Distributed MEMS Transmission Line Research Articles

Flip-Chip Distributed MEMS Transmission Lines (DMTLs) for Biosensing Applications

Design and characterization of a flip-chip distributed MEMS transmission line (DMTL) are presented. The concept of using this DMTL as a biosensor is then introduced. Radio frequency experiments on the DMTL loaded with ldquobiosamplesrdquo have been conducted using the most accessible materials, namely, deionized water and aqueous solutions of salts. Results show that the reflection coefficient (S11) of the solution-loaded DMTL is very sensitive to the salt concentration of the solution in the low-frequency ranges of 10 MHz-1 GHz and 3-4.5 GHz. At high frequencies, the relative dielectric constant of the biosample can also be quantitatively determined from the impedance of the DMTL.

Distributed transmission line phase shifter using MEMS switches and inductors

Distributed MEMS transmission line (DMTL) phase shifter has been developed using planar inductors. The design consists of a coplanar waveguide line capacitively and inductively loaded by the periodic set of electrostatic force actuated microelectromechanical system switches as capacitors and inductors. By applying a single bias voltage on the line, the characteristic impedance can be changed, which in turn changes the phase velocity of the line and creates a true time delay phase shift. The governing equations for the impedance and loss are derived. The ABCD matrix is defined for a unit and multi-cell DMTL phase shifter to extract scattering parameters equations. The device containing 15 cells calculated, simulated, and fabricated. Fabricated results show that the device can be considered as a new type of the DMTL phase shifter with small size, higher phase shift and acceptable scattering parameters.

Analysis of surface micro machined RF MEMS phase shifters

Development of low loss radio frequency micro-electro-mechanical (MEMS) phase shifters for radar and telecommunication applications is presented. Numerical simulation results using electromagnetic simulator tools (CST - Germany) along with fabricated wafer level measurement results of two distributed MEMS phase shifters are presented herein for upstate capacitive bridge position. The distributed MEMS phase shifter consists of coplanar waveguide (CPW) transmission line and several MEMS bridges loading capacitively on transmission lines to create a slow wave structure. Two configurations of phase shifters are presented. 1) Conventional distributed MEMS transmission line (DMTL) 2) coplanar waveguide - microstrip - coplanar waveguide (CPW-MS-CPW), with microstrip as the transmission line and CPW as input and output line. The electromagnetic simulation results of gap height variation to change the phase velocity and, in turn, phase shift is presented. Work is underway to vary the gap height between transmission line and the bridge, applying the actuation voltage to bridge capacitors, which, in turn, will vary the bridge capacitance, changing the phase velocity on fabricated phase shifters. The match between simulated results and wafer level measurements are encouraging and will be presented in the full paper. Work is also underway to validate wafer level measurements along with numerical simulation using circuit models using circuit simulator. The custom model libraries for phase shifters are being developed. The results are encouraging.

$G$-Band Distributed Microelectromechanical Components Based on CMOS Compatible Fabrication

Microelectromechanical systems (MEMS) technology has been used for realizing G-band (140-220 GHz) distributed MEMS transmission line components. Novel dielectric-less MEMS components, as well as switched MEMS capacitors, have been fabricated with CMOS compatible surface micromachining, and experimental results are presented up to 220 GHz.

RF MEMS capacitive switch on semi-suspended CPW using low-loss high-resistivity silicon substrate

A high capacitive ratio RF MEMS switch, with low-actuation voltage is designed, fabricated and experimentally validated on high-resistivity silicon (HRS) substrate. Thanks to very good fabrication control of all steps and to the high dielectric constant of TiO2, a down/up capacitive ratio close to 200 is achieved with 8V pull-in. It is also demonstrated that, using a passivated-surface HRS and semi-suspended conductors on air, the microwave losses in the CPW line are as low as 0.1dB/mm at 20GHz. The reported RF MEMS shunt capacitor is expected to serve as core device for phase shifting applications in the 10–20GHz range, both for switching operations and as a variable capacitor in distributed MEMS transmission lines (DMTLs).

