Low Back Lobe Radiation Research Articles

Filtering Antenna With Quasi-Elliptic Response Based on SIW H-Plane Horn

A filtering antenna with a quasi-elliptic response based on the substrate-integrated waveguide(SIW) H-plane horn is presented. It is mainly composed of two symmetrical horn elements embedded with the trapezoidal dual-mode cavity. By exploiting the cross couplings of the dual-mode cavity, two radiation nulls are introduced on the gain curve showing a quasi-elliptic filtering response without the increase of horn size. Then, a modified transition is printed in front of the horn aperture on both sides of the substrate, which acquires wider impedance bandwidth and maintains a low backlobe radiation throughout the bandwidth. Besides, the proposed antenna is designed, fabricated, and measured at Ku-band. Two measured radiation nulls can be observed at 14.02 and 17.98 GHz, where the gain drops significantly to below -28 and -38 dBi, leading to high frequency selectivity. A wide measured impedance bandwidth of 12.2% and a large front-to-back ratio of more than 20 dB are achieved. To the author's best knowledge, it is the first time that the filtering horn antenna with radiation nulls, wide bandwidth, and excellent radiation is designed.

A compact dual-fed highly isolated SIW based self-diplexing antenna

A compact high-isolation self-diplexing antenna is designed on a single-layered substrate integrated waveguide (SIW) cavity for dual-frequency communication in C-band. The antenna design procedure is straightforward. The antenna is backed by an SIW cavity for possible low back-lobe radiation and easy circuit integration. One rectangular and one triangular patch are created on the top-side of the SIW cavity to radiate at 4.18 GHz and 7.8 GHz respectively. Two planar inset-feed lines orthogonal to each other, are employed to excite the resonator. The inset depths of the feedlines are designed to obtain low interference and high isolation. The antenna achieves peak gain of 5.88 dBi and 6.62 dBi at lower and upper resonant frequencies respectively. The antenna supports independent frequency tuning-design and easy frequency-ratio control. The proposed design is fabricated on a RT/Duroid 5870 substrate and is characterized for validation.

UAV-Based Antenna Measurements for Polarimetric Weather Radars: Probe Analysis

One of the principal challenges in the calibration of polarimetric weather radars is achieving the strict requirements in the measurement of the antenna radiation pattern of the system; e.g., a co-polarization mismatch of at most 0.1 dB, and cross-polarization levels less than approximately −40 dB are highly desirable. In a UAV-based antenna pattern measurement system, the radiation characteristics of the probe antenna can be adversely affected by scattering off of the UAV platform itself, and by the relative orientation of the probe antenna with respect to the UAV frame. It is hypothesized that such extraneous reflections depend on the type of antenna used as a probe, and in this context, a more directive probe antenna (i.e., with low back lobe radiation) would be necessary to achieve the required measurement accuracy for weather radar applications. This work studies the effect of UAV and probe antenna interaction for different types of antennas through EM simulations, and this is validated with chamber measurements. For the patch array antenna under study, co-polarization mismatch levels of approximately 0.13 and 0.05 dB, and maximum cross-polarization levels of −37 and −34 dB, are achieved at boresight in measurements and simulations, respectively, which can be improved to meet the requirements with a careful selection of the gimbal operating angle range.

A Simple Wideband Magnetoelectric Dipole Antenna With a Defected Ground Structure

In this letter, a simple wideband magnetoelectric (ME) dipole antenna with a defected ground structure (DGS) is proposed and investigated. The dimensions of the pair of the quarter-wavelength patch antennas and the half-wavelength electric dipole antennas are changed to extend the impedance bandwidth. A DGS is used for impedance matching, which is novel in the ME dipole antenna design. A prototype of the proposed antenna is designed, fabricated, and measured. On combining impedance bandwidth and radiation pattern, measured results show that the proposed ME dipole antenna achieves an operating bandwidth of 86.9% (1.38–3.5 GHz) for ${{\vert S}}_{11}\vert , and a stable gain of 7.2 ± 1.2 dBi is realized. A low cross-polarization level and low backlobe radiation level are found across the operating bandwidth.

