Neil C. Bird

Amorphous Silicon Image Sensor Arrays

We have developed a technology for 2D matrix-addressed image sensors using amorphous silicon photodiodes and thin film transistors. We have built a small prototype, having 192×192 pixels with a 20μm pixel pitch, and assessed its performance. The nip photodiodes can have dark current densities of less than 10 11 A.cm -2 (up to 5V reverse bias) and peak quantum efficiencies of 88% (at 580nm). We operated the sensor in real time mode at high speed (50 Hz frame rate and 64μS line time). The image sensor has a low noise performance giving a dynamic range in excess of 10 4 . The maximum crosstalk is about 2%, which allows at least 50 grey levels. The bottom contact of the photodiode acts as a light shield from light through the substrate, which enables the sensor to be operated as an intimate contact image sensor to image a document placed directly on top of the array. In this mode, the CTF was 75% at 2 lp.mm 1 . Good quality images are demonstrated in both front projection and intimate contact imaging modes.

Wireless wire-the 60 GHz ultra-low power radio system

This article presents basic issues regarding design and development of a 60 GHz ultra-low power radio system for Ambient Intelligence (AmI) applications. It demonstrates the validity of choosing the 60 GHz frequency band to design low power radios by a mathematical model, and proposes an overview of a cross-layer optimization flow to minimize power dissipation. Moreover, a completed RF front-end architecture, i.e. the transmitter and the receiver, is simulated according to the proposed methodology. Crucial concerns, challenges and solutions are discussed based on it. Simulation results are given, which verify the theoretical conclusions of 120 pJ/bit power consumption.

Large-area image sensing using amorphous silicon nip diodes

Large-area 2D image sensor arrays fabricated on glass substrates have, in recent years, begun to attract increasing interest for use in applications such as 2D document readers and medical imaging. This paper describes investigations into document contact imaging using 2D image sensors which employ amorphous silicon diodes for both the photosensitive and switching elements. The acquisition of high-quality grey scale images is presented, together with a discussion of the issues involved in designing all-diode image sensor arrays.

RFID Security: Cryptography and Physics Perspectives

In this chapter, we provide an overview of mechanisms that are cheap to implement or integrate into RFID tags and that at the same time enhance their security and privacy properties. We emphasize solutions that make use of existing (or expected) functionality on the tag or that are inherently cheap and thus enhance the privacy friendliness of the technology “almost” for free. Technologies described include the use of environmental information (presence of light, temperature, humidity, etc.) to disable or enable the RFID tag, the use of delays to reveal parts of a secret key at different moments in time (this key is used to later establish a secure communication channel), and the idea of a “sticky tag,” which can be used to re-enable a disabled (or killed) tag whenever the user considers it to be safe. We discuss the security and describe usage scenarios for all solutions. Finally, we summarize previous works that use physical principles to provide security and privacy in RFID systems and the security-related functionality in RFID standards.