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A low-profile single-ridge waveguide magic-T is proposed as a combination of two T-junctions at an X band. A slot coupling technique is used to reduce the component dimensions in the E-plane, thus leading to a low profile. The device can assume two configurations by arranging the sum and difference ports in the same or opposite direction, an attractive feature in the design of beamforming networks with complex routing. A magic-T prototype is fabricated using laser powder bed fusion additive manufacturing techniques. Good agreement between simulations and measurements is found.

An X-band H-plane groove gap waveguide magic-T is presented as a combination of an H-plane and an E-plane T-junction. Two architectures can be derived by orientating the sum and difference ports to the same or opposite directions, respectively. Slot coupling allows the reduction of the device dimensions along the E-plane, and such a low profile can be attractive in all groove gap waveguide applications where compactness is required. A proof-of-concept prototype is fabricated with standard low-cost CNC milling machine manufacturing techniques. Good agreement between simulations and measurements is observed.

Hybrid couplers are important devices that combine or divide signals in various microwave applications. Wideband performance, low losses and small size are key features in most modern radar and communication systems. This paper presents a new geometry for single-ridge, air-filled waveguide quadrature hybrid couplers at the X/Ku band on a single layer using multiple pairs of slots cut on a common ridge coupling section. Bandwidth can be progressively extended by increasing the number of slot pairs. Two designs characterized by compact size and state-of-the-art performance are proposed, leading to a fractional bandwidth up to 46.88% and a maximum dimension of 1.18 wavelengths. A tolerance analysis is presented to highlight the design robustness and reliability.

A coaxial-to-groove gap waveguide transition is proposed for the first time, addressing the lack of similar designs in the state-of-the-art literature. An in-line configuration is adopted in case of stringent space requirements in groove gap waveguide systems. This device has no dielectric and makes use of a waveguide multi-step ridged section connected to the inner conductor of a coaxial line. Three versions are presented, covering progressively wider bandwidths depending on the number of employed steps. The three configurations achieve 20-dB return loss fractional bandwidths of 2.63%, 16.79%, and 38.08%, and 30-dB return loss fractional bandwidths of 0.84%, 10.63%, and 33.49%, with a simulated insertion loss always better than 0.05 dB when a realistic metal conductivity of 2 × 10 7 S/m is assumed. A tolerance analysis on the most critical geometrical parameters is provided to assess the mechanical feasibility, preserving a remarkable performance at X band.

A dual-layer 3-dB substrate-integrated waveguide power divider/combiner is designed, fabricated, and tested. Very good input and output matching as well as high isolation are exhibited over a measured 50% fractional bandwidth when a 10-dB reference level is considered. A completely shielded design significantly reduces insertion losses when compared to the majority of other state-of-the-art architectures. This device can be integrated with multilayer planar circuits, and it is fully compatible with the standard printed-circuit board technology.

A new modeling approach for the design of planar multilayered meander-line polarizers is presented. For the first time a multielement equivalent circuit is adopted to characterize the meander-line unit cell. This equivalent circuit significantly improves the bandwidth performance with respect to the state-of-the-art. In addition to this, a polynomial interpolation matrix approach is employed to take into account the dependence on the meander-line geometrical parameters. This leads to an accuracy comparable to that of a full-wave analysis. At the same time, the computational cost is minimized so as to make this model suitable for real-time tuning and fast optimizations. A four-layer polarizer is designed to validate the presented modeling procedure. Comparison with full-wave simulations confirms its high accuracy over a wide frequency range.

In this paper, an innovative patch antenna optimally designed for phase-only beam shaping is presented. The radiating element generates a circularly polarized field and exhibits two separate operative frequency bands. The element is center-fed by a pin connected to the beam forming network (BFN) layer. This unique feature allows us to generate any given phase distribution by simply proportionally rotating the radiating elements with respect to their feeding points. An effective phase-only synthesis method is also illustrated, which takes into account the radiating element rotations. To demonstrate the effectiveness of the proposed solution, two linear arrays for global coverage have been designed, specifically operating in the E1 and E6 frequency bands of the European Global Navigation Satellite System (GNSS) Galileo. The two presented antennas performance have been verified with full-wave simulations, showing excellent agreement with theoretical results and, therefore, confirming the effectiveness of the presented design approach.

A broadband rectangular waveguide to substrate integrated waveguide power divider for hybrid beam forming networks is presented. Rectangular waveguide symmetric E-plane irises are used to realize a multi-section matching network. A hybrid circuit and full-wave design procedure are described and adopted to synthesize three matching networks with one, two, and three irises, progressively increasing the bandwidth and exceeding the state of the art in the last two cases. Three proof-of-concept prototypes are manufactured and tested to validate the design procedure. Good agreement between simulated and measured performance confirms the validity of the proposed solution.

