Rejection Bandwidth Research Articles

Diplexer-Integrated SPDT Switches With Multiple Operating Modes Using Common Fractal Stub-Loaded Resonator

This article presents a method to design new diplexer-integrated single-pole double-throw (SPDT) switches for composite time division duplexing (TDD) and frequency division duplexing (FDD) requirements. The common fractal stub-loaded resonator (F-SLR) is employed to provide four magnetic coupling paths to introduce the mixed electric and magnetic coupling (MEMC) for every channel. Together with the cross-couplings, the ON-state channel with high selectivity bandpass response can be achieved. As examples, a third-order diplexer-integrated SPDT switch and a fourth-order diplexer-integrated SPDT switch operating at 0.9/1.8 GHz are designed and fabricated. These two diplexer-integrated SPDT switches have three major operating modes, i.e., the 0.9-GHz bandpass filter (BPF)-integrated SPDT switch operating mode, the 1.8-GHz BPF-integrated SPDT switch operating mode, and the 0.9-/1.8-GHz diplexer-integrated SPDT switch operating mode. In the design, the loaded positions of p-i-n diodes on the uniform impedance resonators of 0.9-GHz channel are optimized to improve the OFF-state rejection bandwidth. Measured results also show that these two diplexer-integrated SPDT switches have low ON-state passband insertion loss, high port-to-port isolation, and compact circuit size.

Miniaturized tunable bandstop filter using multilayer technology

AbstractA new type of miniaturized tunable bandstop filter (BSF) based on multilayer technology is presented in this letter. One of the transmission zero could be individually tuned by replacing an outer replaceable element, which can be considered as part of the inner resonant cell of the bandstop filter. Thus, a tradeoff between the stopband rejection depth and bandwidth can be conveniently realized according to different applications. A bandstop filter works from 3.1 to 4.2 GHz has been designed and fabricated in a low temperature cofired ceramic (LTCC) substrate to verify the proposed concept. By virtue of the LTCC multilayer technology, the filter occupies a very compact volume of 2.0 mm × 1.2 mm × 0.8 mm.

Design, fabrication, and performance analysis of corporate feed filtenna array using complementary split ring resonators

AbstractThis paper presents the design of a unique “corporate feed‐microstrip filtenna array” to be used as “radiating antenna” of a wireless system. The filtenna is a basic patch antenna fed by 50 Ohms microstrip line, loaded with complementary split ring resonators (CSRRs). When the basic patch antenna is made to resonate at 1.8 GHz, it also introduces unwanted spurious radiations appear at 2.82 and 3.46 GHz. Hence, the array of CSRR consisting of five non‐identical CSRRs are loaded, offers the required wideband rejection characteristic, solving the problem of the basic patch antenna. The five CSRRs resonate at 1.97, 2.43, 2.9, 3.28, and 3.72 GHz, offering an overall rejection band from 2 to 4 GHz is obtained. Incidentally there is a signal attenuation introduced by the passive CSRR filter. To compensate the attenuation, an array of filtenna is designed, using corporate feed configuration. The patch antenna, CSRR filter and filtenna are designed and fabricated on an epoxy flame retardant glass substrate (FR4) having a thickness 'h' of 1.6 mm, dielectric constant 'εr' of 4.4 and loss tangent (tan δ) of 0.02. The simulations are carried out using the HFSS software. The performance of the overall receiving filtenna system, having the size of 13.37 cm × 11.94 cm, is satisfactory. Experiments are carried out using vector network analyzer, verifying the software results. This unique radiating antenna exhibits acceptable gain and noise free reception, much required by upcoming 4G/5G wireless applications, rectenna and medical sensor applications.

A K-Band High Interference-Rejection GaAs Low-Noise Amplifier Using Multizero Control Method for Satellite Communication

This letter presents a 17.5–22.5-GHz low-noise amplifier (LNA) with the high out-of-band rejection in the range of 27.5–32.5 GHz and 4–10 GHz by using 90-nm GaAs p-HEMT technology. The multizero control method is proposed to produce multiple zeros for generating the high out-of-band rejection and expanding the rejection bandwidth. The multizero control is realized by bypass capacitor notch filters at the drain of transistors and shunt capacitor notch filters at the interstage matching circuits. By using this approach, the high rejection can be achieved at unwanted frequencies without additional devices. Also, the multizero control is mainly implemented in the transistor’s bypass branch, which can achieve the low noise figure (NF) well within the whole operating band. The cost and integration of the front end can also be improved. The measured maximum gain is 23.9 dB at 19 GHz, and the 3-dB bandwidth is 17.5–22.5 GHz. The good interference rejection of the proposed LNA is from 57 to 73 dB and 61 to 72 dB in the range of 4–10 GHz and 27.5–32.5 GHz, respectively. The measured NF is 1.1–1.3 dB. The LNA area is 2 mm $\times1.3$ mm including pads.

