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PROJECT REPORT
2.1GHz Passive SAW Sensor Driver
EENG-491 Senior Design Project
ADVISER:
DR. ZHANG, TAO
TEAM MEMBER:
CHEN, FANGZHOU
TOMANELLI, JOSEPH
JIN, RONG
WANG, XIAOXIAO
May 15, 2013
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CONTENTS
CONTENTS................................................................................................................ 1
TABLE OF GRAPHS....................................................................................................2
Executive Summary..................................................................................................3
2.1GHz Passive SAW Sensor Driver
I. Introduction.......................................................................................................4
II. System Design....................................................................................................5
III. Components Description...................................................................................7
A. RF Generator: MAX2752EUA+........................................................................7
B. Power Amplifier: SKY65028-70LF....................................................................9
C. Circulator: SFC2040A....................................................................................11
E. Low Noise Amplifier: SKY65080-70LF...........................................................12
F. LaunchPad: LAUNCHXL-F28027: C2000 Piccolo LaunchPad..........................13
IV. Practical Integration........................................................................................15
V. Conclusion....................................................................................................... 17
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TABLE OF GRAPHS
FIGURE 1 THE BLOCK DIAGRAM OF SAW SENSOR DRIVER........................................................5
FIGURE 2 THE CIRCUIT OF RADIO FREQUENCY (RF) GENERATOR CHIP.........................................8
FIGURE 3 CHARACTERISTIC CURVE OF PORT TUNING............................................................8
FIGURE 4 THE PCB OF RF GENERATOR.................................................................................9
FIGURE 5 THE CHARACTERISTIC CURVE OF ADJACENT CHANNEL LEAKAGE RATIO..........................9
FIGURE 6 THE CIRCUIT OF POWER AMPLIFIER......................................................................10
FIGURE 7 THE PCB OF POWER AMPLIFIER..........................................................................10
FIGURE 8 THE DIMENSIONAL DRAWING OF CIRCULATOR........................................................11
FIGURE 9 THE CIRCUIT USED IN LOW NOISE AMPLIFIER CHIP.................................................12
FIGURE 10 THE PCB OF LOW NOISE AMPLIFIER...................................................................13
FIGURE 11 THE ACTURAL CHIP OF LAUCHPAD WHICH STANDS FOR MICRO-CONTROLLER.............13
FIGURE 12 THE MODEL OF LAUNCHPAD WITH 40 PINS AND EXTRA VCC AND GND OUTPUT.......14
FIGURE 13 THE INTEGRATED PCBS OF POWER AMPLIFIER WITH LOW-NOISE AMPLIFIER (LEFT) AND RF GENERATOR WITH POWER AMPLIFIER (RIGHT)....................................................15
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Executive Summary
Due to the rapid growth of wireless technology, a wireless sensor
would be much more convenient for both patients and
nurses/doctors. The integration of these technologies with medical
sensors could be a great improvement over currently used wired
sensors. Due to the fact that patients are usually confined to a
single room, a near-field wireless signal transmission system to
transmit health-related signals from the sensors on patients, such as
a Body Area Network could effectively be used.
When a SAW sensor is functioning, the reader sends a pulse at a
specific frequency. The pulse can be a single short signal that will
provide power to the SAW sensor. The sensor receives the pulse,
which provides the energy for it to feedback a different pulse to
reader which contains information needed. This information could be
a patient’s temperature, blood pressure, or many other physical
conditions. The SAW sensor is much like a mirror. When light is
pointed onto a mirror, it will then reflect a light back.
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2.1GHz Passive SAW Sensor Driver
I. Introduction
Within the medical field, sensors are often used to continuously monitor a patient’s vital signs or any other physiological phenomena for medical study or determine treatment of a patient’s condition. These sensors are either placed on the surface of the skin or implanted under the skin in various parts of the body. Sensors are electronic devices that will convert a biological signal to an electrical signal that can be used to monitor health conditions by nurses or doctors. All sensors require both power and a means of transmitting the information that has been obtained. Currently most biological sensors use a wired connection to provide power and to transfer and display these signals on computers or other equipment.
Due to the rapid growth of wireless technology, a wireless sensor would be much more convenient for both patients and nurses/doctors. The integration of these technologies with medical sensors could be a great improvement over currently used wired sensors. Due to the fact that patients are usually confined to a single room, a near-field wireless signal transmission system to transmit health-related signals from the sensors on patients, such as a Body Area Network could effectively be used.
