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The novel acoustic transversal topology has demonstrated to be a potential candidate for the development of the next generation of communication filters. The major asset of this topology is its capacity to achieve any filter response without the detriment of limited electro-acoustic coupling. Additionally, this topology prompts for an easy connection of different filters to create multiband and multiplexing responses. This study recalls and further details on the design of multiplexers based on transversal topology using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators. An important practical aspect of this topology is the need of a BALUN stage at one port of the filter.The use of the transversal topology is then applied to another type of acoustic resonator configuration, coupled resonator filter (CRF). Such a resonator configuration offers control over the phase of each transversal path, allowing us to eliminate the BALUN stage. CRF resonators are modeled by means of a different circuit model than BAW or SAW, which calls for a new synthesis procedure. This paper describes the synthesis approach and circuit transformation for the development of multiplexers based on the transversal arrangement of the CRF resonators. An example of a fully simulated 9-plexer is provided to verify this procedure.

This work presents the complete synthesis procedure and circuit transformations needed to go from the characteristic polynomials to the transversal network formed by electroacoustic resonators. This filter topology allows the possibility to achieve any filter response in spite of limited electroacoustic coupling. This is crucial for obtaining very wideband filters with arbitrary positions of transmission zeros. Additional circuit transformations reveal the flexibility of such topology to control other important parameters of the acoustic filter such as the impedance of the resonators and their resonant frequencies, which directly affect the manufacturing process. The transversal topology for electroacoustic filters has been verified by the synthesis, design, fabrication, and measurement of a very wideband filter to meet the requirements of 5G N77 frequency band, centered at 3.75 GHz with 910 MHz of bandwidth. This work was supported in part by the Catalan Gov. through grant 2017 SGR 813, and by the Spanish Gov through grants TEC2017-84817-C2-2-R, TEC2017-88343-C4-2-R and the ESA Contract No. 4000124123/18/NL/CRS.

Transversal networks for electroacoustic filters had been proposed and manufactured recently. One of the main problems that arose in the first prototype were the spurious modes due to the mirror stack of the Solidly Mounted Resonators (SMR). In this work, different approaches for solving this problem are discussed, relying on Mason's circuit-based simulations of each resonator and of the filter topology. The main drawbacks and advantages of the different approaches are discussed in terms of fabrication and mirror efficiency. This work was supported in part by the Catalan Government under Grant 2017 SGR 813, in part by the Spanish Government under Grant TEC2017-84817-C2-2-R and Grant TEC2017-88343-C4-2-R, and was also supported by the Secretary of Universities and Research of the Generalitat de Catalunya and the European Social Fund through grant 2020 FI_B-00967.

The transversal filter topology consists of resonators which require both positive and negative coupling to the input/output which typically necessitates the use of a BALUN. In this paper, transversal filters based on stacked crystal filters (SCFs) are presented. By inverting the polarity in one side of the SCF structure, both positive and negative couplings can be achieved, and the BALUN is no longer needed. In addition, a new approach to suppress spurious modes of SCFs is introduced. © 2021 IEEE.

This paper presents a compact T-type switch that involves three different operational states providing high flexibility in signal routing. Two of the states are between adjacent ports, while the other is a crossover state. T-type switches are mainly used as building blocks of redundancy matrices for satellite communications systems, although mobile applications also take advantage of switching devices. The proposed structure uses p-i-n diodes located in specific points to control each state with a specific bias dc voltage, creating open and short circuits. The symmetry of the structure allows even–odd mode analysis in order to obtain the design equations. To validate the concept, a compact microstrip T-type switch is fabricated and measured. The resulting device shows a good performance in terms of transmission and isolation for each state, in agreement with the simulations. The switch exhibits a band-pass response for the crossover state, while low-pass and high-pass responses result for the other two states.

In a scenario where the segment of wireless communication systems are allocated in an ever more crowded frequency spectrum, the design of filtering structures, stand-alone, duplexers, or multiplexers, become a challenging task. Moreover, filters based on acoustic wave resonators are the more suitable technology in this context due to the small size and the exhibited outstanding performance. However, to accommodate the technological requirements to the mask fulfillment is not straightforward unless a systematic synthesis methodology is used. Taking advantage on the nodal approach, the general synthesis methodology for ladder-type filters based on acoustic wave resonators is presented in this paper. This is a very fast procedure, which allow a better understanding of the interaction between technological constraints and filter performance. An experimental validation is proposed for a B28Rx band filter.

This letter presents a novel circuital extraction possibility for filter prototypes including resonant and non-resonant nodes (NRNs). The proposed technique involves the extraction of a cross-inverter evaluated at infinity and a dangling resonator connected to an NRN at the same time. Therefore, two transmission zeros are extracted in one iteration step. This is an extension upon the results of the outstanding and original synthesis of cross-coupled filters proposed by S. Tamiazzo and G. Machiarella, providing different sets of configurations not considered by their methodology but within the same family of topologies. An example is shown in order to illustrate the proposed technique.

A methodology of synthesis of ladder-type filters based on acoustic resonators directly in band-pass domain as an alternative to the classical low-pass to band-pass frequency transformation is presented in this paper. Special topology requirements are described in order to correctly obtain filtering function for circuits with capacitive and inductive matching elements. Finally, an example with inductive source/load nodes validating the proposed technique is presented.

The undesired package feedthrough is commonly responsible of the isolation limitation of acoustic wave duplexers and filters. In this paper it is demonstrated that considering the source-load coupling as a part of the network, the limits of the out-of-band attenuation given by the signal leakage paths can be overcome. In some cases the introduction of cross-couplings are necessary to implement the complex transmission zeros that appear by the effect of the source-load coupling, degrading the isolation if not properly considered.

With the spectrum more and more overcrowded, filters and duplexers are drivers of the technology in the discrete device mobile market. The user segment of wireless communication systems leverages the outstanding performance of filtering devices based on acoustic wave resonators. But so far, these technologies have not covered the rest of the RF passive elements in a Front End Module. The use of Bulk Acoustic Wave technology overcomes the miniaturization issue. The acoustic technology exhibits key properties which allow a significant size reduction. In an RF-Front End Module, the passive devices are under continuous pressure to shrink. Some conventional power dividers are not adequate for the high level of miniaturization demanded. To contribute on the size reduction demands of dividers, we have studied two different topological designs which applies bulk acoustic wave technology. Specifically the two proposed devices are based on Coupled Resonators Filter structures. Guidelines for the design of both 3-dB power dividers are described on this paper. We illustrate the designs with two splitters based on the two topologies for application on W-CDMA and their simulated performances. Both dividers have embedded passband filtering responses and have all the ports matched. Furthermore, the designed splitters simplify the fabrication of CRF because almost all the multilayer films are uniform.