Coplanar waveguide low pass filter based on square complementary split ring resonator with wide rejection

In this paper, we present a novel coplanar waveguide low pass filter (LPF) structure based on the use of square complementary split ring resonators (CSRRs) in order to enhance the performances of a low pass filter. Especially, to enlarge the bandwidth of the LPF, the insertion losses and to increase the rejection of the LPF. The CSRRs are optimised and inserted periodically along the center conductor of the CPW line with a CPW ground integrating stubs permitting to enlarge the bandwidth. The simulation results of this filter show a -3 dB cut-off frequency equal to fc = 5.28 GHz. The designed filter has a good rejection in the stop band which below -20 dB and presents a good insertion loss in the bandwidth. The proposed filter has been fabricated and tested which give a good agreement between simulation and measurement results, the whole dimensions of the validated filter are 35.48x21.16 mm2. The originality of this work is the wide rejection band and the miniature dimensions. © 2020, Universitas Ahmad Dahlan.

A Fully Integrated FVF LDO With Enhanced Full-Spectrum Power Supply Rejection

This article presents a fully integrated flipped voltage follower (FVF) based low-dropout (LDO) regulator with enhanced full-spectrum power supply rejection (PSR) and unity-gain bandwidth over 400MHz for noise-sensitive circuits. Following the study of three types of FVF LDO's PSR performances, we propose a novel FVF LDO with a low-gain fast loop-1 and a high-gain slow loop-2. In prior FVF LDOs, their PSRs are either full-spectrum, or not, but with low PSR at low frequency. In this article, we fully utilize both dc gains of loop-1 and loop-2 for the low-frequency PSR, while the high-frequency PSR remains unchanged. In addition, we use dynamic compensation to push the loop-2's UGB to higher frequency for a better PSR bandwidth. This work, fabricated in 65 nm complementary metal oxide semiconductor (CMOS), with 1.2-V input and 1-V output, exhibits a measured quiescent current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</sub> ) varying from 27 to 82 μA for a load current I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LOAD</sub> between 5 μA and 20 mA. The circuit achieves a low frequency PSR of -58 dB with the worst full-spectrum PSR of -9 dB in 20 mA I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LOAD</sub> with a 300 pF on-chip output capacitor. Further, with an UGB over 400 MHz, the proposed FVF LDO reaches 0.9 ns response time when I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LOAD</sub> changes between 100 μA and 20 mA with edge times less than 0.8 ns.

Compact Mechanically Tunable Microstrip Bandstop Filter With Constant Absolute Bandwidth Using an Embedded Metamaterial-Based EBG

A mechanically tunable, constant-absolute-bandwidth (ABW) bandstop filter is realized using the metamaterial-based electromagnetic bandgap structure (MTM-EBG). The MTM-EBG is embedded within a microstrip (MS) line and used to produce a bandstop filtering response, with a topology that is compact, uniplanar, and fully printable. A three-cell MTM-EBG-based MS bandstop filter is designed and experimentally verified for operation centered at 4.18 GHz with a 10-dB rejection bandwidth of 247 MHz. This filter is then made tunable by placing a dielectric plate directly on the surface of the MTM-EBGs. Moving this plate across the surface of the MTM-EBGs changes their reactive loading and, consequently, shifts their response. To ensure a constant ABW, the dielectric plate is perforated to produce an effective plate permittivity that varies for each unit cell. The tunable filter is then fabricated, with the dielectric plate applied to the MTM-EBG-based bandstop filter using a 3-D printed superstructure. A tuning range of 3.80 GHz ± 6.2% and a 10-dB bandstop ABW of 244 MHz ± 1.3% are demonstrated, showing good agreement with the simulated data. The MTM-EBG-based tunable bandstop filter has a variation in ABW comparable to 3-D filters (which typically have substantially lower variation in ABW than fully planar filters) while occupying substantially less area than alternate planar realizations.

