Measured Broadside Gain Research Articles

Advanced Design of High-Gain Fabry–Perot Cavity Antenna Offering Wide Common Impedance and Gain Bandwidth

An advanced design of a Fabry-Perot cavity antenna (FPCA) is proposed to achieve wide common impedance and gain bandwidth along with high gain. A compact and lightweight FPCA is achieved by employing a printed primary radiator and superstrate with superior manufacturing capabilities. A wideband primary radiator is employed for the first time to realize such a wideband FPCA. Superstrate dimensions are estimated by using the aperture field theory and the proposed design is validated through both EM simulation and experiment. The measured broadside gain is shown to be better than 11.5 dBi over an impedance bandwidth of 63% (8.2−15.6 GHz). About 40% common impedance and gain bandwidth is achieved while the broadside gain attains a maximum value of 17.4 dBi. To the best of our knowledge, this has never been achieved before from an FPCA made of a printed superstrate and a primary radiator. The cross-polar (XP) radiation remains under −40dB whereas the front-to-back ratio (FBR) remains above 35dB, over the desired bandwidth.

Achieving Continuous Stable Beam Steering with Gain Enhancement Using a Graded-Index Metasurface Lens

In this paper, the design of an ultrathin highly transmissive angular graded-index metasurface (AGIMS) lens is proposed, and a beam steerable high-gain low-profile lens antenna is designed using AGIMS lens and microstrip patch antenna (MPA) radiator operating at 10.10 GHz. An ultrathin graded-index metasurface lens is designed using fundamental unit cells and their modulated forms. The direction and gain control of the microwave radiator’s beam, using a designed modulated metasurface lens with doubled-sided double circular ring resonator as a fundamental unit cell, is presented. The uniform radial and linear movement of AGIMS in the step of 12 mm steer the radiated main beam of MPA continuously in a conical plane from −40° to +40° with a maximum measured broadside gain of 13.15 dBi and minimum broadside gain of 11.80 dBi at 10.10 GHz frequency, indicating maximum and minimum gain enhancement of 8.40 and 7.0 dB in −40° and 0° direction, respectively. The angular movement of AGIMS over the MPA radiator at the centre point results in beam steering from −25° to +25° continuously with a maximum gain variation of 2 dB and a maximum measured gain from 10.00 dBi to 12.00 dBi, indicating gain enhancement of 5.25 dB to 7.25 dB. Using AGIMS, the stable broadside radiation characteristic with beam steering and continuous gain enhancement is achieved. The measured and simulated results are in good agreement.

Millimeter-Wave Dual-Polarized Metal Transmitarray Antenna With Wide Gain Bandwidth

By utilizing the quadruple-ridged waveguide (QRW), a high-gain dual-polarized all-metallic transmitarray (TA) antenna with wide gain bandwidth is proposed. The QRW has a fixed height with four identical ridges symmetrically located inside a square waveguide. The phase compensation is obtained by simultaneously controlling the length of the four ridges. The fully symmetrical structure of the QRW enables the proposed TA to achieve dual-polarization and two-dimensional (2-D) beam scanning. The proposed TA antenna with an aperture of 112 × 112 mm is designed and fabricated by utilizing 3-D metallic printed technology. The measured broadside gain at 30 GHz for the two orthogonal polarizations is 28.2 dBi and 28.1 dBi, corresponding to an aperture efficiency of 41.9% and 40.9%, respectively. The measured 1 and 3 dB broadside gain bandwidth is 27.3% and 34.8%, respectively. The 2-D beam scanning range at 30 GHz for the dual polarized radiation covers ±18°, with a maximum scan loss of 2.3 and 3.2 dB, respectively.

Design and Measurement of a Reconfigurable Transmitarray Antenna With Compact Varactor-Based Phase Shifters

A reconfigurable transmitarray antenna (RTA) with 360° continuous transmission phase controlling capability is designed and experimentally validated in this letter. The proposed RTA element is based on the receiver-transmitter structure. A compact varactor-based analog phase shifter using a coupled-line structure is utilized to provide a 0° to 180° continuous transmission phase. Two PIN diodes integrated on the active transmitter patch are alternatively turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> to generate an additional 180° phase shift using the current reversal mechanism. The element simulations show a magnitude insertion loss varying from 0.95 to 1.35 dB at 5.6 GHz, and a wide 3-dB transmission bandwidth of 16.7%. A prototype composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{16 \times 16}}$</tex-math></inline-formula> elements is fabricated and measured. The measured broadside gain is 23.7 dBi at the design frequency with a 3-dB gain bandwidth of 15.7%. Good two-dimensional (2-D) beam steering capability within ±60° is also experimentally verified.

