Quasi-elliptic Bandpass Response Research Articles

A Wideband Energy Selective Surface With Quasi-Elliptic Bandpass Response and High-Power Microwave Shielding

A Wideband Energy Selective Surface With Quasi-Elliptic Bandpass Response and High-Power Microwave Shielding

Frequency-Selective Surfaces With Quasielliptic Bandpass Response for Filtering FRA Application

Frequency-Selective Surfaces With Quasielliptic Bandpass Response for Filtering FRA Application

A High Selectivity and High Efficiency Filtering Antenna With Controllable Radiation Nulls Based on Stacked Patches

A high selectivity and high efficiency filtering antenna is presented in this communication. A double-layer filtering patch antenna is first proposed, which can generate a radiation null due to the mixed electric and magnetic coupling between the two patches. By changing the length of the slot line on the patch, the position of the radiation null can be flexibly set at the lower band edge or upper band edge. Based on this mechanism, a three-layer patch antenna with two radiation nulls is designed. Two radiation nulls are introduced on both sides of the passband, consequently, a quasi-elliptic bandpass response can be obtained. Moreover, the proposed antenna features high efficiency since no extra filtering circuit is utilized. A prototype antenna operating at 1 GHz is designed, fabricated, and measured for validity verification. The measured results agree well with the simulated one, showing that the prototype antenna has a fractional impedance bandwidth of 16% (0.91–1.07 GHz), a flat passband gain response with peak value of 8.83 dBi, a high efficiency about −0.41 dB in the passband. The band-edge selectivity is highly improved by the radiation nulls near the passband edge.

A Novel Single-Feed Filtering Dielectric Resonator Antenna Using Slotline Stepped-Impedance Resonator

A novel single-feed filtering dielectric resonator antenna (FDRA) with quasi-elliptic bandpass response is proposed in this brief. The proposed FDRA consists of a shunted slotline stepped-impedance resonator (SSIR), a rectangular dielectric resonator antenna (DRA) and a microstrip feedline with a pair of transverse arms. The antenna is excited in the fundamental TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{11\delta }$ </tex-math></inline-formula> mode, the transverse arm mode and the two SSIR modes. Moreover, three radiation nulls are produced near the edges of the passband by the SSIR and the transverse arm of microstip feedline, respectively. A prototype FDRA is fabricated and measured, which offers a bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$| S_{11} | &lt; -10$ </tex-math></inline-formula> dB) of 21.14% (3.13 - 3.87 GHz), and a peak realized gain of 5.3 dBi within passband. The realized gain shows a decline of 20 dB at passband-edge, which exhibits high selectivity.

High Roll-Off Frequency Selective Surface With Quasi-Elliptic Bandpass Response

A high roll-off, third-order frequency selective surface (FSS) with quasi-elliptic bandpass response is presented. It is based on substrate integrated waveguide technology. Its unit cell includes three cavities that support at the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> mode. Interactions of resonators are dominated by magnetic couplings. The coupling matrix is analyzed and used to design FSS. Guidelines for a coupling-matrix-based FSS design are given. Transmission zeros realized close to the lower and upper narrow passband lead to high roll-off characteristics. In addition, a cross-polarization feature is easily achieved. Finally, a prototype is designed and fabricated to validate the proposed structure. A stable frequency response in passband has been obtained with an oblique incidence of 40° for TE polarization. Good agreement between the simulated and measured results verifies the design concept of bandpass FSS.

Frequency Selective Surface With Quasi-Elliptic Bandpass Response Using Radiation Null of Patch Antenna

A novel design of bandpass frequency selective surface (FSS) with high selectivity is proposed based on the antenna-filter-antenna (AFA) concept. Traditional AFA-based FSSs improve filtering performance by adding the order of resonator or the coupling paths. On account of the reciprocity theorem, transmission zeros are here introduced by the antenna's radiation null. The proposed FSS consists of two patch antennas connected with one pin and a C-type slot on the ground. The aforementioned structure generates two controllable radiation nulls related to the lengths of slots without any extra circuits. Therefore, two transmission zeros at both edges of the passband can be controlled by adjusting the dimension of slots. A prototype is fabricated and measured. Numerical simulation and measured results are in good agreement, which demonstrates that the proposed AFA-based FSS exhibits a quasi-elliptic bandpass response and a low profile.

