Filters and antennas are the closest building blocks to the air interface in modern wireless communications systems. Filters allow the transmission of signals in a desired frequency range and eliminate those that operate in the unwanted range. Antennas help radiate signals within their operating range. This thesis focuses on the development of new methods for the synthesis and design of these two building blocks and the integration between them, in other words, filtennas. On the one hand, with the advent of different 5G solutions and the massive deployment of IoT, the need for highly selective filters also arises. With size as a constraint in many applications, the introduction of several transmission zeros at specific frequencies may be necessary. This conversely often leads to intricate topologies and therefore more complicated implementation. Extracted-pole and cascaded blocks are modular topologies that can overcome all these issues, allowing to design of even fully canonical filters, i.e., with as many transmission zeros as resonators. This thesis proposes novel, accurate and analytical methods for the synthesis of extracted-pole and cascade-block filters including resonating and non-resonating nodes. These methods are based on the well-known coupling matrix synthesis of filters. Then, suitable matrix operations are applied to the synthesized circuit to transform it into the target topology. Regarding the extracted-pole filters, these new methods allow to synthesize filters in a more accurate way compared to the state of the art at the time of publication of this work. Regarding the cascaded-block synthesis, these new methods allow to analytically synthesize filters that previously were only possible with optimization methods such as cascaded-doublets or filters with mixed topology (n-tuplets and extracted-poles) with the blocks arbitrarily placed along the circuit. On the other hand, filters and antennas are devices that are usually connected between them. The interconnection between them may increase the filter-antenna footprint as a matching network may be needed. If that is the case, this also adds losses to the link budget. This is particularly critical in the millimeter wave frequency range. That is why the rest of the thesis focuses on the synthesis and design of filtering antennas addressing different use cases. Regarding this topic, this thesis first proposes planar filtering antenna solutions (PCB) for the customer premises equipment (CPE) of a fixed wireless access (FWA) system, as well as for a phased array antenna (PAA) that uses frequency division duplexing (FDD). A circularly polarized horn filtenna for space applications is also proposed. For all these works, a design procedure based on filter synthesis is presented. Synthesis-based designs work on the premise that an equivalent circuit approximates the real model reasonably well. The main advantage of this type of design is that the expected frequency response of the final full-wave prototype is (approximately) known in advance. Therefore, the selection of the best solution that satisfies the given requirements can be done through fast but accurate circuit simulations. When the best solution is found, then the actual full-wave prototype is designed. In this work, this last step is conducted in a modular way, that is, the full wave prototype is designed by blocks according to the synthesized circuit, then all the blocks are assembled. These methodological procedures speed up the design process. Most of the work presented in this thesis has been published or submitted to international peer-reviewed scientific journals and conferences.
Filtri e antenne sono i blocchi più vicini all'interfaccia in aria di un moderno sistema di comunicazione wireless. I filtri consentono la trasmissione di segnali che operano in una gamma di frequenza desiderata e bloccano quelli che operano in un intervallo indesiderato. Le antenne aiutano a irradiare segnali all'interno della loro banda operativa. Questa tesi si concentra sullo sviluppo di nuovi metodi per la sintesi e la progettazione di questi due blocchi, nonché l'integrazione tra di essi. Altrimenti noti con il nome di Filtenna. Da un lato, con l'arrivo di diverse soluzioni 5G e la massiccia implementazione dell'IoT, sorge anche la necessità di filtri altamente selettivi. Poiché la dimensione è una limitazione in molte applicazioni, può essere necessaria l'introduzione di diversi zeri di trasmissione a specifiche frequenze. Al contrario, questo spesso porta a topologie intricate e quindi a un'implementazione più complicata. I blocchi a cascata e i poli estratti sono topologie modulari che possono aiutare a superare tutti questi problemi, consentendo di progettare anche filtri completamente canonici, ovvero con tanti zeri di trasmissione quanti sono i risonatori. A questo scopo, vengono proposti metodi nuovi, precisi e analitici per la sintesi di filtri a poli estratti e blocchi a cascata, compresi i nodi risonanti e non risonanti. Questi metodi si basano sulla ben nota sintesi della matrice di accoppiamento del filtro. Le operazioni matriciali vengono quindi applicate al circuito sintetizzato per trasformarlo nella topologia di destinazione. Per quanto riguarda i filtri a poli estratti, questi nuovi metodi permettono di sintetizzare i filtri in modo più preciso rispetto allo stato dell'arte