Stacked Patch Elements Research Articles

A Conformal Phased Array with Low Profile and Wide-Scanning Performance for SAR Application

A low-profile wide-scanning conformal phased array (CPA), with cavity-backed stacked patch elements, is presented in this paper. To reduce the array profile, a partially dielectric-filled cavity is employed in each element, and to enhance its scanning performance, the cavity walls are deliberately modified. Finally, the designed element operates in a frequency band of 1.45∼1.75 GHz, with a profile of 0.086 λh (λh is the free-space wavelength at 1.75 GHz), and achieves ±60° scanning in the E/H-planes, with the reflection coefficient below −7 dB. The proposed design method and all numerical results are experimentally verified by a 4 × 4 CPA prototype.

Generalized Sequential Rotation Arrays With Full Control of Dual-Circularly-Polarized Aperture-Field Distribution Based on Elliptically-Polarized Elements

In this article, the theory, design, and experimental validation of wideband generalized sequential rotation arrays (GSRAs) are reported. In particular, the GSRA has the ability to provide dual-circularly polarized (dual-CP) beams with different handedness using a single feeding network, whose aperture amplitude and phase distributions can both be independently controlled. Such functionality is achieved by jointly utilizing the dynamic phase and Berry phase, as well as exploiting elliptically polarized (EP) array elements with different axial ratio (AR) values. The proposed technique and the design methodology are verified by two proof-of-concept microstrip GSRAs consisting of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> array of EP stacked-patch elements operating in the K-band. The first prototype exhibits a 3 dB gain difference between the two CP beams, while the other offers a 6 dB gain difference and different sidelobe levels (SLLs) for the generated dual-CP beams. Both arrays are fabricated and measured, experimentally achieving a joint <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11} &lt; -10$ </tex-math></inline-formula> dB, AR < 3 dB, and 3 dB gain bandwidth of more than 28.4% and 20.1% with a beam squinting of less than 3°. In addition, the two GSRAs enable a bandwidth of about 19% and 3% within which the gain difference between the two CP beams of different handedness deviates from the targeted value by less than 1 dB. With the large degree of freedom in aperture field control, the proposed GSRAs could be potential candidates for use in satellite communications, point-to-multipoint communications, and so on.

Conformal Antenna Array Design Using Aperture Synthesis and On-Platform Modeling

Conformal antenna arrays have long represented an attractive solution to challenges imposed by an electromagnetic aperture on an aerospace platform. This allows designers to trade between array positioning and geometry, and avoids the significant aerodynamic drag of a planar array. This is hampered by the expense of the design and computational modelling required to ensure that a conformal array will meet its performance requirements. The proposed approach uses raycasting techniques to predict the rectilinear projection of a conformal aperture onto the farfield to calculate the maximum achievable beam coverage (aperture maximum directivity envelope). In order to compare aperture projection with the performance of the modelled arrays in a consistent manner, the steering efficiency (SE), which is the fraction of the farfield steerable to within 3dB of the maximum directivity, was calculated for the aperture, stacked patch, and conical monopole elements. The stacked patch elements demonstrated a SE of 18% over the steering plane compared with 40% for the arbitrary directional elements, and the optimum of 38% for the aperture overall. The Conical monopole elements achieved a SE of 8%, compared to 20% for the measured elements, and 33% achieved with arbitrary omnidirectional elements. These results demonstrate that, for both omnidirectional and directional elements, the aperture projection method offers a compelling tool for conformal array design, which is consistent with the achieved array performance for the stacked patch and conical monopole elements.

Planar circularly polarized X‐band array antenna with low sidelobe and high aperture efficiency for small satellites

A planar broadband circularly polarized (CP) X-band array antenna with low sidelobe and high aperture efficiency is presented for small satellite applications. The array design is composed of 4 × 4 broadband CP stacked patch elements, which are fed by a feeding network consisted of unequal series-parallel power dividers to achieve the low sidelobe and high aperture efficiency. The final prototype with overall size of 100 mm × 100 mm × 3 mm (2.73λ0 × 2.73λ0 × 0.082λ0 at 8.2 GHz) was fabricated and measured. The antenna has a broadband characteristic with |S11| < −10 dB bandwidth of 15.9% (7.52-8.82 GHz) and 3-dB axial ratio bandwidth of 11.95% (7.63-8.60 GHz). Also, it achieves an excellent broadside CP radiation with a gain of 17.2-20.03 dBic, a sidelobe level of <−20 dB, and aperture efficiency of 65% to 97.5%. With these features, the proposed antenna is a good candidate for high-speed data downlink onboard small satellites (MiniSat, MicroSat, NanoSat, and CubeSat).

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.