In this work, the issue of limited bandwidth typical of microstrip antennas realized on a single thin substrate is addressed. A simple yet effective design approach is proposed based on the combination of traditional single-resonance patch geometries. Two novel shaped microstrip patch antenna elements with an inset feed are presented. Despite being printed on a single-layer substrate with reduced thickness, both radiators are characterized by a broadband behavior. The antennas are prototyped with a low-cost and fast manufacturing process, and measured results validate the simulations. State-of-the-art performance is obtained when compared to the existing literature, with measured fractional bandwidths of 3.71% and 6.12% around 10 GHz on a 0.508-mm-thick Teflon-based substrate. The small feeding line width could be an appealing feature whenever such radiating elements are to be used in array configurations.

This paper presents a feasibility study for a very high data rate receiver operating in the K/Ka-band suitable to future Moon exploration missions. The receiver specifications are outlined starting from the mission scenario and from a careful system analysis. The designed architecture uses a low noise front-end to down-convert the incoming K/Ka-band signal into a 3.7 GHz intermediate frequency (IF). For maximum flexibility, a software defined radio (SDR) is adopted for the I/Q demodulation and for the analog to digital conversion (ADC). The decoding operations and the data interface are carried out by a processor based on field programmable gate array (FPGA) circuits. To experimentally verify the above concepts, a preliminary front-end breadboard is implemented, operating between 27.5 and 30 GHz. The breadboard, which uses components off the shelf (COTS) and evaluation boards (EVBs), is characterized by a 46 dB gain, a 3.4 dB noise figure and a &minus, 37 dBm input-referred 1 dB compression point. Finally, a 40 Msym / s quadrature phase shift keying (QPSK) signal is demodulated by means of a commercially available SDR, demonstrating the above concept. The importance of these results is that they have been obtained exploiting a class of miniaturized and low cost microwave integrated circuits currently available on the market, opening the way to a dense communication infrastructure on cislunar space.

This communication presents an innovative dual-polarization antenna working at Ku band ( $\text{14} \div \text{14.5}\ {\text{GHz}}$ ) based on slotted waveguide array (SWGA) technology. The proposed solution allows to simultaneously generate two orthogonal circular polarizations that are combined to generate two orthogonal linear polarizations with polarization-tracking capabilities and very low cross-polarization level thanks to the symmetry of the structure. The antenna is composed of two interleaved slotted ridge waveguide arrays connected to a polarizer, realized with an array of triangular-base ridged cavities. Slots, located at the waveguide centerline, are excited by means of posts avoiding offsets and leading to a regular grid arrangement. Radiating elements are placed in a triangular lattice to minimize the azimuth sidelobe level and provide high EIRP levels.

In this work a general formulation for the computation of gain, noise figure and third-order intercept of the parallel of a number of branches is presented. These formulas are particularly useful for the characterization of active weighted array antennas, thus for the design of the relevant beam-forming networks.

The design of a Ku-band reconfigurable reflectarray antenna for emergency satellite communications is presented. Bidirectional high data rate satellite links are needed in emergency conditions where other telecommunication infrastructures are not available. In order to operate in this type of scenario, an antenna should be deployable, transportable, and easily repointable. The need of an automatic and fast satellite location and pointing system leads to a completely electronic reconfigurable antenna. The operative bandwidth is from 10.7 to 12.5 GHz for reception and from 14 up to 14.5 GHz for transmission (30% of relative bandwidth). The selected antenna architecture is based on a dual reflectarray system comprising a passive subreflectarray and an active main reflectarray made of reconfigurable 1-bit elementary cells based on PIN diodes.

In this work, an H-plane and an E-plane single-ridge waveguide T-junction exhibiting compact size and broadband performance are presented. Thanks to these features the proposed devices turn out to be key components for the implementation of high-performance multilayer antenna beam-forming networks. Effectiveness and suitability of such T-junctions are demonstrated through the design of a broadband array antenna feeding network. The presented components operate at Ku band, nevertheless the adopted architectures are fully scalable to other frequency band of interest.

This paper presents an innovative accurate ranging system based on FMCW (Frequency Modulated Continuous Wave) Radar. Thanks to a combination of nontrivial solutions a centimetre precision is guaranteed even in tough environments, such as warehouses packed with metallic objects or extremely dusty sites, where conventional RF, laser, ultrasonic or video technology may present severe limitations. The proposed solution is currently being applied in Automatic Guided Vehicle for warehouses. The architecture of the system and the obtained results are presented in details.

