Fernando Teberio

Design of Transmission-Type

In this paper, we propose and demonstrate a new technique for the design of arbitrary-order differentiators, intended for ultra-wideband (UWB) applications in microwave coupled-line technology. The technique employs an exact analytical series solution for the synthesis problem derived by the authors from the coupled-mode theory. This solution allows for the synthesis of microwave devices with arbitrary frequency responses, only limited by the principles of causality, passivity, and stability. The method has been successfully applied in the past to the design of two-port waveguide and transmission-line components operating in a reflection-type configuration. Here, the synthesis technique is extended to coupled-line structures, where the input port is matched at all frequencies and the reflected signal is redirected to the coupled port, enabling an effective transmission-type operation for the device. First-, second-, third-, and fourth-order UWB differentiators have been successfully designed, fabricated, and measured, validating the general design technique proposed.

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In this paper, a method to design high-power low-pass harmonic filters in rectangular waveguide technology is proposed. The new filters consist of a collection of smooth E-plane bandstop elements along the propagation direction and a smooth variation of the filter width. This yields to a broad rejected band for the fundamental TE10 mode, together with higher-order ( TEn0 and non- TEn0) mode suppression. Two different examples with stringent requirements of the space industry are provided to demonstrate the capabilities of the new methodology. By means of high-power simulations and an extensive measurement campaign, it will be shown that the smoothness of the filter profile guarantees high-power operation even with small minimum mechanical gaps. Moreover, unlike classical techniques, our method is not restricted to filters with small gaps. Hence, filters with larger gaps (always fulfilling the demanding frequency specifications) are fabricated for even higher power-handling performance.

th-Order Differentiators in Planar Microwave Technology

A lower-loss, more compact alternative to the classical E-plane corrugated waveguide low-pass filter is proposed in this paper. The novel design is capable of achieving very steep slopes in the fundamental TE10-mode frequency response along with a drastic reduction in terms of insertion loss and size. The design method is based on step-shaped bandstop elements separated by very short waveguide sections. Moreover, the matching of the novel filter is achieved by very short input/output networks based on stubs of optimized heights. A simple method is proposed allowing the designer to obtain a compact low-pass filter fulfilling stringent specifications.

High-Power Low-Pass Harmonic Filters With Higher-Order

In this paper, a multipactor analysis of a new type of high-power low-pass harmonic filter in rectangular waveguide technology is performed. The filter is designed following a novel technique which permits to obtain a low-pass filtering function with suppression of the fundamental and all the higher-order modes over a wide frequency band. This is achieved by means of a smooth variation of the waveguide height and width. Although much larger minimum mechanical gaps than the ones achieved with classical techniques can be obtained with the proposed method, the smooth profile of the novel filter topology is enough to obtain a dramatic increase in the power-handling capability of the device. This is proved by high-power simulations and measurements.

{\rm TE}_{{\rm n}0}

High-performance diplexers are frequently used in satellite systems to isolate the high-power wideband transmission band from the sensitive reception frequency range. A compact broadband waveguide diplexer to cover the Ku transmission and reception bands is proposed in this paper. The overall bandwidth of the diplexer is up to 50 %. The diplexer is composed of an E-plane T-junction which branches to a very compact Ku-band high-power low-pass filter and a band-pass filter based on inductive irises. The low-pass filter is based on λ/4-step-shaped bandstop elements separated by very short (ideally of zero-length) waveguide sections and provides the suppression of all higher-order modes. The size of the low-pass filter is dramatically reduced compared to a classical waffle-iron filter or a corrugated filter of narrowed width for the same frequency specifications. The band-pass filter has been also designed to minimize the overall footprint. The final diplexer has been manufactured by milling and the frequency response has been measured. A very good agreement between the measurements and simulations taking into account rounded corners effects has been obtained, demonstrating that this novel approach fulfills stringent specifications with a very compact implementation.

and Non-

Novel synthesized passive components in microstrip technology, rectangular waveguide technology, and microstrip coupled-line technology have been successfully designed, easily fabricated, and accurately tested for very different applications. A palette of novel microwave synthesis techniques has been surveyed and discussed in this article, confirming that they represent a powerful tool set for the design of microwave components for the emerging and demanding needs in the fields of wireless applications, biomedical engineering, and satellite communications.

{\rm TE}_{{\rm n}0}

We present low loss microstrip transmission line with compact transitions from coplanar waveguide for sub-terahertz applications. The microstrip (MS) transmission line is fabricated on the surface of a thin cyclic olefin copolymer dielectric layer. Among different optimization parameters, we present here the influence of CPW-to-MS transition length. Low loss transmission of the MS line has been demonstrated using Vector network analyzer (VNA) and its loss value is approximately -0.9 dB/mm. We also demonstrate that this topology is well suited for terahertz filters obtained by the combination of split rings resonators along the MS line.

Mode Suppression: Design Method and Multipactor Characterization

We briefly review different synthesis techniques for the design of passive microwave components with arbitrary frequency response, developed by our group during the last decade. We provide the theoretical foundations based on inverse scattering and coupled-mode theory as well as several applications where the devices designed following those techniques have been successfully tested. The main characteristics of these synthesis methods are as follows. (a) They are direct, because it is not necessary to use lumped-element circuit models; just the target frequency response is the starting point. (b) They are exact, as there is neither spurious bands nor degradation in the frequency response; hence, there is no bandwidth limitation. (c) They are flexible, because they are valid for any causal, stable, and passive transfer function; only inviolable physical principles must be guaranteed. A myriad of examples has been presented by our group in many different technologies for very relevant applications such as harmonic control of amplifiers, directional coupler with enhanced directivity and coupling, transmission-type dispersive delay lines for phase engineering, compact design of high-power spurious free low-pass waveguide filters for satellite payloads, pulse shapers for advanced UWB radar and communications and for novel breast cancer detection systems, transmission-type th-order differentiators for tunable pulse generation, and a robust filter design tool.

Low-loss compact ku-band waveguide low-pass filter

In this letter, a methodology is proposed for the design of electromagnetic band-gap (EBG)-assisted coupled-line structures in microstrip technology, controlling independently the forward and backward coupling. It is based on the use of a single-frequency-tuned EBG structure to produce a single backward-coupled frequency band, in combination with the forward-coupled frequency bands produced by the difference between the even- and odd-mode propagation constants present in microstrip technology. Thus, the central frequency of the backward-coupled band is controlled by the period of the EBG structure, while the frequencies of the forward-coupled bands are fixed by the length of the device. The rest of the frequencies go to the direct port giving rise to a device with the input port matched at all the frequencies and where the coupled bands are easily controllable by adjusting the corresponding design parameter. The novel methodology proposed has been successfully demonstrated by designing a triplexer intended for the GSM (900 MHz) and WLAN (2.4 and 5.5 GHz) telecommunication bands.

Multipactor-resistant low-pass harmonic filters with wide-band higher-order mode suppression

From our first proposals of periodic Photonic Bandgap (PBG) structures in microstrip to the complex Inverse Scattering synthesis methods that we use nowadays and that give rise to synthesized structures with smooth profiles in microwave planar or waveguide technology, the UPNA Microwave Components Group (MCG-UPNA) has made significant contributions to the microwave theory (partially related to previous optical developments) and has also made several proposals of applications that will be reviewed in this paper from an historical perspective. Our group is a multidisciplinary group, focused also on the industry needs.