02-05-2012, 11:23 AM
A 2.4-GHz CMOS Short-Range Wireless-Sensor-Network Interface
for Automotive Applications
[attachment=21029]
INTRODUCTION
SENSORS have been applied in automobiles, ever since
the introduction of the manifold air pressure sensor for
engine control in 1979, followed by airbag sensors in the
mid-1980s. Furthermore, microsystems have been increasingly
used throughout the vehicle. The demand of new sensing and
management applications undoubtedly leads to more intelligent
cars and the increased need of a networking infrastructure to
connect the whole range of sensors and actuators. The system
environment of an automobile is becoming more and more
complex. While, formerly, one single supplier delivered all
components of an antilock braking system or all sensors for
airbag control, today, the networked architecture allows merged
sensor systems for different functions. Ambient intelligence,
which means an environment of interacting smart devices, is
opening up new information sources for the vehicle. With the
growing use of bus systems, building exclusive systems for
each function is becoming more and more difficult and too
expensive [1].
CURRENT STATE-OF-THE-ART AND SYSTEM OVERVIEW
Advances made in the electronics industry in general and
government legislation toward the increase of comfort and
safety in cars were the main driving forces that led to the
development of vehicle network technologies. Recently, the autoradio
was considered the only electronic device in a vehicle,
but now, almost every existing component in the vehicle has
some sort of electronic feature. Electronic modules are placed
in the automobile in order to acquire the measures of the sensors
(speed, temperature, and pressure, among others) and to be used
in computations. The orders received by the various actuators
are given by these same modules, which are responsible for
actions, where the switching on the cooling fan and changing
gear (in the case of automatic gears) constitute some examples
of actuation. These modules must exchange data between each
other during the normal operation of the vehicle. An example
of such data exchange is when a communication between the
engine and the transmission of a car is needed in order to
exchange information with other modules when a gear shift
occurs.
Transmitter
The ASK modulated signal is generated by means of a
switched power amplifier. The power amplifier has a cascade of
five inverters in order to drive the ASK output signal to the input
of the power amplifier. Fig. 4 shows the schematic of the whole
transmitter, where one can see the power amplifier, as well as
a power select circuit that makes possible the selection of the
transmitted power. The network L1–C1 is tuned to the carrier
frequency, while the emissions outside the 2.4-GHz band are
reduced by the network L2–C2.
C. Frequency Synthesizer
The phase-locked loop (PLL) has a reference generator circuit
with a crystal-based oscillator at 20 MHz, followed by
a phase-frequency difference circuit (PFD), a current steering
CONCLUSION
A CMOS-SRWSN interface comprising a sensor readout,
electronics of processing and control, a memory, an RF transceiver,
and a planar antenna has been presented in this paper.
Fig. 10 shows the photograph of the RF transceiver die,
which was fabricated in the UMC RF CMOS 0.18-μm process
and occupies an area of 1.5 × 1.5 mm2. The receiver has a
sensitivity of −60 dBm and consumes 6.3 mW from a 1.8-V
supply. The transmitter delivers an output power of 0 dBm
with a power consumption of 11.2 mW. The CMOS-SRWSN
interface can be compared with the other solutions in the
Table I [2].
for Automotive Applications
[attachment=21029]
INTRODUCTION
SENSORS have been applied in automobiles, ever since
the introduction of the manifold air pressure sensor for
engine control in 1979, followed by airbag sensors in the
mid-1980s. Furthermore, microsystems have been increasingly
used throughout the vehicle. The demand of new sensing and
management applications undoubtedly leads to more intelligent
cars and the increased need of a networking infrastructure to
connect the whole range of sensors and actuators. The system
environment of an automobile is becoming more and more
complex. While, formerly, one single supplier delivered all
components of an antilock braking system or all sensors for
airbag control, today, the networked architecture allows merged
sensor systems for different functions. Ambient intelligence,
which means an environment of interacting smart devices, is
opening up new information sources for the vehicle. With the
growing use of bus systems, building exclusive systems for
each function is becoming more and more difficult and too
expensive [1].
CURRENT STATE-OF-THE-ART AND SYSTEM OVERVIEW
Advances made in the electronics industry in general and
government legislation toward the increase of comfort and
safety in cars were the main driving forces that led to the
development of vehicle network technologies. Recently, the autoradio
was considered the only electronic device in a vehicle,
but now, almost every existing component in the vehicle has
some sort of electronic feature. Electronic modules are placed
in the automobile in order to acquire the measures of the sensors
(speed, temperature, and pressure, among others) and to be used
in computations. The orders received by the various actuators
are given by these same modules, which are responsible for
actions, where the switching on the cooling fan and changing
gear (in the case of automatic gears) constitute some examples
of actuation. These modules must exchange data between each
other during the normal operation of the vehicle. An example
of such data exchange is when a communication between the
engine and the transmission of a car is needed in order to
exchange information with other modules when a gear shift
occurs.
Transmitter
The ASK modulated signal is generated by means of a
switched power amplifier. The power amplifier has a cascade of
five inverters in order to drive the ASK output signal to the input
of the power amplifier. Fig. 4 shows the schematic of the whole
transmitter, where one can see the power amplifier, as well as
a power select circuit that makes possible the selection of the
transmitted power. The network L1–C1 is tuned to the carrier
frequency, while the emissions outside the 2.4-GHz band are
reduced by the network L2–C2.
C. Frequency Synthesizer
The phase-locked loop (PLL) has a reference generator circuit
with a crystal-based oscillator at 20 MHz, followed by
a phase-frequency difference circuit (PFD), a current steering
CONCLUSION
A CMOS-SRWSN interface comprising a sensor readout,
electronics of processing and control, a memory, an RF transceiver,
and a planar antenna has been presented in this paper.
Fig. 10 shows the photograph of the RF transceiver die,
which was fabricated in the UMC RF CMOS 0.18-μm process
and occupies an area of 1.5 × 1.5 mm2. The receiver has a
sensitivity of −60 dBm and consumes 6.3 mW from a 1.8-V
supply. The transmitter delivers an output power of 0 dBm
with a power consumption of 11.2 mW. The CMOS-SRWSN
interface can be compared with the other solutions in the
Table I [2].