Heatsink Antenna Array for Millimeter-Wave Applications

In this communication, a novel fin-shaped heatsink antenna array is designed and fabricated by 3-D printing and low-temperature cofired ceramic (LTCC) technologies. Its structure consists of 16 rectangular air cavities in the bottom base, which are used to form the open-ended rectangular waveguide antennas. Combined with the waveguide and metallic fins, a step-profiled horn is formed as the antenna element, which further enhances the radiation performance. This heatsink antenna array is soldered on an LTCC substrate and the feeding network is realized by the substrate integrated waveguides (SIWs) with numerous metallic vias. These metallic vias inherently provide an effective path for transferring the heat from chips to the heatsink. The simulated performance of this heatsink antenna array is in good agreement with the measured one. The measured broadside gain is 18.1 dBi at 60 GHz, and the 10 dB relative impedance bandwidth is 11.7%.

Gain‐enhanced 60‐GHz SIW cavity‐backed slot array antenna using metallic grooves

AbstractIn this article, a 60‐GHz substrate integrated waveguide (SIW) cavity‐backed slot array antenna with metallic grooves is proposed. To feed the four slot antenna elements, an SIW feed structure with a microstrip‐to‐SIW transition is used. To account for the effect of an actual connector on the antenna performance, simulations including the V‐band connector model were carried out. The measured 10‐dB return loss bandwidth of the proposed antenna with the connector is 600 MHz (59.76‐60.36 GHz). Sixteen metallic grooves are used to enhance the gain characteristics. By adding grooves, the electric field is concentrated in the +z direction. The measured broadside gain of the proposed antenna array with grooves is 13.59 dBi. Compared to a conventional SIW cavity‐backed slot antenna array, the proposed antenna array with 16 grooves has an enhanced gain of 5.6 dB.

Dual-Band (28,38) GHz Coupled Quarter-Mode Substrate-Integrated Waveguide Antenna Array for Next-Generation Wireless Systems

A novel dual-band substrate-integrated waveguide (SIW) antenna array topology is proposed for operation in the 28 and 38 GHz frequency bands. Four miniaturized quarter-mode SIW cavities are tightly coupled, causing mode bifurcation, and yielding an antenna topology with four distinct resonance frequencies. A pair of resonances is assigned to both the 28 and 38 GHz band, achieving wideband operation in both frequency ranges. Moreover, owing to the exploited miniaturization technique, an extremely compact array topology is obtained, facilitating easy and straightforward integration. The computer-aided design process yields a four-element antenna array that entirely covers the 28 GHz band (27.5–29.5 GHz) and 38 GHz band (37.0–38.6 GHz) with a measured impedance bandwidth of 3.65 and 2.19 GHz, respectively. A measured broadside gain of 10.1 dBi, a radiation efficiency of 75.75% and a 3 dB beamwidth of 25° are achieved in the 28 GHz band. Moreover, in the 38 GHz band, the measured broadside gain amounts to 10.2 dBi, a radiation efficiency of 70.65% is achieved, and the 3 dB beamwidth is 20°.

Low-Profile Wideband High-Gain Reconfigurable Antenna With Quad-Polarization Diversity

A low-profile, wideband, high-gain reconfigurable antenna, which is capable of switching among four linear polarizations (LPs) at every 45° rotation, namely, 0°, 45°, 90°, and 135° LP, is presented. The proposed structure is based on two half-ellipse-shaped dipoles arranged perpendicularly and is center fed by coaxial cable. The antenna polarization can be switched by selecting the appropriate dipole arms to be excited as well as controlling their phases using p-i-n diodes. To achieve low-profile, high-gain, and unidirectional radiation patterns in a wide range of frequency, a combination of an artificial magnetic conductor and a shallow pyramid-shaped cavity is also utilized in this design. An optimized prototype with low profile of $0.1\lambda $ at the lowest operating frequency yields a measured overlapped impedance bandwidth (BW) of 53.9% for all polarization states. In addition, a radiation efficiency of greater than 78% and measured broadside gain from 6.8 to 10.9 dBi are observed over the entire operation BW.

