Microwave index engineering for slow-wave coplanar waveguides

Álvaro Rosa,Pablo Sanchis,Antoine Brimont,Steven Verstuyft,Dries Van Thourhout

doi:10.1038/s41598-018-24030-w

Álvaro Rosa, Pablo Sanchis + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-24030-w

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Abstract

Microwave index engineering has been investigated in order to properly design slow-wave coplanar waveguides suitable for a wide range of applications in microwave, photonics, plasmonics and metamaterials. The introduction and optimization of novel capacitive and inductive elements is proposed as a design approach to increase the microwave index while keeping the impedance close to 50 Ω to ensure the compatibility with external electronic devices. The contribution of inductive and capacitive elements and their influence on the performance of the slow-wave coplanar waveguide has been systematically analyzed. As a result, a microwave index as high as 11.6 has been experimentally demonstrated in a frequency range up to 40 GHz which is, to the best of our knowledge, the largest microwave index obtained so far in coplanar waveguides.

Highlights

Monolithic coplanar waveguides (CPWs) play a key role in integrated devices technology
Slow-wave CPWs are of paramount importance in several fields such as microwaves, photonics, plasmonics and metamaterials
Slow wave CPWs are required for matching microwave and optical indices to avoid a reduction of the electro-optic modulation bandwidth[22]

Summary

Microwave theory and proposed design approach

In previous works[10,11,20,23,24,25,26], the introduction of periodic capacitive elements (thin fins) to the CPW has been proposed to increase the capacitance without decreasing the inductance, which results in a microwave index increase and an impedance reduction This is an effective method but does not take into account the inductance as a parameter that may be exploited for the design. The same inductive slow-wave CPW but with the crossed T-rails has been considered to evaluate the difference in capacitance and so the influence on the microwave index. In this case, the CPW is depicted in. A constant microwave index and wideband operation is achieved due to the low dispersion of the quasi-TEM propagation mode in the slow-wave CPW

Characterization and Conclusions

Author Contributions

Additional Information