embedded SLR, the proposed quad-mode resonator is compact. Equivalent circuits of the proposed quad-mode resonator are analyzed in detail, and high design freedom is shown because of shifting the passband frequencies individually. Good passband selectivity and isolation of the each passband at 1.8, 2.4, 3.5, and 5.2 GHz can be well achieved due to the transmission zeros appeared near the each passband edges. Experimental results show good agreement with the simulated results.

Assessment of dielectric properties for the microwave phantom production

This research presents an assessment of dielectric properties for the microwave phantom production (MPP). The presented MPP was constructed by mixing organic compounds and inorganic compounds, which having particular dielectric properties. In addition, the fabricated MPP was analyzed to evaluate the relative electromagnetic properties based on the basic concepts of microstrip lines. Moreover, the characteristic parameter of the MPP, such as dielectric constant, was extracted effectively by converting the relative electromagnetic properties.