Distributed transmission line phase shifter using MEMS switches and inductors

A novel 3-state unit cell for distributed MEMS transmission line (DMTL) phase shifters is designed and simulated in this paper. The proposed structure consists of a coplanar waveguide transmission line, a MEMS and two-pair metal-air-metal bridges. The bridges are actuated respectively in three different modes which produce three different phase shifts. The structure is simulated using HFSS software. Based on the simulation results, the return loss in all 3 states is better than -10dB and the phase shift is in good agreement with ideal values. The designed unit cell is very suitable for 5-bit and 6-bit DMTL phase shifters.

This letter reports the design, fabrication, and performance of millimeter-wave transmission lines and devices in a tri-layer thick-copper (Cu) process. Beneath the Cu layers is a low-voltage lead zirconium titanate (PZT) MEMS stackup atop a nitride membrane, on high-resistivity silicon. The 10 μm thick Cu layers enable several transmission-line topologies, and the PZT-MEMS functionality enables tunability. We designed transmission lines and un-optimized noncontact distributed MEMS transmission line (DMTL) phase shifters for 75-110 GHz, and present static measurements here. Simulation and measurements are in close agreement, with measured CPW line loss 0.15 dB greater than simulated (0.27 dB/mm at 95 GHz). Excess loss is attributed to Cu roughness, conductivity, and membrane/strap supports. Measured noncontact DMTL phase shifters exhibit a mean of 40 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> /dB when intrinsic line loss is subtracted.

This paper presents a Tapered Tunable Transmission Line (Tapered TTL) phase shifter that achieves a higher area efficiency than conventional Tunable Transmission Line (TTL) phase shifters while maintaining the same phase shift range with similar insertion losses. A systematic methodology is provided for the optimum design of the proposed phase shifter to maximize its area efficiency while providing the desired phase shift range and satisfying the maximum allowed input/output return and insertion losses. To verify the efficacy of the proposed solution, an eleven-cell phase shifter is fabricated in a standard 65-nm Complementary Metal–Oxide–Semiconductor (CMOS) technology and the measurement results are reported. The fabricated circuit provides a 180-degree phase shift over the frequency range of 16.5 to 31 GHz with an average insertion loss of 7.2 dB. The proposed design presents a 25 percent reduction in the chip area per unit delay in comparison to the conventional design with the same average insertion loss.

Controllable microstrip transmission line phase shifters employing the membrane actuated ground plane are investigated. Simulated data are included for a uniform air gap transmission line phase shifter, as well. A single 10.4 mm diameter membrane had showed phase shifts of 37.07/spl deg/ and 55.48/spl deg/ at 11.01 GHz and 14.25 GHz, respectively, which can be further duplicated and put as an array to cover the desired length of the microstrip line, to achieve a desired phase shift in a particular application. This phase shifter may find applications in phased arrays, and as discrete phase shifter components.

PurposeThis paper aims to design a radio frequency micro-electro-mechanical system (RF MEMS)-based phase shifter using chamfered coplanar waveguide (CPW) transmission line (t-line) with open-circuit interdigital metal–air–metal (ID MAM) capacitors.Design/methodology/approachThe proposed phase shifter achieves maximum differential phase shift with low loss at Ku band. The phase shifter is built with one switchable fixed-fixed beam (MEMS switch) on chamfered CPW t-line in series with two planar open-circuit ID MAM capacitors. An equivalent circuit model for the proposed phase shifter is derived, and its parameters are extracted using an electromagnetic (EM) solver.FindingsThe MEMS switch is actuated using an electrostatic method with the calculated residual stress of 44.26 MPa. The fabricated phase shifter exhibits low insertion loss, close to 0.14 dB at 17 GHz, with the maximum phase shift of 15.06°. The return loss is greater than 23 dB between 12 and 18 GHz.Originality/valueThis phase shifter presents a promising solution for low loss applications in the Ku band with a maximum phase shift. As the maximum phase shift of 15.06° is achieved for a unit cell with low insertion loss, the phase shifter is found to be feasible for modern electronically tunable phased arrays used for satellite communication and radar systems.