This paper presents recent advances on reconfigurable reflectarrays at the University of Perugia. In particular, the activities carried out in the framework of the FP7 project ARASCOM (“MEMS and Liquid Crystal based” Agile Reflectarray Antennas for Security and COMmunication). As for ARASCOM outcomes, the purpose of the project is the design of a very large reconfigurable reflectarray controlled with micro-electro-mechanical systems (MEMS) for mm-wave imaging system at 76.5 GHz. A system with sufficient resolution to detect concealed weapons impose challenging requirements on the antenna, which shall be made of hundreds of thousands elements. The problem has been addressed by exploiting some innovative solutions and architectures that will be described in this document. In particular, the dimensioning of the reflectarray, the proposed 1-bit geometry of elementary cell, and the innovative biasing control architecture are reported together with the MEMS design and fabrication and the experimental results of a demonstrating board that validated the adopted procedure.

The problem of very large reconfigurable reflectarray (RA) antennas based on RF MEMS technology is addressed in connection with a 77 GHz RA for imaging application being developed within the European FP7 project called ARASCOM. Since thousands of reconfigurable elementary cells are employed, reducing the number of tuneable components is of paramount importance for the practical realization of the reflectarray. A dramatic reduction of the number of tuneable devices is shown to be achievable without performance degradation by a proper architecture based on 1-bit digital phase shifting and on the separable illumination of the RA. The elementary cell design, the fabrication technology and the control network architecture are illustrated in some detail showing the feasibility of the approach proposed.

In this work a 2D electronic beam steering array is presented. The 8times8 antenna operates in the frequency range 4.4-5 GHz. Each radiating element is connected to an independently controlled analog phase shifter, thus allowing a continuous steering of the main beam both in elevation and in azimuth. The whole antenna is realized in printed technology, and all the RF and biasing circuitry is realized on a single layer, while the radiating part is realized by an array of cavity-backed slot-fed patches, thus resulting in an extremely compact and modular solution. Preliminary measurements show the good performance achievable and confirm the beam-shaping and interference-nulling capabilities of the presented antenna system.

This paper presents a novel Rotman lens in low-cost substrate integrated waveguide (SIW) technology. An original solution is proposed for the design of the adsorbing load at the sidewalls of the lens and for the phase-shifters at the output ports. A three beam prototype feeding an 8-element array working at Ku band has been fabricated and tested.

This paper presents a novel compact dual band reconfigurable power divider for smart antenna systems. The circuit employs two cascaded dual band hybrid couplers connected through two dual band discontinuities. The dual band discontinuities, consisting of a diplexer and two varactor diodes, can be tuned through two different biasing voltages thus allowing an independent and arbitrary choice of the power ratio in the two frequency bands. A prototype has been designed to operate in the dual band WLAN frequency range, and fabricated in microstrip technology on a 25 mils CER10 substrate. Measured scattering parameters exhibit good performance in terms of return loss, insertion loss and isolation in both WLAN bands, confirming the feasibility of the proposed architecture. The compactness of the circuit makes it suitable for employment in array configurations.

Innovative feeding network architectures for conformal arrays are presented. The WLAN dual band system is chosen as a possible application. The basic components employed in the smart antenna are presented: dual band power divider with independent power ratio in both WLAN frequency ranges; dual band phase shifters with independent phase shift in both ranges; dual band radiating element. Experimental results confirm the feasibility of the proposed architecture.

In this work a compact dual-band microstrip patch antenna for WLAN applications is presented. The two operative frequency ranges are 2.40 ? 2.50 GHz and 5.15 ? 5.35 GHz. The proposed antenna is made of two stacked patches printed on different layers, thus resulting in a planar, light structure, suitable for lowcost mass production. The reduced antenna size allows for the integration in conformal or planar 2-D arrays, the maximum dimension of the resulting elementary cell being smaller than 0.75 ?0 at the higher frequency (5.25 GHz). Measurements and design procedure are provided.

Recent advances in the technology of radiofrequency (RF) circuits, such as RF-microelectromechanical systems (MEMS) make it possible to practically implement electronically reconfigurable antenna arrays paving the way to innovative communication systems including applications such as next generation mobile communications, radar applications, remote sensing and imaging. This paper reviews the basic implementations of such antenna systems, namely phased arrays and reflectarrays, as well as the algorithms allowing for beam shaping, beam steering, null placing etc., as well as the typical RF-MEMS circuitry for both amplitude and phase control.

