Third-order Bandpass Research Articles

22/43 GHz low-insertion-loss dual-polarized multi-layer bandpass frequency selective surfaces for millimeter astronomy

We design a frequency selective surface (FSS) capable of transmitting K-band and reflecting Q-band radio waves. The equivalent circuit approach assists the distribution of multi-layer FSS to achieve a third-order bandpass response with an incident angle of less than 30°. The unit structure consists of three metal layers embedded with two dielectric substrates. Especially, the FSS provides a 3 dB transmission bandwidth range from 18.6 to 26.7 GHz with a maximum measured insertion loss of 0.61 dB. Hence the proposed polarization-insensitive FSS with low insertion loss can be applied in the observation system of millimeter astronomy.

Improvement in Power Transmission Efficiency of Wireless Power Transfer System Using Superconducting Intermediate Coil

We have demonstrated that using a high-quality-factor intermediate (IM) coil with a high temperature superconductor (HTS) wire improves the power transmission efficiency (PTE) of a wireless power transfer (WPT) system for long-distance power transmission. The IM coil is placed at the center of Cu transmitting (Tx) and receiving (Rx) coils and consists of a previously developed double-sided HTS coated conductor (CC) wire. A WPT system with the HTS IM coil was designed on the basis of the design theory for a third-order bandpass filter. The measured PTE of the system was compared with that of one with a Cu IM coil. The resonant frequencies of the Tx, Rx, and IM coils in both systems were each about 9 MHz. When the distance between the Tx and Rx coils was 160 cm, the PTEs of the systems were 49.7% and 17.5%, respectively, demonstrating that the PTE of a WPT system can be greatly improved by using an HTS IM coil rather than a Cu one.

Bandwidth-Controllable Third-Order Band Pass Filter Using Substrate-Integrated Full- and Semi-Circular Cavities

The article presents a novel circular substrate-integrated waveguide (SIW) bandpass filter (BPF) with controllable bandwidth. The proposed BPF was configured using two microstrip feed lines, semi-circular SIW cavities, capacitive slots, and inductive vias. The circular cavity was divided into two halves, and the two copies were cascaded. The resulting bisected and cascaded structures were then connected back-to-back. Finally, by introducing two inductive vias to the circular center cavity, a transmission zero was generated. In order to examine the design concept, a coupling matrix was generated. To demonstrate the theory, a third-order BPF was realized, fabricated, and experimentally validated. The BPF prototype features a wide passband of 8.7%, a low insertion loss of 1.1 dB, and a stopband of 1.5 f0 with a rejection level better than 20 dB, which makes it a potential candidate for microwave sensing and communication industries.

On-Chip mm-Wave Second-/Third-Order BPF and Balun With Wide Stopband and Low Radiation Loss Using SIDGS Resonators in 40-nm CMOS

In this article, two millimeter-wave substrate-integrated defected ground structure (SIDGS) resonators are proposed for filters and balun implementation. Such SIDGS resonators are composed of defected ground structure (DGS) with grounded shield and surrounding vias, which not only exhibit wide stopband with low radiation loss but also are flexible to integrate with active circuits. Using different coupling methods, second-/third-order bandpass filters (BPFs) and filtering balun are designed based on the proposed SIDGS resonators. The filters and balun are fabricated in a standard 40-nm complementary metal-oxide-semiconductor (CMOS) technology. The second-order filter is centered at 28 GHz with an insertion loss of the 2.7-and 3-dB FBW of 20.4%. Meanwhile, the stopband extends to 140 GHz with a rejection level of 30 dB. The third-order filter operates at 28 GHz with an insertion loss of the 2.9-and 3-dB FBW of 47%. Meanwhile, the stopband extends to 170 GHz with a rejection level of 27 dB. The filtering balun operating at 25 GHz with the 3-dB FBW of 32% exhibits in-band amplitude/phase imbalances of 0.6 dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 1.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> , respectively. The minimum in-band insertion loss is 2 dB excluding the theoretical 3-dB loss. The stopband extends to 175 GHz with a rejection level of 30 dB.

