sergio pacheco - Academia.edu (original) (raw)
Papers by sergio pacheco
This paper presents two methods for counteracting the unwanted deflection due to warping or buckl... more This paper presents two methods for counteracting the unwanted deflection due to warping or buckling effects, which are serious potential problems in many fabrication processes of microelectromechanical (MEMS) structures due to thin film phenomena. This study is primarily suited for electrostatically actuated RF MEMS switches whose RF and DC performance can be significantly deteriorated by out of plane warping. It can also be applied to MEMS accelerometers, resonators and other similar systems. The first technique focuses on modifying the support structure and the spring constant of the switch, while the second involves a more complicated fabrication process, which selectively increases the switch thickness. Both these techniques yield switches with two to ten times less warping under the same fabrication conditions. The second method, however, presents the additional advantage of maintaining the actuation voltage almost unaffected.
IEEE Transactions on Microwave Theory and Techniques, 2001
Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff ... more Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff frequency and high stopband attenuation. Stepped-impedance low-pass designs achieve this function best with large ratios of high-to-low-impedance values. In high-index materials, such as Si (11.7) and GaAs (12.9), however these high-to-low-impedance ratios are around five, thereby significantly limiting optimum filter performance. This paper characterizes the use of Si
This paper presents resonant capacitive microelectromechanical switches and their possible applic... more This paper presents resonant capacitive microelectromechanical switches and their possible applications in tunable filtering. Single switches with a down capacitance of 2.9 pF and inductive sections of 3 to 50 pH are demonstrated, resulting in resonant frequencies from 13 to 54 GHz. Designs of resonant switches connected in parallel are also implemented with major advantages in isolation and bandwidth. Finally, tunable filters using these switches are discussed.
Single-pole double-throw (SPDT) X and K-band circuit designs incorporating low-loss microelectrom... more Single-pole double-throw (SPDT) X and K-band circuit designs incorporating low-loss microelectromechanical shunt capacitive switches are reported. The switches incorporate highly inductive connecting beams which aid in further increasing the isolation at the desired operational RF frequency. Measurements show an isolation of better than 40 dB at both 7 and 20 GHz. Insertion loss was measured at -0.95 dB at 7 GHz and -0.69 dB at 20 GHz for the two respective designs.
Two single-pole single-throw (SPST) K-band circuit designs incorporating low-loss microelectromec... more Two single-pole single-throw (SPST) K-band circuit designs incorporating low-loss microelectromechanical systems (MEMS) microwave shunt switches are reported. DC measurements indicate actuation voltages in the order of 20 V with an on-to-off capacitance ratio of 30. RF measurements show an isolation between the input port ad the output arm with the switch in the order of better than 15 dB across most of the frequency band. Insertion loss was measured at ¿0.4 dB at 18 GHz and ¿0.7 dB at 34 GHz for the two respective designs.
This paper presents a novel design scheme for tunable coplanar waveguide components with applicat... more This paper presents a novel design scheme for tunable coplanar waveguide components with applications to compact lumped-element MEMS reconfigurable filters. Shunt MEMS switches are employed for tuning the values of lumped components frequently encountered in microwave integrated circuits. In particular, shunt capacitors, series inductors and shunt inductive stubs are the main tunable circuit elements utilized in this work. Furthermore, accurate equivalent circuits that include the most important parasitics introduced by the tuning mechanism are provided. Finally, the proposed method is applied to the design and implementation of very compact low-pass and bandpass tunable filters. The very high tunability range, the compactness of the resulting networks and their very wideband response constitute the main advantages of this technique.
IEEE Transactions on Microwave Theory and Techniques, 2004
This paper reports on the experimental and theoretical characterization of RF microelectromechani... more This paper reports on the experimental and theoretical characterization of RF microelectromechanical systems (MEMS) switches for high-power applications. First, we investigate the problem of self-actuation due to high RF power and we demonstrate switches that do not self-actuate or catastrophically fail with a measured RF power of up to 5.5 W. Second, the problem of switch stiction to the down
Low-loss microwave microelectromechanical systems (MEMS) shunt switches are reported that utilize... more Low-loss microwave microelectromechanical systems (MEMS) shunt switches are reported that utilize highly compliant serpentine spring folded suspensions together with large area capacitive actuators to achieve low actuation voltages while maintaining sufficient off-state isolation. The RF MEMS switches were fabricated via a surface micromachining process using P12545 polyimide as the sacrificial layer. The switch structure was composed of electroplated nickel and the serpentine folded suspensions had a varying number of meanders from 1 to 5. DC measurements indicate actuation voltages as low as 9 V with an on-to-off capacitance ratio of 48. Power handling measurement results showed no "self-biasing" or failure of the MEMS switches for power levels up to 6.6 W. RF measurements demonstrate an isolation of -26 dB at 40 GHz.
IEEE Transactions on Microwave Theory and Techniques, 2003
This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectr... more This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectromechanical systems (MEMS) switch for high-frequency applications. The mechanical design of low spring-constant folded-suspension beams is presented first, and switches using these beams are demonstrated with measured actuation voltages of as low as 6 V. Furthermore, common nonidealities such as residual in-plane and gradient stress, as well as down-state stiction problems are addressed, and possible solutions are discussed. Finally, both experimental and theoretical data for the dynamic behavior of these devices are presented. The results of this paper clearly underline the need of an integrated design approach for the development of ultra low-voltage RF MEMS switches.
