Giorgio Bertin

Elliptical cavity resonators for dual-mode narrow-band filters

A novel cavity resonator with elliptical cross-section is proposed in order to realize dual-mode narrowband filters without tuning and coupling elements. No discontinuities are required inside the cavities hence significantly enhancing the unloaded Q, the ability to operate with higher power levels, and the ease of manufacturing. Dual-mode coupling is generated by the step discontinuity between the input rectangular waveguide and an inclined elliptical waveguide; a rigorous full-wave electromagnetic model for this discontinuity has been developed. Proper choice of the ellipticity and of the inclination angle allows us to obtain the desired coupling and tuning actions. Representative prototypes of elliptical cavities exhibiting various degrees of coupling have been carefully measured; the favorable comparison between experimental and theoretical results proves the accuracy of the model and its applicability for narrowband X/Ku band filters.

A four-pole dual mode elliptic filter realized in circular cavity without screws

A four-pole dual mode elliptic filter is realized in circular cavity without screws. The desired coupling and tuning actions are achieved by using a novel arrangement consisting in the insertion of a short section of inclined rectangular waveguide in the middle of the cavity body. In this way we realize dual-mode filters by using only junctions of waveguides with rectangular and circular cross sections, thus enabling a very efficient CAD of such filters. This arrangement also proves particularly convenient from the manufacturing viewpoint. Measured response of a breadboard channel filter operating at Ku-Band shows good agreement with theoretical simulations; a sensitivity analysis confirms the validity of the proposed design.

CAD and optimization of compact ortho-mode transducers

We describe a new, efficient, computer-aided optimization technique for compact ortho-mode transducers (OMT). As an example, we refer to the full-wave design of an OMT operating in the 17-18.5 GHz frequency band; this design has been entirely carried out at computer level and demonstrates a significant advantage in terms of development times and no need of post manufacturing adjustments. The very satisfactory agreement between experimental and theoretical results further confirms the validity of the proposed technique.

Full-wave design and optimization of circular waveguide polarizers with elliptical irises

We describe the design and optimization of a new polarizer structure realized in circular waveguide with insertion of elliptical irises. The device is compact, showing a considerable reduction in size and weight when compared to previously known realizations. It requires manufacturing by milling techniques only and, since it is composed entirely by waveguides with separable cross sections, it is also well suited for electromagnetic modeling. Measured and theoretical results for a polarizer with a 90/spl deg//spl plusmn/1/spl deg/ differential phase shift and a return loss better than 35 dB for both polarizations over the operating frequency band confirm the validity of the proposed design.

Switched Beam Antenna Employing Metamaterial-Inspired Radiators

We present a novel switched beam antenna (SBA) consisting of four identical metamaterial-inspired electrically short printed monopoles, vertically placed at the corners of a grounded square board. The antenna is designed to operate in the frequency range 1600-2700 MHz, with global dimensions 120 mm × 120 mm × 30 mm. The SBA has been first numerically simulated and optimized and, then, fabricated and tested. Numerical and experimental results show a good agreement. The obtained switched beam capabilities, the achieved realized gain levels, and the synthesized radiation pattern shapes on the horizontal plane, make the proposed SBA a good candidate as a radiating element of a receiving module for wireless telecommunication systems (DCS, UMTS, Wi-Fi, LTE) in areas with reduced signal coverage and/or high interference levels.

Elliptical cavity resonators for dual-mode narrowband filters

A novel cavity resonator with elliptical cross-section is proposed in order to realize dual-mode narrowband filters without tuning and coupling elements. No discontinuities are required inside the cavities hence significantly enhancing the unloaded Q, the ability to operate with higher power levels, and the ease of manufacturing. Dual-mode coupling is generated by the step discontinuity between the input rectangular waveguide and an inclined elliptical waveguide; a rigorous full-wave electromagnetic model for this discontinuity has been developed. Proper choice of the ellipticity and of the inclination angle allows us to obtain the desired coupling and tuning actions. Representative prototypes of elliptical cavities exhibiting various degrees of coupling have been carefully measured; the favorable comparison between experimental and theoretical results proves the accuracy of the model and its applicability for narrowband X/Ku band filters.

A New Dielectric-Loaded Dual-Mode Cavity for Mobile Communications Filters

A new dielectric loaded cavity structure for dual-mode filters suitable for cellular-radio base stations is presented. The cavity exhibits high unloaded Q-factor, wide spurious-free operating window and possibility of tight coupling either to input or between the dual-mode resonances. Experimental results, on a four-pole filter with an asymmetric transmission zero, confirm the validity of the proposed resonator for realizing transmit filters for UMTS cellular-radio base stations.

Dual-mode filters with grooved dielectric resonators for cellular-radio base stations

Dual-mode filters for cellular-radio base-stations require resonators with high unloaded Q-factor, wide spurious-free operating window and possibility of high coupling values either to input or between resonators. These features are obtained by employing a new cavity resonator loaded by a grooved ceramic disk. The groove, which may increase up to a full air gap, allows the insertion of probes and tuning/coupling screws where the field is stronger. Experimental results of an eight-pole transmit filter show the suitability of the proposed resonator for realizing cellular-radio base stations filters.

A novel rounded-patch dual-mode HTS microstrip filter

A novel dual-mode high-temperature superconducting (HTS) microstrip filter is presented. Resonators are realized with patches of smooth contour that comprise an internal conductor-free region of elliptical shape. Coupling lines are of low impedance in order to reduce peak current density and increase the power handling capability. The elliptical region is inclined at 45/spl deg/ for providing fine control of coupling and tuning. Two 4-pole filters of Chebyshev and quasi-elliptic type with center frequency of 1.95 GHz and bandwidth of 70 MHz were designed and fabricated. Measured results at 77 K are well comparable with theoretical modelling.

An elliptical cavity for triple-mode filters

An empty cavity resonator with elliptical cross-section is proposed for realizing triple-mode narrowband filters. Triple-mode coupling is generated by the step discontinuity between the input rectangular waveguide and an inclined-displaced elliptical waveguide resonator. Proper choice of ellipticity, inclination angle, and displacement of the cavity with respect to input iris, allows one to control generation of the three resonant modes inside the cavity. Representative prototypes of elliptical cavities exhibiting various degrees of coupling have been carefully measured proving the accuracy of the model and its applicability for narrowband X/Ku band filter design. The full-wave analysis of a complete 6-pole triple-mode filter demonstrates the capability of generating elliptical responses with finite transmission zeros.