Improvement In Switching Time Research Articles

CMOS RF Switch With Fast Discharge Feature

A radio-frequency (RF) switch featuring a circuit for fast discharge of the gate oxide capacitance is presented in this letter. Two auxiliary transistors are added between the gate and source/drain terminals of the main switch. They are brought into the ON state for a short time at the beginning of the switching transient, discharging the gate of the main transistor, and speeding up the switching process. An integrated circuit implementing the proposed concept based on a large shunt switch has been designed and fabricated in Infineon 130-nm bulk-CMOS RF-switch technology. The measurements have demonstrated improvement in switching time (defined as the time between the control signal trigger edge and 90% of the target RF amplitude) of above 50% with no penalty in RF performance comparing to the conventional switch without discharge feature. The measured OFF-state insertion loss and ON-state isolation at 824 MHz were 0.12 and 27.2 dB, respectively.

Ion conductor barrier height for the switching time improvement of all-thin-film inorganic complementary electrochromic devices

In this study, an all-thin-film inorganic complementary electrochromic device (ECD) with the lithium doping zirconium dioxide (ZrO2:Li) ion conductor layer has demonstrated for the lower cost ECD applications. Even though the ZrO2:Li has demonstrated a lower lithium (Li) ion conductivity of 1.62 × 10−8 S/cm and ion mobility of 8.67 × 10−12 cm2/Vs, the switching characteristic of the ECDs has been improved. According to the refractive index measurement, the ion conductor ZrO2:Li with the higher refractive index value is also indicated a higher energy bandgap material. As a result, the possible mechanism is due to the electron energy barrier height 1.2 eV between the interface of electrochromic layer tungsten oxide (WO3) and ion conductor layer ZrO2:Li. Besides, the induction of an electric field between the WO3 and high bandgap ZrO2:Li material interface also accelerates the Li ion transported through the interface. Furthermore, the ZrO2:Li with the lower ion conductivity and mobility is due to the dense material structure, which is verified by the cross-sectional field emission scanning electron micrograph profile. Additionally, the dense material structure has also provided better surface morphology for thin-film device structures with the layer-by-layer deposition process.

Gated body-biased full adder

As technology advances into the lower nanometer values, power and delay becomes important parameters to increase the efficiency of the circuit. To reduce the sub-threshold leakage power dissipation in standby mode several low power techniques for CMOS circuits namely drain gating, power gating, drain-header and power-footer gating (DHPF), drain-footer and power- header gating (DFPH) are studied and high speed techniques are achieved by modifying drain gating technique and its variant circuits by adding an additional NMOS sleep transistor at the output node which helps in improvement of switching time are studied. The speed of operation of the circuit is improved by applying Gate Level Body Biasing (GLBB) to the design. Implementation of GLBB technique to the existing design proves to be very efficient in terms of speed. Performance parameters such as average power and average propagation delay are compared using existing and proposed techniques for a full adder circuit. The full adder circuit with various low power techniques are tools in 180nm technology. The circuit is simulated using Cadence Spectre tool. The circuit operates with more speediness after applying biasing and found increase in speed by 15%.

Real-time DC-dynamic biasing method for switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators.

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

DC-dynamic biasing for >50× switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators

This paper presents the design and experimental validation of dc-dynamic biasing for > 50× switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators. The electrostatic fringing-field actuator is used to demonstrate the concept due to its robust device design and inherently low damping conditions. In order to accurately quantify the gap height versus voltage characteristics, a heuristic model is developed. The difference between the heuristic model and numerical simulation is less than 5.6% for typical MEMS geometries. MEMS fixed–fixed beams are fabricated and measured for experimental validation. Good agreement is observed between the calculated and measured results. For a given voltage, the measured and calculated displacements are typically within 10%. Lastly, the derived model is used to design a dc-dynamic bias waveform to improve the switching time of the underdamped MEMS actuators. With dynamic biasing, the measured up-to-down and down-to-up switching time of the actuator is ∼35 μs. On the other hand, coventional step biasing results in a switching time of ∼2 ms for both up-to-down and down-to-up states.

