Microsystems for Bioelectronics

Nanomorphic cell

communication unit

5

CHAPTER OUTLINE

Introduction........................................................................................................................................ 123

Electromagnetic radiation.................................................................................................................... 124

Basic RF communication system .......................................................................................................... 124

EM Transducer: A linear antenna ......................................................................................................... 127

Basic principles ....................................................................................................................127

Short antennas .....................................................................................................................128

Radiation efficiency...............................................................................................................130

Free-space single-photon limit for energy in EM communication............................................................ 131

Thermal noise limit on communication spectrum................................................................................... 134

Thermal background radiation ................................................................................................134

Minimum detectable energy...................................................................................................134

The THz communication option (

l

‡ 100

m

m)....................................................................................... 136

Wireless communication for biomedical applications............................................................................ 139

Optical wavelength communication option (

l

w1

m

m) ........................................................................... 140

Basic principles of generation and detection of optical radiation ...............................................140

Scaling limits of optoelectronic devices ..................................................................................144

Status of

m

-scaled LEDs and PDs ......................................................................................................... 146

Concluding remarks ............................................................................................................................ 147

List of symbols.................................................................................................................................... 148

References ......................................................................................................................................... 150

5.1 INTRODUCTION

Communication is an essential function of autonomous microsystems. Suppose that the nanomorphic

cell collects data that need to be communicated to a receiver external to the body. It follows that the cell

must be equipped to transmit and receive data and, of course, there are space and energy questions that

arise in this connection. The purpose of this chapter is to explore the physical limits for a micron-scale

communication system and especially to obtain lower bound estimates for the energy required to

transmit one bit of data.

For autonomous operation, the communication channel should be wireless since it is assumed that

the nanomorphic cell is untethered. Also, from a practical point of view, it would be advantageous for

transmission from the nanomorphic cell to be omnidirectional, i.e. uniform in all directions

CHAPTER

Microsystems for Bioelectronics the Nanomorphic Cell

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