Israel Arnedo

An Electronic UWB Continuously Tunable Time-Delay System With Nanosecond Delays

We propose and demonstrate an electronic system achieving continuously tunable time-delays with nanosecond-scale delay excursions for ultra-wideband signals. Our demonstration system yields an adjustable delay of up to 1.6 ns for input signals spanning 3 to 7 GHz. The key component is a dispersive length of microstrip line created by etching a chirped electromagnetic bandgap structure in the conducting strip.

Passive Microwave Planar Circuitsfor Arbitrary UWB Pulse Shaping

We propose and demonstrate a new technique for generating customized pulse-shapes intended for use in ultrawideband (UWB) applications. The technique employs tailored microstrip lines that have been designed using an exact analytical series solution of the synthesis problem derived from the coupled mode theory. This solution permits the synthesis of waveguides and transmission lines with arbitrary impulse responses limited only by the principles of causality, passivity and stability. Time-domain measurements are performed demonstrating the generation of two pulse-shapes using microstrip circuits and satisfying pre-established UWB mask requirements.

A Series Solution for the Single-Mode Synthesis Problem Based on the Coupled-Mode Theory

In this paper, we present an exact analytical solution for the inverse scattering problem formulated by using the coupled-mode theory in the microwave range, assuming single-mode operation. The solution is a series that gives the required coupling coefficient for the microwave device as a function of the target frequency response. A clear physical meaning for the terms of the series is discussed, and several useful properties for the synthesis are given, thus providing a deep understanding of the synthesis mechanics. The method allows for the design of microwave devices with arbitrary frequency response only constrained by principles of causality, passivity, and stability. The resulting device is, in general, a nonuniform waveguide that features a continuously varying profile, e.g., a nonuniform microstrip line with continuously varying strip width. As an example of the potential of the synthesis method, a matched filter for ultra-wideband applications is finally designed in microstrip technology and successfully tested.

Experimental Demonstration of Pulse Shaping for Time-Domain Microwave Breast Imaging

We experimentally demonstrate a low-cost hardware technique for synthesizing a speciflc electromagnetic pulse shape to improve a time-domain microwave breast imaging system. A synthesized broadband re∞ector (SBR) fllter structure is used to reshape a generic impulse to create an ad-hoc pulse with a speciflcally chosen frequency spectrum that improves the detection and imaging capabilities of our experimental system. The tailored pulse shape beneflts the system by improving the level of signal detection after transmission through the breast and thus permits higher-resolution images. We report on our ability to use this technique to detect the presence of tumours in realistic breast phantoms composed of varying quantities of glandular tissue. Additionally, we provide a set of images based on this experimental data that demonstrates the increased efiectiveness of the system using the SBR-shaped pulse in the localisation and identiflcation of the embedded tumour.

A Compact Design of High-Power Spurious-Free Low-Pass Waveguide Filter

In this letter, a new technique is proposed for the design of a compact high-power low-pass rectangular waveguide filter with a wide spurious-free frequency behavior. Specifically, the new filter is intended for the suppression of the fundamental mode over a wide band in much higher power applications than the classical corrugated filter with the same frequency specifications. Moreover, the filter length is dramatically reduced when compared to alternative techniques previously considered.

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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This letter reports on a new design method for dispersive delay lines in coupled-line technology. Based on the reflective chirped delay line concept, a continuous modulation of the even- and odd-mode characteristic impedances in symmetrical coupled-lines is shown to produce a new structure that presents a flat magnitude response and a linear group-delay variation along the operation frequency band. The use of coupled-lines avoids the need for a circulator giving rise to more practical devices, where the processed signal is redirected to the coupled port instead of being reflected back to the input port, thus providing a valuable effective transmission-type operation. The technique of designing a device is validated for ultra-wideband signal processing applications.

th-Order Differentiators in Planar Microwave Technology

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.

Dispersive Delay Line With Effective Transmission-Type Operation in Coupled-Line Technology

This letter presents a novel general technique for the design of microwave filters with arbitrary frequency response. It is based on the translation of the microwave specifications to the digital domain, where the well known and readily available digital filter design techniques are applied. By means of these digital techniques, the method provides a straightforward procedure to calculate the poles and zeros corresponding to the analog frequency response that satisfies the target specifications. From the poles and zeros, the microwave filter can be readily obtained using conventional techniques. As an example to demonstrate the proposed technique, a filter with user-defined specifications over two independent passbands has been implemented and successfully tested in microstrip technology.

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

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.