Magdalena Chudzik

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.

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

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.

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

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}

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.

and Non-

A novel chirping technique is applied to the design of very high-power waveguide harmonic low-pass filters. The technique could be used, for instance, to avoid multipactor testing in multicarrier systems such as the output multiplexer of a communications satellite. The novel chirped filter shows low insertion loss, all higher order mode suppression, and broad stopband rejection up to the third harmonic. This paper focuses on the maximization of the filter power-handling capability without affecting its excellent frequency behavior. Given a certain frequency response, the E-plane mechanical gap of the structure and the length (in the propagation direction) of the waveguide sections between its constituent bandstop elements can be considered to improve the high-power behavior. However, the power performance may not be sufficient yet in some applications if we wish, for instance, multipactor testing to be avoided. This becomes feasible by chirping the length (in the propagation direction) of the bandstop elements. An example for Ku band is discussed for relevant frequency specifications. An improvement from

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

\sim 8

Mode Suppression: Design Method and Multipactor Characterization

kW (non-chirped filter) to more than 100 kW (chirped filter) is obtained. As a reference, the equivalent waffle-iron filter can handle only 0.15 kW. Such high-power threshold levels have never been reported before for such kind of filters.

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.