Filtering Antenna Research Articles

Dual‐band single‐layer substrate‐integrated waveguide filtering antennas with independently controllable bands

AbstractA novel design method of dual‐band single‐layer substrate‐integrated waveguide (SIW) filtering antennas with independently controllable bands is proposed in this paper. The basic two‐pole dual‐band filtering antenna is proposed by a dual‐mode rectangular SIW cavity coupled to two single‐mode SIW cavities with respective radiating slots. Single cavity multi‐mode is realised by etching dumbbell‐shaped slots and metallised vias to achieve the purpose of broadening bandwidth and miniaturisation. The dual‐mode SIW cavity acting as a common structure is fed by a coaxial feeder. The two orthogonal modes are coupled to two single‐mode cavities by coupling windows to produce two two‐pole passband filtering responses, respectively. Metallised vias in radiating SIW cavities are employed to realise good impedance matchings in radiating pass‐bands. The two filtering radiation bands can be controlled independently, which is analysed in detail. Based on the basic two‐pole dual‐band filtering antenna, three‐ and four‐pole dual‐band filtering antennas are further proposed and analysed. For demonstration, two‐, three‐ and four‐pole dual‐band filtering antennas with two centre frequencies of 10 and 11.7 GHz are designed, fabricated, and measured. The good agreement between the simulated and measured results verifies the proposed design methodology of single‐layer SIW dual‐band filtering antennas.

Optimization Design of Filter Antenna Based on Improved Gray Wolf Optimization Algorithm

Optimization Design of Filter Antenna Based on Improved Gray Wolf Optimization Algorithm

Broadband Filtering Antenna With Asymmetric Feeding Structure

ABSTRACTA compact highly selective broadband filter antenna with an asymmetric feed structure is proposed. The radiating patch of the antenna unit consists of a central elliptical patch and a pair of semi‐annular patches, and the antenna forms multiple coupling paths from the feed ports to the radiating patches to generate a radiation null (6.28 GHz), which achieves the roll‐off rate of 193 dB/GHz. The innovation of this design is that asymmetric L‐shaped branches of about half a wavelength are added on both sides of the microstrip feedline of the antenna to expand the operating bandwidth and generate a low‐frequency radiation null (4.66 GHz), which achieves the roll‐off rates of 164 dB/GHz. The simulated results show that impedance bandwidth is 23.8% (4.77–6.06 GHz) with the peak gain of 5.86 dBi, which size is 0.5λ0 × 0.5λ0 × 0.09λ0. Then, a 2 × 2 filtered antenna array is designed for experimental validation. The test results indicate that the impedance bandwidth of the antenna array is 21.5% (4.45–5.52 GHz), the in‐band gain is greater than 10 dBi and flat, and the out‐of‐band rejection level is greater than 20 dB. Attributed to the characteristics of easy and inexpensive manufacturing, the designed antenna has well application prospects in modern wireless communication systems.

Wide‐angle band‐pass FSS with high‐frequency selectivity based on SIW cavity technology

AbstractThis work proposes and investigates a wide‐angle band‐pass frequency selective surface (FSS) with two sharp sidebands. The presented FSS element is made up of three metallic layers and two substrate layers in between, which are surrounded by a substrate‐integrated waveguide (SIW) cavity. The top metallic layer is identical to the bottom layer, composed of a square patch etched with a hexagonal groove, while the middle layer is a similar patch but with rectangular notch edges. This structure achieves a second‐order band‐pass response with highly frequency selectivity on either side of the passband. At the same time, this FSS demonstrates excellent stability for both transverse electric and transverse magnetic polarizations with incident angles between 0° and 60°. The electric current and field distributions are demonstrated for deep analysis. Furthermore, an equivalent circuit model is developed to further understand the operating mechanisms. To verify the validity of the design, we construct a prototype of the SIW‐based FSS (SIW‐FSS) and measured it. There is a fair degree of agreement between the measured and simulated results. Finally, we loaded it onto the horn antenna and tested its application in filtering antennas.

