In this article, a novel reconfigurable filtering vector-sum phase shifter (RFPS) with a continuous phase shift range of <inline-formula> <tex-math notation="LaTeX">\ge 300^{\circ } ...</tex-math></inline-formula> and tunable operating frequency range from 1.05 to 1.3 GHz is proposed. It consists of two identical wideband Wilkinson power dividers (or power combiners) (WPDs) and a reconfigurable filtering quadrature coupler (RFQC) that is connected between the two WPDs. Through the first WPD, the split waves are fed into the RFQC and are then combined at the output ports of the RFQC. The phase of the combined waves can be continuously tuned by adjusting different combinations of coupling types between interstage resonators of the RFQC, and the resulted output waves are then summed up through the second WPD with the desired output phase. Different from the conventional active vector-sum phase shifter, the vector summing is realized by the proposed RFQC and is a pure passive design, resulting in a low-cost, low-noise, easy-design, and highly flexible system. A prototype is designed and fabricated to demonstrate the proposed technique. Detailed theoretical analysis and design procedure have been given. The experimental results show that the proposed RFPS features the continuous phase-control range of more than 300° with a tunable filtering response covering the frequency range from 1.05 to 1.3 GHz.
In this article, for the first time, a novel four-port coupler with reconfigurable multifunctions of filtering rat-race coupler (FRC), filtering branch-line coupler (FBC), and conventional ...single-ended two-port multipole bandpass filter (BPF) is proposed. It simply consists of four varactor-loaded stepped-impedance resonators that are arranged symmetrically. Through appropriate coupling-type (electrical coupling or magnetic coupling) conversion, 90° or -90° phase shift between the adjacent resonators can easily be obtained and works as a key factor in the transformation between different filtering coupler modes. With this simple configuration, the proposed coupler achieves reconfigurable FRC and FBC with not only operating frequency tuning over a wide tuning range but also bandwidth and power division ratios (PDRs) control for each filtering mode. In addition, by imposing open circuit at any two ports, the four-port coupler can be converted to the conventional single-ended two-port BPFs with reconfigurable filter orders of second, third, and fourth. The measured results show that the FRC and FBC can continuously cover the frequency ranges of 1.21-1.67 and 1.2-1.61 GHz with -1-dB bandwidth tuning of 60-120 and 55-110 MHz, respectively. The 3- and 6-dB PDRs have been demonstrated for both filtering coupler modes. In single-ended two-port BPF mode, the frequency tuning ranges are measured of 1.12-1.6, 1.16-1.6, and 1.2-1.61 GHz, respectively, for the proposed two-port second-, third-, and fourth-order BPFs. Measured and simulated results are in good agreement, validating the proposed design method.
In this paper, a novel tunable filter with reconfigurable single-to-balanced (SE-BAL), power dividing (PD), and single-to-single-ended (SE) filtering functionalities is proposed, for the first time, ...without any additional switching circuit. The proposed filter only consists of three stepped-impedance resonators, which are loaded and connected by varactors in between. With a very simple and compact configuration, the proposed filter achieves multiple reconfigurable functionalities between SE-BAL filtering, PD filtering, and conventional SE bandpass filtering. Moreover, the reconfigurable SE-BAL, PD, and SE bandpass filter can not only offer continuously frequency tuning over a wide tuning range but also have independent bandwidth tuning and maintain good phase/amplitude balance in each tuning state. The proposed filter is designed and fabricated with the microstrip line technology; the measured results show that the SE-BAL, PD, and SE filtering functions can be continuously tuned from 1.02 to 1.32, 0.96 to 1.27, and 1 to 1.28 GHz, with 1-dB bandwidth tuning from 30 to 60, 30 to 110, and 70 to 130 MHz, respectively. The amplitude and phase imbalances of the SE-BAL and PD bandpass filter are less than 0.4 dB, 1.3° and 0.5 dB, 1.5°, respectively, in the passband of each tuning state. Good agreement was obtained between simulated and measured results.
