Pirjo Pasanen

Significance of Nanotechnology for Future Wireless Devices and Communications

This paper reviews the expected wide and profound impact of nanotechnology for future wireless devices and communication technologies.

Graphene for future electronics

We discuss some aspects of how graphene could be used in mainstream electronic devices. The main focus is on signal processing applications in high-volume, industrially manufactured battery-powered devices, e.g. mobile phones and laptop computers, but we will also discuss applicability to other components like interconnects, wireless communication antennae and camera sensors, as well as novel types of signal processing devices, based on the unique physical properties of graphene.

Nonlinear behavior of three terminal graphene junctions at room temperature

We demonstrate nonlinear behavior in three-terminal T-branch graphene devices at room temperature. A rectified nonlinear output at the center branch is observed when the device is biased by a push-pull configuration. Nonlinearity is assumed to arise from a difference in charge transfer through the metal–graphene contact barrier between two contacts. The sign of the rectification can be altered by changing the carrier type using the back-gate voltage.

Graphene and Carbon Nanotube Applications in Mobile Devices

This paper presents potential carbon nanoelectronic applications in battery-powered mobile devices such as mobile phones and laptop computers. Based on the physical behavior of carbon nanotubes (CNTs) and graphene and the specific requirements for portable consumer electronic devices, the main challenges and restrictions for the adoption of carbon-based components by the industry are presented. The main emphasis is on electronic components, particularly transistors and radio-frequency applications. A circuit theory model is used to predict the feasibility of CNT transmission lines, and technical challenges that have to be solved before graphene transistors are suitable for mobile devices are presented. The performance of graphene transistors is compared with the corresponding parameters of silicon. In addition, other potential carbon-based applications in mobile devices aside from transistors such as displays and memory elements are outlined briefly.

Gate-controlled current switch in graphene

We study numerically cross conductances in a four-terminal all-graphene setup. We show that far away from the Dirac point current flows along zigzag directions, giving the possibility to guide the current between terminals using a tunable pn-junction. The device operates as a gate-controlled current switch, and the electronic properties of graphene are crucial for efficient performance.

Application of Information Theory to the Design of 4th GenerationCellular Communication Systems

The design of 4th Generation Cellular Communication Systems will face manychallenges, including the need to achieve very high spectrum efficiency whencompared to 3rd Generation cellular systems. In this paper, we investigate thefundamental limits of DSSS-CDMA versus TDMA for achieving high spectrumefficiency by presenting the capacity regions for each including the effectsof multiple transmit and receive antennas. To assess the channel capacityregion for local area and wide area coverage, a channel model based uponuncorrelated Rayleigh fading and model with a strong spatial correlation andRicean component are evaluated. For multiple transmit and receive antennas,both open loop and closed loop capacity regions are assessed, where the closedloop capacity assumes channel state information at the transmitter and optimumpower allocation. Conclusions from the work include an assessment of whatapproaches hold the best promise for achieving high spectrum efficiency forfuture cellular communication systems.

Selection diversity in multiple antenna systems with matrix modulation

Scheduling between several users introduces selection diversity and changes the statistics of the channel. Therefore, the problem of choosing the best user/transmission scheme in multiuser MIMO systems needs to be addressed. This work presents the selection diversity in multiple antenna systems with matrix modulation.