Ultraminiaturised Polarisation Selective Surface (PSS) for dual‐band Wi‐Fi and WLAN shielding applications

This study reports on a highly miniaturised polarisation selective surface (PSS) for dual-band Wi-Fi and WLAN applications. The proposed unit cell consists of two independently tuneable square loops. The outer loop is split with a gap of 0.2 mm to introduce polarisation selectivity and miniaturisation for lower-frequency band of 2.5 GHz. The inner square loop is inductively loaded with arms to suppress 5.45 GHz frequency band. These configurations have resulted in a unit element size of at 2.5 GHz, which is not presented before to the best of the authors' knowledge. A wide rejection bandwidth () of more than 600 and 1180 MHz is obtained around 2.5 and 5.45 GHz, respectively. Furthermore, the proposed PSS exhibits an excellent polarisation selective characteristic by generating two stopbands at 2.5 and 5.45 GHz when illuminated by horizontal (TM) incident waves, whereas vertically (TE) polarised incident waves result in the generation of passbands for these two frequencies. Numerical validation through equivalent circuit modelling of the proposed PSS has also been carried out. A finite prototype containing elements is fabricated and tested. The measured results demonstrated that the PSS has excellent potential for applications that employ polarisation separators and wave generators.

Design of Microstrip Filters Using Paired Fan-Shaped Capacitors with Controllable Transmission Zeros

ABSTRACT In this paper, microstrip filters using paired fan-shaped capacitors with controllable transmission zeros are proposed. The paired capacitors are employed to replace the conventional single capacitor to reduce parasitic self-inductance. As a result, the rejection bandwidth and level have both been improved. In the simulated and measured results, several transmission zeros (TZ) have been created in the stopband without any jitters. The frequencies of TZs have been derived in the analysis process using the equivalent circuit. The out-of-band TZs can be controlled flexibly with the component values. The proposed method can be utilized to control the position of out-of-band transmission zeros flexibly to increase figure of merit (FOM) of low-pass filters.

A Robust Fusion Method for Motion Artifacts Reduction in Photoplethysmography Signal

Robustness of estimating cardiorespiratory parameters from photoplethysmography (PPG) signal is highly dependent on the quality of the signal, which is heavily affected by motion artifacts. To increase the estimation accuracy of cardiorespiratory parameters, this article describes a novel fusion method to efficiently and effectively reduce the motion artifacts from the acquired PPG signal. The proposed fusion technique requires simultaneously acquiring data from a PPG sensor and accelerometer. To filter out the frequencies associated with motion, the method uses stopband filters with a central rejection frequency and bandwidth determined by the output signal of the accelerometer. Under such conditions, the proposed method to remove the motion artifacts does not depend on the quality of the reference signal and has almost no impact on the nature of PPG signals (i.e., amplitude, baseline, and periodicity). The effectiveness of the proposed method in the suppression of in-band and out-of-band frequencies of motion is numerically and experimentally evaluated. It is shown that the filtered PPG signal has sufficient information to estimate different cardiac parameters such as heart- (HR), respiration rate (RR), and blood oxygen saturation (SpO2). The motion artifact-free PPG signal obtained using our proposed method can estimate HR, RR, and SpO2 with an accuracy of above 95%. This level of accuracy confirms the usefulness of the proposed fusion method for accuracy improvement of cardiorespiratory parameters monitored by the filtered PPG signal.

CGR-QV: A virtual topology DTN routing algorithm based on queue scheduling

In this paper, we proposed a CGR-QV algorithm in order to solve the problems of low message delivery rate and low throughput problems in deep space communication networks, which are caused by the high delay, asymmetric data transmission rate, and frequent topology switching characteristics. The proposed method separate different message types in the queues, establish the relationship between TTL, wait time and Hurst to prevent the phenomenon of "starvation" and redundancy. In view of the impact of congestion on the network, improved algorithm use the Elastic load balancing strategy establish the relationship between optimal thresholds α and network performance reliability. Simulation result show that the algorithm has improved in throughput as about 19%, message delivery rate improved as about 7.5% and bandwidth rejection rate decreased as about 4.7%, the algorithm can balance the impact of topology updates and resource consumption better in space communication networks.

Progress of liquid crystal adaptive optics for applications in ground-based telescopes

ABSTRACT Liquid crystal (LC) adaptive optics systems (AOS) can potentially be used in ground-based large aperture telescopes, because of their high spatial resolution, low cost and compact size. However, their disadvantages, such as low energy efficiency and slow response speed, still hinder their application. In this paper, we demonstrate solutions to these problems. With newly synthesized fast nematic LC material and using an overdriving technique, the response time of a LC wavefront corrector was reduced to 0.75 ms. Under an open-loop control scheme, a novel optical system was designed to improve the energy efficiency of LC AOS. With those problems resolved, a LC AOS was built for a 1.23-m telescope. This system has a disturbance rejection bandwidth of 80 Hz, and could fully use the energy of 400–900 nm wavebands. Observation results showed that the diffraction limit resolution imaging of the telescope could be obtained after correction, which indicates that the LC AOS is ready to be used in ground-based telescopes for visible waveband imaging.

