Christopher Soell

Remote Powered Medical Implants for Telemonitoring

Chronic diseases like diabetes mellitus often require a permanent monitoring of vital signs. Especially the use of telemedicine will increase the quality of life for affected patients. Therefore, novel systems are necessary which are able to permanently detect and provide health status information. But these systems must not control patients life and should work autonomously. For this purpose, intelligent medical implants are well qualified. This work describes a system for wireless power supply and communication with medical implant applications. Monitoring vital signs will create a big amount of data. Therefore, high data rates are necessary provided by high operating frequencies which in turn lead to electromagnetic far-field conditions. In this case, high attenuation losses due to the permittivity of the human body εr have to be considered. Hence, high frequencies are not suitable for the transfer of energy into the human body. The presented concept is based on two different frequencies for power supply and data transmission. An independent development of both blocks is thereby possible. The power supply operates at a frequency of 13.56 MHz, using inductive coupling. Consequently, the human body does not affect the energy transfer. In contrast, the data transmission is operated at a frequency of the medical implant communication service (MICS) band. The elaborated system consists of a power supply unit, a data transmission unit, and a control unit. The implementation of the power supply and data transmission as well as associated theoretical basics are presented. Performed measurements demonstrate that the realized system is qualified for the use on human beings.

A CMOS image sensor with analog pre-processing capability suitable for smart camera applications

This work presents a novel CMOS sensor which is suitable for analog image processing operations and describes the benefits of analog pre-processing over digital algorithms. All needed modifications to read out a spatial NxN pixel matrix simultaneously are presented regarding pixel wiring, row decoder and column multiplexer as well as descrambling the order of the outputs. The outputs are connected via a buffer stage to the analog pre-processing circuits. As an example for such an analog computation, an averaging filter is described from design constraints to the actual implementation. Simulation results show a very low current consumption of just 55.3 μA under worst-case conditions and a computation time below 200 ns. This corresponds to a power-time product ratio of 1:18.75 compared to a digital state-of-the-art implementation.

Analog computation methods with the help of analog and pseudo-digital carry signals

This work describes new methods of handling ex-ceedings of the supply range in analog computation stages. These are handled as pseudo-digital and analog carry signals and used to regulate the gain of the stage where they occur as well as all computation stages that follow. A complete example for such an analog computation is simulated and presented and critical parts of the architectures are addressed. In addition, more sophisticated extensions are proposed and the “right” way of carry handling is explained for a specific algorithm, together with a discussion of the advantages of different methods for each application.

Low-power analog smart camera sensor for edge detection

This work presents an intelligent analog image sensor system for smart camera applications with the need of edge or marker detection. The system consists of a 3×3 read-out CMOS image sensor, an analog Sobel stage and additional circuitry like operational amplifiers and comparators to compute a 1 bit image with the edges present in the taken photo. This information can then be further processed digitally to detect specific shapes in order to control robot routines, for example. The architecture of the proposed system is highly desirable as dedicated analog hardware has significant advantages in terms of power and speed compared to digital implementations. The overall system is simulated with the help of a 3×3 CMOS image sensor IC as well as Cadence Virtuoso for analog circuit simulation and MATLAB to convert the sequential information back to an image, and compared to other state of the art CMOS image sensors with edge detection capability. The analog Sobel circuit runs with a clock of 10 MHz and consumes less than 0.79 mW average power for the computation of the example image, and the whole 200×200 pixel image sensor consumes only 5.5 mW at a frame rate of 75 fps.

A Tone Mapping algorithm suited for analog-signal real-time image processing

This work presents a Tone Mapping Operator (TMO) which adjusts the High Dynamic Range (HDR) of image sensor data to the limited dynamic range of conventional displays with analog signal processing. It is based on Photographic Tone Reproduction (PTR) and suitable for analog circuit design in a CMOS image sensor in order to reduce the hardware cost and operation time for real-time image processing. For this reason, the characteristic advantage and calculation limitation of analog technology are considered in the TMO algorithm proposal. Furthermore, the appropriate modelling is built and simulated in Verilog-A. The function of the algorithm is feasible for analog processing. The frequency of the analog TMO is upper 52MHz while it consumes 55mW. The simulation results of test images are compared with the digital global TMO and the proposed analog TMO provides a reasonable similar dynamic range compression.

A multi-functional reconfigurable low-power ultra-high PSRR CMOS reference-system

This paper presents a new reference system with emphasis on low power design and high power supply rejection. The untrimmed reference provides a 600 mV output voltage, which only differs by 5.75mV in the temperature range between -40°C and +125°C and a PSRR of -157.2dB at 10Hz. The core part of the reference produces a reference potential of 416.1mV with a deviation of only 1.59 mV. Moreover, the circuit provides a 900mV output, a temperature independent 3 μA current and trimming possibilities for the temperature curves and the amplitude of output voltages and currents. Under all operating conditions, the post-layout Corner- and Monte-Carlo-Simulations show a power consumption of less than 40μA and ensure functionality across process, supply voltage and temperature variations.

Area-efficient fully integrated dual-band class-E/F power amplifier with switchable output power for a BPSK/OOK transmitter

This paper presents a novel dual-band class-E/F power amplifier (PA) with switchable output power. It is targeted to work in a BPSK/OOK transmitter in smart facility applications like an autarkic asset-tracking system based on small sensor nodes. The amplifier is fully-integrated and able to operate at both 434 MHz and 868 MHz without the need for additional inductors, making the design very area-efficient. The output power settings at 868 MHz are controllable between −1.79 dBm and −24.61 dBm at 4.96 mA and 1.43 mA current consumption, respectively. The whole circuit including all inductors and the matching network in front of the antenna consumes only 0.9 mm2 chip area and is fully integrated in a 180 nm CMOS process together with a VCO and a PLL.

Analog non-linear transformation-based tone mapping for image enhancement in C-arm CT

Flat-Panel C-arm Computed Tomography (CT) suffers from pixel saturation due to the detectors limited dynamic range. We describe a novel approach of analog, non-linear tone mapping (TM) for preventing detector saturation. An analog TM operator (TMO) applies a non-linear transformation in a CMOS (complementary metal-oxide semiconductor) sensor and its inverse TMO based on 14-bit digital raw data. This is done in order to prevent overexposure and to enhance image quality to 32 bits. The method was applied to the cases of low-contrast head imaging and to that of imaging both knees. Cone-beam projection data with and without overexposure was simulated for a 200 degree short-scan of the knees and a 360 degree full-scan of a Forbild head phantom. The results show an increased correlation coefficient with respect to ground truth of 0.99 for TMO compared to 0.96 for overexposed knee data and a higher low-contrast visibility (CC=0.99) compared to linear quantization (CC=0.97).