Design Of Feed Network Research Articles

Dual-Band Antenna Array Fed by Ridge Gap Waveguide with Dual-Periodic Interdigital-Pin Bed of Nails.

A dual-band (K-/Ka-band) antenna array is presented. An ultra-wideband antenna element in the shape of a double-ridged waveguide is used as a radiation slot, and a novel dual-periodic ridge gap waveguide (RGW) with an interdigital-pin bed of nails (serving as a filter) is used to realize dual-band operation. By periodically arranging the pins of two different heights in two dimensions, the proposed RGW with interdigital-pin bed of nails is able to realize and flexibly adjust two passbands. The widely used GW-based back cavity boosts the realized gain and simplifies the feed network design. A 4 × 4 prototype array was designed, fabricated, and measured. The results show that the array has two operating bands at 24.5-26.4 GHz and 30.3-31.5 GHz, and the realized gain can reach 19.2 dBi and 20.4 dBi, respectively. Meanwhile, there is a very significant gain attenuation at stopband.

Design of the Monopulse Feeding Network for a Slotted Waveguide Array on an Annular Disk

Design of a monopulse feeding network including a compact power distribution network and a monopulse comparator for a dual polarization slotted waveguide array fabricated on an annular disk is presented in this paper. As the slotted waveguide array is arranged on an annular disk, the feeding network is more complicated than that of a regular array such as a rectangular array. The design details of some key waveguide components, such as the compact assembly of H-plane T-junctions and E-plane elbows used to connect power distribution networks and radiation waveguides, are provided. Quasiplanar magic tees are designed and used to construct the compact sum and difference comparator. The antenna system contains two comparators, which are used to generate sum and difference beams for horizontal polarization and vertical polarization, respectively. Finally, the monopulse slotted waveguide array antenna is divided into two modules, a comparator module and an antenna module (including power distribution network), and fabricated with the layered processing and bonding process. The comparator module is measured using a network analyzer to verify its amplitude-frequency characteristics and phase-frequency characteristics. Screwing the comparator module and the antenna module together, a monopulse slotted waveguide array antenna is obtained, and the sum beam and difference beam characteristics of the antenna are measured in a microwave chamber and presented.

Design of a Low Sidelobe Feed Network Based on the Louver-Shaped Defected Ground Structure

In this paper, a low sidelobe feeding network has been developed utilizing the louver-shaped defected ground structure (DGS). By adjusting the louver-shaped DGS, the output amplitude and phase of the corresponding ports can be altered, minimizing deviations from theoretical values. This enables antenna arrays equipped with this feeding network to more easily achieve low sidelobe performance. The impact of the louver-shaped DGS on the amplitude and phase of each port in the power divider within the feeding network is analyzed, and a 16-channel feeding network incorporating the louver-shaped DGS has been designed, fabricated, and then measured. The test results indicate that the performance of the line-feeding network is effectively improved by designing and adjusting the louver-shaped DGS. Through the debugging procedure, the amplitude deviation of the feeding network has been reduced from ±0.45 dB to ±0.2 dB, while the phase deviation of the feeding network has been reduced from ±8° to ±2.5°, and the maximum value of the first sidelobe has been reduced from −24.2 dB to −28.1 dB.

A simple design of reconfigurable feeding network for antenna array beam scanning

In this letter, a simple approach to design a reconfigurable feeding network (RFN) for antenna array beam scanning is presented. By combining a 3 dB power divider and a reconfigurable delay line group (RDLG), the two output signals with 2m+n sets of uniformly distributed phase gradients (PGs) can be obtained. And by adopting multi two-output RFNs and multi-stage design, a RFN for generating 2m+n continuously distributed beams is constructed. For verifying the design method, a microstrip four-output RFN for generating four scanning beams is implemented, fabricated and measured. The measured results are consistent with the theoretical analysis, which provides the validity of the design. And the design of the RFN can be used as a candidate of the feeding network for antenna array beam scanning.

