M. A. G. Laso

Planar magnetoinductive wave transducers: Theory and applications

Transduction of magnetoinductive waves (MIWs) in planar technology is demonstrated. A transducer consisting of a one-dimensional periodic array of metallic split squared ring resonators (SSRR), placed between a pair of microstrip lines on a planar substrate has been fabricated and measured. The microstrip lines are inductively coupled to the SSRRs located at the ends of the periodic array and excite MIWs that propagate along the array. The theoretical model for the dispersion of MIWs is used to predict the dispersion relation and the delay time in the device. The delay time was measured and a good agreement was found with the theoretical predictions. The transmission coefficient of the device was also measured. The theoretical and experimental results suggest that the proposed configuration can find application in the design of delay lines and other microwave devices. In fact, the behavior of the proposed transducer is similar to that of the conventional ferrite magnetostatic-wave transducer. However, fer...

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.

Super compact split ring resonators CPW band pass filters

Coplanar waveguide (CPW) band pass filters consisting on signal-to-ground wire connections alternating with series gaps, and split ring resonators (SRRs) etched in the back substrate slide, underneath the slots, are presented for the first time. It is demonstrated that by properly tuning SRR dimensions, a narrow pass band below the cutoff frequency of the wired/gaped CPW structure can be obtained. The relevant characteristics of the designed structure are: insertion losses below 4 dBs in the allowed band, out of band rejection above 30 dBs, and very high transition slopes with only three SRR stages. Due to subwavelength operation of SRRs, the proposed structures are very compact with potential application to the fabrication of planar filters for future communication transceivers.

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 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.

Electromagnetic crystals in microstrip technology

Recently, new promising periodic structures called photonic crystals (PCs), or more appropriately electromagnetic crystal (ECs), for the microwave and millimetre wave range, have been considered for both microwave and photonic applications. Planar microstrip waveguides are very attractive in microwave engineering and several innovative designs have been proposed for them to expand the scope of application of the new PC concepts to the microwave domain. We review some of these microstrip EC structures looking at them as counterparts of their analogues in optical wavelengths. Moreover, very recent solutions that open new promising applications both in microwave and millimetre wave integrated circuits and antennas are presented.

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

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.

Optimization of Tapered Bragg Reflectors in Microstrip Technology

The frequency responses of tapered Bragg reflectors made by etching one row of holes on the ground plane of a microstrip line are analyzed, comparing different windows and their effects on the rejection level, the bandwidth, the side lobe level and the abruptness of the main stop band.

ANALYSIS OF THE REFLECTION PROPERTIES IN ELECTROMAGNETIC BANDGAP COPLANAR WAVEGUIDES LOADED WITH REACTIVE ELEMENTS

In this work, we study the reflection properties of coplanar waveguides (CPW) periodically loaded with shunt connected capacitances and periodically perturbed by varying the slot width. These structures are of interest because the low pass frequency response with spurious frequency bands, inherent to the presence of capacitors, can be improved. This is achieved through the attenuation of frequency parasitics that is obtained by the introduction of slot width modulation. Both sinusoidal and square wave patterns are considered and the effects of the relative position of reactive elements with regard to the perturbation geometry is analysed. According to coupled mode theory, the central frequencies of the rejected bands in periodic transmission media are given by the spectrum of the perturbation function. However, it is demonstrated that, due to the presence of capacitors, multiple spurious bands can be simultaneously suppressed even in the case of a singly tuned (sinusoidal) perturbation geometry. This result points out that the frequency selective behaviour associated to the presence of slot width modulation can not be interpreted in the framework of coupled mode theory, since the rejection of spurious bands in periodic loaded CPWs is not merely given by the spectrum of the perturbation geometry.

Design of Microwave Filters With Arbitrary Frequency Response Based on Digital Methods

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.