In this project, we are focusing on building a Body Area Network system with a wireless driver for SAW sensors operating at a specific range of frequency. SAW is an abbreviation for Surface Acoustic
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Wave. The advantage of using a SAW sensor is that they are small in size and also there is no need for a common power supply. This technology would lend itself nicely to wireless medical sensors that would never need a battery to be changed.
When a SAW sensor is functioning, the reader sends a pulse at a specific frequency. The pulse can be a single short signal that will provide power to the SAW sensor. The sensor receives the pulse, which provides the energy for it to feedback a different pulse to reader which contains information needed. This information could be a patient’s temperature, blood pressure, or many other physical conditions. The SAW sensor is much like a mirror. When light is pointed onto a mirror, it will then reflect a light back.
II. System Design
As a transistor, the transmitter part and receiver part are combined together through a circulator to share the same antenna. In the Figure 1, Micro-controller can activate the RF generator and control the output signal’s frequency. The feedback signal received from antenna transmits to the micro-controller via power attenuator, low-noise amplifier, and power amplifier. The
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Figure 1 the block diagram of SAW Sensor Driver.
A. Frequency Generator – This device is an oscillator that will generate a constant
sinusoidal signal to be used in the transmission process. It can also be used to
regulate its output power with a specific frequency.
B. Power Amplifier – The power amplifier is used to increase the amplitude of the
generated signal. This device ensures effective transmission over the antenna to
the SAW sensor. It can convert a low-power radio-frequency signal to a larger
signal of significant power, typically for driving the antenna of a transmitter. It is
usually optimized to have high efficiency and output power compression,
sufficient return loss on the input/output, as well as optimal gain and heat
dissipation.
C. Circulator - The circulator is a passive device with three ports. Power is
transferred from one port to the next in a set order. In this system, power from the
input section will be transmitted to the antenna, and the response signal from the
antenna will be transmitted to the output part of the system only. These devices
improve stability, performance, and reliability of radio frequency system.
D. Power Attenuator – An attenuator is a device used to reduce the power of a
signal without noticeably distorting the waveform and the information carried
within in. When measuring signals, an attenuator can lower the amplitude of the
signal a predetermined amount to enable measurements or to protect the
measuring device from signal levels that might be damaging to it.
E. Low Noise Amplifier – This amplifier is used to amplify the weak signal that is
captured from the antenna to be viewed and tested. The effect of noise from
subsequent stages of the receive chain is reduced by the gain of the low noise
amplifier, while the noise of the LNA itself is injected directly into the received
signal.
F. Microcontroller – Microcontrollers are a small computer on a single integrated
circuit containing a processor core, memory, and programmable input/output
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peripherals. Microcontrollers are designed for embedded applications, in contrast
to the microprocessors used in personal computers or other general purpose
applications. The microcontroller will coordinate all data transfer and save data to
be later analyzed.
III.Components Description
We use ExpressPCB software and parental software called ExpressSCH to design the
schematics. This PCB software is a snap to learn and use. It makes designing circuit
boards a simple work for the beginner and efficient for the professional.
Our PCB board is two layers board. Upper layer is signal layer and device layer.
All devices are inserted on the upper layer and there are signal and Vcc lines on it.
Lower layer is cover layer and ground layer. Our board connects to the ground
through it.
In our graph, yellow lines depict the outline of each component that insert onto
the board. Red lines are the signal line and Vcc line that lied on the upper layer. And
green lines represent ground and the cover layer beneath. All the lines can’t be crossed
and they should keep a 45-degree angle cause we use a high frequency that reaches
2.1 GHz.
We design every connector in the board because they are not default devices in
the software’s library.
A. RF Generator: MAX2752EUA+Features
Guaranteed Frequency Tuning Range: 2025MHz to 2165MHz (Zero IF)
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On-Chip Tank Circuit
Internally Matched Output Buffer Amplifier
Low-Current Shutdown Mode
+2.7V to +5.5V Supply Voltage Range
Miniature 8-Pin μMAX Package
Detailed Description
Oscillator
The MAX2752 VCOs are implemented as an LC oscillator topology, integrating all of
the tank components on-chip. This fully monolithic approach provides an easy-to-use
VCO. A voltage applied to the TUNE pin controls the frequency. The VCO core uses
a differential topology to provide a stable frequency versus supply voltage.
