A highly-directive hybrid-fractal radiator-based printed array for X-band amateur radio applications

Linear antenna arrays exhibit radiation patterns that are restricted to a half-space and feature axial radiation, which can be a significant drawback for applications that require omnidirectional coverage. To address this limitation, the synthesis method utilizing the Taguchi approach, originally designed for linear arrays, can be effectively extended to two-dimensional or planar antenna arrays. In the context of a linear array, the synthesis process primarily involves determining the feeding law and/or the spatial distribution of the elements along a single axis. Conversely, for a planar array, the synthesis becomes more complex, as it requires the identification of the complex weighting of the feed and/or the spatial distribution of sources across a two-dimensional plane. This adaptation to planar arrays is facilitated by substituting the direction θ with the pair of directions (θ,ϕ), allowing for a more comprehensive coverage of the angular domain. This article focuses on exploring various configurations of planar arrays, aiming to enhance their performance. The primary objective of these configurations is often to minimize the levels of secondary lobes and/or array lobes while enabling a full sweep of the angular space. Secondary lobes can significantly impede system performance, particularly in multibeam applications, where they restrict the minimum distance for frequency channel reuse. This restriction is critical, as it affects the overall efficiency and effectiveness of communication systems that rely on precise beamforming and frequency allocation. By investigating alternative planar array designs and their synthesis methods, this research seeks to provide solutions that improve coverage, reduce interference from secondary lobes, and ultimately enhance the functionality of antennas in diverse applications, including telecommunications, radar systems, and wireless communication.

An array of antennas is used to improve gain and directivity. Design of an antenna array gives more design parameters to the designer. In this paper, a new concave linear patch antenna array with 4 elements and concave planar patch antenna array with 4 elements and 16 elements are proposed to study the effect of mutual coupling in arrays. To reduce mutual coupling, concave rectangular patches are proposed in the linear and planar array. The effect of patch concavity on S11 is presented for both linear and planar arrays. Compared to rectangular linear and planar arrays, mutual coupling is reduced in concave linear and planar arrays resulting in increased S11 by 111.068%, 45.64%, and 25.77%, respectively, in the 4-element concave linear array, 4-element and 16-element concave planar array, respectively. The proposed microstrip antenna arrays are simulated using HFSS, and fabricated and tested using vector network analyzer.

In this article, a novel beam shaping technique is developed to synthesize the array factor (AF) radiation pattern of linear and planar antenna arrays. The proposed method is established based on the expanding of AF using Legendre transform in conjunction with an integrand operator. A system of linear equations is derived and its solution is obtained using least-square method (LSM) for the required pattern. In addition, an iterative procedure is introduced to reduce the number of elements of the primary designed array for a specified mean square error (mse). Then, the proposed method is applied to synthesize the AF of planar and ring antenna arrays. To verify the performance of the proposed method, a few comprehensive well-known linear, planar, and ring arrays are examined. The obtained results show that the introduced method can be used to design the AF pattern of many types of practical arrays with good accuracy.

This communication presents for the first time a 16-element planar X-band bidirectional antenna array for beamforming applications. The planar (2D) antenna array is comprised of planar polygon slot antenna elements that utilize a metamaterial inspired reactive coupling element. Simulation and measurement results are presented for both a single antenna element and a 16-element planar array, which resides on a Liquid Crystal Polymer (LCP) substrate. Successful comparison between measured and simulated results verifies that the single antenna element achieves a 10 dB return loss bandwidth of 17.5% and the planar antenna array achieves a 10 dB return loss bandwidth of 25% both at a center frequency of approximately 11 GHz. The measured gain of the planar antenna array is more than 14.5 dBi with an efficiency of 65%. The overall size of the planar antenna array is 3.3λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sub> × 3.6λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sub> × 0.0093λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sub> at 11 GHz.

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A planar antenna array, based on nine identical quasi-Yagi elements, is presented in this paper. Contrary to conventional designs, the feeding network is composed of three-way power dividers, which are carefully designed in order to provide synchronized output signals over a wide frequency range. The use of spline-shaped microstrip lines suppresses coupling effects by parallel lines. Thus, signal distortions within the feeding network are minimized. Compared to conventional designs with eight elements, the additional antenna element will enhance the gain of the array, which is between 10.5 dBi and 13 dBi in the X band. The input return loss of the antenna array is below -15 dB over most parts of the relevant spectrum, with a total bandwidth of 45%. The planar antenna array is well suited as a radiating element in linear phased arrays for multifunction radars, including SAR and MTI. Additionally, the suitability of this antenna for phased-array applications is studied by an experimental setup consisting of five antenna plates.

This article proposed a new geometric design methodology for the systematic expansion of fractal linear and planar array antennas. Using this proposed geometric design methodology any deterministic polygon shape can be constructed. In this article, two element fractal linear and triangular array antennas are examined using proposed methodology up to four iterations of two expansion factors. Due to the repetitive nature of the proposed geometric design methodology, both linear and planar fractal arrays shows multi-beam behavior with excellent array factor properties. The behavior of the proposed arrays shows better performance than linear and planar fractal array antennas generated by concentric circular ring sub array geometric generator. Triangular planar fractal array of expansion factor two at fourth iteration achieved a single valued beam width of 3.80 with -31.6 side lobe level. The suggested fractal arrays are analyzed and simulated by MATLAB-13 programming.