In this article, a reconfigurable Formula Omitted filtering beamforming network (FBFN), which is capable of generating reconfigurable progressive phase difference and amplitude distribution, is ...presented for the first time. It simply consists of one standard Wilkinson power divider and two identical reconfigurable filtering power dividers (FPDs), where the FPD is constructed by four mutually coupled resonators and three nonresonating nodes. By controlling the nonresonating nodes, the coupling coefficients and the resonant frequencies of resonators, arbitrary progressive phase difference, and reconfigurable amplitude distribution can be easily obtained, demonstrating highly flexible reconfigurability. Meanwhile, since the proposed FBFN does not require any individual phase shifter or crossover, it also exhibits a more compact size compared to the conventional beamforming networks based on the Butler matrix. The detailed theoretical analysis of the FBFN is presented and design equations for determining its circuit parameters are deduced. To experimentally demonstrate the proposed concept, a Formula Omitted FBFN prototype is fabricated and measured. Experimental results show that, within a center frequency tuning range from 1.01 to 1.1 GHz, the designed FBFN successfully achieves full reconfigurability, including: 1) continuously tunable progressive phase difference in full 360°; 2) reconfigurable amplitude distribution; and 3) reconfigurable numbers of output ports. Furthermore, a four-element linear antenna array is designed to validate the performance of the FBFN for beam steering. It is shown that, when applied in a phased array, the proposed FBFN is able to perform continuous beam scanning and effective sidelobe level control while maintaining a reasonable filtering performance.
Permeability controls fluid flow in fault zones and is a proxy for rock damage after an earthquake. We used the tidal response of water level in a deep borehole to track permeability for 18 months in ...the damage zone of the causative fault of the 2008 moment magnitude 7.9 Wenchuan earthquake. The unusually high measured hydraulic diffusivity of 2.4 x 10⁻² square meters per second implies a major role for water circulation in the fault zone. For most of the observation period, the permeability decreased rapidly as the fault healed. The trend was interrupted by abrupt permeability increases attributable to shaking from remote earthquakes. These direct measurements of the fault zone reveal a process of punctuated recovery as healing and damage interact in the aftermath of a major earthquake.
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•A novel PN/Anammox system with low ammonia and no temperature control was developed.•Low sludge is advantageous for the suppression of NOB activity by light.•Stable nitrification was ...achieved by light irradiation under mainstream conditions.•Ellin6067 of light-resistant AOB bacteria enhances nitrification system performance.•PN/Anammox achieves a total nitrogen removal rate of > 90 % under mainstream conditions.
PN/Anammox, as an economical and effective nitrogen removal process, is of great significance for reducing carbon emission in municipal wastewater treatment. However, municipal wastewater has mainstream characterized of low temperature and low NH4+-N concentration, and NOB activity is difficult to inhibit, so achieving a stable PN process is the biggest challenge in the application of PN/Anammox to mainstream wastewater. This study developed a method for stable and efficient PN/Anammox based on very low sludge volume (MLVSS = 65 mg/L). Even when the temperature dropped to 15℃ or there was exogenous nitrite-oxidizing bacteria (NOB) interference, the system still had good inhibition of NOB activity. The total stable operation time was 386 days, and the NO2–-N accumulation efficiency could reach more than 90 %. Ellin6067, Nitrosomonas and Candidatus_Brocadia were the dominant functional microorganisms in the system. Nitrospira was the dominant genera of NOB with very low relative abundance (<0.04 %). The mechanism of the long-term stable mainstream PN/Anammox system showed that low sludge content was beneficial to light irradiation on microorganisms in the reactor, while nxrA, the functional gene of NOB, had weak light resistance and oxidation resistance, which makes the system had strong inhibition effect on NOB. The construction of this new system which does not depend on activated sludge volume and complex NOB activity inhibition strategy can better promote the practical application of PN/Anammox under mainstream conditions.
A novel tunable vector-sum filtering power divider (FPD) with arbitrary output phase difference is proposed. It is constructed by a tunable FPD which has reconfigurable in-/out-of-phase output and ...arbitrary power division ratios (PDRs) on the left and a wideband branch-line coupler (BLC) on the right. The output wave from the left FPD forms two orthogonal vectors at each output port of the BLC. The orthogonal vectors are summed up and result in a new vector with phase that is purely determined by the amplitude ratio of the orthogonal vectors. As a result, the phase difference between the new vectors at the outputs of the BLC can be continuously tuned by adjusting the PDR of the left FPD. Detailed theoretical analysis has been given. It shows that the phase difference between the output ports can be flexibly tuned from 0 °C to 360 °C within the full frequency tuning range.
