Roll-off Rate Research Articles

A novel compact lowpass filter with sharp roll-off and wide stopband

AbstractIn this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.

A novel neural-based approach for design of microstrip filters

This paper presents an intelligent design methodology of microstrip filters in which a dynamic neural network model based on Bayesian Regularization Back-Propagation (BRBP) learning algorithm is used. In this approach, a Low-Pass Filter (LPF) composed of multiple open stubs, and stepped impedance resonators is initially designed for which an Artificial Neural Network (ANN) is trained to improve the performance of the filter. The predicted and measured results of the filter verify the effectiveness of the presented method, suggesting an excellent in and out-of-band performance. According to the measurement, the filter has a very small transition band from 2.087 to 2.399 GHz with 3 and 40 dB attenuation points, respectively, leading to a sharp roll-off rate of 118.6 dB/GHz. In addition the optimized filter has an ultra-wide stopband, extending from 2.399 to 15.01 GHz with attenuation level of 22 dB are The overall size of the fabricated filter is only 0.190λg×0.094λg, where λg is the guided wavelength at 3 dB cut-off frequency (2.087 GHz). A performance comparison with some of the recent published LPFs presented, showing the superiority of the proposed filter.

A Lowpass Filter Design Using Curved and Fountain Shaped Resonators

AbstractIn this paper a new lowpass filter (LPF) with curved line resonators and fountain shaped resonators is proposed. The proposed filter has achieved wide stopband, compact size, sharp roll-off rate and low return loss. Two tapered resonators are used to produce transmission zeros and widen the stopband. Also, a fountain shaped resonator is proposed using curved transmission lines to obtain good sharpness in the filter response. The cut-off frequency of the designed LPF is 1.74 GHz and the overall size of the designed LPF is 0.135 λg × 0.132 λgwhere λgis the guided wavelength at the cut-off frequency. The results show that the overall size of the lowpass filter could be reduced using curved line resonators and curved transmission lines.

A novel differential filtering patch antenna with high selectivity

A novel differential filtering antenna with high selectivity is proposed. The antenna is mainly composed of three different-size patches, a slot, a pair of differential feeding lines, and a line resonator. An air gap is adopted to improve the impedance bandwidth and the filtering performance. The line resonator helps to generate high common-mode (CM) rejection. Owing to the parasitic concave and convex patches, the filtering performance and the bandwidth of the antenna are enhanced. The parasitic concave patch affects the lower band-edge selectivity while the parasitic convex patch influences the upper band-edge selectivity. In addition, the frequencies of two radiation nulls can be controlled independently to achieve two high sharp roll-off rates by adjusting the lengths of the parasitic patches. Considerable impedance matching bandwidth is achieved through an aperture coupling. Finally, a prototype of the differential filtering antenna is fabricated and tested. The measured results are in good agreement with the simulated results, showing an impedance bandwidth of 9.9% and an average realized gain of 7.5 dBi. Besides, two filter zero transmissions located at 3.40 and 3.84 GHz produced two radiation nulls.

Compact bandstop filters using coupled lines and open/short stubs with multiple transmission poles

A compact bandstop filter (BSF) using parallel-coupled lines and open stubs with four transmission poles (TPs) is proposed. Through theoretical equation deduction, the positions of these four TPs can be obtained. Good roll-off skirts and stopband suppression characteristics of the BSF can be realised with the help of multiple TPs. To improve transition band roll-off rates, another BSF with five TPs is designed, where a short-circuited T-stub is loaded on the middle of the above BSF circuit structure. For demonstration, two filter examples with centre frequencies at 2 and 1.8 GHz are implemented with generation of four and five TPs, respectively, for theoretically calculated certification. Good agreement between simulated and measured results validates the design method.

Recent Applications of Interfacial Exciplex as Ideal Host of Power-Efficient OLEDs.

