Etude d'un dephaseur large bande en technologie de guide d'ondes integre au substrat.

摘要

Electronic is an emerging field since the 60's. Indeed, from the day that the first transistor has been manufactured, a little bit before the 50's, the complexity of electronic circuits didn't stop increasing. Nevertheless, there are others fields than integrated circuits that become more complex in this area. The "PCB" or "Printed Circuit Board", the component that supports the ICs, is as important as the integrated circuits during the fabrication process of an electronic system. It interconnects the integrated circuits together but also has to process a great part of the microwave signals (filters, phase shifters, antennas).;When a large quality factor is required, it is not possible to use transmission lines. Waveguides have to be used. These guides are usually very efficient but are very expensive and difficult to integrate. A new class of waveguides, the Substrate Integrated Waveguides (SIW), was proposed more than ten years ago. As seen in their name, these guides have the advantage to be integrated directly into the substrate, or into the PCBs. This technology reduces the production costs and the weight. At the same time, it increases the components density while providing an excellent quality factor. It is then interesting to use a lot of SIW in the integration of microwave systems.;This document presents the complete analysis of a new kind of broadband phase shifters designed with the SIW. The proposed method to realize the phase shift consists of a dielectric slab placed in the middle of the structure. Thus, by comparing the phase shift of this waveguide with another having the same dimensions but without this perturbation, a phase difference can be observed. The objective of this project is to develop the required tools to study different phase shifter configurations. The final goal is to study some forms of slot to find the optimal which gives the best results in term of insertion loss and phase shift.;To simplify the theoretical analysis, a SIW can be replaced by an equivalent rectangular waveguide. This model will be applied in the whole project. In chapter 2, a method to evaluate the propagation constant of a rectangular waveguide with a dielectric slab in the middle is developed. From this propagation constant, the complete electric and magnetic field are calculated.;In chapter 3, the mode matching theory is used to calculate the S matrix for a waveguide having a slab discontinuity. A cascade of matrices is then applied to calculate the global S matrix of several discontinuities cascaded. This chapter covers all the tools required to study the phase shifters discussed in the next chapters.;Afterwards, we studied several topologies of phase shifters. The Tchebychev polynomial is sometimes chosen to solve this kind of problems. So, a mathematical development allowed us to prove that it is not possible to apply the small reflection theory to the conception of a wideband phase shifter.;The simplest method to have a phase shift in a structure like this is to drill circular holes in the middle. To obtain a higher phase shift, it is also possible to cascade several holes. Such a phase shifter was manufactured for a phase shift of 42° and the results were similar to those from the simulations. Indeed, both results have an oscillation up to 55° at the beginning of the band, but stabilized afterwards to 41+/-2.5° between 30 and 40 GHz.;To find the phase shifter providing the lower return loss, we studied others topologies. We were interested in phase shifter having a continuous slot. The topology that we first studied is the rectangular slot. Then we studied several others topologies such as the triangle, the exponential form, and the optimal solution, the Hecken distribution. In order to calculate the S matrix of these structures, we have discretized the slot and applied the mode matching theory. The results obtained match very well with simulations results in HFSS. Of course, all these results do not take into account any losses. The Hecken function gives the optimal results with a return loss lower than -60 dB between 30.5 and 40 GHz (the Ka band is used) and lower than -23.7 dB over the whole band. For the Ka band, the phase shift is 130+/-3°.;Then we manufactured and tested some circuits. Thereby, the rectangular, the triangle and the Hecken phase shifters have been measures. Between 30.5 and 40 GHz, the Hecken phase shifter has return loss less than -14 dB and a phase shift of 175.4+/-5.6°. The phase shift difference of 45° with the theoretical value come from some errors in the manufacture. Furthermore, all the circuits have an increase of their phase shift compared to the predicted value.