Millimeter-Wave Dual-Polarized Filtering Antenna for 5G Application

This article presents a novel dual-polarized millimeter-wave (mm-Wave) patch antenna with bandpass filtering response. The proposed antenna consists of a differential-fed cross-shaped driven patch and four stacked parasitic patches. The combination of the stacked patches and the driven patch can be equivalent to a bandstop filtering circuit for generating a radiation null at the upper band edge. Besides, four additional shorted patches are added beside the cross-shaped driven patch to introduce another radiation null at the lower band edge. Moreover, by embedding a cross-shaped strip between these four stacked patches, the third radiation null is generated to further suppress the upper stopband. As a result, a quasi-elliptic bandpass response is realized without requiring extra filtering circuit. For demonstration, a prototype was fabricated with standard PCB process and measured. The prototype operates in the 5G band (24.25-29.5 GHz) and it has an impedance bandwidth of 20%. The out-of-band gain drops over 15 dB at 23 and 32.5 GHz, respectively, which exhibits high selectivity. These merits make the proposed antenna a good element candidate for the 5G mm-Wave massive MIMO applications to reduce the requirements of the filters in the mm-Wave RF front ends.

Quasi‐elliptic bandpass filtering power divider with ultra‐wide stopband

In this Letter, a novel filtering power divider with second-order quasi-elliptic bandpass response is proposed, which has two transmission zeros near to the passband for sharp frequency selectivity. In addition, it is featured by ultra-wide stopband owing to specific topology. For demonstration, a filtering power divider example operating at 3.1 GHz is designed, fabricated and measured. Its 3 dB fractional bandwidth is about 11.9%, and the in-band isolation between two output ports exceeds 20 dB. Specifically, more than 21 dB out-of-band suppression is achieved from the upper side of the passband to 4.8f 0, and more than 12 dB suppression is achieved to at least 20f 0. The measurement agrees well with the simulation.

A Compact Quasi-Isotropic Dielectric Resonator Antenna With Filtering Response

A compact quasi-isotropic dielectric resonator (DR) antenna (DRA) with filtering response is first investigated in this communication. The cylindrical DRA is fed by a microstrip-coupled slot, exciting in its HEM11δ mode which radiates like a magnetic dipole. A small ground plane is used for this DRA and it radiates like an electric dipole. The combination of the two orthogonal dipoles leads to a quasi-isotropic radiation pattern, with gain deviation as low as 5.8 dB in the 360° full space. To integrate the filtering function, the microstrip feed-line and the ground plane are turned upside down, and further two stubs with different lengths are used together to excite the DR. Due to the different loading effects of the feeding stubs, two resonances of the DR HEM11δ mode are excited in the passband, effectively enhancing the bandwidth of DRA (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 20) to 7%. Furthermore, two controllable radiation nulls are generated by the DR loaded microstrip feed-line, bringing about high frequency selectivity at the edges of the passband and a quasi-elliptic bandpass response. For demonstration, a prototype operating at 2.4 GHz was fabricated and tested; reasonable agreement is obtained between the simulated and measured results.

Novel Wideband Microstrip Filtering Power Divider Using Multiple Resistors for Port Isolation

In this paper, a novel wideband filtering power divider with third-order quasi-Elliptic bandpass response is proposed. Its physical mechanism is revealed by the lumped-element equivalent circuit, such as how its transmission poles and zeros are formed. The design of the proposed filtering power divider can be simplified as its even-mode model can be synthesized by conventional filter synthesis technique, and then the initial structure parameters can be analytically determined. Owing to the fact that as many as three resistors are joined, high isolation can be achieved between two output ports. To demonstrate its good performance, an example was designed, fabricated, and measured, whose center frequency is 1.99 GHz and 3-dB fractional bandwidth is 43.7%. Moreover, as great as 34 and 28 dB out-of-band suppression can be achieved in the lower and upper stopbands, respectively. The isolation between two output ports is better than 20 dB for a wide frequency range.

A wideband omnidirectional filtering patch antenna with high selectivity

A wideband omnidirectional filtering patch antenna with high selectivity is proposed in this article. The annular ring is surrounded by the hexagonal patch with inner circle, whereas a series of shorting vias are regularly distributed among them and a copper top hat is suspended right on the top of the radiator, respectively. And, omnidirectional pattern is mainly performed on account of the symmetry and center-fed structure. In addition, broadband performance is achieved by merging three resonant modes, which include the TM01 and TM02 modes of the annular ring and the TM02 mode of the hexagonal patch with inner circle. Taking advantages of the hexagonal patch and six shorting vias in it, two radiation nulls are provided in the upper band. Besides, another radiation null is generated in the lower band by reason of the top hat and other shorting vias. As a result, an ideal quasi-elliptic bandpass response, high selectivity, and good out-of-band rejection are obtained simultaneously. The proposed filtering patch antenna, with a profile of 0.056 λ 0, shows a wide impedance bandwidth of 30.2% from 2.05 to 2.78 GHz. The average gain in the passband is about 6.5 dBi, and the out-of-band suppression level is greater than 15 dB in the wide stopband.

