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In this paper, a parallel transmission-line transformer with complex terminal loads is introduced for dual-frequency design. Through analyzing the different cases of complex terminal loads conditions, there are four different mapping patterns of designable regions on the Electrical Length-Electrical Length ( EL-EL ) plane. By adding an extra vertical Frequency Ratio ( FR ) axis, a novel 3D cube can be created on the FR-EL-EL coordinate system, then the designable ranges of frequency ratio can be easily drawn in this 3D cube. Therefore, the visible 3D mapping approach is newly reported for matching the complex terminal load of parallel transmission-line transformer at two different frequencies. For the certain pattern, a clearly boundary could be drawn to distinguish the designable and undesignable ranges. For verification, two examples are designed, fabricated and measured. Simulated and measured results are matched very well.

In this letter, a novel bandpass filter (BPF) with equal-ripple responses is proposed. The bandpass filter with 4 reflection zeros (RZs) and high attenuation rates (AR) consists of two coupled lines (CLs) and two transmission lines (TLs), which has a very compact size. According to the mathematical analysis, equal-ripple responses can be newly realized respectively in the passband, and the derivation approach is presented as well. By selecting appropriate characteristic impedances of the CLs and TLs, RL from 10 dB to 20 dB and flexible FBW with good AR can be obtained. For demonstration, a proposed BPF with 4 RZs and compact size centered at 2 GHz is designed and fabricated. The simulations and measurements agree with the design theory well.

SnO 2 nanomaterials were synthesized by an ultrasonic assisted precipitation method, and then Pd was doped on SnO 2 by mechanical mixing method. SnO 2 materials were characterized by X-ray diffraction. The micro-hotplate was used as the substrate of the sensor. Finally, the sensing properties were evaluated with a static state measuring system. It has been observed that the response of the microstructure sensor based on 1wt% Pd-doped SnO 2 exhibited a preferable sensing performance. The response to 3000ppm methane was about 33 at 275 °C and the response and recovery time was about 1 s and 3 s, respectively.

Pure and doped γ-Al 2 O 3 by metal oxides including SnO 2 , ZrO 2 , CeO 2 and MgO were used as the supports of the combustion catalysts. The Al 2 O 3 based supports doped with the metal oxides were prepared by coprecipitation method. The noble metal Pd with 15 wt% loading amount was then loaded on the as-prepared supports using isometric impregnation. The measuring results of Brunauer-Emmett-Teller-specific surface areas revealed that the specific surface areas of supports have been improved to a certain extent by doping of metal oxides. The measurement of gas sensing properties showed that the metal oxides have great influences on the sensitivity to CH 4 . The sensing performance of catalytic combustion methane sensors had been improved by doping SnO 2 , ZrO 2 , CeO 2 or MgO in Al 2 O 3 .

A NASICON-based electrochemical device attached with an oxide electrode was developed for the detection of Cl 2 in air at high temperature. Among the oxides tested, Cr 2 O 3 was found to be the best suited for the sensing electrode. The ΔEMF value of the device attached with Cr 2 O 3 was almost linear with the logarithm of 5–50 ppm Cl 2 concentration. It was also observed that the sensor showed a speedy response and recovery kinetics to Cl 2 . In addition, the device exhibited excellent selectivity to Cl 2 against the other interference gases, such as CO, NO, NO 2 , H 2 , C 7 H 8 , C 2 H 4 and CH 4 . The buried reference electrode can effectively improve the sensitivity of the sensor.

This paper focuses on the gas sensing properties of the mixed-potential-type yttria stabilized zirconia (YSZ)-based NO 2 sensor with NiO sensing electrode. The sensing characteristics of the sensors have been improved by controlling the microstructure of NiO sensing electrode synthesized with the microwave. The microstructure of NiO strongly depended on the microwave treatment temperature and the sintering temperature. The largest sensitivity of the sensor was obtained by using the NiO synthesized at 60°C and sintered at 1200°C, the slope of the dependence of EMF on the NO 2 concentration in the range of 20–500 ppm was 54 mV/decade at 850°C. It was also seen that the sensor showed a speedy response and recovery kinetics to NO 2 . The sensing mechanism was confirmed to involve in the microstructure of oxide sensing electrode.

Sensing characteristics of the UV-enhanced gas sensor using the SnO 2 -TiO 2 hollow sphere (HS SnO 2 -TiO 2 ) at room temperature has been investigated. HS SnO 2 -TiO 2 was prepared by coating the TiO 2 on the outer- and inner-surfaces of HS SnO 2 with hydrolysisof the titanium tetrachloride. HS SnO 2 was synthesized by chemically induced self-assembly under hydrothermal condition. The morphology, crystalline structure and optical absorptivity of the HS SnO 2 -TiO 2 were measured by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV-Vis absorption spectra. A sensing mechanism related to the SnO 2 -TiO 2 heterojunction as well as UV illumination was proposed.

Solid state electrochemical sensors using yttria-stabilized zirconia (YSZ) plate and Cr 2 O 3 -WO 3 nanocomposites were fabricated. The effects of the sintering temperature on the electrode microstructure were investigated. It was found that the sensor sintered at 1000 °C exhibited larger sensitivity to NO 2 in the examined range of 20–300ppm than other sensors sintered at 800 °C, 900 °C, and 1100 °C; and it was speculated that the microstructure of the SE was the primary factor. The NO 2 sensing characteristics of the sensors were examined at high temperature.

SUMMARY A solid electrolyte H2S sensor was fabricated by combining a YzO3-stabilized zirconia tube with a semiconductor electrode layer of W83. This device was found to respond well to 0.3-25 ppm H2S in air at 400 "C, with acceptable response rates. The EMF value of the sensor varied logarithmically with H2S concentration with a slope of -74 mV/decade. It is proposed that the H2S sensing signal is attributed to the mixed potential which is determined kinetically by the anodic and cathodic reactions taking place simultaneously at the zirconiaN03 interface. This mechanism was confirmed from the measurements of polarization curves for the both electrode reactions.