This paper presents two methods for counteracting the unwanted deflection due to warping or buckl... more This paper presents two methods for counteracting the unwanted deflection due to warping or buckling effects, which are serious potential problems in many fabrication processes of microelectromechanical (MEMS) structures due to thin film phenomena. This study is primarily suited for electrostatically actuated RF MEMS switches whose RF and DC performance can be significantly deteriorated by out of plane warping. It can also be applied to MEMS accelerometers, resonators and other similar systems. The first technique focuses on modifying the support structure and the spring constant of the switch, while the second involves a more complicated fabrication process, which selectively increases the switch thickness. Both these techniques yield switches with two to ten times less warping under the same fabrication conditions. The second method, however, presents the additional advantage of maintaining the actuation voltage almost unaffected.
IEEE Transactions on Microwave Theory and Techniques, 2001
Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff ... more Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff frequency and high stopband attenuation. Stepped-impedance low-pass designs achieve this function best with large ratios of high-to-low-impedance values. In high-index materials, such as Si (11.7) and GaAs (12.9), however these high-to-low-impedance ratios are around five, thereby significantly limiting optimum filter performance. This paper characterizes the use of Si
This paper presents resonant capacitive microelectromechanical switches and their possible applic... more This paper presents resonant capacitive microelectromechanical switches and their possible applications in tunable filtering. Single switches with a down capacitance of 2.9 pF and inductive sections of 3 to 50 pH are demonstrated, resulting in resonant frequencies from 13 to 54 GHz. Designs of resonant switches connected in parallel are also implemented with major advantages in isolation and bandwidth. Finally, tunable filters using these switches are discussed.
Single-pole double-throw (SPDT) X and K-band circuit designs incorporating low-loss microelectrom... more Single-pole double-throw (SPDT) X and K-band circuit designs incorporating low-loss microelectromechanical shunt capacitive switches are reported. The switches incorporate highly inductive connecting beams which aid in further increasing the isolation at the desired operational RF frequency. Measurements show an isolation of better than 40 dB at both 7 and 20 GHz. Insertion loss was measured at -0.95 dB at 7 GHz and -0.69 dB at 20 GHz for the two respective designs.
Two single-pole single-throw (SPST) K-band circuit designs incorporating low-loss microelectromec... more Two single-pole single-throw (SPST) K-band circuit designs incorporating low-loss microelectromechanical systems (MEMS) microwave shunt switches are reported. DC measurements indicate actuation voltages in the order of 20 V with an on-to-off capacitance ratio of 30. RF measurements show an isolation between the input port ad the output arm with the switch in the order of better than 15 dB across most of the frequency band. Insertion loss was measured at ¿0.4 dB at 18 GHz and ¿0.7 dB at 34 GHz for the two respective designs.
This paper presents a novel design scheme for tunable coplanar waveguide components with applicat... more This paper presents a novel design scheme for tunable coplanar waveguide components with applications to compact lumped-element MEMS reconfigurable filters. Shunt MEMS switches are employed for tuning the values of lumped components frequently encountered in microwave integrated circuits. In particular, shunt capacitors, series inductors and shunt inductive stubs are the main tunable circuit elements utilized in this work. Furthermore, accurate equivalent circuits that include the most important parasitics introduced by the tuning mechanism are provided. Finally, the proposed method is applied to the design and implementation of very compact low-pass and bandpass tunable filters. The very high tunability range, the compactness of the resulting networks and their very wideband response constitute the main advantages of this technique.
IEEE Transactions on Microwave Theory and Techniques, 2004
This paper reports on the experimental and theoretical characterization of RF microelectromechani... more This paper reports on the experimental and theoretical characterization of RF microelectromechanical systems (MEMS) switches for high-power applications. First, we investigate the problem of self-actuation due to high RF power and we demonstrate switches that do not self-actuate or catastrophically fail with a measured RF power of up to 5.5 W. Second, the problem of switch stiction to the down
Low-loss microwave microelectromechanical systems (MEMS) shunt switches are reported that utilize... more Low-loss microwave microelectromechanical systems (MEMS) shunt switches are reported that utilize highly compliant serpentine spring folded suspensions together with large area capacitive actuators to achieve low actuation voltages while maintaining sufficient off-state isolation. The RF MEMS switches were fabricated via a surface micromachining process using P12545 polyimide as the sacrificial layer. The switch structure was composed of electroplated nickel and the serpentine folded suspensions had a varying number of meanders from 1 to 5. DC measurements indicate actuation voltages as low as 9 V with an on-to-off capacitance ratio of 48. Power handling measurement results showed no "self-biasing" or failure of the MEMS switches for power levels up to 6.6 W. RF measurements demonstrate an isolation of -26 dB at 40 GHz.
IEEE Transactions on Microwave Theory and Techniques, 2003
This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectr... more This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectromechanical systems (MEMS) switch for high-frequency applications. The mechanical design of low spring-constant folded-suspension beams is presented first, and switches using these beams are demonstrated with measured actuation voltages of as low as 6 V. Furthermore, common nonidealities such as residual in-plane and gradient stress, as well as down-state stiction problems are addressed, and possible solutions are discussed. Finally, both experimental and theoretical data for the dynamic behavior of these devices are presented. The results of this paper clearly underline the need of an integrated design approach for the development of ultra low-voltage RF MEMS switches.