Series-fed Patch Array Research Articles

Mechanically Controlled, Wide-Angle Scanning, Series-Fed Antenna Array With Low Profile for High-Power Radar Systems

This paper presents the design and implementation of a mechanically-controlled, series-fed antenna array featuring wide-angle beamsteering at the X-band. A theoretical model of a series-fed array, including phase shifters inserted between consecutive elements, is initially developed to derive design rules and gain insight into crucial performance trade-offs. Subsequently, a mechanically-controlled, reflection-type phase shifter consisting of a branch line coupler and two Pi-network reflective loads is presented. A movable metallic overlay tunes the impedance of the reflective loads, thus effectively modifying the output phase. While requiring a minimal linear displacement of only 0.06λ0, this topology provides a maximum phase shift of 300° with an average insertion loss of 1 dB and is exploited for synthesizing a series-fed patch array. Based on simulations and measurements, the proposed antenna offers an almost constant realized gain of about 15 dBi within a wide scanning range of ±50°, and the side lobe level is better than -12 dB. The average total efficiency is 50%, and the cross-polarization levels are at least 11 dB below the maximum realized gain. The main weaknesses are the narrow bandwidth of 2.5% and the slight beam squint as the frequency varies. The proposed design is ideal for radars due to its excellent performance and high power-handling capability.

Compact Dual-Circularly Polarized Traveling-Wave Series-Fed Patch Array for Use as a Non-Linear Tag Antenna for Bio-Sensing Applications

This paper proposes a compact K-band dual-circularly polarized antenna that can be implemented on a non-linear tag based on third-order intermodulation (IM3) for bio-sensing applications. The proposed antenna has the characteristics of being low-profile and lightweight, with opposite circular polarizations (CP) between ports. The non-linear tag-based bio-sensing scenario utilizes K-band millimeter wave frequencies, which allows for compact non-linear tags for attachment to the body. Also, the proposed antenna features dual-CP, which are for the reception and re-radiation of incident transmit signals and the IM3 responses, respectively. To this end, a two-port traveling-wave series-fed patch array with coplanar proximity coupling is designed. Here, to minimize the size of the antenna, we use only four circular patch elements with a modified diamond-shaped microstrip feedline. Through simulation and measurement, we demonstrate that the proposed antenna has an axial ratio of less than 3 dB from 23.25 GHz to 24.1 GHz, with the reflection coefficients below −10 dB and port-to-port coupling below −15 dB. These results indicate the potential utility of the proposed antenna as a tag antenna for non-linear detection-based bio-sensing applications.

An Accordion-Folding Series-Fed Patch Array With Finite Thickness: A folding technique for CubeSat arrays

Combining antenna arrays with physical reconfigurability (i.e., origami) allows for additional degrees of freedom in operation and enables larger structures to be folded into smaller volumes. The packaging ability of origami antennas is of great interest for CubeSat applications in particular. However, traditional origami is based on the manipulation of thin sheets, making physical reconfigurability with thick substrates very difficult. In this article, we present a foldable series-fed patch array designed on a strictly rigid printed circuit board (PCB). Notably, the array does not require any external mechanical folding appendages (i.e., brackets, tapes, or offsets), and it can be manufactured using commercially available PCBs and equipment. The PCB itself is strategically cut to form lamina emergent torsion (LET) joints. When fully deployed, the array operates at 5.7 GHz. A significant shift is not seen in the operational frequency until the folding exceeds 60° (5.7–5.61 GHz). This shows that the array, even in a state of near extreme faulty deployment, will operate as intended. An 8 × 6 prototype array was fabricated using a Rogers DiClad 880. When fully deployed, the array is extended in a surface area of 280 × 198 × 1.524 mm and can be folded into a 35.5 × 198 × 12.5-mm compartment. The array held its integrity well after 100 cycles. (One cycle starts at a state of full deployment, moves to a state of being fully packaged, and goes back to a state of full deployment.) Measurements show that the active reflection coefficients are in good agreement with the finite array simulations. The measured realized gains at 5.7 GHz for 0° and 30° folds were 22.4 and 21.4 dBi, respectively. At the 60° fold, a realized gain of 20.6 dBi was achieved at the frequency of 5.61 GHz.