Synthesis of Reconfigurable Multiple Shaped Beams of a Concentric Circular Ring Array Antenna Using Evolutionary Algorithms

The approach described in this paper uses evolutionary algorithms to create multiple-beam patterns for a concentric circular ring array (CCRA) of isotropic antennas using a common set of array excitation amplitudes. The flat top, cosec2, and pencil beam patterns are examples of multiple-beam patterns. All of these designs have an upward angle of θ = 0◦. All the patterns are further created in three azimuth planes (φ = 0◦, 5◦, and 10◦). To create the necessary patterns, non-uniform excitations are used in combination with evenly spaced isotropic components. For the flat top and cosecant-squared patterns, the best combination of common components, amplitude and various phases is applied, whereas the pencil beam pattern is produced using the common amplitude only. Differential evolutionary algorithm (DE), genetic algorithm (GA), and firefly algorithm (FA) are used to generate the best 4-bit discrete magnitudes and 5-bit discrete phases. These discrete excitations aid in lowering the feed network design complexity and the dynamic range ratio (DRR). A variety of randomly selected azimuth planes are used to verify the excitations as well. With small modifications in the desired parameters, the patterns are formed using the same excitation. The results proved both the efficacy of the suggested strategy and the dominance of DE over GA as well as FA.

High Gain Fan-Beam Pattern Antenna Based on the Utilization of Diffracted Fields From Dielectric Slabs Edges for IoT and Sensing Applications

A high gain, low-cost antenna structure is designed for a smart car parking system. The antenna uses Printed Ridge Gap Waveguide (PRGW) technology, which is fully shielded, and suppresses any parasitic radiation from the feed, and minimizes back-lobe radiation. The proposed antenna uses a single MSL feed point, which eliminates the need for any complex feeding network design, and allows the antenna to be integrated easily with PCB transceiver circuitry. A novel technique for the design procedure is proposed, the technique provides a generalization of using either electric or magnetic excitations with dielectric or magnetic rectangular slabs. A unique physical insight accompanied with a thorough analysis of the propagation mechanism is provided. The technique has a significant impact on reducing the complexity of the feeding network. The realized structure is compact, low profile, and low cost. The beam pattern of the antenna is a Fan-Beam (Elliptical) pattern which is well suited for various sensing and Internet of Things (IoT) applications.

Dual‐band shared‐aperture antenna with high aperture reuse ratio and high isolation

This work presents a dual-band (3.5/26 GHz) shared-aperture antenna with high aperture reuse ratio and high isolation. The proposed 26-GHz 4 × 4 substrate integrated waveguide (SIW) cavity-backed slot array antenna consists of four hybrid TE130–TE310-mode SIW cavities, which can simplify the design of feeding network. The radiating slots are unequally offset and inductance windows are added for good impedance matching. The entire structure of the 4 × 4 slot array antenna also functions as an equivalent TM10-mode patch antenna at 3.5 GHz. The resonant frequency of the patch is fine-tuned by inserting an air gap instead of enlarging the patch length, thus ensuring high aperture reuse ratio. To enhance channel isolation, the patch is designed with a bandpass filtering response centered at 3.5 GHz by introducing a stub-loaded resonator feeding structure. For demonstration, a prototype of the proposed dual-band antenna was fabricated and measured. The measured results show that the proposed antenna achieves excellent dual-band performance, and its aperture reuse ratio and channel isolation are as high as 87.5% and 62 dB, respectively.

Hybrid Waveguide Feed Network for Aperiodic Subarray Beamforming

In this letter, a hybrid waveguide feed network for an aperiodic subarray beamforming antenna is presented. The feed structure is divided into vertical and horizontal parts. Vertical parts have inclined slots with a reduced-height waveguide, and the horizontal part has unequal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane septum power dividers to achieve a compact feed network with acceptable electrical characteristics. The angle of each inclined slot and the position of each septum were designed for amplitude weighting and in-phase characteristics. For comparison, a simple resonant feed network without septum power dividers (i.e., with waveguides and inclined slots) was simulated to access the effectiveness of the proposed network. The proposed structure was fabricated using computer numerical control milling and diffusion bonding. The input reflection coefficient was less than −15 dB, and the transmission phase difference between 20 ports was less than 72° within a bandwidth of 2.4%. This feed network design has potential applications in electronically scanned arrays and subarray antennas for a limited field of view.