SPACE-BORNE MULTIBEAM ARRAY PATTERN SYNTHESIS FOR INCREASING CAPACITY

The traditional pattern synthesis method of space-borne array is to achieve a \iso-∞ux beam coverage via approximating a desired pattern; however, the synthesized pattern may not optimize the whole satellite communication (SatCom) system performance. This paper analyzes the interference in multibeam SatCom system using CDMA, and establishes the relation model between user capacity and multibeam pattern. Additionally, a novel particle swarm optimization (PSO) based on simulated annealing (SA) pattern synthesis method is proposed, which chooses user capacity as synthesis objective function. The numerical analysis, which is performed for a hexagonal array with 19 stacked patch elements, conflrms that user capacity is at least doubled with the \max-gain-∞ux beam coverage implemented by our method, compared to the \iso-∞ux coverage when communication outage probability is 10%.

A Dual-Polarized Series-Fed Microstrip Antenna Array With Very High Polarization Purity for Weather Measurements

The design and analysis of a dual-polarization frequency scanning array antenna, operating in a frequency band of 2.7-3.0 GHz, for weather measurement applications are presented. Stacked patch elements are coupled to feed lines through slots etched on the ground plane. A wall of plated holes in the middle of the antenna column is designed to improve the isolation between the two input ports. Both simulation and measurements results confirm that very high polarization purity is achieved.

A Wideband Reconfigurable Transmitarray Element

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. Two reconfigurable transmitarray elements, using single and stacked patches, based on proximity-coupled feeding and two balanced reconfigurable bridged-T phase shifters are presented. Both designs achieve over 400 of phase range and achieve average insertion losses of 3.6 dB. Compared to existing proposed transmitarray elements, the stacked-patch element has a much smaller physical profile, with a lens thickness of only 0.17 λ in free-space, while achieving a large bandwidth of 500 MHz at 5 GHz (10%). Other considerations such as the mutual coupling and beam squint of an array using the stacked-patch element are also discussed.

Design of a Contoured-Beam Reflectarray for a EuTELSAT European Coverage Using a Stacked-Patch Element Characterized by an Artificial Neural Network

The design of a reflectarray for satellite applications is accomplished in this letter. The use of full-wave electromagnetic methods to compute the reflectarray elements in the design process has been replaced by the characterization of the reflectarray elements by artificial neural networks (ANNs). The antenna is designed to provide coverage in Ku-band to a European region defined by EuTELSAT. The results obtained using ANN in the design are compared to those obtained from the method of moments (MoM), and a good agreement is achieved. The speedup factor between reflectarray optimization by both the ANN and the MoM is in the order of 102. Hence, the use of ANN is presented here as a promising fast technique in the design of reflectarrays.

Stacked Patch Antenna Array on LTCC Substrate Operated at 28 GHz

This study develops a 28-GHz patch antenna array using LTCC (Low Temperature Co-fired Ceramic) technology, for use in applications of LMDS (Local Multipoint Distribution Service). The design comprises 2 × 2 stacked patch elements and parallel-fed networks, yielding a wide bandwidth and superior gain performance. Broadband performance is achieved by varying the dimensions of the parasitic patch. The arrays are excited through using a novel opposite-side feeding structure to prevent any electrical effect on the parasitic patch. Measurements correlate closely with the simulation results: a gain of 10.35 dBi and a bandwidth of 2.85 GHz (26.75–29.6 GHz) are achieved.

A compact broadband stacked microstrip array antenna using eggcup-type of lens

This letter describes a compact broadband-stacked microstrip array antenna with a small novel lens for 60-GHz applications. The proposed antenna consists of 2/spl times/2 stacked patch elements using a multilayer RT/Duroid substrate. The microstrip array antenna achieves a gain of 10dB. By adding a small, novel eggcup-type of lens to the antenna, a gain of /spl sim/15dB is reached. The size of the final antenna including the microstrip patch array and the lens is only /spl sim/1.5 cm/sup 3/. The antenna has good performance over the frequency range from 57 to 63GHz.

Efficient wideband printed antennas on lithium niobate for OEICs

Printed antenna structures for integration with z-cut and x-cut LiNbO/sub 3/ based optoelectronic devices are presented. The designs are based on the hi-lo stacked patch element, which yields a high efficiency broadband antenna. Experimental verification of both printed antennas is given.

A wide-band single-layer patch antenna

The typical single-layer patch printed on a dielectric substrate is a narrow-band element. This well-known fact is mainly due to the limitations imposed by the dielectric substrate. From efficiency and cost considerations, in most of the cases, the substrate cannot be too thick. In order to increase the microstrip element bandwidth, additional resonators in different configurations and combinations can be used: parasitic elements, slots, etc. However, the microstrip antenna element with the widest bandwidth (a variation of the aperture-fed stacked-patch element) is about 40-50%. This antenna, an aperture-fed stacked patch, has a relatively poor front-to-back ratio, due to the fact that it has a slot in the ground plane. In this paper, a new type of patch element is presented. The patch is suspended over the ground plane and supported by a nonconductive pin. It is fed by a three-dimensional (3-D) transition connecting the patch to a perpendicular connector. The typical bandwidth of this element (in terms of VSWR) is 90%. When built on a large ground plane, the front-to-back of this element is better than 25 dB across the band.