Terahertz Resonant-Tunneling Diode With Series-Fed Patch Array Antenna

Resonant-tunneling diodes (RTDs) are promising electronic sources for terahertz (THz) waves. A recently proposed slot-based RTD simplifies the fabrication process by removing the metal–insulator–metal capacitor, which is used for dc separation, and introducing an etch stopper layer for simple air bridge formation. The simplified RTD structure, however, exhibits an unexpected large tilt angle in the main lobe of its radiation pattern due to the coupling between the slot antenna and the bias pads. Here, we present a series-fed patch array design that exploits the biasing structure and directs leakage surface waves to the broadside direction. The simulation result shows that the main lobe is along the broadside, with a maximum directivity over 12 dBi and a 3-dB bandwidth around 20%. The radiation efficiency is improved from 22% to 28% at 275 GHz. An experimental validation with a bullet lens indicates that the RTD device with a series-fed patch array antenna has a narrower beamwidth and a sidelobe level much lower compared with the original RTD. With such improved radiation performance, this simple RTD device becomes a potential source for the development of future array-level designs and flat lens systems.

Universal and Non-Iterative Design Method for In-Phase Radiation of Microstrip Traveling-Wave Series-Fed Antenna Arrays

Microstrip traveling-wave series-fed antenna arrays (MTSAAs) have been popularly developed for radar systems in the millimeter-waveband. Because the antennas are connected and fed in series in MTSAA, in-phase radiation of the antenna elements with properly tapered amplitude for achieving a broadside beam with a low sidelobe level (SLL) is challenging. Although the reported series-fed patch and comb-line arrays accomplished the goal, design equations for the optimum distances between antenna elements in the series-fed array do not guarantee in-phase radiation due to the mutual coupling in array structures. Therefore, optimization of the distances in the array using full-wave simulations is inevitable. In this article, we propose the first universal and non-iterative design equation that compensates for the phase offset generated in patch and comb-line MTSAAs and successfully found optimum distances for broadside beams with low SLLs without optimization. Finally, we fabricated both MTSAAs with ten elements operating at 76.5 GHz and demonstrated almost 13 dB boresight gain and low SLLs near −18 dB without a beam tilt.

Low Sidelobe Series-Fed Patch Planar Array with AMC Structure to Suppress Parasitic Radiation

For automobile radar systems, the antenna array requires a low sidelobe level (SLL) to reduce interference. A low-SLL and low-cost planar antenna array are proposed in this article for millimeter-wave automotive radar applications. The proposed array consists of six linear series-fed patch arrays, a series distribution network using a grounded co-planar waveguide (GCPW), and a bed of nails. First, a hybrid HFSS-MATLAB optimization platform is set up to easily obtain good impedance matching and low SLL of the linear series-fed patch array. Then, a six-way GCPW power divider is designed to combine the optimized linear sub-array to achieve a planar array. However, since CCPW is a semi-open structure, like a microstrip line, the parasitic radiation generated by the GCPW feeding network will lead to the deterioration of the SLL. To solve this problem, a bed of nails—as an artificial magnetic conductor (AMC)—is designed and placed above the feeding networking to create an electromagnetic stopband in the working band. Its working mechanism has been explained in detail. The feeding network cannot effectively radiate electromagnetic waves into free space. Thus, the parasitic radiation can be suppressed. A low-SLL planar array prototype working at 79 GHz is designed, manufactured, and measured. The measured results confirm that the proposed low-SLL planar array has a −10 dB impedance bandwidth of 3 GHz from 77 to 80 GHz and a maximum peak gain of 21 dBi. The measured SLL is −24 dB and −23 dB in the E-plane and H-plane at 79 GHz, respectively. The proposed low SLL array can be used for adaptive cruise control (ACC) system applications.

High-Gain Dual-Band Dual-Sense Circularly Polarized Spiral Series-Fed Patch Antenna

This paper demonstrates a dual-band circularly polarized (CP) two-dimensional (2D) series-fed patch array antenna. The CP rotating sense in each band is opposite to each other, which makes them well-suited for the downlink and uplink in satellite applications. The antenna can be designed to achieve a very high gain with a simple feeding structure using spiral microsip line, which can be integrated on a single-layered substrate. A theoretical framework for this type of antennas has been developed, which facilitates an efficient and fast design procedure requiring minimal computational resource. A prototype has been fabricated and measured, showing operating bandwidths (overlapped 10-dB return loss, 3-dB gain, 3-dB axial ratio bandwidths) of about 7% and 5%, realized broadside gains of 21.5 and 22 dBic at 12 and 14 GHz bands, respectively. This is an outstanding performance considering that the antenna profile is only 0.03 free-space wavelength (at 12 GHz) and the ratio between two operating frequencies is very tight accounting to only 1.17.