Currently, exploring the applications of intermolecular donor-acceptor exciplex couple as host of OLEDs with phosphorescence, thermally activated delayed fluorescence (TADF) or fluorescence emitter as dopant is a hot topic. Compared to other host strategies, interfacial exciplex has the advantage in various aspects, such as barrier-free charge injection, unimpeded charge transport, and the energy-saving direct exciton formation process at the “Well”-like heterojunction interface region. Most importantly, due to a very fast and efficient reverse intersystem-crossing (RISC) process, such a host is capable of regulating singlet/triplet exciton populations in itself as well as in the dopant emitters both under photoluminescent (PL) and electroluminescent (EL) driving conditions. In this mini-review, we briefly summarize and comment on recent applications of this ideal host in OLEDs (including both thermal-evaporation OLEDs and solution-processed OLEDs) with diverse emitters, e.g., fluorescence, phosphorescence, delayed fluorescence, or others. Special attention is given to illustrate the peculiar achievement of high overall EL performance with superiorities of low driving voltages, slow roll-off rate, high power efficiencies and satisfied device lifetime using this host strategy, which is then concluded by personal perspectives on the relevant next-step in this field.

Design and fabrication of a continuous tunable microstrip lowpass filter with wide stopband and sharp response

Tunable microstrip lowpass filters (LPFs) with a good performance are used in most telecommunication systems. In this article, a third-order circuit with stepped impedance resonator is used to design LPF, and suppression cells are used to improve the performance of the filter in stopbands up to 20 GHz. The −3 dB cut-off frequency can be controlled in the range of 0.35 to 1 GHz with the tuning range of 96%. Rejection stopbands of 30 dB (type-I) and 20 dB (type-II) can be extended to more than 20 GHz. For the passband, the insertion loss variations are in the range of 0.35 to 2.12 dB. The proposed tunable LPF has a sharp roll-off rate (42-96 dB/GHz). The varactor-tuned microstrip LPF is designed, simulated, fabricated, and measured. The results of simulation and measurement for the proposed LPF are in good agreement. The size of the proposed tunable LPF is small and the filter dimensions are equal to 0.267λg × 0.13λg.

Tunable Bandpass-to-Bandstop Quasi-Yagi–Uda Antenna With Sum and Difference Radiation Patterns

A design of the double-element E-plane quasi-Yagi–Uda antenna is proposed offering two different radiation patterns and reconfigurable bandpass-to-bandstop frequency-tunable responses. The double-element antenna covers a wide frequency range that is exploited for the realization of the tunable operation modes. This is achieved by the integration of a pair of bandpass-to-bandstop filters, each of which can be reconfigured using two varactor diodes and one p-i-n diode. The p-i-n diode serves the function of switching between bandpass and bandstop states, and the varactors facilitate the frequency tunability for both states of operation. The bandpass filter provides a continuous frequency tuning function with a minimum rolloff rate of 57 dB/GHz and out-of-band transmission coefficient −1 dB. Importantly, the reconfigurable filtering functionality of the two-element antenna is preserved when fed by a wideband hybrid coupler to produce both the sum and difference radiation patterns. To obtain a high beam symmetry, the antenna elements are fed by the difference ( $\Delta $ ) signal to produce the directive radiation pattern and they are fed by the sum ( $\Sigma $ ) port to produce the null in the main radiation direction. The experimental results validate this concept with a measured tunability of 50.0% for the bandpass state and 50.4% for the bandstop state.

