D. Benito

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.

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.

Novel Wideband Photonic Bandgap Microstrip Structures

Novel wide rejected band devices are obtained using chirping techniques in One-Dimensional Photonic Bandgap microstrip structures with the ground plane etched following a periodic pattern. Full-wave electromagnetic simulations and measurements are provided to compare the frequency-responses of structures with linearly varying period (chirped devices) and those of structures with constant period (non-chirped or uniform devices).

Analysis and design of electromagnetic crystals in microstrip technology using a fibre grating model

Electromagnetic crystals (EC) in microstrip technology have been recently proposed as efficient Bragg reflectors. They are implemented by etching the ground plane or by drilling the substrate following a periodic pattern. In this paper we propose a simple and fast fibre Bragg grating (FBG)-based model for the synthesis and analysis of these microstrip ECs with sinusoidal patterns. The method rests on the analogy found between the frequency responses of a microstrip EC and a FBG. Based on this analogy, an equivalence relationship between the physical parameters of a microstrip EC and those of an equivalent FBG has been established. The equivalence assures that the frequency response of the microstrip EC is a down-shifted replica of the one corresponding to its equivalent FBG. This model avoids the use of the time-consuming electromagnetic calculations involved in the analysis of the microstrip ECs as well as the trial method employed until now in the synthesis, since a FBG response arises immediately from coupled-mode theory. At the same time the theoretical difficulties encountered in the formal derivation of coupled-mode theory for microstrip ECs are also avoided by the equivalence relationship found.

A novel electrically tunable dispersion compensation system

We propose a system for tuning with an electrical signal dispersion compensation over a broad range of transmission distances for different transmission bit rates. It is composed of chirped gratings and a phase modulator with an electrical modulation signal varying to achieve the tuning in the link length for which the dispersion is compensated. It is demonstrated that with fiber gratings and a phase modulator in the proposed configuration, a broader tuning range than with the prechirp technique is achieved. The influence of the fiber grating ripples in the system behavior is also considered.

Emulated single-mode fiber-optic link by use of a linearly chirped fiber Bragg grating

A compact and low-cost device that emulates a standard and dispersion-shifted 100-km single-mode fiber-optic link at 1550 nm is proposed. The device, composed of a chirped fiber grating and a monitor coupler, is analyzed by simulation and experimentally proved. A chirped fiber grating synthesis procedure and an explanation for both cases are also introduced.

Third order dispersion compensation of linearly chirped Bragg gratings

The problem of cubic dispersion of linearly chirped Bragg gratings has been discussed. A new system for compensation of this third order dispersion was proposed and numerically analyzed.

On the Measurement of Fiber Bragg Grating's Phase Responses and the Applicability of Phase Reconstruction Methods

A signal processing algorithm is used to reconstruct the phase response of fiber Bragg gratings from easy-to-obtain module data. The algorithm is applied to optical spectrum analyzer measurements, avoiding the use of costly and complex equipment for the direct measurement of the complete frequency response. Reconstructed results, both in transmission and reflection, are then validated by comparison with three of the most common experimental techniques (interferometric, modulation phase shift, and single-sideband modulation).

Real-Time Spectrum Analysis in Microstrip Technology

We report on a time-domain analog to the spatial far-field Fraunhofer diffraction using microstrip lines with chirped distributed Bragg coupling between the fundamental microstrip mode and the same but counter-propagating mode. The chirping of the microstrip impedance yields to linear group delays within the reflected bandwidth. Under the condition of a temporal equivalent of the spatial Fraunhofer inequality, the distortion of a frequency-limited pulse results in an output reflected signal whose complex envelope is, except a phase factor, proportional to the Fourier Transform of the input pulse envelope. This has important temporal applications and, in particular, the devices designed in this paper work as real-time energy spectral density analyzers.

Linearization of electro-optic modulators at millimeter-wave frequencies

We have demonstrated the feasibility of the bidirectional dual parallel linearization technique for reduction of the intermodulation distortion in broadband systems at millimetre-wave frequencies. Moreover, we have shown that the performance can be enhanced reducing the ripple level in the frequency responses. The technique offers less complexity than the standard dual parallel technique and can operate at higher frequencies thanks to the use of a single modulator which allows close control of the frequency responses of the two signal paths.