Peak Power Handling Capability in Groove Gap Waveguide Filters Based on Horizontally Polarized Resonators and Enhancement Solutions

This letter studies the peak power handling capability (PPHC) in groove gap waveguide filters based on horizontally polarized resonators. Moreover, a modification of the resonant cavity is proposed, where the central pins of the original structure are replaced by a rounded metal block. As a result of this change, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> -like mode can still be excited, but the maximum electric field strength is shifted to the center of the cavity, which leads to a higher PPHC. The main advantages of the original structure are maintained, and greater robustness in the manufacturing process is achieved. Next, some guidelines for the design of the coupling windows and the dimensions of the blocks are shown to minimize the electric field strength and, consequently, maximize the PPHC. Finally, two third-order bandpass filters (with pins and with blocks) centered at 16 GHz have been manufactured and tested in a measurement campaign, where a PPHC enhancement of 8.7 dB at high pressures is achieved for the novel solution presented in this work.

Constant absolute bandwidth third-order tunable bandpass filter with reconfigurable bandwidth using single λ/2 resonator

This paper presents a third-order bandpass filter with bandwidth tuning and constant bandwidth center frequency tuning. Based on the analysis of modal voltage waveforms of a varactor-terminated half-wavelength microstrip line, a varactor is loaded at the center to control even modes, four varactors are loaded between two symmetric specific positions to tune, only, odd modes and two varactors at the ends to tune both the even and odd modes. Using these varactors, the passband is formed by bringing the first even and second, third odd modes close to each other. To keep the bandwidth of the passband constant, these three modes are controlled separately. The S-matrix has been derived to analyze and the coupling matrix has been synthesized to design the filter for a specification. An example filter has been designed and fabricated whose band can be tuned from 1.0 to 1.45 GHz (36.73) with absolute bandwidth of 260 MHz and bandwidth is tunable from 130 to 490 MHz.

Compact eighth‐mode ridged substrate integrated waveguide filter

In this letter, a novel eighth-mode ridged substrate integrated waveguide (EMRSIW) is proposed by bisecting the RSIW resonator along the virtual magnetic walls. The EMRSIW shows a size of nearly one-eighth of a conventional RSIW resonator and a significant size reduction compared to the conventional eighth-mode SIW resonator. A prototype of a third-order bandpass filter with transmission zeros has been designed and tested.

Integrated substrate groove gap waveguide and application for filter design

In this article, an integrated substrate groove gap waveguide (Integrated-SGGW) is proposed, which is composed of gap and groove layer in printed circuit board technology, which is considered a highly integrated circuit design technology. Electromagnetic wave is transmitted via the dielectric groove in transverse electric mode. Firstly, the waveguide is analyzed, including dispersion characteristics, transmission characteristics, characteristic impedance and field distribution. Then, the theory of dispersion and characteristic impedance for the Integrated-SGGW are given, and the waveguide is comprehensively analyzed. An Integrated-SGGW is fabricated, verified, and compared with substrate integrated waveguide and other waveguides. To show Integrated-SGGW applications in the design of millimeter wave circuits, a third-order bandpass filter using the Integrated-SGGW is designed, fabricated, and verified.

Tunable bandpass filters with constant absolute bandwidth cascaded trisection topology

A novel cascade trisection (CT) coupling structure, based on half-wavelength resonators, is proposed for designing constant absolute bandwidth (CABW) tunable bandpass filters. The tunable resonators have both electric and magnetic dominant coupling regions with predefined coupling coefficients. The third-order and fifth-order tunable bandpass filters (BPFs), which can realize CABW and a high side cross-coupling transmission zero (Tz), are designed based on the proposed CT structure. Measurement results show that the central frequency tuning of the third-order filter is from 1.47 to 1.83 GHz with −3dB bandwidth of 108.75 ± 2.05 MHz, and the high side 3 to 25 dB attenuation slope is 327.32–623.57 dB/GHz. The tuning range of the fifth-order filter is from 1.45 to 1.92 GHz with −3dB bandwidth of 101.9 ± 1.3 MHz, and high side 3 to 30 dB attenuation slope is 442.75–843.59 dB/GHz.