Sharp Skirt Bandpass Filter-Integrated Single-Pole Double-Throw Switch With Absorptive OFF-State

This paper presents a type of bandpass filter (BPF)-integrated single-pole double-throw (SPDT) switch using common shorted stepped-impedance resonator technique. The BPF-integrated ON-state with reverse-biased p-i-n diodes can be synthesized by classical coupled-resonator filter design theory, and the OFF-state with forward-biased p-i-n diodes is detuned which exhibits high OFF-state suppression (OSS). The transmission zeros due to the direct coupled feed, the cross-couplings and the cancelling effect of mixed electric and magnetic coupling are produced to improve the ON-state passband selectivity significantly. As examples, the third-order/fourth-order BPF-integrated SPDT switches at center frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1 GHz with ripple bandwidth of 110/100 MHz are designed, which show low insertion losses of 1.08/1.58 dB, sharp skirts, high roll-off rate of sidebands, high OSSs of 40.9/40.1 dB as well as high port-to-port isolation of 57.4/47.8 dB. Then, the switched 50-Ω matching circuits are in series with two output ports of above BPF-integrated SPDT switches, resulting in the absorptive OFF-state. The fabricated third-order/fourth-order BPF-integrated SPDT switches with absorptive OFF-state have the matched return losses of 30/28.2 dB, and their OSSs and port-to-port isolations are also improved.

Hydrophobic–Hydrophilic Surfaces Exhibiting Dropwise Condensation for Anti-Soiling Applications

Soiling of solar cover glass is a significant challenge that increases the levelized cost of electricity of solar photovoltaic energy through loss of electrical output and/or increased operation and maintenance costs. Hydrophobic coatings can reduce the cost of cleaning, but an external source of cleaning water is still required. Dew, however, can be harnessed to create a self-cleaning glass surface. To efficiently use condensation (i.e., natural dew) to create a self-cleaning glass surface, we fabricated a hybrid hydrophobic–hydrophilic coating, with an array of isolated hydrophilic circular rings. Water roll-off collection rates were measured in a simulated dew environment. The effect of hydrophilic ring geometry (location, arrangement, diameter, distance, and count) was studied to determine the optimal cleaning efficiency. The hybrid surface increased water collection rates by 95% over an uncoated (bare) glass surface and 51% compared with uniformly coated hydrophobic low-iron glass.

Recent Advances in Conjugated TADF Polymer Featuring in Backbone-Donor/Pendant-Acceptor Structure: Material and Device Perspectives.

Along with the persistent research interest in organic light-emitting diode (OLED) display and lighting technology, a new studying topic is now focused on developing thermally activated delayed fluorescence (TADF) polymer emitters, with the purpose to achieve high-performance cost-effective, solution-processed OLEDs (s-OLEDs) purely from fluorescent-type materials. However, research in this topic is in its infancy about the designing rules of polymer structures, photophysical mechanisms and the correlated devices. In this Personal Account, mainly from our personal experience we will shortly introduce the historical developments, status and perspectives about one representative kinds of TADF polymers, i. e. the conjugated TADF polymers featuring in backbone-donor/pendant-acceptor (BDPA) structure scaffold, which shows very promising electroluminescent (EL) performance even using simple s-OLED structure. Special attention is focused on illustrate the molecular designing & synthesis motivation, chemistry & device tactics towards solving the limiting factors about the quantum yields and aggregation-quenching tendency in solid states. Further challenges and strategies towards optimizing their overall EL performance, e. g. simultaneous achieving extremely high external quantum efficiency, power efficiency and low roll-off rate, are also discussed.

Very Sharp Roll-Off Ultrawide Stopband Low-Pass Filter Using Modified Flag Resonator

In this paper, a low-pass filter (LPF) using modified flag resonators to achieve sharp roll-off and an ultrawide stopband up to 18 times the cutoff frequency ( ${f}_{c})$ is presented. To obtain a sharp roll-off, the inductor value of the prototype LC resonator is increased, and two series prototype LC resonators are considered. To realize compact size, the flagpoles of resonators are meandered. On the other hand, the flag resonators with coupling effect as flag-suppressing cells are designed and utilized in the suppressing structure. The implemented LPF with 3-dB cutoff frequency of 1.94 GHz demonstrates a very sharp roll-off rate of 525 dB/GHz, i.e., transition band of 0.07 GHz and ultrawide stopband from 2.01 to 37.5 GHz. The size of the proposed filter is only $0.165\lambda \text{g}\times 0.067\lambda \text{g}$ , where $\lambda \text{g}$ is the waveguide length at the cutoff frequency. The proposed LPF is designed and fabricated. The measured results demonstrate good agreement with simulation results.