Reconfigurable Reflectarray Antenna Based on Hyperuniform Disordered Distribution

The irregularly located element array within the antenna aperture can be applied to obtain narrow main lobe width and low sidelobe levels with fewer elements as compared with the traditional (periodic) array configurations. In this article, a reconfigurable reflectarray antenna (RRA) combined with hyperuniform disordered distribution is presented. Based on the theoretical radiation pattern of reflectarray, it has been found that the proposed array with reduced elements holds a similar radiation pattern as that of a corresponding periodic array. Meanwhile, the reflectarray avoids the design of complicated feeding network for the disordered phased array antenna. In addition, for a reconfigurable reflectarray to achieve beam scanning, active devices are necessary. In such case, the design of RRA with fewer elements is of particular importance. A 1 bit RRA of 64 elements prototype has been designed, fabricated, and measured. The side length of each element is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.625\lambda $ </tex-math></inline-formula> . Experimental results agree well with the full-wave simulations, and scan beams within ± 50° range have been obtained with a peak gain of 17.4 dBi at 12.5 GHz.

A Compact Omnidirectional Parabolic Shape Tilted Dipole Array With Improved Axial Ratio Bandwidth

Current omnidirectional circularly polarized (CP) antennas meet the difficulty of limited bandwidth and bulky configuration. An exact analytical far-field solution for a conventional tilted dipole array (TDA) has been proposed, where the origin of axial ratio (AR) bandwidth limitation has been investigated. Then, it has been shown that the AR bandwidth can be efficiently improved when a conventional straight dipole is folded into a multi-segment one, where the deviation of two perpendicular far-field components, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{\theta }$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{\phi }$ </tex-math></inline-formula> , can be reduced at both the lower and higher frequencies. The dipole was further modified to be of a parabolic shape, a continuous and optimized variation for the multisegment one, which brings about an even wider AR bandwidth. For a compatible wide impedance bandwidth, several impedance matching techniques like radiator tapering, parasitic loading, and feeding network design have been applied. Measured results show the proposed TDA has a 3 dB AR bandwidth (also the antenna usable bandwidth) of 65%, within which the desired omnidirectional radiation is well maintained. Compared with the performances of some recent omnidirectional CP antennas, our design has a much wider usable bandwidth, and is also superior in the compact size, simple structure, and ease of fabrication.

Sum/Difference Pattern Synthesis With Dynamic Range Ratio Control for Arbitrary Arrays

This article proposes a method which generates a set of weights to synthesize sum or difference pattern with precisely controlled sidelobe level (SLL), null, and dynamic range ratio (DRR) for arbitrary arrays. Our pattern synthesis approach reduces mutual coupling (MC) between the neighboring elements and complexity of the feeding network design. However, the formulated optimization problem is nonconvex due to the nonconvex objective function and fractional DRR constraint. To tackle it, we first introduce two sets of auxiliary variables: one for DRR constraint and the other for sidelobe and null constraints. By doing so, we then decompose the original optimization problem into three sets of subproblems characterized by the auxiliary variables and weight variables. To facilitate the subproblem with weight variables reaching its optimum values, we derive an appropriate range of step size. Finally, we iteratively solve these subproblems to obtain the solution to the original problem. Extensive experiments employing non-equispaced linear and rectangular arrays, concentric ring array, and cylinder array, are implemented to demonstrate that the developed approach can accurately control SLLs, null and DRR for arbitrary arrays.

Compact Broadband Circularly Polarized CPW-Fed Antenna with Characteristic Mode Analysis

A compact circularly polarized (CP) antenna is proposed for low-profile and wideband operation based on characteristic mode analysis (CMA). A ring patch with a gap and two arc-shaped metallic stubs as the radiator is analyzed and optimized by CMA to figure out the orthogonal modes and operating frequency band for potential good axial ratio (AR) performance. The studies of these CP modes provide a physical insight into the property of broadband circular polarization. Such an in-depth understanding paves the way for the proposal of novel CP antenna with separation between the design of radiator and feeding network. A 50-Ω coplanar waveguide (CPW) is introduced and placed appropriately to excite the desired modes based on the information from CMA, which employs two asymmetric ground planes to improve the performance in terms of AR and impedance matching. The antenna with a compact size of 0.71λ0 × 0.76λ0 × 0.038λ0 (λ0 is the free-space wavelength at the center frequency of the 3-dB AR bandwidth) is fabricated and measured for validation. The realized gain varies from 1.6 to 3.1 dBic over the operating bandwidth characterized by the measured 10-dB impedance bandwidth of 83.8% (3.98–9.72 GHz) and 3-dB AR bandwidth of 70.3% (4.59–9.57 GHz), respectively.