A conical beam antenna array with filter characteristics for multi-rotor unmanned aerial vehicle measurement system

ABSTRACT This paper proposed a novel filter antenna with the conical beam, which consists of four magnetoelectric (ME) dipole antennas. By printing parasitic patches and etching open slots on the bottom of the substrate, two radiation nulls near the high frequency of the passband are introduced. Combined with the intrinsic radiation null of the ME-dipole antenna, the filtering response is obtained. In order to verify the design method, a prototype is manufactured and measured. The measurement results show that the impedance bandwidth (VSWR <2) of the antenna is 1.48 ~ 2.61 GHz (55.3%). In addition, the out-of-band suppression is more than 17.4 dB and the maximum radiation direction of the conical beam is stable around to Theta = 30°. The proposed antenna array can be promising candidates for multi-rotor unmanned aerial vehicle (UAV) measurement systems.

Compact metal‐printed filtering antenna with wideband performance

AbstractIn this letter, a wideband cavity‐backed filtering antenna based on 3‐D printing technology is proposed for millimeter wave applications. This antenna is made up of an air‐filled metal cavity, attached with two transverse slots on its upper surface. By exciting one TE110 cavity mode and two slot modes simultaneously, wideband performance can be obtained. Besides, by properly bending one slot into U‐shape, two radiation nulls appear at two sides of the passband, yet causing the increase of the cross‐polarization in H‐plane. To remedy this, the U‐shaped slot is further bent at its ends, successfully suppressing the cross‐polarization by 7 dB. The final proposed filtering antenna is implemented and measured, showing a wide bandwidth of 37.3%, covering from 21.4 to 31.2 GHz. And the measured maximum gain is 6.6 dBi in band, with two radiation nulls at 14.6 and 40 GHz.

Millimeter‐wave filtenna for 5G application with multiple controllable radiation nulls and wide stopband

AbstractA filtenna (filtering antenna) for the fifth generation (5G) mobile communications in millimeter‐wave (mmWave) band is proposed in this paper. The filtenna is fed by a probe, and two radiation nulls are generated at the upper sideband based on the stacked‐patches structure. Then, two shorting pins loaded on the driven patch are introduced, which then result in the third radiation null. An “X‐character” shape radiation loop is added therefore, the fourth radiation null can be generated. Besides, the fifth radiation null at around 34 GHz is generated by adding four parasitic strips on the top radiation patch. The measured −10 dB impedance bandwidth of the filtenna is from 23.07 to 30.99 GHz. The average gain of the antenna is larger than 5.5 dBi, and the stopband suppression can reach 14 dB with a wide stopband. With the merits of low profile, wide stopband, and stable radiation, the proposed filtenna can be a good candidate for 5G mmWave applications.

Modeling and Design of Nonresonant-Node-Based Filtenna for Triband Wi-Fi Application

The triband wireless Wi-Fi router radiated by series-fed antennas suffers from serious mutual coupling, resulting in throughput degradation. To reduce the mutual coupling, the filtering antennas (filtennas) are designed with nonresonant node (NRN) radiators and series-fed antennas. The NRN filtering radiators are characterized by the NRN filtering circuits, which includes the capacitance and inductance NRNs. These NRNs realize a parallel resonance and radiation zero simultaneously. The radiation zero frequency is smaller or larger than the resonant frequency in the capacitance and inductance NRN, respectively. As the mechanism to manipulate the resonant frequency and radiation zero is figured out, the NRN filtering radiators are designed, and the above analysis is validated. Then, the series-fed antenna equivalent to a parallel resonance is fed by the NRN filtering radiator, and a second-order bandpass filtering network is formed. Its filtering response with the radiation zero realizes a high out-of-band rejection to reduce the mutual coupling. For demonstration, a cross-coupling NRN filtenna is designed to work at 2.4–2.5 GHz low band (LB), while the inductance and capacitance NRN filtennas operate at 5.17–5.33GHz mid band (MB) and 5.735–5.835 GHz high band (HB), respectively. Herein, the radiation zero of the MB antenna is designed at HB, while the HB radiation zero operates at MB. The measurement results exhibit that the mutual coupling is reduced, and the throughput of the triband wireless Wi-Fi router is improved.