Substrate Integrated Waveguide Horn Antenna on Thin Substrate With Back-Lobe Suppression and Its Application to Arrays

A substrate integrated waveguide H-plane horn antenna on thin substrate with low back-lobe radiation is presented, and its application to arrays demonstrated. To suppress the back lobe, a pair of slots is employed in the top and bottom metallization. After size and position of the pair of slots are investigated, low back-lobe radiation is achieved. Moreover, the size of the horn aperture is approximately one wavelength, which is suitable for array applications. To highlight this point, the proposed horn antenna is used in a $1\,\times \,4$ planar array on a substrate as thin as one tenth of the wavelength. The array is designed, fabricated, and measured. Measurements show good agreement with simulations and suppressed back-lobe radiation with a 24 dB front-to-back ratio.

WIDEBAND VERTICAL PLANAR PRINTED UNIDIRECTIONAL ANTENNA

A new wideband vertical planar printed unidirectional antenna is presented. The proposed antenna is composed of a bowtie electric dipole, a loop antenna and a microstrip-to-coplanar stripline balun. All of them are printed in the same plane perpendicular to the ground. The antenna has a wide impedance bandwidth of 88.9% for SWR • 2 from 3.3 to 8.58GHz and a stable gain of 7:3 § 1:5dBi over the operating frequencies. Moreover, stable unidirectional radiation pattern with low back-lobe radiation, low cross polarization and nearly identical E- and H-plane patterns is also demonstrated over the frequency of interest. A prototype is fabricated and measured. The measured results indicate that the antenna is suitable for wideband wireless communication system.

A WIDEBAND MAGNETO-ELECTRIC DIPOLE ANTENNA USING CPW STRUCTURE

A new wideband magneto-electric dipole antenna using coplanar waveguide (CPW) structure is proposed in this paper. The proposed antenna consists of a pair of horizontal triangular patches and two vertically oriented L-shaped strips. By introducing triangular patches working as an electric dipole, the antenna can operate in a wide band. With the use of L-shaped strips equivalent to a magnetic dipole, the antenna is low in proflle. A microstrip feed line is located between the two L-shaped strips to form a coplanar waveguide structure and excite the antenna. By carefully adjusting the gap between the feed line and the strips, the impedance bandwidth can be improved largely. A parametric study is performed to provide information for designing and optimizing such an antenna. A prototype is fabricated and measured. The simulated and measured results show that the impedance bandwidth for SWR less than 2 of the proposed antenna is 58.7% (1.95{3.57GHz). Due to the complementary nature of the antenna, the proposed antenna has a unidirectional radiation pattern with low-polarization and low back-lobe radiation over the whole operating band. Furthermore, the gain of the antenna is stable across the entire bandwidth.

Compact Substrate Integrated Waveguide Slot Antenna Array With Low Back Lobe

In this letter, a compact substrate integrated waveguide (SIW) slot antenna array with a comb-shaped choke is proposed for low back-lobe radiation. The comb-shaped choke consists of an array of quarter-wavelength short-end parallel microstrip lines on the bottom surface of the array for lowering the backward radiation by suppressing the diffraction at the edges of the substrate. The proposed antenna array operating at 10 GHz exhibits a 10-dB back-lobe reduction compared to the antenna without the choke.

Design of wideband dual-band dual-polarized dipole for base station antenna

This article put forward a novel dual-band dual-polarized magneto-electric dipole antenna excited by F-shaped strips. The proposed antenna achieved a common impedance bandwidth of 25.5% and 39.5% in the lower and the upper bands at both input ports, ranged from 0.75 GHz to 0.97 GHz and from 1.73 GHz to 2.59 GHz respectively. The antenna has good performance in isolation, which is more than −32 dB between the two input ports, and the gain of the antenna is average 4.3 dB and 7.8 dB in the lower and upper bands. The antenna has a stable broadside radiation pattern with low cross polarization and low back lobe radiation over the operating band. Metallic side walls on the ground are added for better performance in gain and radiation pattern.