Previously, the design of our novel low-dispersion phase-shifter unit cell with two asynchronous MEMS switches was limited to 90°, so that four unit cells (90°, 90°, 90° and 45°) with a total of eight MEMS switches were required for a 3-bit phase shifter. This not only increased the size and loss of the phase shifter, but also decreased its yield and reliability. Recently, we hypothesized that by using two synchronized MEMS switches, the phase shift of a unit cell could be extended to 180° so that only three unit cells (180°, 90° and 45°) with a total of six MEMS switches would be required for a 3-bit phase shifter. This paper confirms the hypothesis with measured characteristics of a fabricated 180° phase-shifter unit cell. The measured characteristics compare well with both equivalent-circuit model prediction and three-dimensional finite-element electromagnetic simulation, provided the worse-than-expected loss from individual MEMS switches is taken into account. The results provide the proof of the design principle, so that with improved MEMS fabrication process such as thicker metallization, the switch loss can be reduced and low-dispersion phase shifters can be realized with compact size, low loss, low cost, and high reliability.

Notice of Violation of IEEE Publication Principles<br><br>"Both the authors and the Editor-in-Chief of Volume 13, number 3 of the IEEE/ASME JMEMS (June 2004, pp. 542-549) of the paper numbered JMEMS 1041 have agreed that this paper, Ka-Band Distributed MEMS Phase Shifters on Silicon Using AlSi Suspended Membrane," should not have been published. The paper would have been withdrawn had this fact been discovered before the IEEE/ASME JMEMS print date for June 2004. The authors have indicated that they will work to provide a new version their paper that will be considered for publication if it is submitted in the future. For help in coming to this decision, I would like to thank those concerned individuals, including the authors, JMEMS editors, and highly respected researchers in the MEMS and microwave communities who contributed their time and consideration to help us assure the integrity of our journal." <br><br>Richard S. Muller, Editor-in-Chief, IEEE/ASME JMEMS<br><br>This paper presents the design, fabrication, and testing of distributed MEMS phase shifters for Ka-band communication systems. The phase shift can be obtained by changing MEMS bridge capacitors located periodically over the transmission line. Simulation results of phase shifters with various structural parameters are analyzed to develop the optimized designs. The phase shifters are fabricated on the high-resistivity silicon substrate, using suspended AlSi bridge membrane. The measured results demonstrate a phase shift of 286° at 36 GHz with the actuation voltage of 25 V, and a return loss better than 10 dB over 0-40 GHz band. In addition, lifetimes of 3×10/sup 6/ cycles have been achieved for the fabricated phase shifter with all MEMS bridges held to be valid. It shows that AlSi alloy has a nice compromise between strength and resilience. <br/> This paper presents the design, fabrication, and testing of distributed MEMS phase shifters for Ka-band communication systems. The phase shift can be obtained by changing MEMS bridge capacitors located periodically over the transmission line. Simulation results of phase shifters with various structural parameters are analyzed to develop the optimized designs. The phase shifters are fabricated on the high-resistivity silicon substrate, using suspended AlSi bridge membrane. The measured results demonstrate a phase shift of 286° at 36 GHz with the actuation voltage of 25 V, and a return loss better than 10 dB over 0–40 GHz band. In addition, lifetimes of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles have been achieved for the fabricated phase shifter with all MEMS bridges held to be valid. It shows that AlSi alloy has a nice compromise between strength and resilience.

Phase shifter is one of the core components for phased-array antennas which find wide applications in satellite systems, telecommunications, wireless systems, radar systems and tracking systems. The current high-frequency phase shifters are mainly built upon active semiconductor technologies which suffer from high fabrication and assembly costs. In this work, we propose a cost-effective approach to fabricate distributed MEMS transmission line phase shifters on a polymer-glass substrate. The fabrication procedure is compatible with CMOS and post-CMOS processes. The polymerglass phase shifter was characterized from DC to 26 GHz. The measurements show a phase shift of 120° and a 2.5-dB insertion loss at 26 GHz.

Based on the structure of composite right/left-handed transmission line (CRLH-TL), a novel phase shifter with higher power capacity is proposed. What's more important, a new accurate equivalent circuit of the CRLH-TL element is proposed and its validity can be proved by the accordance of the theoretical and simulated results. In the present structure, switches of phase shifters are mounted on fingers of CRLH-TLs, thus the power through a single switch is only a fraction of that through the whole phase shifter. As a result, the power capacity of the present phase shifter can be greatly improved. Besides, the present phase shifter possesses other advantages such as low cost, small size and easy fabrication. Phase shifts can be achieved by changing the state of the switches. Then, a 4-bit phase shifter and is designed as examples. Finally we test the power capacity of the phase shifter, and its power capacity is higher than most of the traditional ones.

