Back Lobe Level Research Articles

A Compact Microstrip Antenna With Extended Half-Power Beamwidth and Harmonic Suppression

A half-power beamwidth (HPBW) extended patch antenna with harmonic suppression is proposed in this article. The antenna consists of one driven patch and two parasitic patches. The parasitic patches are placed parallel to the two adjacent edges of a driven patch. By introducing four sets of shorting pins near the outer edges of the patches, surface currents on the patches flow through the pins to the edges of the ground plane periodically, making those edges radiate as electrical dipole elements. Huygens’-like radiation with extended HPBW and low back-lobe level is formed by the interaction of dipole and patch-like radiation sources. On the other hand, the resonance at the second harmonic frequency is suppressed, and resonances at higher order modes are shifted away from the third harmonic frequency because of the joint effect of introducing shorting pins and coupling between patches. The mechanism of the antenna is analyzed. A verifying prototype is implemented. In the measurement, the antenna operates at 5.23 GHz. HPBWs of 135°/132° are found, while front-to-back ratios of 13.5/13.3 dB are achieved in the XoZ / YoZ -plane. Resonances at the second and third harmonic frequencies are successfully suppressed.

A Dual-Band Circularly Polarized Antenna With a Dual-Band AMC Reflector for RFID Readers

This letter proposes a circular patch antenna with dual-band circular polarization at the UHF-RFID and WLAN bands. Two perpendicular slots are etched on the patch to down-shift the first resonance to 915 MHz (UHF-RFID band) and introduce a new resonance at 2.45 GHz (WLAN band). Four slits are etched on the ground plane to improve axial ratio (AR) mainly in the first band. A dual-band AMC reflector having 25 unit cells is placed a small distance below the patch to reduce the backlobe level and improve the gain at both bands. Measured 3 dB AR bandwidths of 5.25% and 2% are achieved at UHF-RFID and WLAN bands respectively with gains of 3.1 dBi (UHF-RFID) and 6.25 dBi (WLAN). The antenna system can be used with RFID readers for detecting tags and sending information via the WLAN band.

Field‐matching at the compact SIW horn antenna aperture using genetic algorithm

AbstractA compact substrate integrated waveguide (SIW) horn antenna is proposed with improvements in antenna gain and back lobe level. By pixelating the metal part of the antenna aperture and considering the presence or absence of metal in each pixel using Genetic Algorithm (GA), the electromagnetic field distribution could be controlled especially in the front panel of the antenna. As a result, an increase of 4 dBi occurs in gain and back lobe level is 10.8 dB better than the conventional SIW horn antenna. The proposed antenna works at the frequency of 30.2 GHz and without adding any parts to conventional SIW Horn antenna we do not leave the antenna in compact mode. In order to verify the simulation results, two commercial software has been used and the results are good both in CST and HFSS.

Wide beamwidth planar self‐balanced magnetic dipole antenna with enhanced front‐to‐back ratio

A design approach to a novel planar self-balanced, wide beamwidth magnetic dipole antenna with high front-to-back ratio (FBR) is advanced. The principle for FBR enhancement is revealed at first. As seen, the back-lobe level can be effectively suppressed by adjusting the unbalanced current ratio (UCR) factor: By varying the radius of the circular sector magnetic dipole antenna on the bottom layer and incorporating an arc-shaped branch at the end of the parasitic strip, the UCR factor can be properly tuned, and the back-lobe level can be flexibly controlled. Then, a set of closed-form formulas is derived to provide basic design guidelines and determine the initial value of key parameters. Parametric studies on FBR are then carried out to attain the ultimate designs in a step-by-step manner. As numerically and experimentally verified at the 2.45-GHz band, the FBR of a planar, air-substrate magnetic dipole antenna is indeed increased to over 30 dB with broadened E-/H-plane half-power beamwidth up to 130°/90°. Good agreement between the theoretical, numerical, and experimental results has evidently validated the proposed antenna design approach.

Planar H-Plane Horn Antenna Based on Groove Gap Waveguide Technology

H -plane horn antenna using gap waveguide technology is proposed. The advantage of this technology is its air-filled feature, which improves the impedance matching compared with substrate integrated waveguide (SIW) horn antennas. Corrugated walls as soft surfaces are used on the outer surfaces of the upper and lower horn plates, which act as barriers around the aperture of the antenna and reduce its backlobe levels. The bandwidth of the antenna for $| {{S_{11}}} |$ < -10 dB is 19–28 GHz and the gain varies between 8.5 and 12 dBi. The total efficiency is better than 88% in the operation bandwidth. This structure has the capability of easily integrating with other planar microwave components. As a demonstration, a coupled-resonator filter is integrated with the antenna to select the desired frequency band and cancel the out-of-band harmonics. For the proof of concept, a prototype model is fabricated and tested, where measurement data agree well with the simulation results.