24 GHz RF-MEMS Phase Shifter with Non-Galvanic Electromagnetic Coupling Fabricated in Silicon-Bulk Technology

This contribution presents a Distributed MEMS Transmission Line (DMTL) phase shifter designed for 24 GHz and fabricated in Silicon-Bulk Micromechanic Technology. Using this technology enables to commonly suspend all capacitive loads on one movable plate and allows full range analog and homogeneous gap adjustment. The first available prototypes of the phase shifter are characterized to provide 5.4 °/mm differential phase shift at 24 GHz and to show 0.1 dB/mm insertion loss. An asymmetric coplanar signal coupler with a center frequency of 24 GHz and 10% bandwidth is used to contact the signal through the substrate of the phase shifter chip and back to a supporting printed circuit board. The normalized measured insertion loss of the coupling structure after simulated optimization is 0.13 dB - 0.17 dB.

New approach for modelling distributed MEMS transmission lines

The paper presents a new and more accurate model for the distributed MEMS transmission line (DMTL) structures. In this new model, the MEMS bridges that are used as the loading elements of the DMTL structures are represented as low-impedance transmission lines, rather than a lumped CLR circuit. The model also includes LC networks at the transition points from the MEMS bridges to the unloaded parts of the DMTL, which are simply high-impedance transmission lines. These LC networks are employed to model the effects of the impedance discontinuities. The accuracy of the model is verified with simulations and measurements in the range 1-20 GHz on various DMTL structures that are fabricated with an RF MEMS process based on electroforming on a glass substrate. The measurement results of the fabricated devices are in good agreement with the model with an error less than 5%. It is shown that this new model provides better agreement than the conventional method for the DMTL structures with a bridge width larger than 50 /spl mu/m.

An Improved Design for Ka-Band Phase Shifter Using Distributed MEMS Transmission Line Structure

The paper presents a model which describes the stage circuit of Distributed MEMS Transmission Line (DMTL) phase shifter at Ka band and an approach for DMTL design utilizing the saw-shaped coplanar waveguide(CPW). The result of circuit simulation and full wave analysis prove that the model is in good agreement with theoretical analysis. The model can effectively simplify the design complexity after optimization. Simulation results show that the S11 and S21 can achieve -20 dB and -2.5 dB, respectively, and the phase shift arrives at −180 ◦ at Ka band. Comparing with literature data, it has been predicted that S11 improves about 8 dB and the phase shift can increase about 100 ◦ in the same condition.

DESIGN OF A NOVEL MICROWAVE MEMS TUNABLE FILTER

International Journal of Computational Engineering ScienceVol. 04, No. 02, pp. 377-380 (2003) Wireless MEMS/RF MEMSNo AccessDESIGN OF A NOVEL MICROWAVE MEMS TUNABLE FILTERA. B. YU, Q. X. ZHANG, and A. Q. LIUA. B. YUSchool of Electrical & Electronic Engineering, Nangyang Technological University, Singapore 639798, Singapore Search for more papers by this author , Q. X. ZHANGInstitute of Microelectronics, Science Park II, Singapore 117684, Singapore Search for more papers by this author , and A. Q. LIUSchool of Electrical & Electronic Engineering, Nangyang Technological University, Singapore 639798, Singapore Search for more papers by this author https://doi.org/10.1142/S1465876303001319Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThis paper reports a novel design of radio frequency microelectromechanical systems (RF MEMS) tunable bandpass filter (BPF), which is made up of two quarter-wavelength resonators, and each resonator is laterally loaded with two area-tuning tunable capacitors between the signal line and one of the grounds of the coplanar waveguide (CPW). The tuning range is between 8.3 GHz to 8.9 GHz, with 3.5 dB minimum insertion loss. The loss mainly comes from the thin coating metal layer and the coupling gap. The out of-band rejections at 8 and 10 GHz are higher than 25 dB in all the tuning range, and the return loss is better than 15 dB in passband.Keywords:RF MEMSBPFTunable CapacitorCPW References J. H. Parket al., J. Micromech. Microeng. 11, 706 (2001). Crossref, Google Scholar J. Brank, Zh. J. Yao, and M. Eberly et al., RF MEMS-Based Tunable Filters, Int. J. RF and Microwave Computer-Aided Eng., Special issue, (2001) 276-283 . Google Scholar D. Peroulis, S. Pacheco, K. Sarabandi and L. P. B. Katehi, Tunable Lumped Components with Applications to Reconfigurable MEMS Filters, IEEE MTT-s Symposium Digest, (2001) 341-344 . Google Scholar Y. Liu, A. Borgioli, A. S. Nagra and Robert A. York, Distributed MEMS Transmission Lines for Tunable Filter Application, Int. J. RF and Microwave Computer-Aided Eng., Special issue, (2001) 254-259 . Google Scholar G. L. Matthaei , L. Young and E. M. T. Jones , Microwave Filters, Impedance-Matching Network, and Coupling structures ( Artech House Inc. , Dedham, Massachusetts , 1980 ) . Google Scholar FiguresReferencesRelatedDetails Recommended Vol. 04, No. 02 Metrics History KeywordsRF MEMSBPFTunable CapacitorCPWPDF download

