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A broadband and wide-angle scanning linear polarization (LP)-to-circular polarization (CP) converter based on a dual-layer structure is presented. The elementary cell is composed of conventional Jerusalem crosses (JCs). The design procedure is based on transmission line circuit model and on full-wave simulations. The proposed equivalent circuit has been generalized to include the oblique incidence in the model. Simulated results demonstrate a 24% axial ratio bandwidth for an incidence angle $\theta = \pm 50^{\circ }$ in both x z and y z planes. The proposed converter provides a unique combination of wide bandwidth, thin profile, and stable response with respect to the angle of incidence. It can be integrated into any LP antenna system to generate CP without significantly affecting the antenna performances.

This paper presents the integration and channel characterization of a highly integrated dual-band digital beamforming space-borne synthetic aperture radar (SAR) receiver. The proposed SAR sensor is a low-cost, lightweight, low-power consumption, and dual-band (X/Ka) dual-polarized module ready for the next-generation space-borne SAR missions. In previous works, by the authors, the design and experimental characterization of each sub-system was already presented and discussed. This work expands upon the previous characterization by providing an exhaustive experimental assessment of the fully integrated system. As it will be shown, the proposed tests were used to validate all the instrument channels in a set-up where the SAR sensor was illuminated by an external source minim the ground reflected waves. Test results demonstrate how the system channels are properly operating allowing the reception of the input signals and their processing in the digital domain. The possibility to easily implement a calibration procedure has also been validated to equalize, in the digital domain, the unavoidable amplitude differences between the different channels.

A polarization rotator based on substrate integrated waveguide (SIW) is proposed in this article. The rotator is designed as a dual-band, single-layer, frequency-selective surface (FSS) that transmits a wave rotated of 90° with respect to the incident one in one of the two bands maintaining unchanged the polarization in the other one. Other than the design and characterization of the rotator, its application to a linear-to-circular dual-band polarizer is also investigated. To this purpose, the rotator is coupled to a conventional meander line polarizer generating orthogonal circular polarizations (CP) in the two bands. This configuration is useful in SatCom applications where the required high isolation between TX and RX channels is obtained assigning orthogonal polarizations to the two bands. As a design example, a prototype is designed and experimentally validated in the SatCom K-/Ka -bands. Measured performance shows an isolation between the TX and RX channels of more than 35 dB and insertion losses which do not exceed 1.5 dB in the two operating bands.

A novel dual-band cylindrical reflector antenna with a hat feed is presented. A horn in a parallel-plate waveguide illuminates a parabolic surface to generate a TEM wave that is used to illuminate a corrugated feed. The feed is designed using a double step corrugation optimized to obtain good radiation patterns and good matching on the two bands of interest. The design of the grooves is based on the analysis of the radiation characteristics of the corrugated surface. In particular, the power re-radiated by the corrugation is considered to ascertain features which prove to be extremely useful in simplifying the design of the feed. The solution proposed in this communication makes possible to realize an antenna with compact size and low cost without sacrificing efficiency and compliance with radiation masks.

This paper presents the first experimental assessment of a highly integrated dual-band dual-polarized antenna tile designed for synthetic aperture radar (SAR) digital beamforming (DBF) satellite applications. The demonstrator described in this paper is the first comprehensive experimental validation of an RF module providing the X-band and Ka-band (9.6- and 35.75-GHz) operation with custom downconversion stages. All the antennas, transitions, and downconversion chips are integrated in the same antenna tile fabricated using a customized 15-layer high density interconnect process. The designed tile goes to the limits of the proposed technology and for the high trace density and for the size of the vertical transitions. The proposed results represent the state of the art in terms of compactness for a DBF SAR RF module even though the demonstrator was manufactured with a standard low-cost technology. The experimental assessment proves the validity of the proposed manufacturing and integration approaches showing a substantial agreement between the performance of the individual blocks and of the integrated system.

