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This article proposes a new class of box-like substrate integrated waveguide (SIW) filters with wide stopband. First, a two-pole doublet bandpass filter with one finite-transmission zero (FTZ) is proposed using a new planar dual-mode rectangular SIW cavity, which is realized by TE201 and TE103 modes. TE102, TE202, and TE104 modes are suppressed intrinsically by arranging feeding lines at the horizontal centerline of the dual-mode SIW cavity. Then, a four-pole box-section filter with one FTZ is proposed using one dual-mode and two single-mode rectangular SIW cavities, and the two single-mode cavities have different width-length ratios to further improve the stopband performance. To further improve the cutoff skirt, a new design method for five-pole quasi-elliptic SIW filter is proposed, which is achieved by the four-pole filter loaded by one single-mode SIW cavity. Some design examples with the center frequency of 10 GHz are presented to verify the performance of the proposed dual-mode SIW filters and the design method.

This brief presents a novel shape tunable reflective analog predistortion (RAPD) linearizer with a simple structure. The power-dependent impedance matching network (PIMN) based on parallel Schottky diode is applied to the RAPD linearizer to achieve the shape tuning function. Influence of the PIMN on the impedance of the nonlinear load is analyzed in detail. Two different types of shape tunable linearizers for the solid state power amplifier (SSPA) and the travelling wave tube amplifier (TWTA) are proposed and simulated. The shape tuning capability has been verified by a fabricated C-band RAPD linearizer. Good linearity improvement has been achieved for a C-band 20 W SSPA with the proposed linearizer.

A novel design method, which can transform the nonlinear circuits design to the impedance matching network (IMN) design, is proposed for wideband analog predistoter (APD) with the characteristics of frequency-dependent gain and phase conversions in this paper. First, the design method for the desired gain and phase conversions is introduced. The ABCD parameters of the IMN can be computed. To simplify the design, the obtained parameters are transformed to the IMN terminal impedance. Then we can only need to design the IMN terminal impedance to obtain the desired transfer characteristics. In the meanwhile, an APD with 4.5 dB gain conversion and 50° phase conversion is designed and simulated to validate the design method for specify gain and phase conversions. The simulated results show good effectiveness of the design method. Second, for wideband application, the complex gain and phase conversions surface design is transformed to the IMN terminal impendence curve versus frequency design. This gives the designers a well-defined strategy for wideband APD design focusing on frequency-dependent phase conversion as well as gain conversion. To validate the proposed method, a wideband APD operating at K-band (17-20 GHz) is designed, fabricated and measured. A linearized 100W K-band TWTA is shown to achieve a noise power ratio (NPR) >20 dB at 3 dB output power back-off, and phase change

The oxidation of pyrite is often one of the main drivers affecting groundwater quality during managed aquifer recharge in deep aquifers. Data and techniques that allow detailed identification and quantification of pyrite oxidation are therefore crucial for assessing and predicting the adverse water quality changes that may be associated with this process. In this study, we explore the benefits of combining stable sulphur isotope analysis with reactive transport modelling to improve the identification and characterisation of pyrite oxidation during an aquifer storage and recovery experiment in a chemically and physically heterogeneous aquifer. We characterise the stable sulphur isotope signal (δ34S) in both the ambient groundwater and the injectant as well as its spatial distribution within the sedimentary sulphur species. The identified stable sulphur isotope signal for pyrite was found to vary between −32 and +34‰, while the signal of the injectant ranged between +9.06 and +14.45‰ during the injection phase of the experiment. Both isotope and hydrochemical data together suggest a substantial contribution of pyrite oxidation to the observed, temporally variable δ34S signals. The variability of the δ34S signal in pyrite and the injectant were both found to complicate the analysis of the stable isotope data. However, the incorporation of the data into a numerical modelling approach allowed to successfully employ the δ34S signatures as a valuable additional constraint for identifying and quantifying the contribution of pyrite oxidation to the redox transformations that occur in response to the injection of oxygenated water.

A low insertion loss (IL) analogue predistorter using non-linear composite right–left-handed transmission line (CRLHTL) is presented. The proposed predistorter consists of two symmetrical CRLHTL unit cells. In the experiment, this predistorter can achieve about 2.2 dB gain expansion and 17° phase shift during 4.4–4.5 GHz with only 4.3 dB IL. A C-band 40 W solid-state power amplifier observes 8.1 dB enhancement in the intermodulation at −6 dB output power backoff when linearised by the proposed predistorter.

Uncontrolled leakage from mine tailing ponds can pose a serious environmental threat. Groundwater quality in a semi-arid region with extensive worries about the leakage from one of world's largest tailing ponds is studied herein through an integrated hydrogeochemical analysis and multivariate statistical analysis. Results show that elevated concentrations of NO2(-), B, Mn, NH4(+), F(-), and SO4(2-) in groundwater were probably caused by leakage from the tailing pond and transported with the regional groundwater flow towards downstream Yellow River. While NO2(-) contamination is only limited to areas close to the pond, high B concentrations persist within the contaminated plume originating from the tailing pond. Our current study shows that there is no geochemical evidence for U and Th contamination in groundwater due to leakage from the Bayan Obo tailing pond. Combining effects which includes regional variations, pond leaking and downstream mixing, mineral precipitation and dissolution, redox processes, ion exchange processes and agricultural activities, controlled groundwater hydrogeochemical signatures in the studied area. This study demonstrate that an increase in knowledge of evolution of groundwater quality by integrating field hydrochemical data and multivariate statistical analysis will help understand major water-rock interactions and provide a scientific basis for protection and rational utilization of groundwater resources in this and other tailing-impacted areas.

A reconfigurable analog predistoter (APD) based on tunable impedance matching network (TIMN) is proposed in this brief. Firstly, a design method to specific gain and phase conversions is introduced. The equivalent circuit parameters of the impedance matching network (IMN) can be computed for the desired gain and phase conversions. To simplify the design, these parameters can be transformed to the terminal impedance of the IMN. Then the complicated nonlinear circuits design can be transformed to the IMN design. Secondly, a reconfigurable APD using the proposed method is presented for high tuning capability. By designing the coverage area of the TIMN, an experimental reconfigurable APD for traveling-wave tube amplifiers (TWTAs) & solid-state power amplifiers (SSPAs) is designed and fabricated. The fabricated APD shows more than 21 dB tuning range of gain conversion and 114° tuning range of phase conversion in 5.7–6.3 GHz. Good linearity improvement has been obtained for a 45 W C-band TWTA and a 5 W SSPA only by changing the APD bias voltage.