Transversal Coupled Triple-Mode Spherical Resonator-Based Bandpass Filters

In this letter, we present an innovative filter configuration employing transversal coupled triple-mode spherical resonators while capable of realizing transmission zeros (TZs). Transversal coupling involves simultaneous source and load-controlled couplings to all the three modes of the spherical resonator. Spherical resonators inherently have very large quality factor (Qu) and exhibit a farther spurious response thus yielding bandpass filters (BPFs) with lower insertion loss and wider spurious-free window. The design methodology for transversal coupling is explained and is employed for designing a third-order bandpass filter with TZs. In addition, a sixth-order bandpass filter using cascaded trisection is also presented. A third-order BPF with symmetric TZs is fabricated for verifying proof of the concept. The filter designed at 6.545 GHz with a bandwidth of 120 MHz has an insertion loss better than 0.1 dB and a spurious-free window better than 1.7 GHz. The proposed filter promises to be useful in aerospace applications that demand high Qu, low volume, and wider spurious-free window.

A Third-Order Bandpass Three-Dimensional Frequency Selective Surface with Multiple Transmission Zeros

We present a third-order bandpass three-dimensional frequency selective surface (3D FSS) with multiple transmission zeros in this paper. The unit cell of the proposed 3D FSS consists of an air-filled square waveguide and a cuboid dielectric block with three concentric metallic square loops. Due to its inner electromagnetic coupling in the unit cell, this FSS provides a flat passband with three transmission poles, a wide out-of-band rejection with three transmission zeros, and high frequency selectivity. In order to explain the working principle, an equivalent circuit model is established and investigated. Finally, an FSS prototype is fabricated and measured, and the results exhibit good stability for both TE and TM polarizations under incident angles from 0° to 50°. Besides, this FSS has a relatively compact unit cell.

Multi‐objective control and operation of grid‐connected small hydro‐solar PV‐battery energy storage‐based distributed generation

This work deals with the implementation, control and operation of a reconfigurable small hydro-solar photovoltaic (PV)-battery energy storage (BES)-based distributed generation system (DGS) working in isolated mode (IM) and grid connected mode (GCM). The DGS consists of a hydro generation-based on a PMSG integrated with a PV array supported by the BES. It operates in an IM during the grid outage and when the grid is available, it synchronizes and operates in GCM. A frequency adaptive comb filter-frequency locked loop (FLL)-based control is adopted to estimate errorless phase angles of the hydro generator and grid voltages for quick and accurate grid synchronization. A third-order band pass filter-based control technique is used to extract fundamental component of load currents and determine switching pulses to VSC. The overall multi-objective control is used to maintain voltage and frequency of the system at the point of common coupling during IM and GCM. The power quality of grid and generator currents are maintained at non-linear loads. The modified perturb and observe-based control technique is used to extract maximum power from the PV array and it provides drift-free operation during the change in insolation with de-rating capability to protect the BES from overcharging in IM.

Design Method for Tunable Planar Bandpass Filters With Single-Bias Control and Wide Tunable Frequency Range

A design method for a frequency-tunable planar bandpass filter is demonstrated. With the method, all reasonators can be designed with identical capacitances, allowing the filter to be tuned with identical varactors using a single bias control. This allows not only low-cost fabrication, but also a simple structure and design procedure. Moreover, the filter is based on miniaturized transmission lines. Therefore, a wide tuning range is achieved with a small size and outstanding out-of-band response. Most importantly, the method facilitates the design of a filter to vary the fractional bandwidth in a predetermined way as the center frequency is tuned. Thus, a tunable filter can be designed not only to maintain the fractional bandwidth, but also to expand or to reduce the bandwidth as the frequency is tuned. The experimental results of a compact third-order bandpass filter based on CPW lines with a 0.11λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.8λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> size show a very wide frequency tuning range of 62.8% with a 3-dB fraction bandwidth that remains within 28.65±1.55% and an outstanding spurious suppression of under -40 dB up to as high as 3f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> .