Compact D-CRLH resonator for low-pass filter with wide rejection band, high roll-off, and transmission zeros

AbstractA compact low-pass filter (LPF) with wide rejection band based on T-type circuit of an enhanced dual composite right-/left-handed (D-CRLH) resonator is presented in this paper. The resonator has only one cell with series and parallel tank circuit. The parallel LC tank circuit has been realized by an interdigital capacitor and one shorted finger, whereas its series LC tank circuit is realized by an air gap capacitance and a short circuit stub. The filter has wide rejection band bandwidth with three transmission zeros (TZs). The filter bandwidth and TZs frequencies are controlled by the D-CRLH element values. The results of the proposed filter demonstrate minimum insertion loss in passband, high roll-off rate, and good figure of merit. The measured results are in good agreement with the simulated results. The detailed filter design is discussed in terms of circuit modeling, dispersion analysis, and full-wave simulation. Finally, the filter size is compact (0.10 λg × 0.15 λg) at cut-off frequency.

Planar tunable graphene based low-pass filter in the terahertz band.

In this paper, design and analysis of planar graphene-based low-pass filters in the terahertz band are proposed. Using the proposed approach, it is possible to design plasmonic low-pass filters with the desired properties in the form of open stubs. The transfer matrix method is used based on the transmission line model for analyzing filters. The propagation constant and characteristic impedance required for this method are obtained according to the electrostatic scaling law and power-current approach, respectively. A typical fifth-degree low-pass filter is designed and analyzed according to the mentioned process. The frequency response of the low-pass filter indicates insertion loss of less than 2dB, roll-off rate of 17dB/THz, return loss higher than 10dB, and constant group delay of 0.3ps. The results of the full-wave simulation confirm the analytical ones. Also, the theory of graphene equivalent circuit variation to the different chemical potentials is expressed so the filter frequency response can be explicitly predicted for any bias value. These filters, due to their compact structure and integrated electrical and physical shape, are the suitable choice for use in full-integrated planar circuits of terahertz systems.

A New Lowpass Filter Unit Cell with Sharp Roll-off and Improved Stopband Performance in Coplanar Waveguide Technology

In this paper, a new compact unit cell for a coplanar waveguide (CPW) lowpass filter (LPF) is proposed. By combining a pair of coupled parallel stepped impedance resonators (SIRs) and high impedance short stubs in the CPW line, a fifth-order elliptic lowpass filter unit cell (LUC) is designed. The extra transmission zero introduced by parallel coupled SIRs is used to extend the stopband and increase the roll-off rate. The characteristics of the proposed LUC is investigated to achieve a sharp roll-off and a wide stopband. The measured results are in accordance with the simulated results. It has an insertion loss less than 0.9 dB from dc to 6 GHz, and a wide -15 dB stopband from 7.5 to 18 GHz. In addition, the filter dimensions are as small as 4.9 mm × 8.7 mm, that is, 0.046λg2, where λg is the guided wavelength at the cut-off frequency. The filter structure is simple and easy to fabricate as well.

A &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$C$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-Band Compact Wideband Bandpass Filter With High Selectivity and Improved Return Loss

In this letter, a C-band compact wideband bandpass filter (BPF) with high selectivity and improved return loss (RL) is proposed. Two pairs of short-circuited stubs are employed on a transmission-line model to generate three transmission poles and two transmission zeros (TZs), where the odd- and even-mode analysis is used to analyze the resonant frequencies of the BPF. By applying the transversal signal-interference technique, two additional TZs can be generated in the upper and lower stopbands, respectively. The measured results show that the 3-dB fractional bandwidth is 62.8% at the center frequency of 5 GHz. The RL and the insertion loss within the passband are better than 22 and 0.6 dB, respectively. Moreover, the roll-off rate is up to 100 dB/GHz.

