Trond Sæther

Current-Mode Capacitive Sensor Interface Circuit With Single-Ended to Differential Output Capability

This paper presents a current-mode interface circuit for capacitive sensors, with the main features being its ability to produce a differential output from a single-ended sensor (using a fixed reference capacitor) and its simplicity in realization. These advantages make it a potential candidate for applications where differential sensors are not available and where a simple design is required. The principle is, however, easily applicable to differential sensors as well. The interface concept can be realized in different ways; however, to present a proof of concept on silicon, a prototype has been fabricated and tested in a commercially available 0.8-mum CMOS process. The circuit has been designed using common analog building blocks such as a fully differential operational transconductance amplifier (OTA), a high-output-resistance wide-swing current source, and a single clock phase. The estimated linearity error was 0.2% relative to full-scale swing with a simple two-point calibration. The circuit consumes 145 muA from a 5-V power supply.

Real-time reconfigurable linear threshold elements implemented in floating-gate CMOS

This paper describes using theory, computer simulations, and laboratory measurements a new class of real-time reconfigurable UV-programmable floating-gate (FGUVMOS) linear threshold elements operating with current levels typically in the pA to /spl mu/A range, in standard double-poly 0.6 /spl mu/m CMOS, providing an ultra low-power potential. A new design method based on using the same basic two-MOSFET circuits extensively is proposed, meant for improving the opportunities to make larger FGUVMOS circuitry than previously reported. By using the same basic circuitry extensively, instead of different circuitry for basic digital functions, the goal is to ease UV-programming and test and save circuitry on chip and I-O-pads. Matching of circuitry should also be improved by using this approach. Compact circuitry can be made, reducing wiring and active components compared to previously reported FGUVMOS. 2-MOSFET circuits able to implement CARRY, NOR, NAND, and INVERT functions are demonstrated by measurements on chip, working with power supply voltages ranging from 800 mV down to 93 mV. The basic linear threshold element proposed is considered as a potential basic building block in neural networks.

Modeling of Spring Constant and Pull-down Voltage of Non uniform RF MEMS Cantilever

In this paper, we are going to present a model of spring constant and pull down voltage for non uniform RF MEMS cantilever. In order to reduce the pull down voltage, it is usual to use a beam, which is narrower close to anchor and wider at the end or electrode area for a cantilever. Compare to uniform beam, this beam have lower spring constant which reduce the pull down voltage. A comprehensive model for spring constant and pull down voltage of the nonuniform cantilever is developed through basic force deflection mechanism of the suspended beam

TUNABLE BAND-PASS FILTER USING RF MEMS CAPACITANCE AND TRANSMISSION LINE

In this paper we present the design and fabrication of an RF MEMS tunable band-pass fllter. The band-pass fllter design uses both distributed transmission lines and RF MEMS capacitances together to replace the lumped elements. The use of RF MEMS variable capacitances gives the ∞exibility of tuning both the centre frequency and the band-width of the band-pass fllter. A prototype of the tunable band-pass fllter is realized using parallel plate capacitances. The variable shunt and series capacitances are formed by a combination of parallel plate RF MEMS shunt bridges and series cantilevers. The fllter operates at C-X band. The measurement results agree well with the simulation results.

Feedback Biasing in Nanoscale CMOS Technologies

This work rediscovers the attractiveness of feedback biasing when applied to circuits designed in nanoscale CMOS technologies. It is shown that very compact amplifiers can be obtained by utilizing a type of biasing that imposes minimal area overhead. We discuss how the undesired features of the nanoscale CMOS technologies actually help in the revival of this simple biasing method in newer technology generations. The measurement results of prototyped common-source (CS) amplifiers utilizing feedback biasing for application in medical ultrasound imaging systems are presented in this brief. The proposed feedback biasing is also suitable for amplifying signals from high-impedance sources that pose challenges on maintaining high input impedance for the voltage amplifiers while maintaining a very low input capacitance value. Measurements show that the proposed amplifier achieves a voltage gain of 28 dB, an output noise power spectral density of 0.11 (muV)2 Hz at center-frequency, and a total harmonic distortion of -30 dB, with the full-scale output at 30 MHz, while drawing 120 muA from a 1-V power supply. The amplifiers were fabricated in 90-nm CMOS technology and measured to be just 20 mum times10 mum.

Modeling, design and simulation of tunable band pass filter using RF MEMS capacitance and transmission line

In this paper we have shown design of a RF MEMS band pass filter. A high capacitance ratio and low actuation voltage RF MEMS shunt switch was designed and modeled the switch as a variable capacitance. The capacitance can be varied as a function of the actuation voltage. The capacitance is modeled as a lumped component, as used in a conventional LC filter. The design uses a novel approach to implement both distributed transmission line and RF MEMS capacitance together to replace the lumped elements. The use of RF MEMS variable capacitance gives the flexibility of tuning the cut-off and center frequency of bandpass filter. In this paper we show a design of 5.8 GHz center frequency band pass filter using the theory of stepped impedance transmission line and MEMS capacitance filter.

A 220mW 14b 40MSPS gain calibrated pipelined ADC

In this paper, a pipelined ADC based on digital calibration of gain errors is presented. The ADC achieves 85dBFS SNDR and 84dBFS SFDR with a 50dB DC gain OTA in the first stage. The calibration algorithm is based on test signal injection. At 40MSPS the power dissipation is 220mW from a 2.5V supply. The ADC is designed in a 0.25/spl mu/m CMOS process and occupies an area of 6.5mm/sup 2/.

High-level continuous-time sigma delta design in Matlab/Simulink

This paper presents a framework for behavioral simulations of continuous time delta-sigma modulators (CTSD) developed in Matlab/Simulink. Error sources in CTSD designs are reviewed and it is explained how sub-module specifications can be derived from a system-level target performance. The paper also discusses considerations of importance when using Simulink for CTSD modelling, like the choice of solver and simulation speed optimization. An example CTSD design is used throughout to illustrate the results and error models.

Tunable Lowpass Filter with RF MEMS Capacitance and Transmission Line

We have presented an RF MEMS tuneable lowpass filter. Both distributed transmission lines and RF MEMS capacitances were used to replace the lumped elements. The use of RF MEMS capacitances gives the flexibility of tuning the cutoff frequency of the lowpass filter. We have designed a low-pass filter at 9–12 GHz cutoff frequency using the theory of stepped impedance transmission lines. A prototype of the filter has been fabricated using parallel plate capacitances. The variable shunt capacitances are formed by a combination of a number of parallel plate RF MEMS capacitances. The cutoff frequency is tuned from C to X band by actuating different combinations of parallel capacitive bridges. The measurement results agree well with the simulation result.

Design and simulation of RF MEMS switches for high switching speed and moderate voltage operation

In this paper we present the design and simulations of an RF MEMS switch with regard to its switching speed and pull-down voltage. The switch is required to fulfill the requirements of high speed and a moderate pull down voltage for the switching of CMUT (capacitive micromachined ultrasonic transducer) elements used for ultrasound imaging.