Dual-Beam Rectenna Based on a Short Series-Coupled Patch Array

The multibeam multiport antenna is a promising solution for effectively harvesting wireless low-density power in a wide angle range. The traveling-wave series-fed patch array antenna without the requirement of additional beamforming circuits is a good option. However, its application is limited by its large length or low radiation efficiency. In this work, a periodic circuit model consisting of coupled resonators is proposed and analyzed for enhancing the radiation attenuation. A series-coupled patch array based on the model is then designed. It presents a much shorter configuration and could be well applied in a scenario where a tradeoff between size and gain exists. The dc combining method that accumulates currents of rectifying branches corresponding to multiple beams is adopted in the rectifier design. The rectenna exhibits an enhanced spatial or angular coverage with a simple configuration. In the measurement, the output dc power can be more than 0.5- 32 μW in an angle range of 90° in the H-plane and reach a maximum value of 1.1- 50.3 μW and a maximum efficiency of 19.5%-44.6% when the power density ranges from 0.05 to 1 μW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 2.45 GHz.

Generation of Ka-Band Accelerating and Self-Bending Beam by Series-Fed Patch Array

In this letter, a novel method is proposed to design a Ka-band series-fed antenna that is applied to generate the accelerating and self-bending beam. The leaky-wave feature of the series-fed array is also investigated by the simulation of the unit patch. Fundamental relationship between width and length of the resonant patch is acquired based on the five-unit model. The fabricated prototype is composed of 40 different-size units that control the aperture magnitude. To adjust the phase difference between the two patches, the length of the transmission line is adjusted. Two symmetrically designed series-fed arrays reduce the cross-polarization level. The shape of the beam varies with the frequency from 33 to 36 GHz, and |S11| is below -15 dB in this operating band, which also illustrates the property of frequency scanning. This model can be easily fabricated, and it suggests the realization of the self-bending beam in the microwave band. Meanwhile, the fabricated Ka-band antenna can be easily fed, and it has the advantages of low profile and low cost.

Single-Layer Series-Fed Planar Array With Controlled Aperture Distribution for Circularly Polarized Radiation

We propose a compact circularly polarized series-fed patch array with enhanced radiation performance at $S$ -band. To our best knowledge, no similar single-layer structure has been designed, measured, and reported in the literature with equivalent radiation performances in terms of reduced sidelobe level (SLL) and aperture efficiency as well as compactness and simplicity. The planar array consists of a 50- $\Omega $ microstrip single feed point, offering uniform and efficient excitation of all its elements that enable a broadside beam with high-gain and low sidelobes. A feeding network for such aperture control is designed and optimized to provide good impedance matching with a two-point excitation per radiating element, which is based on 0° and 90° meander lines to enable circularly polarized radiation. A structure made by a $4\!\!\times \!\!1$ arrangement of square patches is simulated, optimized, and manufactured, providing a realized gain of about 10 dBic and an SLL below −15 dB. Very good axial ratios and high efficiencies are obtained. The proposed antenna may be of interest for next-generation far-field wireless power transmission systems and other applications including target tracking, radar, and internet of things technologies requiring efficient circularly polarized radiation.

A Wideband and Low-Sidelobe Series-Fed Patch Array at 5.8 GHz for Radar Applications

In this letter, a novel series-fed patch array working in the 5.8 GHz industrial, scientific, and medical (ISM) band for healthcare radar monitoring applications has been proposed. The single patch has been opportunely shaped to solve two critical problems of this antenna topology: reduced bandwidth and highsidelobe level (SLL). The bandwidth enhancement has been obtained with a dual-band structure, resulting from the superposition of two tapered patches with different lengths. For the sidelobes, a nonconventional technique, based on the modulation of the power transferred by one patch to the following one, has been proposed. An electrical two-port model of the single patch has been developed to significantly speed up the design process of longer series-fed arrays. The model impedance matrix shows a good agreement with the one extracted from electromagnetic simulations. The designed antenna shows a fractional bandwidth of 5.92% (more than twice the available one at 5.8 GHz) and an SLL of about -20 dB inside all the bandwidth. A prototype has been realized, and both reflection coefficient and radiation pattern at 5.8 GHz have been measured showing an excellent agreement with simulation results.

Extreme Offset-Fed Reflectarray Antenna for Compact Deployable Platforms

A design of a 5.8 GHz reflectarray antenna for operational conditions driven by a compact deployable unmanned aerial vehicle needy for RF systems but lacking space is discussed. Reflectarray surface is mounted on the underside of an unmanned aerial vehicle (UAV) wing allowing compressed fit in the deployment launcher. A series-fed patch array, mounted on the fuselage, is used as a feed source. The platform and its deployment mechanism limit the reflectarray size to 11.6 λ × 1.9 λ . Moreover, the offset feed illuminates reflectarray at angles ranging from 14° to 83° contributing to the operation seldom discussed in the literature. A single-layer subwavelength unit cell composed of concentric metallic loops is adopted due to its wider bandwidth, lower sensitivity to incidence angles, and enhanced phase distribution for efficient beam control. The impact of in-flight mechanical forces and high offset angles on performance and bandwidth is also studied. A scaled prototype is fabricated and tested at 15 GHz. The measurements show an antenna gain of 17.1 dBi with distinct directive beam pointing downwards.