고출력 GPS 재방송 교란을 위한 무선 교란 장치

In this study, we propose a wireless meaconing jamming system for use in high-power GPS meaconing. The purpose of GPS meaconing is to ensure that the target GPS receiver calculates the intended jammer position by repeating the jammer-received GPS signal. In this case, because the received and transmitted signals have the same frequency, the front–back Ratio(FBR) of the antenna should be −160 dB when the effective radiated power(ERP) is 1 W(30 dBm). Thus, the meaconing jammer can malfunction by reducing the back-lobe level of the antenna when the receiver and transmitter are located in a jammer device. In general, the receiver and transmitter are isolated by the time-division or duplex-communication method in order to eliminate reception/transmission interference; however, this performance is still limited. Thus, we designed a wireless meaconing jammer to eliminate reception/transmission interference by long-distance separations.

Optimal design of planar terahertz Yagi-Uda antenna using adaptive chaos optimization algorithm

This paper presents a compact planar Yagi-Uda antenna for terahertz applications at 300 GHz for maximum gain and minimum return loss by optimizing the spaces between directors’ elements beside their lengths and widths. The antenna parameters are optimized using the adaptive chaotic fruit fly optimization algorithm (CFOA) as a recent evolutionary-based algorithm. To show the convergence capability of the CFOA, the results are compared with those obtained by other evolutionary algorithms such as particle swarm optimization algorithm (PSO). The optimized antenna showed a return loss of -53 dB with high antenna gain of 14.2 dB. This enhancement is attributed to the efficient coupling between optimized array elements as well as reduced side and back-lobe levels. The comparison between different algorithms showed that the CFOA technique is superior to other evolutionary algorithms such as PSO by 39%.

Estimation and Utilization of Ground Effects on Conformal Dielectric Resonator Antennas

Ground effects on arc-shaped conformal dielectric resonator antennas (DRAs) working in the TE $^{\mathrm {z}}_{11 \delta }$ mode are investigated and utilized to attain various radiation performances. Manipulation of directivity patterns are achieved with the help of the three-dimensional curved metal ground. The backlobe, beamwidth, broadside gain, backscattering, and cross-polarization level of the antenna are all readily controllable. The geometric theory of diffraction is applied to provide an intuitional explanation for the radiation changes. Detailed analysis is then conducted from the perspective of ground current. It is found that the current distribution is affected by configurations of both the arc DRA and ground plane. Based on this, analytical methods are developed to calculate the ground effects exclusively for conformal arc-shaped DRAs. Next, the design theory of arc DRAs with curved ground is proposed. To demonstrate it, two conformal DRAs owning directional and wide beams, respectively, are designed as paradigms. At last, a prototype is fabricated and measured for validation.

A high gain 60 GHz antipodal Fermi‐tapered slot antenna based on robust synthesized dielectric

AbstractA high performance antipodal Fermi taper slot antenna based on unique synthesized dielectric is presented for ultra‐wideband radar applications at 60 GHz band. Specifically, the synthesized dielectric is implemented based on machined holes concentrates only at aperture area to improve its mechanical robustness for lengthy antenna. Further, it is able to suppress back lobe level by 2.5 dB through curving tapered end of the antenna. Concurrently, sine corrugations and dielectric loading are adopted to improve radiation pattern and gain of the antenna for over 20 dB.

A Broadband Dual-Polarized Antenna With Front-to-Back Ratio Enhancement Using Semicylindrical Sidewalls

A novel dual-polarized antenna, with a large bandwidth and a high front-to-back ratio, is proposed in this communication. The antenna is composed of printed dipoles and tapered baluns above a square ground plane to yield a wide bandwidth. Semicylindrical walls are loaded on the edge of the ground plane to suppress the back lobe and produce a stable gain. Backward radiation is suppressed by the diffraction effect of the semicylindrical sidewalls. Simulation shows that the back-lobe level can be reduced below −13 dB in a large frequency range without degrading the antenna bandwidth. The proposed antenna is fabricated and the measured results show that it has an impedance bandwidth of 69.6% (1.46–3.02 GHz) for voltage standing wave ratio <1.5. Within the bandwidth, the gain varies between 7.1 and 8.4 dBi, and the front-to-back ratio is above 20 dB. The proposed antenna is suitable for outdoor base station applications, and the back-lobe suppression technique can be applied easily to base station antennas.

