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Abstract-A novel ultra-wideband bow-tie slot antenna fed by CPW is proposed in this paper. This antenna has been demonstrated to provide an UWB with return loss less than −10 dB from 9.5 GHz to 22.4 GHz. The bandwidth is up to 80%, which is quite better than the traditional bow-tie slot antenna. Simulated and measured results are presented.

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Abstract-A novel compact Archimedean spiral antenna with gaploading is investigated in this paper. A circular frame sharing the same centre with the spiral elements introduces a capacitive gap. By adjusting the width of the gap and the width of the circular frame, the initial resonant frequency of the proposed antenna is shifted from 2.79 to 1.93 GHz. Compared with the traditional Archimedean spiral antenna with the same lowest operation frequency, the area of the proposed antenna can be reduced by more than 30simulated radiation pattern results.

Poly(vinylidene fluoride)/sulfonated poly (phthalazinone ether sulfone ketone) (PVdF/SPPESK) blend membranes are successfully prepared by solution blending method for novel proton exchange membrane (PEM). PVdF crystallinity, FTIR-ATR spectroscopy, thermal stability, morphology, water uptake, dimension stability, and proton conductivity are investigated on PVdF/SPPESK blends with different PVdF contents. XRD and DSC analysis reveal that the PVdF crystallinity in the blends depends on PVdF content. The FTIR-ATR spectra indicate that SPPESK remains proton-conducting function in the blends due to the intactness of ASO 3 H group. Thermal analysis results show a very high thermal stability (T d1 ¼ 246-261 C) of the blends. PVdF crystallinity and morphology study demonstrate that with lower PVdF content, PVdF are very compatible with SPPESK. Also, with lower PVdF content, PVdF/SPPESK blends possess high water uptake, e.g., P/S 10/90 and P/S 15/85 have water uptake of 135 and 99% at 95 C, respectively. The blend membranes also have good dimension stability because the swelling ratios are at a fairly low level (e.g., 8-22%, 80 C). PVdF/SPPESK blends with low PVdF content exhibit very high proton conductivity, e.g., at 80 C, P/S 15/85 and P/S 10/90 reach 2.6 Â 10 À2 and 3.6 Â 10 À2S cm À1, respectively, which are close to or even higher than that (3.4 Â 10 À2 S cm À1) of Nafion115 under the same test condition. All above properties indicate that the PVdF/ SPPESK blend membranes (particularly, with 10-20% of PVdF content) are very promising for use in PEM field.

In this research, the novel concept of a resonance-based reflector (RBR) was proposed, and a ring-shaped RBR was utilized to design a unidirectional antenna with low-profile and broadband characteristics. Research found the ring operates as two half-wavelength (λ/2) resonators. Then, the resonance effect transforms the reflection phase of the ring RBR, and achieves a reflection phase of 0° < ϕ < 180° in a wide frequency range above the resonance. Then, the in-phase reflection characteristic (−90° < ϕ < 90°) can be obtained in the wide frequency band by placing an antenna above the RBR with a distance smaller than λ/4. Two unidirectional antennas, named Case 1 and Case 2, were designed with the ring-shaped RBRs and bowtie antennas (RBR-BAs). The impedance bandwidths of Case 1 and the Case 2 are 2.04–5.12 GHz (86.3%) and 1.97–5.01 GHz (87.1%), respectively. The front-to-back ratio (FBR, an important parameter to measure the unidirectional radiation) of Case 1 ranges from 5–9.9 dB for frequencies 2.04–2.42 GHz, and the FBR of Case 2 ranges from 5–16 dB for frequencies 2.16–3.15 GHz. The proposed concept of RBR is desirable in wideband unidirectional antenna design, and the designing antennas can be used at the front end of wireless systems—such as indoors communication, remote sensing, and wireless sensor systems—for signal receiving or transmitting.

Four ultra-wideband (UWB) antennas are proposed: one referenced antenna without notch and three novel antennas with one, two and three notched bands, respectively. The UWB referenced antenna consists of a beveled rectangular metal patch, a 50 Ω microstrip line and a defective ground plane. Then, by utilizing one, two and three electromagnetic band-gap (EBG) structures on the UWB antenna, the antennas present one, two and three notchedband responses, respectively. The frequency domain characteristics including VSWR, transfer coefficient S 21 , radiation patterns and group delay are investigated. It is found that the EBG design approach is a good candidate for frequency rejection at the certain frequencies, owing to high performance of notch design and the notched-band bandwidth control abilities. Meanwhile, these abilities also enable less useful frequencies rejected. The design examples exhibit good bandrejected characteristics in the WiMAX/WLAN interference bands (3.4, 5.2 and 5.8-GHz bands). Moreover, good time-domain characteristics of the antennas are checked based on group delay, waveform response, correlation coefficient and pulse width stretch ratio (SR).