Traveling-Wave Series-Fed Patch Array Antenna Using Novel Reflection-Canceling Elements for Flexible Beam

The methodology of designing traveling-wave series-fed patch array antennas (TSPAAs) based on reflection-canceling elements for flexible radiation pattern has been proposed. By introducing a quarter-wave transformer as the reflection-canceling structure, the cascaded patch antenna with tapered width can be used as the reflection-canceling element for a nonuniformly spaced TSPAA. Because of its simple structure, the parameters of the transformer can be determined directly by the corresponding equivalent circuit. To achieve a flexible radiation pattern, the array aperture distribution can be controlled by changing the element width (for amplitude distribution) and the element spacing (for phase distribution). In this method, the initial array is synthesized through a genetic algorithm approach, and a simulation-based iterative process considering the accurate mutual coupling is developed to optimize the initial array. To evaluate the proposed method, two different types of 14-element linear arrays operating at ISM 24GHz are implemented for a low sidelobe pattern and shaped-beam pattern, respectively. The two arrays are both simulated, fabricated and measured, the measured results show reasonable agreement with the simulation results, which verifies the effectiveness and correctness of the proposed method in this paper.

63.5–65.5-GHz Transmit/Receive Phased-Array Communication Link With 0.5–2 Gb/s at 100–800 m and ± 50° Scan Angles

This paper presents a 32-element phased array centered at 64 GHz using multiple SiGe chips on a single printed-circuit board. The antenna element is a series-fed patch array, which provides directivity in the elevation plane. The transmit array results in an effective isotropic radiated power of 42± 2 dBm at 63–65.5 GHz, while the receive array provides an electronic gain of 24 dB and a system noise figure <7.7 dB, including antenna loss, T/R switch, beamformer, and transceiver. The arrays can be scanned to ±50° in the azimuth using a 5-bit phase shifter on the SiGe chip without degradation in sidelobes and maintaining a near-ideal pattern. A communication link between two phased arrays at 100, 300, and 800 m is also demonstrated, and employs one array on the transmit side and another array on the receive side, together with external mixers and IF amplifiers. The link performance was measured for different scan angles and modulation formats. Data rates of 0.5–2 Gb/s using 16-QAM and QPSK waveforms are demonstrated at 100–800 m, with 2-Gb/s data rate at 300 m and ~500-Mb/s data rate at 800 m. To the best of our knowledge, this is the first system-level demonstration of a silicon-based Gb/s 60-GHz phased array over hundreds of meters. Application areas are in point-to-multipoint links, back-haul and front-haul links, and reconfigurable mesh networks for advanced communication systems.

An Array Antenna for Both Long- and Medium-Range 77 GHz Automotive Radar Applications

A novel array antenna with a flat-shoulder shaped radiation pattern is proposed as the transmitting antenna for 77 GHz automotive radar application. When it is used in an automotive radar comprising one transmitter and multiple identical receivers, it can meet the demands of both long-range and medium-range detections without switching the operation mode back and forth between the long-range radar scenario and the medium-range radar scenario. The proposed antenna concept is fully introduced to explain its mechanism. An unconventional array was synthesized to achieve the desired flat-shoulder shaped radiation pattern. Prototype of the proposed array antenna was also designed according to the array synthesis result, which consists of several linear series-fed patch arrays and a substrate-integrated waveguide power and phase distributing network. Fabrication and measurement of the prototype array antenna were completed, showing a good agreement between the measured data and the synthesized as well as the simulation results, thereby validating the design.

Radiation Efficiency of Longitudinally Symmetric and Asymmetric Periodic Leaky-Wave Antennas

This letter derives efficiency formulas and establishes fundamental limitations for longitudinally symmetric periodic leaky-wave antennas (LWAs). The proposed approach is based on an equivalent transmission-line model for periodic structures, which is derived from a lattice topology providing a perfect decoupling between the series and shunt immittances and their respective radiation contributions. A central result of this letter is that a 2-D array composed of uniformly excited 1-D LWAs cannot exceed a radiation efficiency of 50%. The presented theory is validated by comparing measured and finite-difference time-domain (FDTD) simulated radiation efficiencies with the ones predicted by the lattice model for several symmetrical and asymmetrical series-fed patch (SFP) array antenna and composite right/left-handed (CRLH) antenna configurations.