Compact Single-/Dual-Polarized Filtering Dielectric Resonator Antennas

A compact single-polarized filtering dielectric resonator (DR) antenna (DRA) with high selectivity is investigated. The DRA is fed by hybrid microstrip line/conformal strip, excited in its fundamental TE $_{1\delta 1}^{y} $ mode. Owing to different loading effects of the microstrip stub and conformal strip, the resonance frequency of TE $_{1\delta 1}^{y}$ mode excited by the two feed lines is slightly different. Such stepping resonances yield a wide bandwidth of 21.9% and a very flat gain of 5.1 dBi. The hybrid-feeding scheme also establishes a cross-coupled structure in the DRA, which introduces two radiation nulls right near the band edges. A compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is, therefore, obtained without requiring any specific filtering circuit. This single-polarized design is also modified to realize a dual-polarized FDRA by adding another orthogonal port with the same feeding scheme. To reduce mutual coupling between the two ports, the microstrip stubs are folded to L shape, and four additional metal posts are inserted into the DR. As a result, the isolation is improved by 14 dB, from 7.2 to 21.2 dB.

Wide-/Dual-Band Omnidirectional Filtering Dielectric Resonator Antennas

A wideband omnidirectional dielectric resonator antenna (DRA) with filtering response is investigated. The DRA is placed on a circular patch and excited by a hybrid feed that consists of a probe and a metallic disk. Two omnidirectional DR modes (TM $_{01\delta }$ and TM013 modes) along with a patch mode and a probe mode are simultaneously excited by the hybrid feed, providing a broad bandwidth of 52.8%. The feeding scheme also establishes a cross-coupled structure in the DRA, which introduces a radiation null at the upper edge of the passband. A ring slot and four shorting pins are loaded on the patch to provide another radiation null at the lower edge of the passband. Consequently, a compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is obtained without requiring specific filtering circuits. This wideband design is also modified to realize a dual-band FDRA. The metallic disk of the hybrid feed is moved to touch the upper DR face of the cylindrical hole. It divides the wide passband into two separate bands, giving a flat stopband between them. Four additional rectangular ring slots and shorting pins are fabricated on the ground plane to further widen the bandwidth and improve the filtering performance of the second band. As a result, a dual-band FDRA with the bandwidths of 10.1% and 3.73% is achieved. In each design, both the measured and simulated out-of-band suppression levels are about 15 dB.

Dual-Polarized Bandpass Frequency-Selective Surface With Quasi-Elliptic Response Based on Square Coaxial Waveguide

A new dual-polarized 3-D frequency-selective surface (FSS) with quasi-elliptic bandpass response is proposed by virtue of the square coaxial waveguide (SCW). By utilizing the SCW as one propagation path in the unit cell, two resonators can be generated intrinsically without introducing any extra structures. In addition, the parallel-plate waveguide constructed by sandwiching the ABS frame between outer conductors of adjacent SCWs will provide a second propagation path and create another resonator. With the help of these resonators, a passband with two transmission poles can be obtained. Furthermore, there are two finite transmission zeros locating at both sides of the passband due to the fact that the signals passing through these two propagation paths are combined out of phase, leading to both-sided sharp roll-off skirt. The E-field analysis and equivalent circuit model presented offer a physical insight into the operating principle of the proposed 3-D FSS. For the purpose of validation, the FSS is fabricated through the 3-D printing technique. The measured results exhibit high frequency selectivity, dual polarizations, and stable bandpass response under a variation of the incidence angle.

Compact Microstrip Filter With Third-Order Quasi-Elliptic Bandpass Response

In this paper, a novel microstrip filter is proposed, which can realize a third-order quasi-elliptic bandpass response. In order to reveal the physical mechanism of the microstrip filter, a lumped-element equivalent circuit is set up and the equivalence relations between its circuit elements and the electrical parameters of the microstrip filter are presented. According to filter specifications, the initial structural parameters of the microstrip filter can be easily calculated through these equivalence relations. As demonstration, an actual microstrip filter was designed, fabricated and measured, whose center frequency is at 2.50 GHz and fractional bandwidth is 36%. There are two transmission zeros near to the passband to improve the frequency selectivity, which makes the roll-off rate at each side of the passband as high as 125 and 50 dB/GHz, respectively. The out-of-band suppression from 3.6 to 6.1 GHz is greater than 40 dB. The size of the fabricated filter is $0.21\lambda \text {g} \times 0.18\lambda \text{g}$ , which is very compact.

