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A highly sensitive, large throughput and wide dynamic range (in the aspect of size and material type) broadband tunable microwave interferometer based rectangular waveguide wear debris detection system is presented. Passing of (non)ferrous and (non)conductive particles through the sensor, which causes inductance and/or capacitance changes, are detected as transmission signal variations of the system. We first demonstrate the sensing principle with the aluminum particle of 800 μm and epoxy resin particle of 1 mm3 at 6 GHz. Then, the effects of particle size and flow speed are tested with aluminum particles ranging from 200 μm to 1.8 mm. The measurement results show that the system is able to measure particle sizes with known material and differentiate nonconductive particles from conductive ones. With the proposed data processing techniques, this system is capable of detecting as small as 76 μm particles within an 8 mm outer diameter tube. And with future improvements on sensitivity and particle material characterization, the proposed system has the potential to differentiate (non)ferrous and (non)conductive particles and measure their sizes as a real-time wear debris sensing devices for rotating and reciprocating machines.

This paper presents a novel class of resonators suitable for the design of waveguide pseudoelliptic filters. The basic structure is a rectangular ridge arbitrarily located and oriented within a rectangular waveguide sized to allow the propagation of the fundamental TE10 mode. The ridge has the capability to provide both a reflection and a transmission zero, thus behaving as a singlet. The coupling coefficients of the resonator can be controlled by varying the position and orientation of the ridge, or by additional elements such as irises or ridge taps. Compact pseudoelliptic filters can be designed by cascading multiple ridges and half a wavelength waveguide sections. A practical design procedure is presented. The experimental results of a fifth-order filter with three resonant ridges validate the proposed approach.

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.

An innovative ultra-compact dual-mode waveguide filter is presented. The basic idea consists of using a pair of TMmn0 degenerate cavity modes, while non-resonant modes provide a direct input-to-output coupling. In this manner, the single cavity provides two reflection and two transmission zeros, and is at the same time very compact in the longitudinal direction. Theoretical and experimental results of a two-cavity filter with four transmission zeros demonstrate the feasibility of the approach.

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.

This paper presents an innovative resonant Y-junction for the design of compact rectangular waveguide diplexers. The junction contains an elliptic ridge which serves as common dual-mode resonator for both channel filters. The junction itself constitutes therefore the first resonators of the filters, thus allowing for considerable size reduction with respect to the conventional diplexer implementation. The orientation of the input branch and the insertion of irises and ridge taps are used to control the coupling coefficients within the junction. An X-band diplexer employing the proposed junction in combination with H-plane cavity filters has been designed, manufactured, and successfully tested.

A new class of compact rectangular waveguide filters is proposed in this paper. The key element is a square ridge resonator realized within a rectangular waveguide supporting the fundamental TE10 mode. The square ridge can support two modes resonating along orthogonal directions in the gap between the ridge and the opposite waveguide wall. This structure enables dual-mode degeneracy without the need of oversized cavities, thus allowing for considerable size reduction with respect to the conventional dual-mode implementations. Different filter structures employing one or more ridges within short waveguide sections are proposed as attractive solutions for pseudo-elliptic band-pass or dual-band filters. The experimental results of a manufactured fourth-order pseudo-elliptic pass-band filter validate the feasibility of the proposed class of filters.

A broadband reconfigurable coupler has been realized at Ku band making use of RF-MEMS switches. The coupler is directly printed on the same Silicon substrate on which the MEMS are built. The device works at 16-20 GHz, and it is designed to provide two different coupling levels of -10 dB and -17 dB, maintaining good matching and isolation in both states. Performance significantly matches the simulations, verifying how close the MEMS switches perform to the predicted behavior. This also demonstrates that the MEMS fabrication process is repeatable and predictable.

This paper presents a novel resonant structure for the design of compact pseudo-elliptic filters in waveguide technology. The resonator consists of a rectangular ridge which is arbitrarily located and oriented within a rectangular waveguide. Under certain conditions, by exciting the ridge with the fundamental TE 10 mode of the waveguide, the resonator exhibits a transmission zero besides the transmission pole, thus behaving as a singlet. This element can be used as a basic building block for the design of higher order filters. In this work an in-line 5th order filter with three transmission zeros has been fabricated and tested, demonstrating the feasibility of the proposed design.

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.

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.

We review the waveguide filter design process starting from a classical approach and introducing novel possibilities. In particular, analysis and design of folded filters and filters with multiple aperture irises are investigated. The design of a compact waveguide diplexer illustrates the advantages of using folded filters, while the design of multiple aperture irises filters is carried out by using a robust optimization scheme based on the position of the filters poles and zeros.

A compact wide-band microstrip diplexer working in the 0.9/spl divide/2.5 GHz frequency range is presented. This component is a key part of the feeding network of a multifunctional antenna, working at five frequency bands associated to terrestrial and satellite radio services. By using interdigital capacitors in conjunction with the stepped impedance technique, very good results in terms of compactness and performances have been obtained. An unconventional arrangement of the filters has led to a further reduction of the dimensions.

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.

We propose a single and rigorous procedure for the full-wave analysis of folded filters and diplexers. By following this procedure, and assuming the availability of a code producing the generalized scattering matrix (GSM) of the step discontinuity, it is shown that, in many cases, it is possible to analyze folded filters and diplexers, avoiding the development of specific routines for bends and T-junctions modelling. The analysis of the entire structure is obtained by simple matrix manipulation of the GSM and by a suitable partitioning of the device. Numerical examples validate the proposed approach.

The well known Elliott (1983, 1985) design method for resonant slotted waveguide arrays is limited to a pure real slot voltage distribution synthesis. In the present work this method has been extended to the case of an arbitrary complex slot voltage distribution including the effects of mutual coupling. Comparison with full-wave analyses confirm the accuracy and computational efficiency of the method.