This paper presents a new improved gain array configuration well suited for mid-range V-band backhauling applications. The proposed solution is based on a cavity-backed shorted annular patch (SAP) antenna loaded with a parasitic patch element for gain maximization. This solution is proved by designing and measuring a 4 × 4 array which presents a reflection coefficient bandwidth covering the frequencies from 58.7 to 63.25 GHz (7.6% at 60 GHz). The experimentally validated array gain is equal to 18 dBi corresponding to 37.9% of aperture efficiency. The antenna and array configurations presented in this paper are optimized to minimize the manufacturing cost and complexity. This result is achieved through a novel beamforming network (BFN) configuration, implemented using a dual-layer substrate-integrated waveguide (SIW) technology, and partly integrated on the array aperture. The achieved results demonstrate how the performance of the cavity backed SAP array is comparable to the ones achieved with more complex and expensive solutions.

A new configuration of a planar grid array antenna for automotive radar applications operating in the 77–81 GHz frequency band is introduced. The proposed array is based on miniaturized loop elements, which are designed to maintain the mutual interelement distance along the azimuthal plane to less than half free-space wavelength, thus allowing a better scanning performance in the final radar system. Moreover, to enhance the gain bandwidth performance, the antenna adopts multiresonant cells realized using variably dimensioned radiation elements. The proposed design was validated experimentally and it is fully compliant with multichannel monolithic microwave integrated circuits (MMICs) designed for automotive radar sensor applications.

Phased arrays are one of the most critical blocks in 5G networks. In the case of the point-to-multipoint link, they have to provide beam reconfigurability over a large scanning range while maintaining a low profile and a limited cost. Moreover, operation at millimeter wave frequencies poses several critical challenges especially in terms of integration and, in turn, analysis. This work provides an introduction to the different simulation challenges involved in the design of a phased array differentiating them into two categories: i) cross-domain effects due to the different integration and packaging technologies present in the array along its vertical dimension and ii) mutual coupling effects taking place across the array horizontal dimension. As a design example, an ultra-low profile Magneto Electric (ME) dipole antenna design for 5 G applications is reported.

This paper introduces a gain enhancement technique for monolithically integrated monopole antennas. The proposed configuration has been designed in a standard 0.13 µm SiGe BiCMOS process. The gain improvement was achieved by combining the on-chip monopole antenna with some parasitically coupled Split Ring Resonators (SRRs). The size of the SRR was firstly fixed to adapt their length to the monopole geometry while their resonant frequency was fine-tuned by using a capacitive load which serves to control the resonance frequency without changing their length. Thanks to this solution, it was possible to achieve a gain improvement of about 1 dBi with respect to an unloaded monopole. An experimental assessment showed a maximum measured antenna gain of 1.61 dB at 81.5 GHz and the antenna maintains good performance from 77 to 87 GHz.

Some recent work on Ka Band Circular Linear-to-Polarizers carried out at the Microwave Group of University of Calabria (Italy) are presented. Four types of Linear Polarization (LP) to Circular Polarization (CP) converters, including three transmission type and one reflection type, are developed by using low cost standard Printed Circuit Board (PCB) technology. Experiments show that good performances are obtained for all proposed solutions.

Two gain enhancement techniques for monolithically integrated monopole antennas are presented in this work. The proposed configurations have been designed in a standard 0.13 μm SiGe BiCMOS process. In the first one, Split Ring Resonators (SRRs) have been combined with Localized Backside Etching (LBE). These etched parts are removed locally from the silicon substrate, reducing the losses and thus contributing to increase the gain of the monopole antenna. In the second technique, an on-chip monopole antenna is paired with parasitically coupled SRRs. The latter elements are tuned using a capacitive load which serves to control their resonance frequency without changing their physical dimensions. These techniques have been compared with an unloaded monopole and they provide a gain enhancement of about 1 dBi within the band of interest without significantly increasing the overall antenna size which was fixed to 1.296 × 1.508 mm2.