Millimetre‐wave high‐gain circularly polarised SIW end‐fire bow‐tie antenna by utilising semi‐planar helix unit cell

In this work, a high-gain circularly polarised (CP) substrate integrated waveguide (SIW) bow-tie antenna is presented. The proposed antenna includes a pair of bow-tie radiators. To centralisation radiated pattern and recede side lobe and back lobe level two tilted rows of metalised via hole at the end of the SIW feed line is used. The methods of increasing the antenna gain and generating the CP are discussed. The proposed antenna was fabricated to validate simulated results. The designed structure operates across 40-68 GHz and exhibits a gain of 10-12.5 dBic. In addition, the proposed antenna exhibits a 3-dB axial ratio bandwidth from 54 to 64.3 GHz.

A Simple Tri-Polarization Reconfigurable Magneto-Electric Dipole Antenna

A simple magneto-electric (ME) dipole antenna with reconfigurable polarizations has been designed. The proposed ME dipole antenna mainly comprises three pairs of horizontal rectangular patches, a Γ-shaped feed, a metallic cavity, and four PIN diodes. By independently controlling the on/off state of the PIN diodes, the horizontal rectangular patches can be connected/disconnected, thus exhibiting linear polarization, right-hand circular polarization, and left-hand circular polarization. The experimental results demonstrate that the proposed ME dipole antenna has a wide effective bandwidth of 33.9% from 1.74 to 2.45 GHz for both S 11 ≤ −10 dB and axial ratio ≤3 in all polarization states, and a stable gain of 8.2 ± 0.8 dBi. Good unidirectional radiation characteristic and low backlobe level are achieved over the whole operating frequency band. A prototype was fabricated, and good agreement between measured and simulated results validates polarization diversity of the proposed antenna.

A High Gain Dual Polarized Ultra-Wideband Array of Antenna for Chipless RFID Applications

In this paper, an ultra-wideband, orthogonally polarized, and high-gain microstrip patch antenna array with $8\times8$ -element for the chipless radio frequency identification (RFID) applications is proposed. This planar-structure antenna has a high front-to-back ratio in a wide frequency band. The element comprises an interleaved aperture-coupled dual polarized stacked microstrip patch antenna with air gaps and complementary back reflectors. The stacked patch elements are etched on Taconic TLX-8 substrate and the complementary back reflectors are etched on FR-4. The presence of back reflectors reduces the back-lobe level significantly. The antenna array operates over 4.2–7.1 GHz and yields 26-dBi gain. Overall, the antenna yields 51.3% fractional bandwidth centred at 5.65 GHz. The antenna can read a multi-bit chipless RFID at a distance of 8 m with a transmit power of −10 dBm.

Super directive Yagi–Uda nanoantennas with an ellipsoid reflector for optimal radiation emission

In this paper, the optimal designs of silicon Yagi–Uda nanoantennas (NAs) with an ellipsoid reflector have been proposed and analyzed using the 3D finite-difference time-domain method. The combination of nanospheres, nanowires, and ellipsoid reflectors has been employed to enhance the antenna directivity. The nanoantenna geometrical parameters are optimized using the particle swarm optimization algorithm. The optimized spherical NA with an ellipsoid reflector shows high directivity of 19.89, which is higher than the conventional counterpart by 65.75%. This enhancement is attributed to the different supported modes by the ellipsoid reflector, which increases the forward radiation and suppresses the backward one. Further, the optimized nanowire design with an ellipsoid reflector has achieved a directivity of 23.4. In addition, the radiation efficiency has been increased to 80.2% and 75.9% for optimized spherical and nanowire antennas, respectively. This enhancement is attributed to the efficient coupling between array elements as well as reduced sidelobe and back-lobe levels.

Sidelobe Reduction in a Planar Array using Genetic Algorithm under Backlobe Reduction Condition

The peak sidelobe level (PSL) minimizing amplitude weights for planar array, with 3D beamforming under the backlobe level reduction (BLL) condition is proposed. Binary genetic algorithm (BGA) is performed on the amplitude weights to achieve low PSL. BLL reduction condition for the inter-element distance between the antenna elements is applied to achieve reduced BLL. Earlier studies only focus on minimizing sidelobe level of planar array. BLL reduction condition has not yet been applied for planar array case. Hence a different way of achieving the amplitude weights to reduce PSL with 3D beamforming using BGA, under the BLL reduction condition is proposed in this paper. Obtained PSL and BLL for planar array by applying optimized weights under BLL condition is -20.89 dB and -2.37 dB respectively. PSL is reduced by 8.84 dB compared to uniform planar array. BLL is reduced by 2.37 dB compared to planar array discussed in existing research work.

