In-band Gain Research Articles

An 8-way series-parallel combiner based power amplifier for mm-wave 5G communication in 40-nm CMOS

This paper presents a power amplifier (PA) with an 8-way series–parallel power combiner for 5G communication. By theoretical analysis of the S-parameters matrix and the equivalence of the impedance network, the design of the multi-port combiner is transformed into a dual-port on-chip transformer, and the bandwidth expansion is achieved without increasing the in-band gain ripple based on the mismatch-consistent magnetically coupled resonator (MCR) technique. As a validation of the methodology, the 8-way series–parallel power combiner PA is implemented in 40-nm CMOS Bulk process. The large-signal performances of the PA at 31 GHz are 21.36 dBm, 17.1 dBm, and 25.7 % for Psat, OP1dB, and PAEmax, respectively. The proposed PA has a peak S21 of 25.1 dB and a 3-dB bandwidth of 23.5–46.4 GHz, which fully covers the 5G new radio (NR) frequency range2 (FR2) operating band, and the S21 ripple is less than 1-dB in the range of 26.0–42.3 GHz, which achieves a broadband flat frequency response and supports the feasibility of the design.

Low-cost and precise automated re-design of antenna structures using interleaved geometry scaling and gradient-based optimization

Design of contemporary antennas is an intricate endeavor involving multiple stages, among others, tuning of geometry parameters. In particular, re-designing antennas to different operating frequencies, makes parametric optimization imperative to ensure the best achievable system performance. If the center frequency at the current design is distant from the target one, local tuning methods generally fail, whereas global algorithms (e.g., nature-inspired procedures) incur prohibitive computational expenses, especially when antenna evaluation is performed using full-wave electromagnetic (EM) analysis. In this paper, a novel technique involving automated decision-making has been developed, whose main objective is low-cost and precise re-design of antenna structures over wide ranges of operating frequencies. The employed methodology involves knowledge-based simultaneous scaling of antenna dimensions and gradient-based performance improvements. The two stages are automatically interleaved, and embedded into an iterative optimization procedure. The problem-specific knowledge allows for carrying out the scaling phase, in which fast relocation of the center frequency of the antenna is performed, based on a single EM analysis of the structure. The gradient-based tuning phase enhances the design quality with regard to the assumed objectives. The process defaults to local optimization after the antenna center frequency becomes sufficiently close to the target. The main novelty of the proposed algorithm consists in development of an automated knowledge-based framework of quasi-global search capabilities linking brute-force scaling and design refinement. Our technique has been demonstrated with the use of three microstrip antennas, optimized for best matching and maximum in-band gain. The main findings are that for all structures, satisfactory designs have been identified despite poor starting points, with operating frequencies being away from the assumed targets. At the same time, the computational cost is comparable to conventional local search. The proposed approach is versatile, simple to implement and easy to handle, in particular, its control parameters do not require tailoring to a specific antenna structure at hand.

A 6 to 18 GHz flat high gain power amplifier using mismatch-consistent MCR technique in 40-nm CMOS

This paper presents a power amplifier (PA) based on the mismatch-consistent magnetically coupled resonator (MCR) technique, which employs adjustable dual-pole to achieve a wide operating frequency range. The in-band no gain ripple condition of the proposed mismatch-consistent MCR is systematically analyzed and derived. By applying this condition to the mismatch-consistent MCR technique, the in-band gain flatness in broadband is improved. An ultra-wide wiring method for the power-combining structure is proposed to further improve the in-band gain flatness by reducing parasitic effects. Meanwhile, an active broadband matching network without any on-chip inductor is used to obtain a -11 dB input return loss (S11) across the whole bandwidth. Implemented in 40-nm CMOS process, the proposed PA achieves a saturated output power of 19.2 dBm, an output 1 dB compression point of 17.8 dBm, a peak power added efficiency of 29.7 %, and only 0.5 dB in-band gain ripple at 8.2-16.2 GHz. The amplifier achieves a 3 dB bandwidth from 6 to 18 GHz while the fractional bandwidth reaches 100 %, realizing wideband and flat frequency response.