Dual‐polarized filtering antenna and its application for compact multi‐array

AbstractThis article presents a ±45° dual‐band dual‐polarized filtering antenna. The filtering antenna element is a dual‐polarized patch antenna that loads a parasitic patch with two rectangle slots to achieve compact multi‐array. Multi‐array consists of three 1×2 subarrays arranged, which are designed for 1.8/2.1 GHz FDD band applications. Very close‐arranged antennas exhibit radiation pattern invariance as well as in‐band radiation property. Radiation patterns are conformal with a compact subarray distance of 45 mm (0.29λ0), which is 56% smaller than that of the array using traditional filtering elements. Moreover, the total width is only 180 mm for three subarray‐composed antenna arrays. The average gain is 8.7 dBi with a low profile of 0.069λ0. The proposed array exhibits the filtering property of the subarrays with a very simple structure.

A single‐layer substrate‐integrated waveguide filtering antenna with three independently controllable radiation nulls

AbstractIn this paper, a single‐layer substrate‐integrated waveguide (SIW) filtering antenna with three independently controllable radiation nulls is presented. The antenna consists of a single‐layer SIW loaded with two radiation gaps, four metallization columns, and folded‐type slots etched on the chip. The back‐cavity double slots are responsible for extending the bandwidth and realizing the radiation function. Three radiation nulls are generated by analyzing the current distribution of the radiation chip, radiation gap, and folded slots. By adjusting the radiation gap distance, the length of the radiation gap, and the folded slot, three broadside radiation nulls are independently controlled without influence on each other. Therefore, flexible out‐of‐band suppression characteristic is obtained. For demonstration, a prototype is fabricated and tested. The measurements match the simulation results better. The filtering antenna operates at 3.70 GHz with a bandwidth of 5.68% (3.59–3.80 GHz), achieving an average realized gain of 5.10 dBi in a flat passband. The out‐of‐band rejection level exceeds 20 dB.

Millimeter-Wave Monopulse Filtenna Array with Directive Dielectric Resonators

This paper presents a new millimeter-wave monopulse dielectric resonator (DR) filtering antenna (filtenna) array based on substrate-integrated waveguide (SIW) technology. The monopulse comparator realized by a square dual-mode (&lt;i&gt;TE&lt;/i&gt;&lt;sub&gt;102&lt;/sub&gt; and &lt;i&gt;TE&lt;/i&gt;&lt;sub&gt;201&lt;/sub&gt;) SIW feed cavity uses diagonal irises, of which couplings between the feed and next-stage cavities lead to almost identical filter responses for the sum and difference channels with compact size and a planar single-substrate structure. Both dielectric resonator antennas (DRAs) adopting &lt;i&gt;HEM&lt;/i&gt;&lt;sub&gt;133&lt;/sub&gt; mode for enhanced directivity are implemented with two filters based on SIW. The DR acts as the last resonator and the radiator in the filtenna. The prototype is designed at the Ka-band with a center frequency of 27.65 GHz and an operation bandwidth of 700 MHz. The measurement shows a 15-dB fractional bandwidth of 2.36%, a gain of 10.84 dBi for the sum channel, and a null depth of -15.6 dB for the difference channel.

A Novel Compact Filtering Antenna for 5.0-GHz WLAN Communication System

The proposed antenna presents a microstrip filter antenna with both filter out-of-band rejection characteristics and antenna radiation characteristics for WLAN communication system. The antenna consists of four U-shaped microstrip resonators, one Γ-shaped antenna, and one parallel coupling line. The Γ-shaped antenna has the filtering function as the last order resonator, and the parallel coupling line integrates the filter and antenna as the conductance converter. After simulation and test, the results show that the center frequency of the filter antenna is 5.25 GHz, the fractional bandwidthis 8.0% (5.0 − 5.42 GHz), the in-band gain changes smoothly, the maximum in-band gain is 3.059 dBi, the gain at 150 MHz outside the passband rapidly decreases to 10.0 dBi, and the overall out-of-band gain drops to below −24 dBi. The filter antenna has a simple structure and thin substrate, which optimizes the overall size of the filter and antenna, reduces the transmission loss between them, and is applicable to the RF front-end of wireless communication systems.