Low-Cost Circularly Polarized Millimeter-Wave Antenna Using 3D Additive Manufacturing

An efficient single-layer printed feed is used with a low-cost 3D printed polarizer. The feed is made on a single substrate layer. The proposed antenna gain is 15 dBi, and the overlapped impedance-axial ratio bandwidth is 20%. The proposed structure is a low-cost structure that can be fabricated in any modest fabrication facility. The feed does not require any plated vias, which tremendously simplifies the fabrication process and lowers the cost. The feed is very well suited for integration with integrated circuit transceiver systems. The proposed structure does not require any feeding network design. Hence, it relaxes the design process and avoids the losses associated with such feeding network. The proposed element can be employed in an array configuration with adequately suppressed side lobes. The element cost, simplicity, and gain performance are superior to other proposed solutions in the literature.

Design and simulation of low side lobe micro-strip array antenna at multiple frequencies

In this paper, we present a simple design of a feed network for the antenna to achieve a lower side lobe level. Side Lobe Levels (SLL) are critical issues in the detection of an object. Higher side lobe levels can increase the false detection of objects in an autonomous vehicle system. The array is designed and simulated for four different frequencies, one at a time to make it a scalable design. The chosen frequencies are 10 GHz, 15 GHz, 20 GHz, and 24 GHz. The feed network design consists of eight patch elements with an equal power divider and CST studio software is used for simulations. From simulation results, it can be observed that VSWR is equal to 1.26, 1.16, 1.62, and 1.05 at respective frequencies. So, the radiation efficiency can be achieved as -1.14 dB, -0.92 dB, -0.46 dB, -0.41 dB. The results substantiate that proposed design can reduce the SLL more than -24.5 dB in the elevation plane and also it is greater than 14.4 dB at all the aforementioned frequencies.

A Dynamic Invasive Weeds Optimization Applied to Null Control of Linear Antenna Arrays with Constrained DRR

In the present work, a dynamic stochastic method is proposed and used for the synthesis of uniform linear antenna arrays. The proposed method combines the classical invasive weeds (IWO) and the mutation process, which makes it robust, simple and shows flexibility to be adapted. The dynamic IWO applies the mutation process in the calculation of standard deviation during the spatial dispersal process of produced seeds while keeping the mean at the parent plants. In the mutation process, if special conditions were achieved, the standard deviation would be re-initialized. This proposed method tries to achieve an optimal array pattern by acting on the relative amplitude excitation of each element in the linear array for an optimal inter-element spacing. The optimal array pattern has deep or broad nulls in some directions of interferences with low sidelobes level. The objective of the synthesis is to get amplitude excitations with low dynamic range ratio (DRR), which facilitates the design of beamforming feed network. To illustrate the robustness of the proposed method, numerical examples are presented and compared with the obtained results using bees algorithm (BA), bacterial foraging algorithm (BFA), real genetic algorithm (RGA), and the corresponding reference array pattern for each example.

Frequency-Dependent Feeding Methods for Broadband Vivaldi Arrays With Minimum Half-Power Beamwidth (HPBW) Variation

This paper reports on the design of frequency-dependent feed networks for linear antenna arrays with minimum half-power beamwidth (HPBW) variation in more than one octave of the frequency spectrum. The proposed approach is based on: i) frequency-dependent power dividers that gradually shift the RF power from the outer elements of the array to the inner ones with the increase of frequency and ii) uniformly or non-uniformly-spaced directive antenna elements. The operating principles and design trade-offs of the concept are presented through ideal simulations of four- and six-element antenna arrays shaped by isotropic or directive radiators. It is shown that by employing directive antenna elements and non-uniform spacing, minimum HPBW variation can be obtained in a broad bandwidth (BW, e.g., 3:1). For physical verification purposes, two frequency-dependent feed networks and Vivaldi antenna elements were designed, manufactured, and measured. The first network feeds a uniformly-spaced four-element array of Vivaldi antennas and demonstrates a 58% HPBW variation in a 3:1 of BW. The second network feeds a non-uniformly-spaced six-element Vivaldi array and results in a 67% HPBW variation in a 2.5:1 of BW.