A Broadband Gain-Enhanced Conical-Beam Antenna Loaded With the Multicircle Sectored Metasurface

A broadband gain-enhanced monopole antenna loaded with metasurface is designed in this paper, which is suitable for sub-6 GHz fifth-generation (5G) applications. The multi-circle sectored metasurface antenna is analyzed through the evolution process and field distribution. With the addition of the metasurface, the antenna’s relative bandwidth is increased from 23.25% to 48.5%, and the in-band gain is improved by 2 dBi. To validate the proposed working principles and design guidelines, the proposed antenna is fabricated and measured. Measured results agree well with the simulated ones and show that the -10 dB impedance bandwidth is 56% (3.25-5.78 GHz), covering the 5G frequency band (3.3-3.6, 4.8-5 GHz). The average gain in the desired band is 7 dBi with a variation of ±1 dBi, which is suitable for 5G indoor micro ceiling base station applications.

Wideband Filtering Omnidirectional Substrate-Integrated Dielectric Resonator Antenna Covering Ku Band

A filtering omnidirectional substrate integrated dielectric resonator antenna (SIDRA) covering K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> band is proposed. With the boundary realized by arrays of nonmetallic vias, the cylindrical SIDRA possesses a high level of integration, low profile, and easy assembly. The SIDRA operates at the dominant mode fed and coupled by a capacitive-loaded probe with a wide band. One array of shorted and another array of open metallic vias are set in the SIDRA to introduce radiation nulls in the low and high stopbands, and to simultaneously generate two radiation pin modes. The two via arrays could further broaden the fraction bandwidth of gain to 49.5%. The proposed SIDRA shows good omnidirectivity and good frequency selectivity with high in-band gain and without the risk of utilizing blind holes. For demonstration, a prototype is designed and fabricated. The simulated and measured results showcase a good agreement.

A SiGe HBT D-Band LNA Utilizing Asymmetric Broadside Coupled Lines

This letter presents a D-band low noise amplifier (LNA) implemented in 90 nm SiGe BiCMOS technology and is intended for next-generation communications systems. The LNA is a five-stage staggered common-emitter and cascode design used to simultaneously achieve wide bandwidth and high gain. The LNA utilizes asymmetric broadside coupled lines as interstage impedance transformers to achieve a wideband gain response while constraining power consumption. The presented LNA achieves an in-band gain of 26.5 dB and a bandwidth of 37.6 GHz. The minimum measured NF is 7.2 dB, and the dc power consumption is 20.6 mW. This D-band LNA achieves high gain, wide bandwidth, and low power consumption, resulting in a competitive performance with other D-band LNAs in the literature. The die area of the fabricated LNA is 0.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 0.86 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> , including pads.

Stereoscopic UWB Yagi-Uda Antenna with Stable Gain by Metamaterial for Vehicular 5G Communication.

In this paper, a stereoscopic ultra-wideband (UWB) Yagi-Uda (SUY) antenna with stable gain by near-zero-index metamaterial (NZIM) has been proposed for vehicular 5G communication. The proposed antenna consists of magneto-electric (ME) dipole structure and coaxial feed patch antenna. The combination of patch antenna and ME structure allows the proposed antenna can work as a Yagi-Uda antenna, which enhances its gain and bandwidth. NZIM removes a pair of C-notches on the surface of the ME structure to make it absorb energy, which results in two radiation nulls on both sides of the gain passband. At the same time, the bandwidth can be enhanced effectively. In order to further improve the stable gain, impedance matching is achieved by removing the patch diagonally; thus, it is able to tune the antenna gain of the suppression boundary and open the possibility to reach the most important characteristic: a very stable gain in a wide frequency range. The SUY antenna is fabricated and measured, which has a measured -10 dBi impedance bandwidth of approximately 40% (3.5-5.5 GHz). Within it, the peak gain of the antenna reaches 8.5 dBi, and the flat in-band gain has a ripple lower than 0.5 dBi.

Bandwidth Enhancement of Metasurface Antennas by Shifting and Reshaping High-Order Mode

In this letter, a new bandwidth enhancement method for metasurface antennas (MAs) is proposed, by shifting the distant resonant frequency closer and reshaping the distorted radiation pattern of a high-order mode (HOM). A dominant mode (DM) and a far-separated HOM of the MA are excited simultaneously by a half-square loop. By scaling the central, corner, and edge patches with nonuniform factors while hardly affecting the DM, the HOM is shifted to merge the DM under the guidance of the characteristic mode analysis. Moreover, in order to improve the current distribution, the distorted radiation patterns as well as the gain flatness under the HOM without affecting the DM, the U-shaped slots with a band-notch characteristic are introduced on the central patches. The proposed antenna is fabricated and measured. The measured results are coincidental with the simulated ones. The results also show that the proposed antenna has a 10 dB return loss of 35.8% (4.34–6.23 GHz) and an in-band gain of 6.8−11.3 dBi with a single-layer structure and low profile of 0.06 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (the free-space wavelength at the center frequency).