Output Buffer
The oscillator signal from the core drives an output buffer amplifier. The amplifier is
internally matched to 50Ω including an on-
chip DC blocking capacitor. The amplifier
boosts the oscillator signal to a level suitable
for driving most RF mixers.
Tuning Input
The tuning input is typically connected to the
output of the PLL loop filter. The loop filter
provides an appropriately low-impedance
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Figure 2 the circuit of Radio Frequency (RF) Generator chip
Figure 3 Characteristic Curve of Port TUNING
source. Any excess noise on the tuning input is directly translated into FM noise,
which can degrade the phase-noise performance of the oscillator.
PCB
When an input of 1.5-2 voltage is applied to
the pin 3, the RF generator can generate an
output of range from 2.0 to 2.1 GHz.
In the four left connectors, the first is the
connector where voltage is put in. The
second is the connector that can shut down
the RF generator. The third connector is Vcc
connector, which is connected to the voltage
source. The fourth connector is ground
connector. And the coaxial cable connectors
on the top contain four ground connections
and an output connection.
B. Power Amplifier: SKY65028-70LFFeatures
Wideband frequency range: 250–2700MHz
Highlinearity:OIP3>40dBmandP1dB>24dBm
High efficiency: PAE48%
High gain: 20dB
Single DC supply, 3Vor5V
Description
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Figure 4 the PCB of RF Generator
Figure 5 the Characteristic Curve of Adjacent Channel Leakage Ratio.
Skyworks SKY65028-70LF is a high performance, ultra-wideband linear amplifier
with superior output power, linearity, and efficiency. The device is fabricated using
Skyworks high reliability Aluminum Gallium Arsenide (AlGaAs) Heterojunction
Bipolar Transistor (HBT) technology.
The SKY65028-70LF achieves a high linearity and superior Adjacent Channel
Power Rejection/Adjacent Channel Leakage Ratio (ACPR/ACLR) performance. This
makes it ideal for use in the driver stage of infrastructure transmit chains for Trans-
European Trunked Radio (TETRA) transceivers, multi-band (GSM, AMPS, PCS,
DCS) handsets, and many other wireless applications
PCB
The core component is the amplifier that
is showed as a small red square.
When an input is transferred from RF
generator, it will receive at Input
connector, and it will magnify the signal
to twice or even more. The signal
magnified will be sent out from Output
connection.
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Figure 6 the Circuit of Power Amplifier
Figure 7 the PCB of Power Amplifier
On the button, there are two coaxial cable connectors. The left one is the input
connector, and the right one is the output connection. The four connectors around are
ground connectors. On the top we have three connectors. The left one is Vcc
connector, the middle one is ground source, and the right one is signal source. And we
use six resistances to partial voltage pressure. In the circuit design, we try to use a 180
ohm and 390 ohm resistances to partial voltage. But we found that we can’t buy these
two resistances. So we use six resistances of 100 ohm to replace the two resistances
we designed.
C. Circulator: SFC2040A Features
FREQUENCY: 2-4 GHZ
IMPEDANCE: 50 OHMS
VSWR: 1.4:1 TYPICAL
INSERTION LOSS: 0.5 DB
AVG POWER: 10 W CW
ISOLATION: 16 DB TYP
Description
Circulators are passive non-reciprocal
three-port devices, in which a microwave
or radio frequency signal entering any
port is transmitted to the next port in
rotation (only). A port in this context is a
point where an external waveguide or
transmission line (such as a microstrip line or a coaxial cable), connects to the device.
For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal
applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of
port 1.
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Figure 8 the Dimensional Drawing of Circulator
In radar, circulators are used as a type of duplexer, to route signals from the
transmitter to the antenna and from the antenna to the receiver, without allowing
signals to pass directly from transmitter to receiver.
E. Low Noise Amplifier: SKY65080-70LFFeatures
Wideband frequency range: 1500 to 2500 MHz
Low Noise Figure: 2.3 dB
Output P1dB = +21 dBm
High gain: 15 dB
Single DC supply: +5 V
Description
SKY65080-70LF is a high performance, ultra-wideband Power Amplifier driver with
superior output power, low noise, linearity, and efficiency. The device provides a 2.3
dB Noise Figure and an output power at 1 dB compression of +21 dBm, making the
SKY65080-70LF ideal for use in the driver stage of infrastructure transmit chains.