A broadband and broad-angle linear-to-circular polarization converter based on a dual-layer substrate is presented. The elementary cell of the proposed converter is composed by a Jerusalem Cross (JC). The design procedure is based on transmission line circuit theory and on full-wave unit cell analysis in frequency domain. Simulated results demonstrate a 24% axial ratio bandwidth for an incidence angle θ = ± 50° in both x-z and y-z planes. The proposed converter provides a unique combination of wide bandwidth, thin profile, and stable response with respect to the angle of incidence. It can be integrated to any linearly polarized antenna to generate circular polarization without affecting the antenna performances.

Battery-based energy storage systems are forecasted to have a rapid diffusion in the next future, because they can support the diffusion of renewable energy sources and can offer interesting ancillary services for the distribution grid. Consequently, energy management strategies for batteries and inverters present in storage systems will play a fundamental role in order to guarantee effective energy transfer processes between storage systems and the grid. This paper proposes an efficient management strategy which allows maximizing the overall energy efficiency of grid-connected storage systems taking into account the actual relationship between the efficiency and the charging/discharging power of the storage system. The effectiveness of the strategy is as shown by analysis results, the proposed strategy can allow a remarkable efficiency increase compared with strategies which are not aimed at the efficiency optimization.

The cost of multilayer printed circuit boards (PCB) for microwave applications depends on several parameters which affects the fabrication costs with different weights. In this work we consider the metallized via holes. Each type of via hole is related to the number of fabrication steps as it requires dedicated manufacturing iterations. In general, if the number of vertical transition typologies is reduced the fabrication complexity and costs is greatly reduced. On the other hand, limiting the typologies of vertical transitions is harmful in terms of performance, especially at millimeter wave applications. This work explores the effects of via stubs in multilayer through numerical simulations and analytical models.

A W-Band on-chip monopole antenna with SRR (Split Ring Resonator) and LBE (Localized Backside Etching) in a standard 0.13 µm BiCMOS process is presented. The AMC, composed by the SRR and the LBE, has been inserted in order to enhance the on-chip antenna gain by minimizing the losses of the substrate through the creation of constructive reflections. The enhancement of the gain has been fulfilled by etching the silicon substrate and thus reducing the losses. These etched parts are called Localized Backside Etching (LBE). Despite the other on-chip monopole antennas, the proposed element combines these two techniques to improve the radiation properties of monopole on-chip antenna. The proposed configuration provides a gain enhancement of 1 dB. The final AoC has a compact size of 1.11x1.28 mm2 and provide a peak gain of 2.29 dBi at 83 GHz.

A dual-band, Tx/Rx, self-diplexing phased array is presented. The antenna has been designed to cover Tx/Rx satellite communications at K/Ka band with a frequency ratio 1.5:1. To obtain dual-band operations with a single radiating surface, a novel dual-band radiator is adopted and placed in a configuration in which dual-band and single-band elements are interleaved. The proposed configuration reduces the number of radiating elements required by other solutions while avoiding the insurgence of grating lobes. The tightly packed arrangement of the elements poses many integration issues, which are solved with a novel integration technique. The array elements are optimized to scan the beam in excess of 50° in both bands. A subarray with 49 Rx elements and 105 Tx elements was built and measured confirming the results obtained in simulations.

A K/Ka band polarizer obtained stacking a SIW polarization rotator and a meander-lines polarizer is presented. The rotator is realized with SIW cavities that selectively twist the polarization of the incident wave. In this way, incident 30GHz horizontally polarized waves are converted in RHCP signals, while incident 20GHz waves with the same polarization are converted in LHCP signals. The proposed polarizer may be used with linearly polarized aperture antennas and, for this reason, it can be considered as an after-market add-on that does not affect the performance parameters of the antenna itself.

In this work a dual band circular polarized array antenna is presented. The proposed terminal consist of an array antenna in which the radiating elements operating around 20GHz and 30GHz are nested one into the other in order to form a dual band antenna. A meander-line polarizer is used to realize circular polarization. Using this system, a low level of Axial Ratio is obtained on both bands of interest.