An innovative dual band reconfigurable beam forming network for conformal arrays is introduced, based on a dual band power divider with independent power ratio in both WLAN frequency ranges. Each divider employs two dual band quadrature hybrids connected through two dual band phase shifters. Measured results show good performance in terms of return loss, isolation and power ratio accuracy, confirming the feasibility of the proposed architecture.

This paper presents a dual band reconfigurable power divider for WLAN smart antenna systems. The circuit employs two dual band quadrature hybrids connected through two dual band phase shifters. With this simple and compact architecture any power ratio can be independently produced in both frequency ranges. Each dual band phase shifter consists of two diplexers and two switched line phase shifters operating at the lower and higher WLAN frequency bands. A 3-state dual band reconfigurable power divider realized in microstrip technology is presented. Measured results show good performance in terms of return loss, isolation and power ratio accuracy, confirming the feasibility of the proposed architecture.

In this work, a novel low-cost solution for efficient adaptive nulling in large 2D phased arrays is proposed. The array phase distribution is controlled by a properly biased resistive or capacitive polarization network. Interference nulling is performed by using only a few biasing signals independently of the number of radiating elements of the array. A dramatic reduction of the overall complexity of the system is consequently achieved, without affecting the adaptive nulling capability of the antenna with respect to arrays in which each element is phase-controlled. The system shows excellent performances in terms of convergence speed and robustness, thus making this approach particularly suited for real-time applications.

A programmable power divider/combiner is proposed for applications to low-cost reconfigurable antenna systems. The circuit employs two 3dB branch line couplers and a programmable reflection-type phase shifter that produces the required power ratio. A 5-state programmable power divider has been designed using microstrip technology and 8 RF MEMS devices. The circuit has been designed on a 525 /spl mu/m high resistivity silicon substrate using a well established micromachining process at ITC-irst in Trento, Italy. The circuit is presently being fabricated; the simulated results show return loss better than 25 dB and isolation better than 20 dB with power ratios of 1:0, 4:1, 1:1, 1:4, and 0:1 with a maximum error in the power ratio lower than 4.5%. An example of reconfigurable antenna system based on the proposed device is shown.

Beam scanning reflectarrays represent an attractive alternative to MMIC-based phased array antennas, particularly at mm-wave frequencies, thanks to their potential low costs and high performance. In this paper, a simple but effective reconfigurable reflecting element is presented and the design procedure is described. An architecture for 2D electronic beam steering with reduced number of control signals, suitable for large reflectarray antennas, is presented. To demonstrate the feasibility of the proposed solution, a prototypal reflectarray antenna operating at 25 GHz has been designed and fabricated. Comparison with measured results shows very good agreement and confirms the capability to electronically steer the antenna beam.

A new method for phase-only synthesis of linear array antennas is proposed. The phase distribution of the array excitation can be described by a weighted sum of proper basis functions. By optimising the weights of this sum, rather than the phase of each element, the problem becomes almost independent of the size of the array. The present work shows that with this method both beam shaping and interference nulling can be achieved. The very fast convergence of the optimisation makes it suitable even for real-time applications.

An iterative procedure is presented for a fast and accurate analysis of scanning slotted waveguide arrays including the effects of mutual couplings and their dependence on the scanning angle. The analysis takes also into account the input transitions from the feeding network; each slotted waveguide being excited either at one end or at the centre. The procedure is applied to the simple case of a linear array of four slots, for which a full-wave analysis could be carried out for comparison. The proposed method is shown to provide excellent agreement with the full-wave computation still requiring extremely short computation times.

Because of its good efficiency and relatively low cost slotted waveguide technology is a promising candidate for the fabrication of electronically scanning antennas for advanced communication services. Such antennas can typically be used for mobile satellite terminals. For practical implementation of the beam steering, however, the problem of grating lobes must be solved. In this paper, Elliott design method [1,3] has been extended to large slotted waveguide scanning arrays. Dielectric filling has been employed to reduce the distance between radiating elements. The synthesis of the scanning planar array is based on a rigorous FDTD characterization of the isolated slot in terms of an equivalent shunt admittance. The computed results are shown to be in good agreement with other methods. As an example, a 30° ÷ 50° scanning array with 32 × 20 slots has been designed showing 30dB minimum gain over 500 MHz bandwidth at 30 GHz; a pointing error less than 0.5° is obtained with 3-bit phase shifters.

In this work a new low-cost solution for the implementation of electronically scanning active antennas for mobile satellite terminals in Ka-band is presented. The proposed antenna is made of a slotted post-wall waveguide array with integrated active feeding network. The small size of this antenna, its flat profile, lightweight and low fabrication costs, together with its high performances in terms of antenna efficiency, high gain and scanning capabilities, make it a very attractive solution for mobile satellite terminal applications.