A Compact Dual-Mode Bandpass Filter with High Out-of-Band Suppression Using a Stub-Loaded Resonator Based on the GaAs IPD Process

In this letter, a compact dual-mode bandpass filter (BPF) with an ultra-wide stopband that employs two folded open-loop resonators (FOLRs) and stub-loaded resonators (SLRs) is proposed. The dual-mode resonators are optimized by loading two SLRs onto the folded open-loop resonators, and this process is analyzed using the dual-mode theory. To miniaturize the device size and increase chip performance, the proposed BPF is fabricated by a III–V compound semiconductor-fabrication process using a high-performance GaAs substrate based on the integration passivation device (IPD) fabrication process. A compact dual-mode BPF with low insertion loss and high return loss is designed and fabricated. Two extra transmission zeros (TZs) located in the high-frequency range increase the wide stopband, and the two TZs near the passband result in a higher selectivity. A resonant frequency centered at 7.45 GHz with an insertion loss of −1.21 dB and a measured return loss of higher than −23.53 dB and 3 dB fractional bandwidths of 5.8% are achieved. The stopband can be suppressed up to 20 GHz owing to the two tunable TZs resulting in higher selectivity and wideband rejection. The size of the filter was drastically optimized using a simplified architecture of two FOLRs and SLRs.

Design of a miniaturized tri-band bandstop filter using spur microstrip lines and via-hole grounding

PurposeThe purpose of this paper is to propose a miniaturized tri-band bandstop filter that finds application in a modern dense communication system where size and multi-band plays a vital role.Design/methodology/approachIn this paper, the authors propose a miniaturized tri-band microstrip bandstop filter which combines the conventional bandstop filter and spur microstrip line structures such that this design achieves tri-band operation at 1.8 GHz and 3 GHz. The overall length of the microstrip filter is found to reduce from 126 to 45 mm because of introduction of spur lines and via-hole grounding. The addition of spur lines replaces two resonators, introduces two additional resonant frequencies and enhances the −6 dB bandwidth of the center frequency by 14 %.The addition of via-holes in each resonator reduces its length into half of its original length, thereby reducing filter size.FindingsResonance occurs at three different frequencies 1.8, 2.4 and 3 GHz. The filter size reduces from 126 to 45 mm, and the −6 dB rejection bandwidth of center frequency improves by 14 %.Originality/valueThe overall filter size is reduced by 65% and it resonates at three different frequencies 1.8, 2.4 and 3 GHz with an improved bandwidth of 10 % around the center frequency.

Angularly Stable Bandpass Frequency Selective Surface Based on Metasurface

A novel bandpass frequency selective surface (FSS) working at 2.4 GHz is proposed in this paper based on metasurface with independent-polarization, wide rejection band and good angular stability. The 10-dB upper stopband could cover 3.35-9.4 GHz with a fractional bandwidth of 94.9%. In addition, the filtering response could remain stable under different polarizations and incidence angles. Parameter analysis and equivalent circuit model are illustrated to explain the resonance behavior of the proposed FSS. It is demonstrated that the lower resonant point in the stopband could be tuned independently by changing the length of small rectangular patches in the top layer. While the higher resonant point could be changeable independently by adjusting the diameter of circular gap in the bottom layer. A prototype of the proposed FSS is fabricated and its simulated results are coincided with measurements.

Control System Loop-Shaping as a Mathematical Optimization Problem: An Ensemble of Models

This paper proposes an extension to the established loop-shaping method, where the loop-shaping method is modeled mathematically and solved as a mathematical optimization program. In this process, a novel cost function is proposed and employed as the objective of optimization in the controller tuning problem. This cost function evaluates different characteristics of the system in the frequency domain, such as the stability margins and the operability bandwidth. These characteristics reflect the quality of load disturbance rejection, set-point tracking, and operability bandwidth of the control system. Consequently, the proposed technique circumvents running a time-domain simulation completely. More importantly, the proposed technique can be used with any controller structure. The generic cost function can be customized to fit any control objective and application. This is conducted in the second half of this paper, with the aim of obtaining a system with near-optimum time-domain performance with respect to the integral of time times absolute error (ITAE) criterion. At the same time, the control system obtained with the customized cost function has better operability bandwidth than that of a system optimized in the time-domain for the ITAE criterion. The proposed optimization model is analyzed for two plant models: first order and second order plus dead-time (FOPDT), (SOPDT), respectively.

