[Show abstract][Hide abstract] ABSTRACT: Extraction techniques of circuital coupling parameters from measured or simulated scattering data have become a cornerstone of modern microwave filter synthesis. These procedures allow to compare the extracted parameters to an ideal coupling matrix (golden goal) and to infer from it precise and localized corrections on the filter. Circuital extraction techniques relying on optimization, lead by construction to a unique coupling matrix. This is in contradiction with the fact that numerous coupling topologies admit multiple solutions for the coupling matrix synthesis problem. Identifying an erroneous circuit can however destroy the whole tuning process, leading to incoherent corrections on the filter. In this paper we present a filter tuning method that systematically extracts all admissible coupling matrices and eventually identifies the physical one, that is the one that the DUT implements. The method is then illustrated and validated by the synthesis of a filter with a cascaded quadruplet topology, in microstrip technology. Index Terms—microstrip filter, parameter extraction, computer aided design
[Show abstract][Hide abstract] ABSTRACT: In this work, we characterize transfer functions that can be realized with standard electronic components in linearized form, e.g. those commonly used in the design of analog amplifiers (including transmission lines) in the small signal regime. We define the stability of such transfer functions in connection with scattering theory, i.e. in terms of bounded reflected power against every sufficiently large load. In the simplest model for active elements, we show that unstable transfer functions exist which have no pole in the right half-plane. Then, we introduce more realistic transfer functions for active elements which are passive at very high frequencies, and we show that they have finitely many poles in the right half-plane. Finally, in contrast to the ideal transfer functions studied before, the stability of such "realistic" transfer functions is characterized by the absence of poles in the open right half-plane and the positivity of the real part of the residues of the poles located on the imaginary axis.
This report is written in a way which is suitable to the non-specialist, and every notion is defined and analyzed from first principles.
[Show abstract][Hide abstract] ABSTRACT: In this paper, a new methodology for synthesizing self-equalized filters is introduced. The methodology consists of optimizing the polynomial transfer and reflection functions considering amplitude and phase constraints simultaneously. The algorithm gives access to a more general class of functions than generalized Chebyshev (also called quasi-elliptic) functions. Two self-equalized filters are designed using this new methodology, and their performances are compared to general Chebyshev filters in order to put into evidence the interest of the proposed optimization algorithm. The first design leads to reduced group-delay variations, and the second one leads to a simplification of the hardware, reducing the number of resonators.
IEEE Transactions on Microwave Theory and Techniques 08/2014; 62(8):1671-1677. DOI:10.1109/TMTT.2014.2332135 · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ce rapport présente une approche utilisée pour résoudre un problème d'identification rencontré par le CNES lors de la synthèse et du réglage de filtres hyperfréquences. Étant données des mesures fréquentielles de la fonction de transfert inconnue d'un filtre dans sa bande de fréquences, on souhaite obtenir une fonction rationnelle d'ordre donné - déterminé par la géométrie et les paramètres physiques du filtre - qui rende compte de façon satisfaisante de ces mesures. Ce problème peut être abordé par deux étapes successives d'approximation dans des espaces de fonctions analytiques qui ont été étudiées en détail dans le projet. Cette approche a donné lieu à des algorithmes de résolution qui ont été implémentés dans le logiciel Hyperion décrit ici. Les paramètres physiques du filtre sont ensuite estimés à l'aide d'une représentation d'état adaptée.
[Show abstract][Hide abstract] ABSTRACT: In this work we study a generalized Nevanlinna Pick interpolation problem, where transmission zero locations are imposed. Unlike in other variant of this problem considered by T.T. Giorgiou et al. the interpolation points are chosen on the boundary of the analyticity domain: that is, in our framework, on the real axis. This problem is motivated by important questions in electronic and microwave system design, and it relates to the broadband matching theories of Youla and Helton. An existence and uniqueness theorem is proved. The constructive proof is based on continuation techniques.