Very low-loss distributed X-band and Ka-band MEMS phase shifters using metal-air-metal capacitors

2-bit wide-band distributed coplanar-waveguide phase shifters have been developed on a 500-/spl mu/m quartz substrate for X- and Ka-band operation. The designs utilize microelectromechanical system (MEMS) switches in a distributed MEMS transmission line periodically loaded by MEMS switches and high Q (/spl ges/250 at 30 GHz) metal-air-metal capacitors. The MEMS switches are actuated by a /spl plusmn/20-V voltage waveform using a high-resistance bias line. Estimated spring constant and switching time is 30 N/m and 9 /spl mu/s, respectively. The Ka-band 2-bit design results in a reflection coefficient better than -11.5 dB, an average insertion loss of -1.5 dB and phase shifts of 0/spl deg/, 89/spl deg/, 180/spl deg/, and 270/spl deg/ at 37.7 GHz. The X-band 2-bit design results in a reflection coefficient better than -12.5 dB, an average insertion loss of -1.2 dB and phase shifts of 0/spl deg/, 94/spl deg/, 176/spl deg/, and 270/spl deg/ at 13.6 GHz. These results are very competitive with switched transmission-line and reflection-based phase shifters. The distributed design can be easily scaled to V- and W-band frequencies for wide-band low-loss performance.

Distributed MEMS transmission lines for tunable filter applications

This paper describes the design and fabrication of a distributed MEMS transmission line (DMTL), used to realize a transmission-line with a voltage-variable electrical length for microwave circuits. The DMTL is a coplanar waveguide periodically loaded with continuously-variable MEMS capacitors. A tunable bandpass filter was designed and fabricated on 700 μm thick glass substrates using three capacitively coupled DMTL sections as variable shunt resonators. The measured results demonstrate a 3.8% tuning range at 20 GHz with 3.6 dB minimum insertion loss. Issues for future improvement are discussed. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 254–260, 2001.

2-bit MEMS distributed X-band phase shifters

A wideband distributed coplanar-waveguide (CPW) phase shifter has been developed for X-band operation. The design is based on the distributed MEMS transmission line (DMTL) loaded with MEMS bridges and MIM capacitors. A 2-bit distributed phase shifter was fabricated on a 500-μm quartz substrate, and achieved a true-time delay operation from 1 to 20 GHz with a reflection coefficient less than -11 dB from 2 to 20 GHz and above. Insertion loss is dominated by a low-Q MIM capacitor (14 at 10 GHz) and the effect of this Q is shown, Increasing the MIM capacitor Q will result in an excellent 2-bit phase shifter with wideband performance at X-band frequencies.

Distributed MEMS transmission-line BPSK modulator

The application of a distributed microelectromechanical system (MEMS) transmission line as a binary phase shift keying modulator is presented. This modulator has the advantages of low loss and low required drive power compared to a typical semiconductor-based phase modulator. However, the modulation rate is limited by the mechanical resonant frequency of the MEMS bridges.

Low-loss cascadable MEMS distributed X-band phase shifters

A wideband distributed coplanar-waveguide (CPW) phase shifter has been developed for X-band operation. The design is based on the distributed MEMS transmission line (DMTL) loaded with high capacitance-ratio varactors. The varactors are fabricated using a series combination of MEMS bridges and fixed-value MIM capacitors. A high-capacitance ratio varactor (1.5-2.5) results in a large loading on the CPW line and therefore a large phase shift. A distributed phase shifter was fabricated on a 500 μm quartz substrate, and achieved a true-time delay operation from 1 to 10 GHz with a reflection coefficient less than /spl sim/15 dB, and 1800/dB of insertion loss at 8-10 GHz. It is possible with this design to cascade the DMTL to result in 2- and 3-bit phase shifters with excellent wideband performance at X-band frequencies.