Design of Broadband Dual-Band Dipole for Base Station Antenna

A novel dual-band unidirectional antenna composed of an irregular shorted patch and planar dipole elements is presented and studied. This proposed antenna employs an L-shaped feeding strip for exciting dual-band operations. For the lower frequency band, a V-slot is loaded on the planar dipole for acting as a capacitive loading for having wide impedance matching of the antenna. Then, two additional smaller planar dipoles are placed and connected to the irregular short patch for achieving another wideband performance at the higher frequency band. The proposed antenna has wide dual-band impedance bandwidths of 34% and 49.5% in the lower and the upper bands, ranged from 0.78 GHz to 1.1 GHz and from 1.58 GHz to 2.62 GHz, respectively. More importantly, the antenna has stable gains of 7 dBi and 8 dBi across each band, demonstrating the high stability of the radiation characteristic for the two radiation modes. The radiation patterns are symmetric, low back-lobe radiation and low cross-polarization. Analysis and parametric studies of the proposed antenna are provided.

A UWB Unidirectional Antenna With Dual-Polarization

A novel ±45° dual-polarized unidirectional antenna element is presented, consisting of two cross center-fed tapered mono-loops and two cross electric dipoles located against a reflector for ultrawideband applications. The operation principle of the antenna including the use of elliptically tapered transmission line for transiting the unbalanced energy to the balanced energy is described. Designs with different reflectors-planar or conical-are investigated. A measured overlapped impedance bandwidth of 126% (SWR <; 2) is demonstrated. Due to the complementary nature of the structure, the antenna has a relatively stable broadside radiation pattern with low cross polarization and low back lobe radiation over the operating band. The measured gain of the proposed antenna varies from 4 to 13 dBi and 7 to 14.5 dBi for port 1 and port 2, respectively, over the operating band, when mounted against a conical backed reflector. The measured coupling between the two ports is below -25 dB over the operating band.

A Magneto-Electric Dipole With a Modified Ground Plane

A wideband unidirectional antenna element composed of a magnetic dipole and an electric dipole is designed. Simulated and measured results are presented. The antenna achieves an impedance bandwidth of 91% (SWR < 2). Due to the complementary nature of the antenna and the incorporation of a modified grounded structure, the antenna has a relatively stable broadside radiation pattern with low cross-polarization and low back-lobe radiation over the operating band. The gain of antenna is about 9.3 dBi.

Active feedback microstrip leaky wave antenna-synthesiser design with suppressed back lobe radiation

The design of an active leaky-wave antenna which integrates the antenna with a feedback synthesiser is introduced. The measurement result shows that the antenna has very low back lobe radiation compared with that of traditional single-terminal feeding leaky-wave antennas. Single frequency measurement shows that the radiated power difference between the main beam and back lobe is &gt; 15 dB at 8.2 GHz. For the designed feedback synthesiser antenna, the measured radiated power difference between the main beam and back lobe is &gt; 15 dB at 9.25 GHz, and the scanning angle is ~5° as the synthesiser frequency sweeps from 9.25 to 9.37 GHz.

Characteristics of aperture-coupled coplanar microstrip subarrays

The characteristics of aperture-coupled microstrip antennas with parasitic elements are studied. Four configurations for increasing the bandwidth of aperture-coupled microstrip antennas are described. Additional patches are gap-coupled to the nonradiating edges of the rectangular fed patch. The spectral domain Green function approach and the reciprocity method are used for the analysis. The SWR bandwidth and the E- and H-plane beamwidths can be improved by changing the sizes and the locations of the parasitic patches. Low backlobe radiation can be achieved by locating a plane reflector slightly below the microstrip feedline. The bandwidth of the microstrip subarray can also be enhanced with the addition of the plane reflector. The theory is confirmed by experimental data.