A novel approach to co-design microwave devices with distributed switches

This paper deals with a novel approach to co-design a microstrip line associated with a distributed PIN switch in a semiconductor substrate. An High-Resistivity Silicon (HR-Si) substrate was chosen to optimize the trade-off between semiconductor effects and microwave propagation. Indeed, thanks to this particular substrate, the novel co-design concept is illustrated by an integrated and distributed switch based on an N⁺PP⁺ junction. This concept offers great flexibility in the design of tunable microwave devices. Moreover, applied to tunable distributed systems (antennas, filters, etc) in planar technology, it makes it possible to avoid the need for reported components or metalized holes. The coupling between semiconductors and microwave devices is taken into account thanks to a new co-design flow. Two demonstrators, with switchable doped microstrip lines, are manufactured and measured to validate the approach. The performances achieved in terms of insertion losses (IL) and isolation (Iso) were lower than 2.8 dB and higher than 40 dB, respectively, over the whole frequency band under consideration (from DC to 20 GHz).

I. Introduction

Device tunability has become a fundamental aspect of the telecommunications field due to multiple standards operating at different frequencies. Many solutions are used to achieve this frequency tunability, based on technologies such as liquid crystals [1], liquid metals [2], ferroelectric thin films [3] or on discrete reported components. The first kinds of technologies are very promising but still suffer from weaknesses in terms of losses, size and tunability. The discrete components are still often used and operate as ON/OFF switches such as PIN diodes [4]–[5], FET transistors [6], or RF MEMS (Micro Electro Mechanical System) [7]–[8], and are associated with passive microwave devices (filters, antennas, phase shifters, etc) to enable tunability. Usually, these tunable microwave devices are designed not only with some reported lumped components, but also by using wire bondings and/or metalized via-holes. They induce interconnection problems and a low flexibility in the design.