Compact microstrip lowpass filter with ultrasharp response using a square-loaded modified T-shaped resonator

A miniaturized lowpass filter (LPF) with ultrasharp response, good figure of merit (FOM), and simple structure is proposed. The designed structure is fabricated and measured with a 2.9 GHz cut-off frequency. The proposed LPF consists of high impedance lines that are loaded by three similar resonators and two uniform suppressing cells. The filter size is only 0.08~$\times $~0.23~$\lambda $g, which indicates small circuit size. The proposed design exhibits good features, such as an ultrasharp roll-off rate of about 1609 dB/GHz and a good FOM of 162,820. The insertion loss of the proposed LPF is less than 0.14 dB in the passband. With these excellent obtained specifications and flat group delay, this structure can be used in wireless antennae.

Solving a combined economic emission dispatch problem using adaptive wind driven optimization

A miniaturized lowpass filter (LPF) with ultrasharp response, good figure of merit (FOM), and simple structure is proposed. The designed structure is fabricated and measured with a 2.9 GHz cut-off frequency. The proposed LPF consists of high impedance lines that are loaded by three similar resonators and two uniform suppressing cells. The filter size is only 0.08~$\times $~0.23~$\lambda $g, which indicates small circuit size. The proposed design exhibits good features, such as an ultrasharp roll-off rate of about 1609 dB/GHz and a good FOM of 162,820. The insertion loss of the proposed LPF is less than 0.14 dB in the passband. With these excellent obtained specifications and flat group delay, this structure can be used in wireless antennae.

Dual-Beam Filtering Patch Antennas for Wireless Communication Application

A dual-beam filtering patch antenna consisting of a slotted patch, a metal strip underneath the patch, two pins, and a ground plane is proposed for wireless communication application. A wide operation band with stable symmetrical dual-beam far-field radiation pattern is obtained, and two radiation nulls at the lower and the upper band edges, respectively, are controlled to ensure a sharp rolloff rate at the band edges for both reflection coefficient and realize gain. Undesired higher modes can be suppressed over the stopband by changing the spacing between the patch and ground pane With entire height of $0.058~\lambda _{0}$ , the proposed antenna is implemented to show a −10 dB bandwidth of 3.0–3.8 GHz, a consistent realized gain of about 6.8 dBi within the passband for both two radiation beams directed at ±30°, out-of-band radiation suppression level of higher than 17 dBi, and good band-edge selectivity.

Taner filter settings and automatic correlation optimisation for cyclostratigraphic studies

Cyclostratigraphy and astronomical tuning utilize the imprint of quasi-cyclic insolation changes in geological records to establish chronologies. In this context, filtering of time series in specific frequency bands is commonly applied to extract information on astronomical forcing from geological datasets. This approach is performed on specific insolation components (precession, obliquity or eccentricity) and sometimes also their amplitudes either in depth or time domain. In this study, we design and apply a simulation technique to determine the optimal Taner filter settings to extract precession-, obliquity- and eccentricity-related interference signals from astronomically tuned geological datasets. This is done by testing a variety of filter settings on several astronomical and artificial datasets. Based on our results, we propose specific filter settings (cut-off frequencies and roll-off rates) for the best extraction of astronomical (interference) signals from tuned geological datasets. Focus here lies on datasets shorter than ca. 1 million years and interference patterns between astronomical components.A second step utilizes these filter settings for an automated alignment, where geological data on a tuned time scale are matched to a suite of astrochronologic correlation targets. This is done by aligning filter minima and maxima to astronomical targets. This approach is particularly useful for the determination of the relative contributions of astronomical parameters in a specific dataset and allows for the automatic determination of phase shifts between well expressed insolation components in datasets.