Steerable miniaturised printed quadrifilar helical array antenna using digital phase shifters for BGAN/GPS applications

A novel electronically steerable phased array antenna is developed for global positioning system/broadband global area network (GPS/BGAN) navigation applications. The array is composed of 2 × 2 printed quadrifilar helical antennas (PQHAs) integrated with digital phase shifters for beam steering over the transmit/receive bands. The feed network of each PQHA is based on a sequential rotation to achieve wideband circular polarisation (CP). An elegant control network with the embedded microcontroller is designed to provide driving bits to the phase shifters with reduced phase error. The meandered line design maintains high-performance CP radiation up to ±60° off-axis, within 1525 to 1660 MHz, and its size is 44% of the design with straight lines. The array gain is positive over 1450-1800 MHz beyond the BGAN band, with better than 13 dB return loss and <;2.2 dB axial ratio. The measured broadside gain of the array exceeds 8.5 dBi at 1600 MHz, and has a wide beam steering of ~±80° over the BGAN band. The developed antenna represents a significant technical advance to the design and manufacturing of PQHA array, it has a compact size, low cost and lightweight with a relatively large bandwidth and almost hemispherical coverage with excellent right-hand circularly polarized radiation.

A Millimeter-Wave Dual-Feed Square Loop Antenna for 5G Communications

A millimeter-wave (mm-Wave) dual-feed square loop antenna is presented in this paper for 5G communications. It synthesizes identical far-field radiation patterns as a conventional single-feed square loop antenna. The dual-feed antenna (DFA) also simplifies or even eliminates the lossy power-combining network between the transmitter and antenna, achieving direct on-antenna power combining. The proposed antenna concept significantly improves the total radiated power and power efficiency of a wireless transmitter, particularly useful for 5G transmitters that normally require large output power to compensate the high mm-Wave path loss. Compared with antenna-array-based spatial power combining, the DFA only requires a single-antenna footprint and maintains the single-element beamwidth, ideal for mobile 5G communications. The dual-feed square loop antenna is designed and characterized at two potential 5G bands, i.e., 38.5 and 73.5 GHz. Conventional single-feed square loop antennas are implemented as reference designs. Closely matched antenna characteristics are achieved in measurement between the proposed DFA and conventional single-feed antenna. The dual-feed square loop antenna has measured broadside gain of 2.9 and 3 dBi, and fractional bandwidth of 13% and 14%, at 38.5 and 73.5 GHz, respectively. High-speed modulation test is also performed. A 4.3% error vector magnitude (EVM) with a −33.2-dBc adjacent channel leakage ratio (ACLR) for 6-Gb/s 64QAM is achieved at 38.5 GHz, and a 5.6% EVM with a −33.4-dBc ACLR for 6-Gb/s 64QAM is measured at 73.5 GHz, which demonstrates the viability of the proposed DFA for high-speed and complex modulations required by 5G communications.

Compressed Dipoles Resonating at Higher Order Modes With Enhanced Directivity

A compressed dipole operating at higher order modes is proposed and investigated for the enhancement of boresight directivity. Compared with conventional dipoles in free space, the length of the proposed dipole is compressed although the currents on the compressed dipole still sinusoidally distribute. The traces of calculated compressed dipole’s directivity against compressibility show that the directivity of a compressed dipole operating at higher resonant modes is larger than conventional dipoles for the well selected compressibility. This paper shows that printing the dipole onto a piece of dielectric substrate can achieve the desired compressibility. The relationship between the compressibility and relative permittivity of the dielectric slab provides the guidance to realize the selected compressibility. As an example, a thin linear compressed dipole resonating at the third mode is designed, fabricated, and measured to validate the method. The measured broadside gain of the proposed compressed dipole reaches up to 4.6 dBi, 75% or 2.45 dBi higher than a conventional dipole.

