Nadine Pesonen

Optimization of Wireless Sensors Based on Intermodulation Communication

Intermodulation communication principle has been recently developed to wirelessly read-out passive sensors. Intermodulation communication sensors reply the sensor information at an intermodulation frequency when interrogated by a reader device with two tones. This paper derives an analytical expression for optimizing the electrical circuitry of such a sensor. The derived equations are verified by harmonic balance simulations. An optimized sensor is designed and fabricated and experimentally characterized. Results show that 1% change in the sensor capacitance can still be detected at a 13 m-distance and the read-out principle could enable an extreme resolution at shorter distances (less than per mille below 5 m). A wireless electrocardiography measurement is demonstrated.

MEMS-based AC voltage reference

An ac root-mean-square (RMS) voltage reference based on a microelectromechanical system (MEMS) component is presented. The device stability is investigated in various experiments. A time stability at a level of a few /spl mu/V/V in 24 h was measured using an accelerometer MEMS component at an operating frequency of 100 kHz.

Application of conformal mapping approximation techniques: parallel conductors of finite dimensions

This paper describes a novel approach to the application of conformal mapping to capacitance evaluation. A particular structure composed of an array of identical lines and located below a conductive plate is studied. Results show the application of conformal mapping can reduce computing time when using three-dimensional electrostatic modeling and it can be the basis of algorithms of practical applications, especially in the semiconductor industry.

Multi-system, multi-band RFID antenna: bridging the gap between HF- and UHF-based RFID applications

In this paper a multi-system, multi-band antenna structure for RFID applications is presented. The antenna covers two UHF bands allocated for RFID use in Europe (866-868 MHz) and N. America (902-928 MHz) with a dual-band PIFA element as well as HF 13.56 MHz band with a near-field coil. Both systems in the antenna are shown to perform well on free space and on metal, allowing a wide use of the same tag antenna on different environments and systems.

Wideband Microwave Power Sensor Based on MEMS Technology

An optimized transmission-type MEMS RF power sensor is presented. The design is based on microwave filter theory. It is shown that the thermal resolution of the sensor can be reduced below -50 dBm for RF bandwidths up to les 40 GHz

Maximum-Likelihood Estimation for Passive Wireless Intermodulation Communication Sensors

The intermodulation communication principle has recently shown several advantages over other passive wireless sensor readout techniques. The advantages include a large readout distance and the possibility of using generic sensor elements. In this paper, we derive an algorithm to estimate the quantity measured by the wireless sensor from its intermodulation response and verify the algorithm experimentally with a passive wireless inclinometer sensor operating at 860 MHz. The results can be further used to realize a reader device for intermodulation communication sensors, maximize its operational parameters, and optimize the sensor structure for the best readout resolution.

AC Voltage Reference Based on a Capacitive Micromechanical Component

The design and characterization of a high stability capacitive MEMS device intended for an AC voltage reference at 100 kHz or higher frequencies is presented. Preliminary results from a first prototype device show that the pull-in voltage of the device is stable to within 10 ppm over 60 hours. We discuss an optimised device design which is expected to show greater stability

Achieving long reading ranges with passive wireless intermodulation sensors

This paper presents a system architecture combining batteryless wireless intermodulation sensors and their associated reader, and analyses the achievable read range of such sensor-reader system. The computed read range is compared to those provided by harmonic and passive UHF RFID sensor systems. Effects of both reader thermal noise and third-order distortion by the reader itself on the read range of the system are considered, by means of theoretical analysis, simulations and measurements. The presented reader with a distortion-limited sensitivity of -70 dBm at the receiver input provides a 7 m measured and a 9 m simulated read range.

Activation and identification of fully passive wireless sensors

A key barrier to the penetration of IoT technologies is the need for an independent power source for sensor nodes, increasing complexity and cost and hindering the convenience of deployment and maintenance. To address this formidable challenge, the authors have been developing a fully passive wireless sensor network platform, the Zero Power Sensor. The sensing mechanism is by now maturing and a platform has been implemented and readout distances in excess of 10 meters have been demonstrated. A method of addressing and activating the sensor nodes using bias applied by passive UHF RFID with digital output is demonstrated on one sensor node at a distance of 2m.

Review of passive wireless sensors utilizing the intermodulation communication

This paper reviews different kinds of passive wireless sensors utilizing the intermodulation communication principle. The reviewed sensor architectures are based either on a mechanical resonator, electrically non-linear sensing element, or on a separate mixer, low-frequency resonance circuit and a sensing element. The benefits and drawbacks of different architectures are compared and some experimental measurement results are presented.