A fast and efficient full-wave hybrid method for the analysis of a multilayered substrate integrated waveguide (SIW) based slot antenna/array radiating into a dielectric slab radome is presented. The antenna structure is modeled as a stacked parallel-plate waveguide hosting metallic posts and coupling and/or radiating slots. To account the radome effects on the SIW antenna, the physical optics method in conjunction with three-dimensional ray trace technique are used to analyze a dielectric slab radome staked on the aperture of the antenna. The field in the SIW structure is expressed by using an expansion in terms of vectorial cylindrical eigenfunctions. Enforcing the boundary conditions on posts yield the scattering amplitude, while slots are modeled as unknown magnetic currents which are found by solving the integral equation derived from the continuity of the field on the slot surface. A double-layered SIW cavity backed slot antenna radiating into a dielectric slab radome is analyzed, and the results compared with high frequency simulation software (HFSS) simulations. It will be shown that the proposed method is fast and efficient and gives results in very good agreement with the most common simulation tools.

A compact high-gain stacked multi-layered antenna in SIW technology for array at 60GHz band is proposed. A single radiator composed by a shorted circular patch with a stacked element is studied in order to fulfil the desired performances. The simulated stacked antenna attains 9.1dBi of maximum gain and 10% of impedance bandwidth with a size of 3.75 × 3.75 × 2.94 mm3. The proposed antenna is an excellent candidate for integrated low-cost millimetre-wave array systems.

This paper presents a very fast and highly efficient full-wave hybrid method for analyzing an integrated dielectric lens antenna (ILA) fed by multilayered substrate-integrated waveguide (SIW) slot antenna/array. The feeding antenna structure is modeled as a stacked parallel-plate waveguide with metallic posts, coupling, and radiating slots. Physical optics method in conjunction with three-dimensional ray tracing technique is employed to analyze the effect of the dielectric lens on the SIW feeding slots. Fields in the SIW structure are computed by considering the Dyadic Green's function expressed as an expansion of vectorial cylindrical eigenfunctions and taking into account scattering at the conducting posts. Slots are modeled with equivalent magnetic currents expressed as a sum of domain basis functions. By imposing continuity of the tangential components of the fields an integral equation is obtained that is solved with the application of method-of-moments. In order to validate the proposed technique, a hemispherical ILA fed by a double-layered SIW cavity which is backed with slot antenna is analyzed. Excellent agreement is obtained with HFSS software together with significant improvement in computational time and memory requirements.

A 60-Channels ADC (Analog to Digital Converter) board for space borne Digital Beam Forming (DBF) Synthetic Aperture Radar (SAR) applications is described. The purpose of the board is to digitize analog signals detected by a dual band SAR receiving array operating at X and Ka band. It contains 48 high speed ADCs, which sample synchronously the incoming data of the antenna front end at Ka band. Other 12 ADCs are used to sample the coming data from the X band antennas. The board is composed by an analog section, a digital section and a clock distribution network used to synchronize the ADCs. Output digital signals from the board are routed to digital boards were are processed in the Digital Beamforming Network (DBFN).

In this work, it is presented a new configuration of planar power combiner/divider based on an H-plane sectoral horn antenna. This component is proposed to realise the basic building blocks of printed power-combining amplifiers. It will be shown how the sectoral horn elements can be implemented on substrate integrated waveguide and multilayer printed circuit board technologies, thus obtaining a high integration level. In the following, the design procedure will be described reporting an example of an 11-stage power divider/combiner in C-band. A prototype has been fabricated, and the measured results compared with the numerical model. Experimental results are in good agreement with theoretical expectations showing a single-stage efficiency of about 90% and a bandwidth of 40%.

