No abstract

C entral to the concept of smart spaces is the sensor module, which collects data from the environment and communicates this to other modules and a central unit. One of the many challenges associated with such networks is how to transmit data and power the sensors.Sensing multiple parameters in the environment requires miniaturized sensor nodes, relatively powerful programming platforms to interface with and process the data, and reliable long-term power solutions. Batteries provide the most obvious power source as long as the modules are reasonably big (a few square centimeters), easily accessible, and few in number so that the batteries can be easily replaced or recharged. In the vision of ubiquitous computing, where modules are embedded into everyday objects, computer hardware should be invisibleand replacing batteries isn't compatible with this vision.Several solutions to the power problem exist, such as reducing power consumption to the point where batteries can last the module's lifetime. Another solution is energy scavenging-that is, extracting energy from ambient sources such as vibrations, heat, light, and water.Our approach to providing power and fast data communication to off-the-shelf sensors is based on the well-established inductive coupling principle (see the "Related Work in Radio Frequency ID Research" sidebar on page 49). Inductive coupling provides both a power and a communication solution, so the module being powered has no need for an on-board energy source. Although inductive powering will never result in a global solution to powering sensor modules because of its inherently limited range, it can provide an attractive solution for embedded sensors, which are completely inaccessible. Our approachAn important design consideration for multiple sensor modules for the smart environment is the ability to rapidly power a node and read the corresponding sensors. To comply with both power and communications constraints, we investigated the feasibility of a working frequency of 13.56 MHz. We were particularly interested in understanding how much power an inductively coupled system can transfer at this frequency and how far that power can be transmitted. Figure 1 shows a simplified block diagram of our system. Like all RFID systems, it consists of a reader and a transponder. The reader provides the energy, which is inductively coupled to the transponder module through tuned A new approach provides a power source and fast communication for miniaturized modules' sensor nodes using a 13.56 MHz carrier. Although its powering range is limited, this method is well suited for applications in which communication must be fast but the sensor modules are hard to access.

No abstract

This p q e r piwen& how to design a RF transmitter with on[v two CMOS d@td inverters. The RF oscillalor Is controlled by aJirndnmerztd mode quarl~ crystal operating in loa! resonance. The RF mnpl~er consisfi Df one CMUS imHer, having the cqubili& to produce an output power of IO mU! An 8 elements matching imd Jltering nefwork har been designed in order to makh the CMOS tvansmitter's ou@t to a SO Q m t m , and b conlplr with the European TekcommunicuCion regidation$. INDEX TERMSRF Trmiitler, ChKX, Digital radio, c t y~t d conh-olled oscillator, FSK RFmplijer, impdance matching.