Filtering Doherty power amplifier

At present, it is a trend in wireless communication to integrate conventional separate components into a single one for further miniaturisation and whole performance optimisation. In this study, a novel filtering Doherty power amplifier topology is proposed, which incorporates a bandpass power divider for power division. The power divider is characterised by third-order bandpass response and good out-of-band performance, and then it can purify the input spectrum for the whole amplifier. For demonstration, an example of this filtering Doherty power amplifier at 2.0 GHz was designed, fabricated and measured. The measured results show that at least 21 dB of the out-of-band suppression is obtained up to fourth harmonic for purifying the input spectrum. Meanwhile, high back-off efficiency is still retained for this filtering Doherty power amplifier.

Low-Profile Circularly Polarized Transmitarray for Wide-Angle Beam Control With a Third-Order Meta-FSS

In this article, we develop a low-profile high-gain transmitarray antenna (TA) with a meta-frequency-selective surface (FSS) operating in the X-band. The employed metaFSS element is designed to realize a third-order bandpass filter, which has a high transmission and wide angular stability. A phase difference of 180° can be introduced between the two orthogonal directions with optimized parameters. Based on element rotation theory, the meta-FSS elements are arranged with the desired rotation angles to convert the incident quasi-spherical wave to the outgoing plane wave with the reverse polarization, e.g., a left-hand circularly polarized (LHCP) wave to a right-hand circularly polarized (RHCP) wave. To experimentally validate the focusing ability and wide-angle beam control ability of the proposed structure, principle prototypes are designed, fabricated, and measured. The experimental results show that the full transmitarray can achieve a 1 dB gain bandwidth of 13.0%, an aperture efficiency of 40.2%, and a 3 dB axial ratio bandwidth of 24.0% in the broadside direction. In addition, good circular polarization radiation performance can be successfully realized with the proposed structure at beam tilt angles from θ = 0° to 600°.

Compensation control and parameters design for high frequency resonance suppression of MMC-HVDC system

Large time delay is one of the inherent features in modular multilevel converter (MMC) based high voltage direct current (HVDC) system. It is the main factor leading to the unfavorable ‘negative resistance and inductance’ characteristics of MMC impedance. Researches indicate that such unfavorable characteristics interacting with the capacitive characteristics of AC system is the reason causing high frequency resonances (HFRs) in YuE HVDC project. As the current controller is one of the main factors to shape the MMC impedance, a compensation control to imitate the paralleled impedance at point of common coupling (PCC) is proposed. Therefore, the structure and parameter design of the compensation controller are the core to realize HFRs suppression. There are two potential risky frequency ranges of HFRs (around 700Hz and 1.8 kHz) in the studied AC system within 2.0 kHz. The core concept of HFRs suppression is to make the phase angle of MMC impedance smaller than 90° in the two risky frequency ranges according to impedance stability theory. Hence, the parameters designing are to coordinate the phase angle of MMC impedance in the two risky frequency ranges. In this paper, three types of compensation controller are studied to suppress HFRs, namely, first-order low pass filter (LPF), second-order LPF, and third-order band pass filter. The results of parameters design show that the first-order LPF cannot suppress the both HFRs simultaneously. The second-order LPF can suppress the both HFRs. However, it will bring DC component into the current control loop. Therefore, a high pass filter is added to form the recommended third-order controller. All the parameter ranges of compensation controller are derived using analytical expressions. Finally, the correctness of the parameters design is proofed by the time-domain simulations.

