Simone Bastioli

A New Class of Waveguide Dual-Mode Filters Using TM and Nonresonating Modes

An innovative class of very compact and selective waveguide dual-mode filters is presented in this paper. The basic structure is the TM dual-mode cavity. Such a cavity employs both resonant and nonresonating modes so as to provide two reflection and two transmission zeros. The high design flexibility in terms of transmission zero positioning and response bandwidth has been demonstrated by means of several single cavity designs. The design of Nth-order multiple cavity filters with N transmission zeros is presented and discussed. Different filter topologies are obtained depending on the waveguide structure used to connect adjacent cavities. An efficient mode-matching analysis method is proposed and verified for fast filter optimization. An eighth-order filter with eight transmission zeros has been designed, manufactured, and tested to demonstrate the potentialities of the filter class proposed.

Generalized TM Dual-Mode Cavity Filters

A new cavity arrangement, namely, the generalized TM dual-mode cavity, is presented in this paper. In contrast with the previous contributions on TM dual-mode filters, the generalized TM dual-mode cavity allows the realization of both symmetric and asymmetric filtering functions, simultaneously exploiting the maximum number of finite frequency transmission zeros. The high design flexibility in terms of number and position of transmission zeros is obtained by exciting and exploiting a set of nonresonating modes. Five structure parameters are used to fully control its equivalent transversal topology. The relationship between structure parameters and filtering function realized is extensively discussed. The design of multiple cavity filters is presented along with the experimental results of a sixth-order filter having six asymmetrically located transmission zeros.

Waveguide Pseudoelliptic Filters Using Slant and Transverse Rectangular Ridge Resonators

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.

Inline Pseudoelliptic

A new class of dielectric resonator filters with in-line structure and pseudoelliptic response is presented in this paper. The basic idea consists of using TE01δ single-mode resonators cascaded along an evanescent mode waveguide and oriented along orthogonal directions. By exploiting multiple evanescent modes, which can alternatively excite or bypass a resonator depending on its orientation, cross-coupling between nonadjacent dielectric pucks can be established and controlled. Various configurations, such as triplets, quadruplets, and quintuplets, can be obtained by properly orienting the various pucks and by exploiting a prescribed set of evanescent modes. In contrast with conventional techniques, pseudoelliptic filters can be implemented without using cumbersome cross-coupled architectures or reduced spurious performance multimode resonators. The experimental results of two sixth-order filters with two arbitrarily located transmission zeros, and a fifth-order filter with three transmission zeros validate the proposed filter class.

{\rm TE}_{01\delta}

A novel dual-mode resonator for the design of compact waveguide filters is proposed in this paper. The resonator consists of a nearly-square ridge realized into a rectangular waveguide that supports the fundamental TE10 mode. With this configuration two degenerate modes can resonate along orthogonal directions within the gap between the ridge and the opposite waveguide wall. By combining multiple ridges, higher order filters with pseudo-elliptic response can be realized within compact waveguide sections. A 4th order filter with two transmission zeros has been designed, manufactured and tested proving the feasibility of the proposed class of filters.

-Mode Dielectric Resonator Filters Using Multiple Evanescent Modes to Selectively Bypass Orthogonal Resonators

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.

A Novel Class of Compact Dual-Mode Rectangular Waveguide Filters Using Square Ridge Resonators

In the last 10 or 15 years, exciting new developments have occurred in the field of filters and multiplexers. The two words that best explain this phenomenon are “topology” and “technology.” Thus, this paper will cover new connections, new materials, and new processes. This paper summarizes what is new, describes the new devices, and avoids simply surveying the entire field. It is not possible to cover everything, and regrettably, some new and possibly exciting areas are omitted (such as filters fabricated using liquid crystal polymers, active element inclusion, extreme power devices used in accelerators), and others, ..., because something has to be left for the next paper! The paper does cover bandstop filters, intrinsically switched film bulk acoustic resonator, and barium-strontium-titanate filters, brand new derivations of lossy filter synthesis and dual-band filter synthesis, multimode networks, new work on optimal multiplexer (multiport network) configurations, and substrate integrated waveguide filters. In each of these areas significant new work has been recently performed and is presented in a summary format suitable for those thinking that the area of filters and multiplexers has become mature (stagnant) with nothing interesting to learn. Nothing could be further from the truth!

A Novel Compact Dual Band Reconfigurable Power Divider for Smart Antenna Systems

This work presents the design, manufacturing and testing of three 5-bit K-band MEMS phase shifters based on similar architectures (combination of switched line and loaded line) but employing different MEMS switch typologies (cantilevers & air-bridges) and RF junctions (SP2T & SP4T). All devices have been monolithically manufactured on 200 μm thick high resistivity silicon substrate (4”) by using the FBK MEMS process. The performance of the different devices have been compared in order to identify the best configuration to be implemented in electronically steerable phased arrays antennas for Satellite COTM (Communication On The Move) Terminals. Excellent performances were measured for the dielectric-free pad MEMS switches as well as the single bits constituting the phase shifter. The three 5-bit devices show return loss better than 15 dB for all states, with average insertion loss of 3.5dB for the clamped-clamped, SP2T-based design, 2.2 dB for the cantilever, SP2T-based device and 2.1 dB for the cantilever, SP4T-based design. The measurements of the packaged devices are on-going.

Present and Future Trends in Filters and Multiplexers

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.

Development of different K-band MEMS phase shifter designs for satellite COTM terminals

This paper presents a new class of very compact pseudoelliptic dual-mode filters. The basic idea consists of using a pair of resonant TMmn0 modes, while nonresonating modes are exploited so as to produce a direct coupling between the input and the output of the cavity. In this way, a single cavity can provide two reflection and two transmission zeros, thus leading to Nth order dual-mode filters having N transmission zeros. In addition, the proposed configuration yields very compact and geometrically simple structures that can be properly analyzed by a fullwave mode-matching technique, thus dramatically easing the design procedure. The analysis technique has been validated by comparison with commercial EM tools and by the measurement of a manufactured prototype. Several filter examples are proposed showing the design flexibility of the proposed filter class.