Dirk Jansen

RFID Technology for Continuous Monitoring of Physiological Signals in Small Animals

Telemetry systems enable researchers to continuously monitor physiological signals in unrestrained, freely moving small rodents. Drawbacks of common systems are limited operation time, the need to house the animals separately, and the necessity of a stable communication link. Furthermore, the costs of the typically proprietary telemetry systems reduce the acceptance. The aim of this paper is to introduce a low-cost telemetry system based on common radio frequency identification technology optimized for battery-independent operational time, good reusability, and flexibility. The presented implant is equipped with sensors to measure electrocardiogram, arterial blood pressure, and body temperature. The biological signals are transmitted as digital data streams. The device is able of monitoring several freely moving animals housed in groups with a single reader station. The modular concept of the system significantly reduces the costs to monitor multiple physiological functions and refining procedures in preclinical research.

Formal Description of Inductive Air Interfaces Using Thévenin's Theorem and Numerical Analysis

With the development of new integrated circuits to interface radio frequency identification protocols, inductive air interfaces have become more and more important. Near field communication is not only able to communicate, but also possible to transfer power wirelessly and to build up passive devices for logistical and medical applications. In this way, the power management on the transponder becomes more and more relevant. A designer has to optimize power consumption as well as energy harvesting from the magnetic field. This paper discusses a model with simple equations to improve transponder antenna matching. Furthermore, a new numerical analysis technique is presented to calculate the coupling factors, inductions, and magnetic fields of multiantenna systems.

Every student makes his own microprocessor

This paper presents the actual curriculum and goals of education in digital system design at the University of Applied Sciences, Offenburg, Germany. In a master course, following a seminar style, students are guided in their own development of a tiny microprocessor in 6 concluding tasks during no more than 10 weeks, using modern design tools. They follow a top down flow from specification via VHDL programming, simulation, synthesis to FPGA and final emulation on hardware. The students are getting deep insight into actual computer architecture, how processors are working, the interdependence of hard- and software as well as into the software tool chain, used to program this device via C-Language. The course is running now the 5th time with increasing interest and number of students.

An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications

Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18 μm CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7 mm2. The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107 μW. The analog part of the design consumes only 36 μW, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches.

A RFID/NFC based Programmable SOC for biomedical applications

A new RFID/NFC (ISO 15693 standard) based inductively powered passive SoC (System on chip) for biomedical applications is presented here. The proposed SOC consists of an integrated 32 bit microcontroller, RFID/NFC frontend, sensor interface circuit, analog to digital converter and some peripherals such as timer, SPI interface and memory devices. An energy harvesting unit supplies the power required for the entire system for complete passive operation. The complete chip is realized on CMOS 0.18 μm technology with a chip area of 1.5 mm × 3.0 mm.

A digital low frequency transceiver for biomedical implants with enclosed titanium housing

Due to the demand of communication for medical implants with titanium housing, the introduced transceiver enables a simple and inexpensive, and power efficient solution with optimized modulation for high data rates at low frequency transmission.

Semi-passive RFID sensor implant

Based on common RFID technology the University of Applied Sciences Offenburg is developing a new bio-telemetrical system called μTrans. Semi-passive RF transponders implanted in small animals measure ECG, pressure, temperature, oxygen saturation and activity. Using modern cloud technology, it is possible to build up a sensor network of a nearly unlimited size.

Electromagnetic Analysis, Characterization and Discussion of Inductive Transmission Parameters for Titanium Based Housing Materials in Active Medical Implantable Devices

The growing demand for active medical implantable devices requires data and or power links between the implant and the outside world. Every implant has to be encapsulated from the body by a specific housing and one of the most common materials used is titanium or titanium alloy. Titanium thas the necessary properties in terms of mechanical and chemical stability and biocompatibility. However, its electrical conductivity presents a challenge for the electromagnetic transmission of data and power. The proposed paper presents a fast and practical method to determine the necessary transmission parameters for titanium encapsulated implants. Therefore, the basic transformer-transmission-model is used with measured or calculated key values for the inductances. Those are then expanded with correction factors to determine the behavior with the encapsulation. The correction factors are extracted from finite element method simulations. These also enable the analysis of the magnetic field distribution inside of the housing. The simulated transmission properties are very close to the measured values. Additionally, based on lumped elements and magnetic field distribution, the influential parameters are discussed in the paper. The parameter discussion describes how to enhance the transmitted power, data-rate or distance, or to reduce the size of the necessary coils. Finally, an example application demonstrates the usage of the methods.

A disposable passive temperature sensor with RFID ISO15693 interface

The idea behind the ThermoTag is the need to develop a complete passive tag with a simple circuit for measuring temperature. This paper focuses on the development of the tag which includes the proper designing of the antenna, which is very important for the passive development and also the measuring principle and the technique used for measurement. As a result a small and thin transponder (45mm in diameter and 3.5mm in thickness) is developed which is used for measuring temperature over a wide range. The transponder is one of its kinds because of its size, simplicity and by using a NTC helps to produce a “disposable passive sensor device”.