MTNS-21st Symposium on Mathematical System Theory, Groningen (The Netherlands); 07/2014
[Show abstract][Hide abstract] ABSTRACT: In this paper we present a method to recover electrical parameters of filters embedded in a multiplexer for which scattering measurements are given. Unlike other approaches proposed for this problem, this method does not require a priori knowledge of the scattering parameters of the junction. This feature renders the procedure well suited for tuning purposes or for fault diagnosis. Technically the algorithm starts with a rational approximation step, in order to derive a rational representation of certain scattering parameters of the multiplexer. This representation is then used in a second step to identify the electrical model of each filter. This second step relies on a rational interpolation technique used to extract the filter's responses.
2014 IEEE/MTT-S International Microwave Symposium - MTT 2014; 06/2014
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a method to extract the characteristics of the filters composing a multiplexer. Scattering measurements of the multiplexer are given at some frequen-cies, together with information regarding the location of the transmission zeros of each filter. From these measurements we first compute a stable rational approximation of the scattering matrix (transfer function). Then we show that the chain matrices of the filters can be recovered, up to a constant matrix, by unchaining suitable components at each port of the multiplexer. The unchaining operation relies on a Schur reduction for an interpolation problem formulated for the structure thereby obtained, with the interpolation points being precisely the transmission zeros of the filter. Since transmission zeros are often located on the imaginary axis, we are dealing with a boundary interpolation problem.
Conference on Decision and Control CDC, Florence (Italy); 12/2013
[Show abstract][Hide abstract] ABSTRACT: In this paper, an original self-equalized filter and a compact diplexer are presented. New methodologies for synthesizing and designing these devices are introduced. Implementation in dual-mode cavities is preferred since this technology offers compactness and good electrical specifications required for space applications.
[Show abstract][Hide abstract] ABSTRACT: In this paper, an original approach to frequency identification is explained and demonstrated through an application in the domain of microwave filters. This approach splits into two stages: a stable and causal model of high degree is first computed from the data (completion stage); then, model reduction is performed to get a rational low order model. In the first stage the most is made of the data taking into account the expected behavior of the filter. A reduced order model is then computed by rational H2 approximation. A new and efficient method has been developed, improved over the years and implemented to solve this problem. It heavily relies on the underlying Hilbert space structure and on a nice parametrization of the optimization set. This approach guarantees the stability of the MIMO approximant of prescribed McMillan degree.
[Show abstract][Hide abstract] ABSTRACT: Precise formulas to express the formal relationship between the time average stored energy in the resonators of a low-pass filter network and the sensitivity of the reflection S -parameter with respect to the coupling matrix terms are demonstrated in this paper, considering the normalized frequency axis. These relationships are found in the modern context of the N+2 coupling matrix, and for both diagonal and general nondiagonal coupling elements of the matrix. The results are valid for any type of coupling topology represented by the N+2 coupling matrix. Different examples are included as validation. Furthermore, important implications and applications derived from the new relationships are highlighted.
IEEE Transactions on Microwave Theory and Techniques 11/2012; 60(11):3369-3375. DOI:10.1109/TMTT.2012.2216286 · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, we propose a compact dual-band microwave output diplexer for the next generations of communication satellite. For reducing bulk, the designed diplexer is exclusively composed of coupled resonators and channel filters realize dual-band filtering functions. Compared to classical multiplexing architectures, the proposed design eliminates additional waveguide elements and leads to a more compact device. On the other hand, dual-mode cavity implementation is chosen for getting more compactness, and suiting with payloads output multiplexers, since this technology is largely used for OMUX applications.
[Show abstract][Hide abstract] ABSTRACT: This paper introduces the synthesis of microwave inline filters of narrow or moderate bandwidth which include, in addition to the cavities, “reactive nodes”, which can be implemented either by lumped components or by non-resonating, open or short circuited stubs. The synthesis is approached by means of an equivalent circuit, directly defined in the bandpass frequency domain, where the cavities are represented by shunt or series resonators and the reactive nodes by capacitors and inductors (such network has no lowpass equivalent representation). The filter includes transmission zeros, realized by means of shunt-connected series resonators (or parallel resonator connected through an admittance inverter). The paper gives general indications about the evaluation of the polynomials associated to the equivalent circuit and the subsequent circuit synthesis. Some examples, which demonstrate the improvements which are obtained in comparison to the classical in-line synthesis based on non-resonating nodes, are also reported.