Multibeam Characteristics of a Negative Refractive Index Shaped Lens.

Narrow beam width, higher gain and multibeam characteristics are demanded in 5G technology. Array antennas that are utilized in the existing mobile base stations have many drawbacks when operating at upper 5G frequency bands. For example, due to the high frequency operation, the antenna elements become smaller and thus, in order to provide higher gain, more antenna elements and arrays are required, which will cause the feeding network design to be more complex. The lens antenna is one of the potential candidates to replace the current structure in mobile base station. Therefore, a negative refractive index shaped lens is proposed to provide high gain and narrow beamwidth using energy conservation and Abbe’s sine principle. The aim of this study is to investigate the multibeam characteristics of a negative refractive index shaped lens in mobile base station applications. In this paper, the feed positions for the multibeam are selected on the circle from the center of the lens and the accuracy of the feed position is validated through Electromagnetic (EM) simulation. Based on the analysis performed in this study, a negative refractive index shaped lens with a smaller radius and slender lens than the conventional lens is designed, with the additional capability of performing wide-angle beam scanning.

Optimal Synthesis of Sum and Difference Beam Patterns With a Common Weight Vector for Symmetric and Asymmetric Antenna Arrays

To alleviate the complexity of feeding network design and reduce the dependence of sum and difference beam pattern synthesis on the central symmetric antenna arrays, a method generating a common weight vector to simultaneously produce these two beam patterns for symmetric and asymmetric antenna arrays is proposed. By considering the main-lobe radiation power of the sum beam pattern, sidelobe level (SLL), null depth of the difference beam pattern at the direction of the target, and difference-to-sum ratio as design parameters in the beam pattern synthesis, a new optimization problem with a nonconvex objective function and two quadratic fractional constraints is formulated. To tackle it, we first use the variant penalty method to convert the original constrained optimization problem into a nonsmooth unconstrained one and then adopt smooth functions to approximate the nonsmooth components to obtain a smooth unconstrained optimization problem that is then solved by steepest descent. Four representative examples, namely, symmetric linear, asymmetric linear, asymmetric rectangular, and symmetric flower arrays, are implemented to demonstrate that our algorithm can simultaneously synthesize the sum and difference beam patterns with accurately controlled SLLs even in asymmetric array configurations.

Sparsely Excited Tightly Coupled Dipole Arrays Based on Irregular Array Techniques

An innovative architecture for sparsely excited tightly coupled dipole arrays is proposed, based on the irregular array techniques. In such a framework, an improved maximumentropy model considering the difference of embedded element patterns is applied to optimize the irregular partition to suppress the grating lobes. Meanwhile, guidelines for the entire design procedure including antenna elements, power dividers, and optimization design of irregular feeding networks are presented. In order to achieve large elevation angle scanning, the differential evolution (DE) algorithm is used to synthesize active pattern and active reflection coefficient simultaneously. Finally, a 192-port prototype operating at 8-12 GHz has been fabricated and measured, where the port spacing is 0.576λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> is the free-space wavelength at the highest frequency). Numerical and experimental results show that the prototype array is able to achieve the reduction of gain <; 1 dB for scanning to near broadside and about 2.7 dB for scanning up to 60°, in comparison with that of conventional Taylor arrays.

A Compact Pattern Reconfiguration Antenna Based on Multimode Plane Spiral OA

Orbital angular momentum (OAM) has attracted great interest in the past few decades due to its helical phase characteristics. It has been proved that Plane spiral OAM (PSOAM) has potential in pattern reconfiguration of azimuthal domain because it solves the difficulty of mode superposition caused by different main lobe directions of different modes. However, the absence of a compact high-purity multimode PSOAM antenna hinders the development of PSOAM applications. In this paper, a compact high-purity 8-mode PSOAM antenna consisting of a coaxial resonator group (CRG) and a rotating parabolic reflector (RPR) is designed. It works in the X-band with the bandwidth of 140 MHz, and its efficiency is greater than 90$\%$. Amplitude and phase of each PSOAM beam generated by this antenna can be controlled independently owing to its feed network and separate resonators design, hence any target pattern in azimuthal domain can be approximately reconfigured by modes weighting. The simulation and experiment results show that this antenna can make the PSOAM based pattern configuration possible, which will have potential in the OAM based applications.