This article demonstrates a 10.23-15.7-GHz varactor-tuned microstrip bandpass filter (BPF) with fully controllable center frequency, bandwidth, and transmission zeros. The concept of cascading a ...tunable low-pass unit together with a tunable high-pass unit is adopted to achieve the reconfigurable BPF. A comprehensive loss analysis is carried out to determine the preferable circuit topologies for low-pass filter (LPF) and high-pass filter (HPF), respectively. This not only overcomes the limitation of low quality factor of varactor at high frequency, but also contributes to a highly flexible reconfigurability of the BPF. A reconfigurable LPF using defected ground structure (DGS) and a quasi-elliptic HPF using microstrip technology are then proposed to demonstrate the improved BPF performance at high frequency. The measured results show that the designed BPF is capable of operating in five working modes, with a center frequency tuning range from 10.23 to 15.7 GHz and a fractional bandwidth (FBW) tuning range from 32.48% to 95.76%. The minimum in-band insertion loss reaches 2.55 dB. A steep cutoff characteristic and ultrawide stopband with high rejection level are successfully achieved and are well preserved during the whole tuning process, demonstrating the superiority of the designed BPF.
This brief presents a novel filtering single-pole-double-throw (SPDT) switch with continuously tunable center frequency and insertion phase. It is comprised of six varactor-loaded microstrip ...resonators and three tunable non-resonating nodes (NRNs) at source and loads. The controllable mixed electromagnetic couplings are introduced on the two main paths of each channel of the switch. At ON-state, the designed filtering switch can generate a 4 <inline-formula> <tex-math notation="LaTeX">^{\mathrm{ th}} </tex-math></inline-formula>-order bandpass filtering performance with high selectivity, and the insertion phase can be continuously tuned with a full 360° tuning range by changing the reactances of NRNs and switching the dominated modes of the mixed couplings. At OFF-state, the mixed electromagnetic couplings are set to zero, and hence high isolation can be realized. To validate the proposed technique, a circuit prototype is designed and fabricated. The measured results suggest that the designed filtering SPDT switch can operate with a tunable center frequency ranging from 1.65 GHz to 1.84 GHz, and its insertion phase at ON-state channel can be continuously tuned from -180° to 180°. During the whole tuning process, the measured in-band isolation for OFF-state channel keeps better than 40 dB.
In this article, a novel tunable isolation network and a novel ring-type reconfigurable single-to-balanced (SE-BAL), power-dividing (PD), and single-to-single-ended (SE) bandpass filter is proposed. ...The tunable isolation network consists of a simple \pi -type resistive network with tunable varactors, while the proposed filter consists of three ring-type stepped impedance resonators (SIRs) connected by varactors in between. By simply combining the proposed tunable isolation network and the proposed ring-type reconfigurable filter, it can achieve multiple reconfigurable functions among SE-BAL filtering, PD filtering, and conventional SE filtering with fully matched three ports, arbitrary power-division ratios (PDRs), high output isolations, and excellent amplitude and phase balance, in addition to continuous frequency and independent bandwidth tuning. The proposed filter is demonstrated using the microstrip line technology. The measured results show that the SE-BAL, PD, and two SE filtering functions can continuously cover the frequency ranges of 1.03-1.61, 1.01-1.53, 1.03-1.56, and 1.06-1.48 GHz with -1-dB bandwidth tuning of 35-80, 50-140, 60-130, and 70-140 MHz, respectively; the 1-, 3-, and 5-dB PDRs have been demonstrated for both SE-BAL and PD filtering modes. The measured output return losses and isolation are better than 19 and 18 dB, respectively, for SE-BAL filtering mode and 20 and 16 dB, respectively, for PD filtering mode. Good agreement is obtained between the simulated and measured results.