Smart antenna system has been studied extensively for the fifth generation of wireless communication systems, because it has made a system better performance of higher capacity and coverage as well as of power-saving. The present paper introduces a design of planar microstrip patch antenna array for a smart mobile system operating at 28 GHz. The present smart antenna has an adaptive radiation pattern that adjusts its main beam automatically to the desired direction by following the signal environment. This is based on the processing of an algorithm called the Least Mean Square (LMS) resulting in a change in the magnitude and phase of the feeding current for each element in the antenna array. From the obtained results, the main beam can be steered 180 degrees in the phi (azimuth) plane at a constant theta (elevation) angle. The planar antenna array was designed and simulated using CST Microwave Studio and MATLAB software that is used to find the required exciting current for each element. It is found that the antenna bandwidth is greater than 1 GHz while its gain is about 21 dB.

An analytical synthesis method for linear, ring and planar antenna arrays based on ultra-spherical polynomial

Ultrawideband phased antenna array has been widely used in communications, radars and detection. However, the high profile and poor wide-angle scanning characteristics have always been the critical limitation for many available ultrawideband antenna applications. In this paper, an ultra-thin loading window (UTLW) is proposed to replace the wide-angle impedance matching (WAIM) superstrate in the planar ultrawideband modular antenna arrays (PUMA), and reduces the profile height greatly. The UTLW consists of two strips in parallel, and each strip is loaded with two resistors and one capacitor. Following the equivalent circuit model (ECM) of the PUMA, the resistance and capacitance are specially designed to make the complex impedance of the UTLW equal to the impedance introduced by the WAIM. A dual-polarized PUMA with an UTLW achieves 6-18 GHz impedance bandwidth with active VSWR≤2.6 for scanning up to 60° and active VSWR≤3 for scanning up to 70° in E/D/H plane. The profile height of the proposed PUMA is only less than 0.07λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>l</i></sub> , or, 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>h</i></sub> with reference to the typical Nyquist half-wavelength spacing frequency. A 20×20 prototype PUMA with the UTLW was fabricated and its measured results were found consistent with the simulation results.

In this paper, a planar comb-shaped antenna array for terahertz sensing based on the excitation of spoof surface plasmon modes is proposed. The structure is constructed by an array of three periodic rectangular grooves perforated through metal stripes on top of a silicon substrate. The effective detection of lactose is given as an example to demonstrate the ability of this structure to enhance detection sensitivity. In transmission mode, the sensing signal of lactose using the antenna array was 7.6 times larger than that of using a silicon substrate. In reflection mode, the sensing signal of lactose increased almost 13 times using our proposed antenna array compared to that of using a silicon substrate, exhibiting high sensitivity in terahertz sensing. Further, lactose thickness could be predicted based on the reflectance at the peak using our proposed structure. Our results indicate that the proposed structure has great potentiality in the field of biological and chemical sensing.

The paper describes a method for compensating for the effects of mutual coupling in small, circularly symmetric planar antenna arrays such as those used as feeds for parabolic relector antennas. This is achieved by breaking down the array excitation into a series of orthogonal circularly symmetric phase modes, as used in the case of circular antenna arrays. The compensation may then be achieved by means of fixed compensating impedance matches at the phase-mode excitation ports. Once applied, the compensation is independent of the subsequent aperture excitation. It is also shown how the scheme can apply to 4-element planar arrays used as a monopulse cluster feed for a parabolic reflector. Although presented as a physical method to compensate for mutual coupling, the concept may also be used to compute the correct array excitation needed to achieve this compensation.

In this paper, two types of passive, planar Van Atta antenna array are considered to study their performance in detail. For the edge-fed patch antenna array, the transmission lines are difficult to arrange and the whole size of the reflector becomes very large when the number of array element increases. For the aperture coupled patch antenna array, the feed lines and the radiating patch can be isolated from each other by the ground plane between the layers, which can minimize the spurious radiation of the feed and improve the radiation characteristics. The retrodirective angle range obtained by the aperture coupled antenna array is wider than that of edge-fed antenna array. For such case, the monostatic SCS is maintained about 160deg with 10 dB loss. To obtain more gain, a larger array can be composed by this 4times4 subarray, which can still keep the retrodirective performance with some affection in the bandwidth. More discussion and results will be presented at the conference.

Design equations are presented for three-dimensional (volumetric) multiple-beamforming lenses for planar arrays. The minimum lens size for given array dimensions is derived. Theoretical multiple-beam patterns are predicted for a particular lens configuration, using flared waveguide ports, feeding a 37-element planar array. This lens has been constructed and tested, operating over the frequency band 8–12 GHz, and the results show good agreement with theory in most respects. Mutual coupling between lens ports has a significant influence on the lens insertion loss.

This paper presents a novel bidirectional planar monopole antenna array, with its feeding network, to apply for WiFi/Bluetooth and LTE mobile standards. The planar array is comprised of monopole antenna elements that utilise Archimedean spiral slots, inspired as resonance paths, in order to generate multi-band performance. Contrary to conventional structures, the feeding network is composed of three Wilkinson power dividers, for the purpose of providing synchronised output signals over the required frequency range, miniaturising dissipation losses and decreasing mutual coupling. Simulation and measurement results are presented for a single antenna element, an initial Wilkinson power divider and a four-element planar array, which reside on FR4 substrates. Successfully comparison between simulated and measured results verifies that the single antenna element achieves a 10 dB reflection coefficient from 2.2GHz to 2.9GHz, and the planar antenna array illustrates a 10 dB return loss bandwidth from 2.4GHz to 3.1GHz, which could cover WiFi/Bluetooth (2.45GHz) and LTE (2.6GHz) mobile applications. The proposed planar monopole antenna array also obtains large gain, high efficiency, narrow beam, low side lobe level and highly symmetric bidirectional radiation pattern in both E- and H-plane.