AN OUT-OF-LINE SERIES-FED MICROSTRIP ARRAY FED BY NOVEL CURLED-HORN-SHAPED STUB WITH LOW CROSS-POLARIZATION

A novel out-of-line series-fed patch array with low cross- polarization is presented in this paper. The element in the array is fed by a stub through one-port. The feeding stub is designed to be a novel curled-horn-shaped geometry, which can efiectively suppress the cross-polarization due to its symmetry. The linear array consists of two identical subarrays which are located oppositely. By the antiphase feeding of two subarrays, the cross-polarization is further reduced. Furthermore, the theory analyses of the series-fed array indicate that it is competent for being applied to phased array systems. The simulated results show the cross-polarization levels of the linear array with 20 novel elements in E and H plane are lower than i30dB and i60dB, respectively. And, a prototype array is fabricated. Its low cross- polarization levels conflrm the efiective performance of the proposed design.

Wideband and Low Sidelobe Slot Antenna Fed by Series-Fed Printed Array

A combination of slots and series-fed patch antenna array is introduced leading to an array antenna with wide bandwidth, low sidelobe level (SLL), and high front-to-back ratio (F/B). Three structures are analyzed. The first, the reference structure, is the conventional series-fed microstrip antenna array that operates at 16.26 GHz with a bandwidth of 3%, SLL of -24 dB, and F/B of 23 dB. The second is similar to the reference structure, but a large slot that covers the patch array is removed from the ground plane. This results in a wide operating bandwidth of over 72% for , with a 3 dB gain bandwidth of over 15.9%. The SLL of this structure is improved to more than at 16.26 GHz, and stable SLL of over 15.5-16.4 GHz band is also exhibited. This structure has a bi-directional radiation pattern. To make the pattern uni-directional and increase the F/B, a third structure is analyzed. In this structure, rather than one single large slot, an array of slots is used and a reflector is placed above the series-fed patch array. This increases the F/B to 40 dB. The simulated and measured results are presented and discussed.

A Planar Electronically Steerable Patch Array Using Tunable PRI/NRI Phase Shifters

This paper presents a planar electronically steerable series-fed patch array for 2.4-GHz industrial, scientific, and medical band applications. The proposed steerable array uses 0deg tunable positive/negative-refractive-index (PRI/NRI) phase shifters to center its radiation about the broadside direction and allow scanning in both directions off the broadside. Using the PRI/NRI phase shifters also minimizes the squinting of the main beam across the operating bandwidth. The tunable PRI/NRI phase shifters employ 0.13-mum CMOS tunable active inductors, as well as varactors in order to extend their phase tuning range and maintain a low return loss across the entire phase tuning range. The feed network of the proposed array uses lambda/4 impedance transformers. This allows using identical interstage phase shifters, which share the same control voltages to tune all stages. Furthermore, using the impedance transformers in combination with the CMOS-based constant-impedance PRI/NRI phase shifters guarantees a low return loss for the antenna array across its entire scan angle range. The antenna array was fabricated, and is capable of continuously steering its main beam from -27deg to +22deg off the broadside direction with a gain of 8.4 dBi at 2.4 GHz. This is achieved by changing the varactors' control voltage from 3.5 to 15 V. Across the entire scan angle range, the array return loss is less than -10 dB across a bandwidth of 70 MHz, and the relative sidelobe level is always less than -10 dB. Furthermore, the proposed design achieves very low beam squinting of 1.3deg/100 MHz at broadside and a 1-dB compression point of 4.5 dBm.

Design of dual-polarized series-fed microstrip arrays with low losses and high polarization purity

The design of a dual-polarized microstrip series-fed linear traveling-wave array is described in this paper. The array is composed of two identical subarrays formed by cascading an equal number of four-port aperture-coupled cross-patch elements and terminated on a two-port radiating matched load. By properly exciting the array, dual linear or circular polarization can be accomplished and by virtue of the symmetric arrangement of the antenna cross-polarization is annihilated. A straightforward design strategy is proposed for the synthesis of a desired current distribution along the array antenna. Some proof-of-concept linear arrays are developed and the corresponding numerical results, obtained through a full-wave approach based on the method of moments (MoM), are provided. As an independent validation, supplementary analyses by the finite integration technique (FIT) are also reported. Very close agreement is found between prescribed and synthesized array performance, which qualifies the proposed design approach as an accurate and effective tool for the synthesis of series-fed aperture-coupled patch arrays.