Design, fabrication and characterization of miniature RF MEMS switched capacitor based phase shifter

A novel distributed Micro-Electro-Mechanical-Systems (MEMS) impedance matching network is presented in this paper. This impedance matching network is based on DMTL (Distributed MEMS transmission line) having periodically loaded MEMS switches on a coplanar waveguide (CPW) transmission line. In order to miniaturize the physical size of the DMTL, a combination of a slow-wave (SW) structure and defect-ground-structure (DGS) is utilized. As a result, the distribution of the impedance coverage on the Smith chart can be improved for the limited physical length or reducing its size for a certain desired impedance distribution can be achieved. The parameter values of the equivalent circuit of the proposed structure are extracted from numerical simulation results using the FDTD simulator EMPIRE and are implemented for the calculation the uniformity factor to describe the uniformity of the impedance distribution on the Smith chart.

The results of an analysis of an optically controlled millimeter-wave phase shifter are presented. The phase shift is obtained when electron-hole pairs are created in a thin region in the interior of a semiconductor waveguide. The device exhibits maximum phase shifts for the transverse electric mode. This behavior is different from phase shifters using surface excitation, which give maximum phase shifts for the transverse magnetic mode. The new configuration gives higher phase shifts per decibel attenuation than devices employing surface excitation.

This paper reports a study of the effect of wafer tilt during dopant implantation on the performance of silicon PN phase shifter and traveling-wave Mach-Zehnder modulator. The PN phase shifter is designed and process simulated to include the effects of different fabrication processes in the device performance. The wafer tilt during implantation is varied from 0° to 3°, 5°, and 7°. The resulting crystal damage during dopant implantation to form the PN junction and the active concentration profile upon annealing, along with the formation of dopant–defect clusters, are discussed. Compared to 0° tilt, 7° tilt results in $1.58\times $ higher phase shift and better modulation efficiency. The overall phase shifter performance is improved using 5° wafer tilt for implantation resulting in $1.23\times $ lower absorption, $1.45\times $ better modulation efficiency, and $3.14\times $ higher 3 dB $RC$ modulation bandwidth for lumped-driven phase shifter. A traveling-wave electrode to enhance the modulation bandwidth is used, and the modulator performance for non-return-to-zero on-off-keying modulation with–2.5 V bias and 2.5 $\text{V}_{pp}$ drive signal across each arm is evaluated using a dual-arm push-pull drive. The sample with 5° tilt shows better traveling-wave and modulator high-speed characteristics compared to the other samples. Among the four samples with different wafer tilts, the sample with 0° tilt shows the worst phase shifter performance, and the sample with 3° tilt shows the worst modulator characteristics. The best overall performance is obtained for the sample with 5° tilt. Compared to the modulator with implantation at 0° tilt, the 5° tilted sample shows $2.3\times $ higher 6.4 dB electrical bandwidth and $1.36\times $ higher 3 dB electro-optic bandwidth at–2.5 V using a traveling-wave electrode with $1.48\times $ lower energy-per-bit for 5 km transmission at the KP4-forward-error-correction bit-error-rate threshold. The comparison of the effect of wafer tilt angles on various device metrics is presented and discussed.

Phase shifters are performing very important role in the performance of electronically steerable phased arrays. In this paper we have demonstrated the performance of microstrip line and planar phase shifters on (Ba-Sr)TiO3 (BST) substrate. It requires very low drive power and has low production cost. Because of the large tunability of the dielectric constant of the BST materials with the dc bias voltage, these materials are suitable for the electronically steerable antenna applications. The performance of the filter phase shifter and microstrip line phase shifter are evaluated and it is observed that the filter phase shifter shows better performance compared to the microstrip line phase shifter.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper explores the usefulness of RF MEMS and reconfigurable antennas in the context of modern communication systems and other applications. Simulation studies on a fractal antennas with switches and phase shifters provide beam steering and beam scanning characteristics. A brief description of the design aspects of two MEMS based coplanar waveguide (CPW) phase shifters for microwave and millimeter wave antenna applications are also provided here. One phase shifter design consists of a unique bilateral interdigital structure on a silicon substrate deposited with a thin film of electrically tunable barium strontium titanate. The dielectric constant of the thin film, and hence the effective permittivity of the transmission line changes by the application of a bias voltage. The second device is a distributed microelectromechanical system (MEMS) phase shifter fabricated on a high resistivity silicon substrate using microstereolithography technique is presented here. The distributed MEMS phase shifter consists of a high-impedance CPW transmission line and several MEMS bridges of uniform height. By applying a voltage the height of these bridges can be adjusted. This results in a variation in the distributed capacitance of the segment of the transmission line, which manifests in the phase shift at the output terminal. The fabrication procedure described here shows significant promise for the use of microstereolithography techniques for RF MEMS devices.