Cylindrical parabolic reflectors have been widely used in those applications requiring high gain antennas. Their design is dictated by the geometric relation of the parabola, which relate the feed location, f, to the radiating aperture, D. In this work, the use of reflectarrays is proposed to increase D without changing the feed location. In the proposed approach, the reflecting surface is loaded with dielectric panels where the phase of the reflected field is controlled using continuous metal strips of variable widths. This solution is enabled by the cylindrical symmetry and, with respect to rectangular patches or to other discrete antennas, it provides increased gain. The proposed concept has been evaluated by designing a Ka-band antenna operating in the Rx SatCom band (19&ndash, 21 GHz). A prototype has been designed and the results compared with the ones of a parabolic cylindrical reflector using the same feed architecture. Simulated results have shown how this type of antenna can provide higher gain in comparison to the parabolic counterpart, reaching a radiation efficiency of 65%.

This letter reports the design and measurements of a SiGe BiCMOS duplexer developed for T/R (transmit/receive) Ka-band SatCom on-the-move user terminals. The IC presented in this work is designed for the integration in a hexa-core chip for dual-band phased array applications. Due to the particular configuration of the chip, the duplexer has four ports: one common port, one input port for the R channel and two output ports for the T channels. The chip size is 570 $\,\times\,$ 400 $\mu$ m $^{2}$ including the measurements pads. Simulated and measured results demonstrate that the proposed device achieves good performance in both frequency bands in terms of input matching, transmission losses and isolation.

A fast frequency analysis of lossy substrate-integrated waveguides based on the asymptotic waveform evaluation (AWE) and Pade approximant technique in conjunction with the dyadic Green's function technique, is presented. The derivatives needed to evaluate moments in the AWE method are computed in a simple way thanks to an efficient method that reduces their computational cost. Numerical results demonstrate the efficiency and the accuracy of the proposed approach. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2435–2437, 2015

In this paper, empirical relations for the evaluation of both the resonant frequency fr and the quality factor Q for the dominant TM010 mode of a circular substrate integrated waveguide (SIW) cavity resonator are proposed and validated. These formulas are based on well established analytical expressions valid for the case of circular metallic cavity resonator, in which an equivalent radius Req, empirically derived, is employed. Their efiectiveness is demonstrated by comparing the empirical predictions with the full wave results.

In recent years, Artiflcial Neural networks (ANNs) have been intensively employed to build smart model of microwave devices. In this paper a characterization of lossy SIW resonators by means of Multilayer Perceptron Neural Networks (MLPNNs) on Graphics Processing Unit (GPU), is presented. Once properly selected and trained, a MLPNN can evaluate the lossy SIW resonator's resonant frequency fr and the pertaining quality factor Q at a shorter time than the full-wave rigorous model. In this way, fast parametric models of SIW structures to employ for the design and optimization of microwave devices, exploiting the computational power of GPUs, can be obtained.

In this paper the derivation of a rigorous expression of the input admittance of a coaxially fed, inflnite, lossy parallel plate waveguide (PPWG) is presented. The derivation makes use of the dyadic Green's function of the PPWG expressed as series a cylindrical wave-functions. Losses into the dielectric plates and on the conductors are considered rigorously. The approximation used in results presented in the past literature are critically discussed. Numerical experiments are performed to show the efiects of the flnite conductivity on the input impedance of the PPWG.

The paper presents a K/Ka band radiating element for TX/RX phased arrays. Dual band operations is obtained using a single radiating surface: a novel radiator is adopted and placed in a configuration in which dual band and single band elements are interleaved. The array elements are optimized to scan the beam in excess of 50° in both bands. A subarray with 49 Rx elements and 105 Tx elements was built and measured confirming the results obtained in simulations.

A dual band (Q-V) hat fed cylindrical reflector antenna is presented. The proposed antenna is fed with a dual band corrugated hat feed. The hat feed is designed using a dual corrugation optimized to obtain a similar radiation pattern and a good matching on the two bands. The feed is illuminated by a parallel plate waveguide fed with a rectangular horn which provides large bandwidth and good efficiency. Results show that the proposed design provides an efficient solution for dual band high gain antennas operating at mmw.