Design of a Low Profile and Compact Omnidirectional Filtering Patch Antenna

A low profile omnidirectional patch antenna with filtering response is investigated in this paper. The triangular patch antenna is axially fed by a probe at its center, exciting both its TM10 and TM11 modes. Comparing with the traditional circular patch, the triangular patch can not only minimize the patch size but also can generate a radiation null at the upper band edge. A ring slot and a series of shorting vias are introduced into the patch to merge the two modes, enhancing the bandwidth of the passband. The combination of the two elements simultaneously generates a radiation null at the lower band edge. Consequently, a compact filtering patch antenna with quasi-elliptic bandpass response is obtained without involving specific filtering circuits. The prototype with profile of $0.03~\lambda _{0}$ has a 10-dB impedance bandwidth of 8.9% (4.3–4.7 GHz), an average gain of 6.0 dBi within passband, an out-of-band suppression level of more than 30 dB within lower stopband (0–3.6 GHz), and more than 20 dB within upper stopband (5.1–6.3 GHz).

Wideband Omnidirectional Slotted Patch Antenna With Filtering Response

A wideband omnidirectional patch antenna with filtering response is investigated in this paper. The circular patch antenna is centrally fed by a probe, with its TM01, TM02, and TM03 modes simultaneously excited. Two ring slots are meticulously introduced into the patch and ground plane to merge the three modes of a kind, realizing a wide omnidirectionally radiating passband. The introduction of the slots also generates two radiation minimums at the lower and upper band-edges, leading to an enhanced suppression level in the stopbands. Hence, a compact wideband filtering patch antenna with quasi-elliptic bandpass response is obtained, without using any extra circuit. The proposed antenna has a low profile of $0.027~\lambda _{0}$ , a 10-dB impedance bandwidth of 19.5%, an average gain of 7.5 dBi within passband, and an out-of-band suppression level of over 23 dB within stopband.

A Compact Filtering Dielectric Resonator Antenna With Wide Bandwidth and High Gain

A rectangular filtering dielectric resonator antenna (FDRA) with low profile, wide bandwidth, and high gain is first investigated in this communication. It is fed by a microstrip-coupled slot from bottom, with open stub of the microstrip feedline elaborately designed to provide two radiation nulls at band edges for a filtering function. A separation is introduced in the slot to provide a good suppression level in lower stopband, while two parasitic strips are parallelly added to the microstrip feedline to offer good suppression in the upper stopband, and consequently, a compact FDRA with a quasi-elliptic bandpass response is obtained without involving specific filtering circuits. Based on the design, a modified DRA fed by a pair of separated slots is proposed to further enhance the gain by $\sim 4$ dB. A prototype operating at 5 GHz has been fabricated and measured for demonstration. The reflection coefficient, the radiation pattern, and the antenna gain are studied, and reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 20.3%, an average gain of 9.05 dBi within passband, and an out-of-band suppression level of more than 25 dB within a wide stopband.

Frequency selective surface with wideband quasi‐elliptic bandpass response

A frequency selective surface with a new type of three-dimensional element which produces a quasi-elliptic bandpass response is presented. The element exhibits an elliptic bandpass response with a −3 dB bandwidth (BW/f 0) of ∼ 70%, where f 0 is the centre frequency. The design has been adapted to a form that can be conveniently fabricated by utilising printed technology. The measured results for the frequency response show good agreement with those predicted via numerical simulations.

Dual-band frequency selective surface with quasi-elliptic bandpass response

Based on the substrate integrated waveguide technology, we present a dual-band frequency selective surface (FSS) with a quasi-elliptic bandpass response. The characteristics of the quasi-elliptic bandpass response are realized by shunting two substrate integrated waveguide cavities of different sizes, with the same slots on both sides of the metal surfaces. Four cavities of different sizes and two slots of different sizes are used to design the novel FSS. Every bandpass response with sharp sidebands is induced by two transmission nulls that are generated by the coupling between the slot aperture resonance and the cavity resonance. The simulation results show that such dual-band FSS has the advantages of high selectivity and stable performance at different oblique incident angles. Moreover, it is easy to fabricate.