al momento della pubblicazione di questo lavoro. Per quanto riguarda la sintesi di blocchi a cascata, questi nuovi metodi consentono di sintetizzare analiticamente filtri che in precedenza erano possibili solo con metodi di ottimizzazione, come doublets a cascata o filtri con topologia mista (n-tuplets e poli estratti) con i blocchi posizionati arbitrariamente lungo il circuito. D'altra parte, filtri e antenne sono dispositivi generalmente interconnessi tra loro. L'interconnessione tra loro di solito aumenta le dimensioni del blocco antenna-filtro anche poiché può essere necessaria una rete di adattamento. Se questo è il caso, questo influenza negativamente il budget di potenza aumentandone le perdite. Ciò è particolarmente critico nelle bande delle onde millimetriche. Questo è il motivo per cui il resto della tesi si concentra sulla sintesi e la progettazione di antenne filtranti focalizzate su diversi casi d'uso. In primo luogo, le soluzioni planari sono proposte in circuiti stampati per apparecchiature presso le abitazioni (CPE) di un sistema di accesso wireless fisso (FWA) e array di antenne (PAA) per applicazioni duplex a divisione di frequenza (FDD). Un'Antenna a trombino (Horn) con polarizzazione circolare integrata con funzione filtrante è proposta anche per applicazioni spaziali. Per tutti questi lavori viene presentata una procedura di progettazione basata sulla sintesi. La maggior parte del lavoro descritto in questa tesi è stato pubblicato o inviato a riviste scientifiche e conferenze.
Synthesis of filters and filtering antennas for micro and millimeter wave applications
Caicedo Mejillones, Steven Kleber
2022/2023
Abstract
Filters and antennas are the closest building blocks to the air interface in modern wireless communications systems. Filters allow the transmission of signals in a desired frequency range and eliminate those that operate in the unwanted range. Antennas help radiate signals within their operating range. This thesis focuses on the development of new methods for the synthesis and design of these two building blocks and the integration between them, in other words, filtennas. On the one hand, with the advent of different 5G solutions and the massive deployment of IoT, the need for highly selective filters also arises. With size as a constraint in many applications, the introduction of several transmission zeros at specific frequencies may be necessary. This conversely often leads to intricate topologies and therefore more complicated implementation. Extracted-pole and cascaded blocks are modular topologies that can overcome all these issues, allowing to design of even fully canonical filters, i.e., with as many transmission zeros as resonators. This thesis proposes novel, accurate and analytical methods for the synthesis of extracted-pole and cascade-block filters including resonating and non-resonating nodes. These methods are based on the well-known coupling matrix synthesis of filters. Then, suitable matrix operations are applied to the synthesized circuit to transform it into the target topology. Regarding the extracted-pole filters, these new methods allow to synthesize filters in a more accurate way compared to the state of the art at the time of publication of this work. Regarding the cascaded-block synthesis, these new methods allow to analytically synthesize filters that previously were only possible with optimization methods such as cascaded-doublets or filters with mixed topology (n-tuplets and extracted-poles) with the blocks arbitrarily placed along the circuit. On the other hand, filters and antennas are devices that are usually connected between them. The interconnection between them may increase the filter-antenna footprint as a matching network may be needed. If that is the case, this also adds losses to the link budget. This is particularly critical in the millimeter wave frequency range. That is why the rest of the thesis focuses on the synthesis and design of filtering antennas addressing different use cases. Regarding this topic, this thesis first proposes planar filtering antenna solutions (PCB) for the customer premises equipment (CPE) of a fixed wireless access (FWA) system, as well as for a phased array antenna (PAA) that uses frequency division duplexing (FDD). A circularly polarized horn filtenna for space applications is also proposed. For all these works, a design procedure based on filter synthesis is presented. Synthesis-based designs work on the premise that an equivalent circuit approximates the real model reasonably well. The main advantage of this type of design is that the expected frequency response of the final full-wave prototype is (approximately) known in advance. Therefore, the selection of the best solution that satisfies the given requirements can be done through fast but accurate circuit simulations. When the best solution is found, then the actual full-wave prototype is designed. In this work, this last step is conducted in a modular way, that is, the full wave prototype is designed by blocks according to the synthesized circuit, then all the blocks are assembled. These methodological procedures speed up the design process. Most of the work presented in this thesis has been published or submitted to international peer-reviewed scientific journals and conferences.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/195593