Design of Microstrip Antenna Array with Suppressed Back Lobe

A practical procedure to reduce the back lobe level of microstrip antenna arrays is presented in this paper. The novel concept consists in the design of the radiators asymmetrically positioned with respect to the ground plane. In order to validate this technique, a four-element linearly-polarized array is designed in the HFSS software and a prototype is manufactured. Furthermore, the design of beamforming circuit to achieve broadside radiation and -20 dB side lobe level is detailed. Very good agreement between simulated and experimental results is obtained. Although the technique is presented for linearly polarized arrays, it is general and can also be applied in the circularly polarized ones.

A Novel Dual-Broadband Dual-Polarized Electrical Downtilt Base Station Antenna for 2G/3G Applications

A novel dual-broadband dual-polarized base station antenna array with compact structure and low profile is proposed in this paper for the existing mobile communication system operating over 0.79–0.96 GHz (European Digital Dividend/CDMA/GSM) and 1.71–2.17 GHz (DCS/PCS/UMTS). The antenna array is mainly composed of five lower-band elements, ten upper-band elements, some U-shaped metal baffles, and a metal reflector with specific shape. In order to reduce the overall size of the antenna array, lower-band element is designed as octagon aperture shape that upper-band elements can be embedded in it. Two kinds of radiation elements (five for each kind of element) are applied in the antenna array as upper-band elements to achieve better radiation performance. The proposed antenna array achieves electrical downtilt (0°–14° and 0°–10° at lower frequency band and upper frequency band, respectively) by adjusting input amplitude and phase of each array element. Measured results demonstrate that the antenna array has good broadside radiation characteristics, including low voltage standing wave ratio (VSWR 28 dB), low backlobe level (>25 dB), high cross-polarization discrimination (>20 dB), and stable radiation pattern with horizontal half-power beamwidth (HPBW) 65° ± 5° at both frequency bands and all electrical downtilt angles. The peak gains of 15.1 and 17.3 dBi are obtained at lower and upper bands respectively. Owing to these advantages, the antenna array is suitable for existing 2G/3G applications in modern mobile communication systems.

A Wideband Circularly Polarized Magnetoelectric Dipole Antenna

This letter proposes a novel wideband circularly polarized magnetoelectric dipole antenna. In the proposed antenna, a pair of rotationally symmetric horizontal patches functions as an electric dipole, and two vertical patches with the ground act as an equivalent magnetic dipole. A Γ -shaped probe is used to excite the antenna, and a metallic cavity with two gaps is designed for wideband and good performance in radiation. A prototype was fabricated and measured. The experimental results show that the proposed antenna has an impedance bandwidth of 65% for SWR≤2 from 1.76 to 3.46 GHz, a 3-dB axial-ratio bandwidth of 71.5% from 1.68 to 3.55 GHz, and a stable gain of 8 ± 1 dBi. Good unidirectional radiation characteristic and low back-lobe level are achieved over the whole operating frequency band.

Leaky-Wave Thinned Phased Array in PCB Technology for Telecommunication Applications

We present a practical implementation of a leaky-wave thinned phased array in printed circuit board (PCB) technology. In this paper, we demonstrate that a reduction of the grating lobes, and therefore an improved gain in a thinned phased array, with respect to standard solutions, is achieved by virtue of the angular filtering introduced by a leaky-wave cavity in the far field. The presented array is designed in PCB and integrated with an inductive partial reflective surface. A full study of the performances of the $7\times 7$ phased array antenna for several scanning angles and frequencies is presented. This paper shows an improved gain, directivity, grating lobe level, back lobe level, beam efficiency, and active reflection coefficient with respect to a reference solution based on $2\times 2$ subarrays. The results are validated via the measurements of a $3\times 3$ array prototype.

Design and implementation of a Q‐band millimeter wave planar lens antenna

ABSTRACTA Q‐band planar lens with four substrates separated by air gaps is investigated. The efficiency, gain, and back lobe level are improved by shifting the sizes of the cells with dual square slot loops on different substrates. Besides, the compensated phase of each compound cell which consists of the corresponding square slot loop cells distributed in the four substrates is calculated using an equivalent phase other than the phase at the center of the cell. Three hundred and sixty degree compensated phase can be achieved by changing the sizes of the outer and inner slot loops of the cell. The side length of the lens is 144 mm or 20 wavelengths. The air gap between the substrates is 2 mm. The number of cells is 2025 or 45 by 45. The lens is fed by a linear polarized horn antenna with a gain of 15 dBi approximately. The measured peak gain is more than 33 dBi at 44 GHz, and the half power beam width of E‐plane and H‐plane are about 2.9°. The lens could cover from 43 to 47 GHz or more than 9% bandwidth. The side lobe level is under −20 dB, and the measured front‐back‐ratio is better than 20 dB. The measured data are in agreement with the simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2322–2330, 2015