Perruisseau-Carrier, J.

Skrivervik, A. K.

Infoscience - École polytechnique fédérale de Lausanne

Tunable Differential Phase Shifters Using MEMSPositive/Negative Phase Velocity Transmission LinesJulien Perruisseau-Carrier and Anja K. SkrivervikLaboratory of Electromagnetics and Acoustic (LEMA),Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), Switzerland.In this work, we present new designs of reconfigurable phase shifters for ku band based on MEMS devices.The principle of the phase shifters is shown in Fig. 1 and relies on the particular dispersion properties ofartificial transmission lines (TL) with positive/negative phase velocity, referred to here as variable compositeright/left handed TL (V-CRLHs). Using this topology and V-CRLHs allows achieving versatile differentialphase shift functions φ by adjusting the length and dispersion of each line section.In particular, we will demonstrate here two types of devices. In the first case, the phase shifter is designedto obtain φ constant in frequency on a wide bandwidth (BW) and this device is thus referred to as theMEMS constant-phase shifter (M-CPS). This application is the reconfigurable counterpart of the structurepresented in (M. Lapine and al., 36th European Microw. Conf., Manchester, UK, pp. 427-430), where weadded a usual right-hand TL section in one of the branch to compensate for the difference between the slopesof the dispersion curves of each V-CRLH, as explained by the diagram of Fig. 1. Each V-CRLH sectionin Fig. 1 is first implemented by analog MEMS V-CRLH as presented by the authors in (J. Perruisseau-C.and al., MOTL, 48, 12, pp. 2496-2499). Since each element in the structure is well matched, the differentialphase shift is simply φ = φB − φA = φB − φA,0 − φRH . This quantity is plotted in Fig. 2 on a 5% fractionalBW in the passband of the CRLHs. The two curves in solid lines correspond to the maximum and minimumdifferential phase shifts and the 3 curves in dashed lines represent intermediate states within this analogrange. The range obtained is 55o at the center of the BW and the maximum phase error is less than 3.5o(resp. 9o) on a on 5% BW (resp. 10% BW). Nevertheless, it can be shown that this range can be significantlyextended by using digital MEMS V-CRLHs, whose measured results will be presented at the conference.In a second stage, we show that the topology of Fig. 1 also allows realizing devices providing a tunabledifferential group delay which is constant in frequency on a significant BW. The difference with the M-CPSdescribed above is simply that the two branches must be designed so that the phase difference is linear(rather than constant) with frequency. A comparison with distributed MEMS transmission lines on thesame technology (J. Perruisseau-C. and al., IEEE T-MTT, 54, 1, pp. 383-392) showed that such structureis advantageous for some applications in terms of delay/losses and footprint, at the cost of reduced BW.Figure 1: Principle of the MEMS constant-phase shifter(M-CPS).Figure 2: Differential phase shift of the analog M-CPS.

Tunable differential phase shifters using MEMS positive/negative phase velocity transmission lines

Abstract

Similar works

Full text

Available Versions

Infoscience - École polytechnique fédérale de Lausanne