An Optimized Wideband High Directive Microstrip Fractal Patch Antenna based on Near-Zero-Index Metamaterial Superstrate

ABSTRACTIn this article, a wideband near-zero-index metamaterial (NZIM) unit cell, for gain improvement of a broadband microstrip fractal patch antenna is proposed and designed. The near-zero refractive index characteristics of metamaterial superstrate is used, which gathers the radiated waves from the source antenna and collimates them toward the normal direction. The reference fractal patch antenna operates at a relatively wide frequency range covering from 2.38 to 3.61 GHz, corresponding to a 40% fractional bandwidth. In order to effectively enhance the broadside gain of the antenna, a proposed unit cell is optimized using invasive weed optimization (IWO) algorithm to have the widest bandwidth at the required frequency band, in which the refractive index is less than unity (approaches zero). A prototype of the antenna was fabricated and tested. Measured results are in good agreement with the simulation. The measured −10 dB relative impedance bandwidth for the loaded antenna with NZIM is found to be 31%. The maximum measured broadside gain is about 3.1 dB higher than that of the reference antenna without NZIM, which corresponds to 86% aperture efficiency.

Wideband Linearly Polarized Transmitarray Antenna for 60 GHz Backhauling

This communication presents the design of a linearly polarized transmitarray antenna for backhauling applications at V-band (57-66 GHz). The antenna is composed of a planar circular-shape array with 1264 unit-cells (UCs) printed on a three-metal layer standard printed circuit board, an ad hoc focal source, and a radome layer. A 3-b phase resolution has been selected to achieve a gain higher than 31 dBi over the whole unlicensed 60 GHz band and low sidelobe levels. The presence of the radome near the array is taken into account in the UC design. Experimental results are in line with the theoretical ones provided by an in-house CAD tool based on analytical model and electromagnetic simulations. The proposed design presents a measured broadside gain of 32.5 dBi at 61.5 GHz with an aperture efficiency of 42.7% and a wide 1-dB gain bandwidth of 15.4% (57-66.5 GHz).

Beam Scanning Antenna with Wideband Broadside Radiation Based on Multilayered Substrate Integrated Waveguide Composite Right/Left-Handed Structure

Abstract In this paper, a novel multilayered substrate integrated waveguide (SIW) composite right/left-handed (CRLH) structure is proposed to design beam scanning antenna for wideband broadside radiation. The unit cell of the SIW-CRLH structure is formed by spiral interdigital fingers etched on the upper ground of SIW, and a parasitic patch beneath the slot, has a continuous change of phase constant from negative to positive value within its passband. The proposed beam scanning antenna, which consists of consists of 15 identical elementary cells of the SIW-CRLH, is simulated, fabricated and measured. According to the measured results, the proposed antenna not only realizes a continuous main beam scanning from backward –78° to forward +80° within the operating frequency range from 8.25 to 12.2 GHz, but also obtains the measured broadside gain of 11.5 dB with variation of 1.0 dB over the frequency range of 8.8–9.25 GHz (4.99 %). Besides, compared with the same works in the references, this one has the most wonderful performance.

Low-Loss Circularly Polarized Transmitarray for Beam Steering Application

We present the design and demonstration of a low-loss circularly polarized (CP) transmitarray. The proposed transmitarray is composed of a receiver cell with a 180° analog phase shifter and a transmitter cell integrating 1-bit phase shifting and linear-circular polarization transformation properties. By the analysis of numerical simulation, the transmitarray is verified to transform the incident linearly polarized (LP) wave into outgoing CP wave in the frequency band of 4.75-4.85 GHz. In addition, it can realize the 360° continuous phase modulation, and its insertion loss is less than 2 dB for all the transmission phases. We fabricate a fully reconfigurable 6 × 6 CP transmitarray, and it is experimentally demonstrated to achieve 360° phase tuning range with the average loss of ~2.2 dB. When the proposed CP transmitarray is excited by a LP horn antenna, it produces a CP pencil beam at 4.8 GHz and its measured broadside gain is 14.8 dBi with axial ratio (AR) of 0.65 dB. By tuning its transmission phase, the CP transmitarray can also achieve beam steering at the angle of ±45°, and the value of AR is less than 3 dB at most of the scan angles.

Circularly Polarized Transmitarray With Sequential Rotation in Ka-Band

We present here the design and demonstration of a circularly polarized (CP) transmitarray antenna operating in Ka-band and illuminated by a linearly polarized (LP) source. The proposed design is based on a CP unit-cell with simulated insertion loss of 0.2 dB at 30 GHz. In order to improve the axial ratio (AR) bandwidth, the sequential rotation technique is applied to the full array configuration. A model based on a hybrid in-house simulation tool is also proposed to predict accurately the array performance. The realized prototype, formed by 400 unit-cells, has 1 bit of phase resolution. The measured broadside gain is 22.8 dBi at 30 GHz with a 3-dB bandwidth of 20% in right-handed CP (RHCP). The obtained 3-dB AR bandwidth of 24.4% is comparable with higher resolution designs.