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.

A Single-Fed Wideband Circularly Polarized Cross-Fed Cavity-Less Magneto-Electric Dipole Antenna.

In this paper, we proposed a new wideband circularly polarized cross-fed magneto-electric dipole antenna. Different from conventional cross-dipole or magneto-electric dipole antennas, the proposed simple geometry realizes a pair of complementary magnetic dipole modes by utilizing the two open slots formed between the four cross-fed microstrip patches for achieving circular polarization and high stable gain across a wide frequency band. No parasitic elements are required for extending the bandwidths; therefore, both the radiation patterns and in-band gain are stable. The simulated field distributions demonstrated the phase complementarity of the two pairs of magnetic and electric dipole modes. A parametric study was also performed to demonstrate the radiation mechanism between the electric and magnetic dipole modes. The radiating elements are realized on a piece of double-sided dielectric substrate fed and mechanically supported by a low-cost commercial semirigid cable. The overall thickness of the antenna is about 0.22λo at the center frequency of axial ratio bandwidth. The measured results show a wide impedance bandwidth (|S11| < -10 dB) of 70.2% from 2.45 to 5.10 GHz. The in-band 3-dB axial ratio bandwidth is 51.5% from 3.0 to 5.08 GHz. More importantly, the gain of the antenna is 9.25 ± 0.56 dBic across the 3-dB axial ratio bandwidth.

Low-Profile Single-Layer Half-Mode SIW Filtering Antenna With Shorted Parasitic Patch and Defected Ground Structure

A low-profile single-layer half-mode substrate integrated waveguide (HMSIW) filtering antenna with compact circuit size is presented in this brief. The antenna features simple structure and consists of a half-mode substrate integrated waveguide cavity (HMSIWC), a shorted parasitic patch, and a folded defected ground structure (DGS) etched into the metallized ground plane. The half-mode technology is employed to reduce the overall dimension in the design. The shorted parasitic patch and the HMSIWC, both operating at half-mode states, are coupled with each other to form a second-order filtering response. And also a radiation null at higher stopband is introduced owing to the effects of the cross coupling. Furtherly, by etching a folded DGS into the metallized ground plane, an additional resonance in the passband and a controllable radiation null at lower stopband are simultaneously generated to broaden the impedance bandwidth and improve the selectivity of lower stopband respectively. For verification, a prototype of the developed HMSIW filtering antenna is designed, fabricated, and measured. The measured and simulated results are in good agreement, showing a wide impedance bandwidth of 9.2% at center frequency of 2.84 GHz, a flat in-band gain response with two controllable radiation nulls at both edges of the operating band, and a maximum boresight realized gain of 5.75 dBi. The proposed HMSIW filtering antenna demonstrates good in-band and out-of-band performance even with a very low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.015~\mathbf {\mathrm {\lambda }} _{0}$ </tex-math></inline-formula> .

Planar Multi Notch Band Antenna In-band Gain Enhanced by Epsilon-near-zero Non-absorptive Metasurface

Planar Multi Notch Band Antenna In-band Gain Enhanced by Epsilon-near-zero Non-absorptive Metasurface

A Dual-Band Dual-Circularly-Polarized Slot Antenna With Stable In-Band Gain and Reduced Frequency Ratio Under Triple Resonance