Compact Dual-Polarized/Duplex Filtering Antenna With High Isolation

Compact Dual-Polarized/Duplex Filtering Antenna With High Isolation

A Compact Filter and Dipole Antenna With Its Phased Array Filtenna and ADMM-BO Learning for Use-Case Analog/Hybrid Beamforming in 5G mmWave Communications

In this article, a 5G compact millimeter-wave dipole antenna with high gain and its array filter-antenna is proposed, following a theoretical discussion is proposed. To increase the gain and focused mainbeam, the double dipole is inserted at the ground plane. The results show that the proposed antenna has an impedance band-width (IBW) of around 7.14% and 6.7 dBi gain at 28 GHz. Next, a 5G filter is proposed with 4% IBW and lower than 0.6 dB gain insertion loss. A simple phase-shifter with 2-bit structure is designed in an 8-elemens array filter-antenna with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.35\lambda $ </tex-math></inline-formula> spacing between the two elements which uses a meander-line to reduce mutual-coupling. First, the phased-array filtenna (filter-antenna) is fabricated to meet the analog beamforming challenge. The IBWs of the array filter antenna are approximately 3.5% with a high gain of 15 dBi. Second, a novel machine learning method is proposed as an alternating direction method of multipliers and Bayesian Optimization (ADMM-BO) is used in the hybrid beamforming for such partially-connected phased-array structures. Simulation and measurement results show that the proposed antenna and its array have a high gain in analog and hybrid beamforming and acceptable data rates. The data-rates of this array reach 100 Mb/s in SNRs higher than 10 dB. The amount for 0 dB SNR is 75 Mb/s. These results also indicate that the mainbeam shift is in the range of [−50°, 50°] with a gain in variations of around 1.5 dB and side lobe level (SLL) of about −10 dB at 50°.

Wideband polarization rotating frequency selective surface composed of antenna–filter–antenna arrays

In this work, a wideband polarization rotating frequency selective surface (PR-FSS) is proposed. The PR-FSS consists of a square array of antenna–filter–antenna (AFA) modules, and the upper and lower antennas in each AFA module are both a wideband one, moreover, the polarization directions of the two antennas are mutually orthogonal, so that the PR-FSS can realize frequency selection and 90° polarization rotation simultaneously in a wide frequency band. Numerical simulations demonstrate that the relative bandwidth of the PR-FSS can reach up to 20.60%, and the maximum insertion loss in the band is only 0.23 dB. Finally, a prototype of the PR-FSS is fabricated and measured, a reasonable agreement is observed between the measured and simulated results.

High-Selectivity FA-FA-Based Frequency Selective Surfaces Using Magnetoelectronic Dipole Antennas

A new method for frequency selective surface (FSS) with high selectivity, namely, filtenna–filtenna (FA-FA)-based technique, is proposed, which consists of two filtering antennas and impedance matching network. Based on the reciprocity theorem, the radiation null of filtenna can provide a stopband of the proposed FSS. In this work, it is validated by using a periodic array of back-to-back magnetoelectronic (ME)-dipole antennas with split-ring resonators (SRRs), and a slotted GND plane is used to connect the two ME-dipole antennas for impedance matching. Bandpass response of the proposed FSS is realized by the intrinsic high-pass characteristic of ME-dipole antennas and the bandstop characteristic of SRRs. Four transmission zeros (TZs) and three transmission poles (TPs) are generated, exhibiting a high-order filtering response. TZs and TPs are analyzed by equivalent circuit model and current distributions. The 3 dB fractional bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {FBW}}_{\mathrm {3\,dB}}$ </tex-math></inline-formula> ) of 38.5% in the passband and the 20 dB fractional bandwidths <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({\mathrm {FBW}}_{\mathrm {20\,dB}})$ </tex-math></inline-formula> of 8.7% in the lower rejection band and 13.8% in upper rejection band are obtained in this design. Finally, a prototype is fabricated and measured to further validate the proposed FA-FA-based technique. Simulated and measured results show that the proposed FA-FA-based FSS is with the distinct advantages, including wide passband, low profile, tunable TZs, and dual-polarized application, which verifies the proposed method of FSSs.