UWB loop antenna with stable broadside radiation characteristics

ABSTRACTIn this article, a circular loop antenna with stable broadside radiation characteristics for ultrawideband (UWB) applications is proposed. It consists of a circular loop and circular sectors, and the circular sectors are used to directly match a 50‐Ω feed line over a UWB frequency band. The geometry of the proposed antenna is optimized to cover the 3.1–10.6 GHz UWB frequency band with stable broadside radiation patterns. The input impedance and voltage standing wave ratio (VSWR) characteristics of three different structures (a center‐fed circular loop with thin strips, a structure with circular sectors as an end‐truncated semicircular dipole, and the proposed loop antenna with circular sectors) are compared. The optimized proposed antenna is fabricated on a Teflon substrate. It exhibits a measured impedance frequency band of 3.08–12.27 GHz (120%) for a VSWR &lt; 2, which ensures operation in the UWB band. Measured broadside gain is 3.0–7.0 dBi, and stable broadside radiation patterns are observed in the entire UWB band. Measured group delay remains almost constant with a variation of less than ±0.5 ns for the face‐to‐face orientation, and this indicates good time domain performance of the antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2515–2519, 2015

Tapered composite right/left-handed leaky-wave antenna for wideband broadside radiation

A leaky-wave antenna (LWA) based on tapered composite right/left-handed unit cell sections is proposed for wideband broadside radiation. The substrate-integrated-waveguide metamaterial based antenna consists of three sections with varying slot lengths for unit cells. The measured broadside gain of the proposed tapered antenna prototype is higher than 9.0 dBi over a bandwidth of 4.7% (8.825–9.250 GHz). The bandwidth of the proposed tapered LWA for 1-dB gain variation doubles that of the conventional LWA with non-tapered unit cells. In addition, the proposed antenna is able to scan the beam from −72° to +75° over a frequency range of 8.0–13.0 GHz with the gain greater than 9.0 dBi. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:624–629, 2015

Waveguide Fed Broadband Millimeter Wave Short Backfire Antenna

A broadband millimeter-wave short backfire antenna (SBA), excited by a bowtie dipole and fed by an E-band rectangular waveguide, is presented in this paper. Its subreflector is replaced by two simple strips printed on the opposite sides of the same supporting substrate of the bowtie exciter for ease and accuracy of fabrication. For reference of practical designs, detailed parametric studies are performed in this paper. Measurements and simulations show that the proposed antenna can feature an improved operating bandwidth and broadside gain compared to the previously reported conventional SBAs. The measured impedance bandwidth for SWR $\leq$ 2 is 57%, from 55.7 to 100 GHz, in which the measured broadside gain is from 13.8 to 18.5 dBi with the peak gain at 85 GHz. Finally, high illumination efficiency of the bowtie exciter is highlighted by comparisons with a straight dipole excited SBA.

A $W$-Band Micromachined 3-D Cavity-Backed Patch Antenna Array With Integrated Diode Detector

A 2 × 2 array of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i> -band air-dielectric cavity-backed patch antennas is presented. The array and its components are fabricated using a sequential surface micromachining technique known as the Polystrata process. Each antenna has a simulated 4.1% 10-dB return-loss bandwidth of about 94.5 GHz, a radiation efficiency of 95%, and a gain of 8.3 dB at broadside with a 76° 3-dB beamwidth. The simulated gain of the entire array is 13 dB. To facilitate system integration and measurement, several methods of interface are explored, including ground-signal-ground probing, direct transition to WR-10 waveguide, and hybridly integrated detector diodes. A measured return loss of 32 dB at 94 GHz with a 10-dB bandwidth of 3.25 GHz is measured for a single antenna, and 18 dB with a 10-dB bandwidth of 4.6 GHz is measured for an array. Measured <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> - and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane 3-dB beamwidths of 25° are reported. Antenna pattern measurements show good correlation with simulated results. The measured broadside gain for the antenna array is 13.5 dB at 94 GHz.