6. Conclusions

In this chapter, we have developed a parametric model for a capacitive RF MEMS switch in the frequency range between 1 and 40 GHz. A comparative study was carried out to analyze the theoretical model's mechanical characteristic with COMSOL and to compare the theoretical electrical properties (return loss, insertion loss, and phase) to those obtained using HFSS. The proposed model computes the input data swiftly and efficiently and produces results similar to those obtained with the aforementioned simulation software, while being much faster and less resource-demanding.

It was also presented the design, the analysis, and the simulation of the reflection-type phase shifter, using integrated RF MEMS switches. The proposed phase shifter at 18 GHz, which has approximately a constant insertion loss (≈1 dB) with a significant return loss (<30 dB) and phase shift (138.822 and 128.15), can be used in different RF applications, namely, it is suitable for radar applications.

We have analyzed a new contribution for RF MEMS to obtain a tunable resonator. The idea of this reconfigurable resonator is based on the use of two meander inductors and a variable capacitance. The simulation of this component was made by two electromagnetic design tools, and there was good agreement between them for different tuning conditions (spacing states of g = 2, 2.5 and 3 μm). The obtained resonance frequencies for the three considered states were, respectively, 21.9, 24, and 25.1 GHz. The bandwidths were [15.6, 25.7], [17.8, 27.6], and [19.5, 29] GHz, respectively, demonstrated for the three resonant frequencies (|S11| = 35 dB and |S12| = 1 dB). This resonator switches can be used in different RF applications, for example, at K and Ka bands.

We have also proposed a reconfigurable antenna based on the association between the last resonator and the CPW antenna to obtain tunability at Ka band. For g = 2 μm, a single resonant frequency of 26.3 GHz was obtained, with a return loss of 15.1 dB and a realized gain equal to 3 dB; for g = 2.5 μm, two resonant frequencies of 27 and 29.8 GHz were obtained, with a return loss of 23 and 18 dB and a realized gain 3 and 2 dB. Finally, for g = 3 μm, it also allows two resonant frequencies, 27.5 and 30.6 GHz, with a return loss of 19.84 and 26.62 dB, showing a realized gain of 2 and 1 dB, respectively.