Electrostatic fringing-field actuation for pull-in free RF-MEMS analogue tunable resonators

This paper presents the design, fabrication and measurement of the first pull-in free tunable evanescent-mode microwave resonator based on arrays of electrostatically actuated fringing-field RF-MEMS tuners. Electrostatic fringing-field actuation (EFFA) is the key on achieving a wide tunable frequency range that is not limited by the conventional pull-in instability. Furthermore, total lack of dielectric layers and no overlap between the pull-down electrode and movable beams significantly enhance the robustness of our proposed tuning mechanism by making it devoid of dielectric charging and stiction and amenable to high-yield manufacturing. The proposed electrostatic fringing-field tuners are demonstrated in a highly loaded evanescent-mode cavity-based resonator. The measured unloaded quality factor is 280–515 from 12.5 to 15.5 GHz. In addition, a 10× improvement in switching time is demonstrated for the first time for EFFA tuners in a tunable microwave component by employing dc-dynamic biasing waveforms. With dynamic biasing, the measured up-to-down and down-to-up switching times of the resonator are 190 and 148 μs, respectively. On the other hand, conventional step biasing results in switching times of 5.2 and 8 ms for up-to-down and down-to-up states, respectively.

Electro-optic and dielectric studies of silica nanoparticle doped ferroelectric liquid crystal in SmC* phase

We present the results based on the electro-optic and dielectric properties of silica nanoparticle (SNP) doped ferroelectric liquid crystal (FLC) in SmC* phase. Switching time, spontaneous polarization and rotational viscosity decreases with increase in the silica concentration. An improvement in switching time after doping the silica nanoparticle is due to enhancement in anchoring energy exist between silica nanoparticle and ferroelectric liquid crystal. We noticed that the dielectric permittivity and dielectric strength decreases with increasing the concentration of silica nanoparticle in SmC* phase. Relaxation frequency increases with increasing the silica concentration and temperature in SmC* and decreases as we approaches towards transition temperature.

Improvement of switching time in a thermocapillarity optical switch

The switching time of existing thermocapillarity optical switches is about two orders of magnitude larger than that of other optical switches, such as a thermooptics switch and a free-space switch using microelectromechanical system technology. This paper reports a thermocapillarity switch whose switching time is comparable to that of the thermooptics and free-space switches. The greatly improved switching time is achieved by lowering the absolute viscosity of the refractive-index matching liquid and improving the switch design.

Invited Lecture. Ferroelectric liquid crystalline polymers and related model compounds with a low–moderate degree of polymerization

Abstract Ferroelectric liquid crystalline polymers (FLCPs) with a low-moderate degree of polymerization were synthesized. These had a comb structure; the main chain was polyacrylate and the side chain consisted of a flexible spacer, a core and an optically active chiral end group. They exhibited electro-optic switching times ranging from a few milliseconds to a few seconds in the S*c phase. As the molecular weight M n increased, the range of the S*c shifted to higher temperatures. At a given temperature, the switching time increased with M n . Spontaneous polarizations P s , apparent cone angles 2θ, electro-optic switching times τ and rotational viscosities η of some polyoxyethylene FLCPs and corresponding low molecular weight ferroelectric liquid crystal materials (FLCs) were also measured. This is the first report of polyoxyethylene FLCPs. There was no significant difference in P s and 2θ, which shows that the arrangement of the side chains in the FLCP is similar to that of the molecules in ordinary FLC. On the contrary, τ and η for the FLCPs were 102–103 times as large as those for FLCs. The rotational viscosity of the FLCP was mainly dependent on the side chain structure rather than on the spacer. Therefore collisions between adjacent side chains cause large η values in FLCPs rather than hindrance to side chain gyration due to the spacer group. By combining FLCPs with ITO-coated plastic substrates, a large area matrix driven display has been made. Although an improvement in switching time is still needed, a flexible and lightweight display like a sheet of paper will be available in the near future.

Demonstration of electro-optical switching at the 26 cm × 26 cm aperture using plasma electrodes

We have constructed and tested a longitudinal Pockels cell with a clear aperture of 26 cm x 26 cm. Transparent plasma electrodes formed in a low-pressure glow discharge were used to apply a uniform electric field to a 1-cm thick KDP crystal. Optical switching times of 50 nsec were achieved with a bare KDP crystal. Significant improvement in switching time resulted from using a glass-plate-KDP-crystal sandwich.