Ivan Arregui

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.

N

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 novel technique to synthesize microwave filters by inverse scattering is proposed. It provides an exact solution for the synthesis problem, by means of a closed-form expression, with very low computational cost. The technique is valid when the target frequency response can be expressed as a rational function. The coupled-mode theory is used to model microwave propagation along the filter, and therefore, the synthesis technique is applicable to filters implemented in a wide range of technologies, such as planar and nonplanar transmission lines, and many waveguides. The synthesis method is exact for all the frequency range of interest, preventing the degradation of the frequency response that can be troublesome for wideband applications or to satisfy the out-of-band requirements of the filter. The resulting synthesized filter is, in general, a nonuniform transmission line or waveguide that features a continuously varying smooth profile, avoiding the presence of sharp discontinuities and their detrimental effects. To demonstrate the potential of the proposed synthesis technique, a multiband microwave filter, fulfilling stringent specifications, will be designed in rectangular waveguide technology. The prototype will be fabricated by electroforming and carefully measured with a vector network analyzer, confirming the accuracy of the novel synthesis method reported.

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

In this paper, a new technique to design low pass filters in microstrip technology is proposed. The technique is based on the use of the transverse microstrip resonant mode and it is an excellent tool for the design of filters with stringent requirements like sharp cutoff frequency response and wide rejection bandwidth. Due to the fact that these features are not easily achieved with conventional methods, it is a very promising technique. As an example, a design with a cutoff frequency of 2 GHz and a rejection band up to 15 GHz is shown. As it will be seen, the steep slope achieved in the example is equivalent to that obtained with a classical 29th -order Chebyshev low pass filter.

and Non-

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.

Mode Suppression: Design Method and Multipactor Characterization

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.

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

This paper explores a general synthesis technique previously developed by the authors for designing microwave devices with fully customized temporal/spectral responses and its communications. The theoretical foundations of the exact analytical series solution for the synthesis technique enables the passivity and stability. A simple and efficient implementation of the synthesis algorithm is also presented. Finally, we demonstrate the application of the microwave synthesis technique for UWB applications: key components for the generation and optimal demonstrated. In particular, an UWB pulse-shaper and a matched-filter are experimentally demonstrated in conventional microstrip technology.

Synthesis of Microwave Filters by Inverse Scattering Using a Closed-Form Expression Valid for Rational Frequency Responses

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.