Conformal transmitarray based on metasurface fed by miniaturized filtering antenna

AbstractTo realize the requirements of 5G MIMO technology for high‐performance antennas, a novel high‐gain transmissive array antenna with conformal capability is designed in this study. The antenna consists of a single‐layer dielectric‐based conformal transmission array and a substrate‐integrated waveguide filter antenna. The transmission array is composed of a cross element and spiral elements that can achieve conformal capability. Each metasurface element is a single‐layer medium, and the same metasurface patches above and below are connected by four metal pillars. A filter antenna array fed by a substrate integrated with a waveguide fed by small‐scale low‐temperature cofired ceramic technology is used as the feed antenna of the transmission array. The physical test results are consistent with the simulation results, and the directivity of the antenna is greatly improved. The frequency range where the reflection coefficient S11 is less than −10 dB is 26.6–29.1 GHz. At the center frequency of 28.0 GHz, the gain of the conformal antenna array is greatly improved, and the peak gain is increased from 8.2 to 24.5 dB. The sidelobe level is substantially suppressed. Its high gain and beamforming characteristics make it have a high application value in 5G MIMO technology.

Design of miniaturized dual‐band filtering antenna with improved selectivity utilizing square complementary split ring resonator for 5G MM‐wave automobile applications

Design of miniaturized dual‐band filtering antenna with improved selectivity utilizing square complementary split ring resonator for <scp>5G MM‐wave</scp> automobile applications

Enhanced-Stopband Dual-Polarized Filtenna Without Extra Circuit for Tile Array Applications

In this communication, a dual polarized (DP) stacked patch filtenna (filtering antenna) with a wide stopband is developed for tile array applications. The bandpass filtering property is realized by improving the feeding network and patch without adding extra bandpass circuit or size. An elaborate feeding structure with complementary pair of a short-circuited stub and an open-circuited stub (CSSOS) is developed, which generates two transmission nulls effectively enhancing the selectivity and suppressing the harmonic. Moreover, CSSOS has a small size and broadens the impedance bandwidth apparently by introducing an in-band resonance. By properly etching four U-shaped slots on the driven patch, a radiation null in the upper stopband is also generated. The nulls generated by the two approaches can be adjusted independently in wide ranges. For further harmonic suppression, bandstop striplines (BSSs) with ultralow insertion loss are developed. Measured results show that the filtenna performs a wide operating band (3.10–3.95 GHz) and a wide stopband up to 8 GHz with a rejection level higher than 16 dB. Besides, a 32-element tile phased array employing the filtennas is also fabricated and measured. A compact configuration, high selectivity, and good beam steering capacity are exhibited.

Compact millimeter‐wave 3‐D filtering antenna based on low temperature cofired ceramic substrate integrated waveguide

In this study, a low temperature cofired ceramic (LTCC) based compact millimeter-wave (MMW) 3-D substrate integrated waveguide (SIW) filtering antenna was proposed. First, a band-pass filter with two transmission zeros in the upper and lower sidebands was designed, with a fractional bandwidth of 2.03% at a center frequency of 98.1 GHz. The filtering antenna was developed and manufactured on this premise, by adopting an E-shape patch antenna, achieving a superior frequency selection characteristic with a 1.63% impedance bandwidth and out-of-band gain dropped over 15 dB at 92.7 and 101.2 GHz, respectively. With a compact structure size of 2.4 × 1.6 × 0.5 mm3 (0.78 λ0 × 0.05 λ0 × 0.016 λ0), high gain and high selectivity were realized in the MMW band.