A Compact Dual-Wideband Bandpass Filter Based on Open-/Short-Circuited Stubs

A dual-wideband bandpass filter is proposed and analyzed, which is based on loaded open-/short-circuited stubs. The dual-band filter consists of a second-order bandpass filter and a third-order bandpass filter, which can be designed separately. The bandwidth of two passbands can be adjusted by tuning the impedance and the length of the stubs. A dual-band bandpass filter prototype operating at 2.4/5.2 GHz is designed for demonstration. It shows a low insertion loss of 0.3 dB and wide bandwidth of 51.9% at 2.4 GHz and 23.3% at 5.2 GHz. The filter structure is simple without narrow coupling gap between resonators, which is easy for fabrication.

Compact bandpass filter with wide-stopband using substrate integrated waveguide cavities and short-circuited coplanar line

AbstractThis article presented a compact bandpass filter with wide-stopband performance. Two substrate integrated waveguide (SIW) cavities and a short-circuited coplanar line introduced between the two cavities are used to realize a compact third-order bandpass filter. The passband is generated by combining the resonant frequency of TE101 mode of the SIW cavities and the fundamental resonant frequency of the short-circuited coplanar line. The size of the proposed filter reduces significantly in comparison with conventional third-order SIW filters. Moreover, the center frequency (CF) and the bandwidth of the filter can be controlled by adjusting the structural parameters of the filter. In addition, the first higher-order mode TE102 of the SIW cavity is suppressed by minimizing the coupling of TE102 mode in order to obtain wide-stopband performance. The proposed filter is designed, fabricated, and measured, and the simulation and measurement results show a good agreement. The filter exhibits compact size, low loss, and a rejection higher than 20 dB up to 1.94f0.

Spurious harmonic suppression in compact coupled-line bandpass filter with asymmetric perturbations

ABSTRACTPresent article exhibits the design of a third-order compact parallel-coupled line bandpass filter at 5.25 GHz having asymmetric perturbations to suppress the second harmonic. Initially, the effects of compactness on filter characteristics have been studied by synthesising the distributed filter network into its equivalent circuit model. The design has been initiated by computing the unit cell model, which leads to the first-order and third-order design instances with an improvement in compactness over the traditional parallel-coupled line filter. In contrary, compactness in the filter characteristics degrades the second harmonic level subject to enhanced imbalances among the odd- and even-mode velocities at the coupled lines. Subsequently, the improvement in the harmonic suppression of 53 dB and 58 dB has been achieved by incorporating different non-uniform perturbations to the outer and coupled edges of the compact filters. Accordingly, compactness of 58% and 71% have been obtained subject to the folded and in-line designs over the conventional layout.

Design of Wideband Third-Order Bandpass Filters Using Broadside-Coupled Resonators in 0.13-$\mu$ m (Bi)-CMOS Technology

In this paper, two third-order bandpass filters (BPFs) designed for millimeter-wave applications are presented. Unlike previously published ones, the proposed designs use a “cell-based” approach, which utilizes identical broadside-coupled resonators (BCRs) with series and shunt capacitors. The capacitors are mainly used as $J$ -inverters to achieve the desired frequency responses. To fully understand the operational mechanism of the presented approach, both the BCR and BPFs are analyzed using the simplified LC -equivalent circuit models. To prove the concept, both BPFs are implemented in a standard 0.13- $\mu \text{m}$ silicon–germanium bipolar complementary metal–oxide–semiconductor technology. According to the on-wafer measurement results, the BPFs exhibit the excellent performance including flat in-band responses with relatively large harmonic suppression. The first design has a 1-dB bandwidth from 23.9 to 39.7 GHz with an insertion loss of 3.9 dB at the center frequency of 31 GHz. The stopband attenuation is better than 45 dB at 58 GHz. The 1-dB bandwidth of the second design covers from 26.7 to 44.3 GHz with an insertion loss of 3.1 dB at the center frequency of 35 GHz, and stopband attenuation up to 35 dB is achieved at 59 GHz. Both designs occupy an identical area of 0.073 mm2 ( $0.248\times0.294$ mm2), excluding the G–S–G testing pads.