A Fully Integrated K-Band Dual Down-Conversion Receiver for Radar Applications in 90 nm CMOS

A fully integrated K-band dual down-conversion receiver for phased array radar applications in 90 nm CMOS is presented. The receiver utilizes the dual down-conversion architecture to achieve superior performance. The integrated 1.15 GHz image-rejection filter (IRF) provides enough wideband (22 MHz) image rejection ratio at 140 MHz offset before the second down-conversion by utilizing the Q-enhancing and frequency staggering techniques to compensate the component loss. The low noise amplifier realizes the single-to-differential-ended conversion at the input with a transformer and achieves good common-mode rejection. The 70 MHz intermediate frequency baseband consists of two cascaded 3rd-order band-pass active RC filters (BPFs) and one automatic gain control (AGC) loop, with the integrator frequency compensation technique to lower down the requirements on the embedded Op-Amps. Two phase-locked loop (PLL) frequency synthesizers are integrated to provide the local oscillation (LO) signals for the down-conversions, where the matching of the charge-pump is improved by adding one extra current compensation branch. The measurements of the prototype show that the receiver converts the targeted mm-wave signal to 70 MHz intermediate frequency while achieving 8.3 dB noise figure (NF), 51-95 dB variable gain range and >45 dB image rejection ratio at 140 MHz offset with >22 MHz signal bandwidth. The receiver draws 74 mA current (excluding 2 PLLs) from the 1.2 V power supplies and occupies a core area of 4.58 × 0.53mm 2 (excluding 2 PLLs).

Active Damping of Parallel Robots Driven by Elastic Cables using On-Off Actuators through Model Predictive Control Allocation

This work studies the vibration rejection on elastic cable-driven parallel robots (CDPRs). Additional cold-gas thrusters are embedded on the robot in order to improve the rejection bandwidth. Such Unilateral Force Generators (UFGs) work as on-off actuators. Under the framework of optimal control, a Model Predictive Control (MPC) is designed to compute the control law and allocate the control signals to the available actuators by assigning their binary on-off states, thus forming a Mixed Integer Quadratic Programming (MIQP)-based MPC controller. Simulations highlight the benefits of the proposed predictive approach that yields a better rejection, fuel efficiency, and a reduced switching between ON and OFF states with respect to previous approaches.

Planar Wideband High-Selectivity Impedance-Transforming Differential Bandpass Filter With Deep Common-Mode Suppression

In this brief, a novel balanced filter named impedance-transforming differential bandpass filter (ITDBPF) is proposed, which is the first differential device to realize both wideband impedance transformation and bandpass filtering simultaneously. A core block consisting of cascaded transmission lines and parallel stubs forms this presented circuit with two additional open stubs. Under differential-mode excitation, the transfer function of the equivalent circuit is the same as the one of Chebyshev, and the filtering characteristics are obtained corresponding to the specified filtering parameters. The open stubs increase multiple transmission zeros under common-mode excitation to greatly broaden the bandwidth of common-mode rejection. To verify the proposed theory, a wideband balanced filter centered at 2 GHz with a theoretical 3-dB bandwidth of 72% is designed and measured to prove the correctness of the design theory.

Design and Synthesis of Band-Pass Frequency Selective Surface With Wideband Rejection and Fast Roll-Off Characteristics for Radome Applications

In this article, we proposed an equivalent circuit-based design to synthesizing second-order band-pass frequency selective surfaces (FSSs) with wide out-of-band rejection and fast roll-off characteristics. An equivalent circuit model (ECM) is established in order to depict the desired frequency response. Then, based on the ECM, a generalized composite structure comprised of three FSS arrays separated by two dielectric substrates is proposed. The main advantage of this method is that it allows us to acquire optimized structural parameters according to the desired frequency response. With this method, an FSS based on the proposed composite structure is designed. The designed FSS can provide a second-order pass-band within the stop-band ranging from 1 to 40 GHz and the pass-band is operating at 10 GHz with 12% fractional bandwidth. Meanwhile, the bandwidth of the two transitional bands on both sides of the pass-band is only 0.26 and 0.6 GHz, respectively. Also, the frequency response of the designed FSS is stable at 60° for both TE and TM polarizations. For further verification, an FSS prototype is fabricated and experimentally characterized. Good agreements between the simulated and measured results can be observed.