In this article, a dual-band dual-circularly polarized (CP) narrow slot antenna with stable in-band gain and reduced frequency ratio (FR) is proposed by resonating the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5\lambda $ </tex-math></inline-formula> -, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it \lambda }$ </tex-math></inline-formula> -, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{\it \lambda }$ </tex-math></inline-formula> -modes. For this purpose, two critical issues are significantly investigated and explored. The first effort is attempted to construct two pairs of orthogonal polarization with opposite rotation, i.e., ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it \lambda }$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5{\it \lambda }$ </tex-math></inline-formula> -modes) and ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5{\it \lambda }$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{\it \lambda }$ </tex-math></inline-formula> -modes), by properly reshaping the equivalent magnetic currents of the slot radiator. Another attempt is to reallocate these modes in proximity to each other in virtue of stub-loaded technique and ensure them to resonate in the designated sequence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\it \lambda }$ </tex-math></inline-formula> -, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5{\it {\lambda }}$ </tex-math></inline-formula> -, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{\it \lambda }$ </tex-math></inline-formula> -modes instead of the inherent sequence. With these improvements, the dual-CP performance can be successfully realized for our designed antenna. Finally, for experimental verification, a dual-band dual-CP slot antenna in virtue of the proposed design approach is implemented and tested. It proves that the left- and right-hand CP radiation patterns toward the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${z}$ </tex-math></inline-formula> -axis are satisfactorily obtained around 1.88 and 2.39 GHz by simultaneously employing the triple resonance, thus revealing a small FR of 1.27. Moreover, the dual operation bands hold stable in-band gains of about 2.8 and 3.5 dBic. In addition, the CP antenna still maintains the single-layer, single-fed, and single-radiator properties, which evidently confirms the validity and effectiveness of the proposed design.

A Transparent Wideband Dual-Polarized Antenna for Sub-6 GHz Application

In this letter, a novel transparent dual-polarized antenna has been developed for sub-6 GHz application. The proposed antenna composed of transparent conductive mesh and polycarbonates material is of optical transparency. Based on characteristic mode analysis, the proximity-coupling fed driven patch operates in TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode. By stacking the parasitic patch and strips above the driven patch with a cross slot, three resonances are generated. With the T-shaped slots on the parasitic patch, the impedance matching at low frequencies is improved. By etching the slots on the ground and cutting off the corners of the driven patch, good port isolation and stable in-band gain are achieved. The prototype of proposed antenna is fabricated. The measured results show that the proposed antenna exhibits a wide impedance band of 2.76–4.13 GHz with a fractional bandwidth of 39.8%, a good isolation better than 22 dB, a low cross polarization ratio better than 20 dB within the operating band.

Design and Characterization of a Planar Structure Wideband Millimeter-Wave Antenna With Wide Beamwidth for Wearable Off-Body Communication Applications

This letter presents the design of a planar single-layer wideband antenna featuring wide beamwidth has well as high and stable in-band gain. The proposed antenna is a planar monopole fed by a bottom-grounded coplanar waveguide to realize wide beamwidth in both the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xz</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">yz</i> -planes. Simultaneous optimization of all adjustable antenna parameters, carried out at the full-wave electromagnetic simulation level. The constructive interference of the radiated fields resulting in impedance bandwidth of more than 2 GHz, from 27 to 29 GHz. Along with a stable realized gain (>11 dBi) in the operating frequency band. The proposed antenna maintains a directional radiation pattern in the broadside direction. Merging the radiated modes of the slots and the parasitic patch elements also extends the antenna beamwidth to roughly ±35° with respect to the broadside direction. Following a detailed theoretical analysis, the antenna is validated numerically and experimentally, both in the free space and on a human volunteer chest and arm.

Design Approach for a Dual-Band Circularly Polarized Slot Antenna With Flexible Frequency Ratio and Similar In-Band Gain

This letter presents an effective approach to design a dual-band circularly polarized (CP) slot antenna with flexible frequency ratio (FFR) and similar in-band gain under the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode radiation. Initially, a CP slot antenna is realized in virtue of two orthogonal slot radiators. Then, by folding both slot radiators at a 1/4 length position from the short-circuited terminal, a CP slot antenna operating at two distinct bands is successfully realized based on the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, where stable gain with similar level for the dual working bands is achieved. After that, two pairs of slot stubs are properly introduced to effectively reallocate the higher band based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, thus acquiring for a wide frequency ratio ranging from 1.85 to 1.26. Finally, for experimental validation purposes, two specific CP slot antennas with distinctive frequency ratios of 1.85 and 1.26 are implemented and tested. A similar-level gain within their dual operating bands can be achieved as another merit in addition to the FFR.

Bandpass Filter Prototype Inspired Filtering Patch Antenna/Array

Planar filtering patch antenna and its related array inspired by a novel bandpass filter (BPF) prototype are proposed in this article. It is reasonable to replace the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> tank of a BPF prototype with a half-mode (HM) patch resonator with reference to their lumped circuits. That is, the HM patch would serve as a part of the BPF, as well as a radiator. This design method of implementing the filtering antenna is verified by a newly developed prototype. The physical model is realized in a simple form of a patch antenna fed by differential coupled lines. A microstrip-to-slotline transition is implemented to excite the coupled lines. Two radiation nulls beside the passband are obtained, thereby leading to a sharp band skirt. Based on this filtering antenna, a two-element patch array is designed. A CPW-to-slotline transition is designed to excite the united coupling lines, which serves as both a balun and a power divider. A high out-of-band rejection level within a wide stopband is achieved. For demonstration, the proposed filtering antenna and array are fabricated and measured. Reasonable agreement between the measured and simulated results is observed. Besides, the measured in-band gain of the filtering antenna array is over 10 dBi and flat, whereas the out-of-band rejection level is almost 30 dB.

A Broadband Spectrum Channelizer With PWM-LO-Based Sub-Band Gain Control

A broadband spectrum channelizer employing pulsewidth-modulated local-oscillator (PWM-LO)-based sub-band amplitude control is demonstrated. The channelizer has an analog bandwidth of 800 MHz and partitions the input spectrum into eight contiguous sub-bands. The design employs an approach based on frequency folding from harmonics of multi-phase periodic clocks and allows for scaling the relative gain of the sub-bands over a 20-dB range. This relaxes the compression performance of the channelizer baseband and sub-analog-to-digital converter (ADC) dynamic range in the presence of large sub-bands. Gain control on individual sub-bands is performed by employing customized PWM-LO waveforms, where the PWM-LO pulses are generated using delay-locked loops (DLLs). Off-chip learning employing a neural network is used to estimate the PWM symbol pulsewidths required for setting the desired LO harmonic levels. A 1.6-GS/s spectrum channelizer integrated circuit (IC) is implemented in a 65-nm CMOS process to verify the architecture. The measured channelizer gain is 51.6–56.5 dB without gain scaling and provides a range of 37–59 dB with PWM-LO gain control. Gain scaling at a specific harmonic improves blocker compression in an unattenuated sub-band from −34 to −16 dBm. The in-band gain compression with gain scaling also increases from −32 to −17 dBm.

A Compact Wideband Filtering Omnidirectional Dipole Antenna Without Extra Circuits

This article presents a design of a compact wideband filtering dipole antenna with an omnidirectional radiation pattern. We analyze the radiation of three kinds of half-wavelength dipoles (strip, U-shaped strip, and folded strip). It is found that these three diploes produce omnidirectional radiation patterns when they work on half-wavelength mode. In the proposed design, we make these three dipoles couple with each other to achieve wide bandwidth. In addition, both electric coupling and magnetic coupling are observed at the lower band and the upper band, respectively. Therefore, two radiation nulls can be achieved without any extra circuit, which makes the proposed antenna filtering property and compact. A prototype is fabricated and measured to verify our idea. The results show that the proposed antenna has a 10 dB bandwidth of 42.51%, an in-band gain of ~2.4 dBi, and an out-of-band radiation suppression of more than 10 dB with a total size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0.4}{ {\lambda }}_{{0}}\,\,{\times }\,\, 0.06{ {\lambda }}_{{0}}$ </tex-math></inline-formula> . The above advantages of wide bandwidth, filtering property, small size, and easy fabrication make the proposed antenna have potential applications on various wireless communication systems.

SLA printed horn antenna with filtering network based on dual‐mode ellipsoid resonator

This paper presents a horn antenna with a 5th-order dual-mode ellipsoid resonator filtering network, fabricated by stereo lithography apparatus 3-D printing technic. The filtering part employs two dimpled ellipsoid dual-mode resonators, operating at the fundamental TM101 mode. Compared to the filters employing cylindrical resonators with tuning posts, the proposed filtering network is with lower loss (due to the high Qu resonator) and the performance is less sensitive to the fabrication errors. The antenna was demonstrated at Ku band (12–18 GHz), with a measured RL >10 dB across the passband of 14.6–15.4 GHz. The measured gain of the antenna is 11.4 dBi at 15 GHz and maximum in-band gain variation is 0.4 dB.