PCB
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Figure 9 the Circuit Used in Low Noise Amplifier Chip
For the signal in has two parts – low freq. component and high freq. component. The
lower part is not used which is called noise and need to be eliminated for advance. By
the meantime, the efficient high freq. signal is too small to be detected, and this
amplifier can increase the amplitude of high freq. signal in the particular range of
spectrum.
The four connection of coaxial
cable connector laid on left are
connected to ground. The middle
connection of the coaxial cable
connector is input connection. The first
connection of the three connectors on
the top is Vcc connector that is
connected to the voltage source. The
second connection is ground source,
and the third connection is the signal
source. The ground source and signal
source are connected to an external component. The coaxial cable connector on the
right contains four ground connections and an output connection.
F. LaunchPad: LAUNCHXL-F28027: C2000 Piccolo LaunchPadFeatures
High-Efficiency 32-Bit CPU (TMS320C28x™)
Integrated Power-on and Brown-out Resets
Three 32-Bit CPU Timers
Enhanced Pulse Width Modulator (ePWM)
Enhanced Capture (eCAP)
Analog-to-Digital Converter (ADC)
Comparator
~ 14 ~
Figure 10 the PCB of Low Noise Amplifier
Figure 11 the Actural Chip of LauchPad which stands for Micro-Controller
Description
The F28027 provides the power of the C28x™ core coupled with highly integrated
control peripherals in low pin-count devices. This device is code-compatible with
previous C28x-based code, as well as providing a high level of analog integration.
An internal voltage regulator allows for single rail operation. Analog comparators
with internal 10-bit references have been added and can be routed directly to control
the PWM outputs. The ADC converts from 0 to 3.3-V fixed full-scale range and
supports ratio-metric VREFHI/VREFLO references.
CPU
The 28027 based controllers have the same 32-bit fixed-point architecture as existing
C28x MCUs. It is a very efficient C/C++ engine. The 32 x 32-bit MAC 64-bit
processing capabilities enable the controller to handle higher numerical resolution
problems efficiently. The device has an 8-level-deep protected pipeline with pipelined
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Figure 12 the Model of LaunchPad with 40 Pins and Extra Vcc and GND Output
memory accesses. This pipelining enables it to execute at high speeds without
resorting to expensive high-speed memories.
Memory Bus (Harvard Bus Architecture)
As with many MCU-type devices, multiple busses are used to move data between the
memories and peripherals and the CPU. The memory bus architecture contains a
program read bus, data read bus, and data write bus.
IV. Practical Integration
For the purpose of the device portable and decreasing the cost, the module for each
component has been integrated together, basically connect two parts into one as the
design of block diagram.
~ 16 ~Figure 13 the Integrated PCBs of Power Amplifier with Low-Noise Amplifier (left) and RF Generator with Power Amplifier (right).
The left board in the Figure 13 is the combination of Power Amplifier and Low-
Noise Signal Amplifier. Main two parts are sharing the same AC power of 5V, while
the ground line for each component has been separated into two different connection
pins. Thus there will be three-pin connection on the top of left side. The bottom
connector is the signal input and the top right one is the output. For the checking
usage, in between there is another connector for activating part of the whole board.
The right side board of Figure 13 is the integration of RF Generator and Power
Amplifier. Four-pin connection on the top is the same as the usage in the module of
RF Generator. The beneath coaxial connector is the checking point, and the bottom
right connector is for the output.
In both two boards, Power Amplifier has been used and, at the same time, only
one amplifier will be activated for signal magnifying to the maximum 5 Volts.
Therefore, the next step, where we plan to integrate these two PCBs together, is
eliminating the need of duplicate devices, such as the same capacitor and multiple
resistors. The final PCB will be much smaller than two boards.
For the reason of our boards have not been shipped to us yet, we cannot insert the
component onto it and checking its performance. The possible problem of these two
boards is whether that when inserted the component, the size of each is match or not.
Although we put the standardized size of each, the reality is that actual size of the
component will not be exactly the same as the design model. Furthermore, the
connection pin and the model of RF Generator chip is not the standardized shape
which is all made by us. We are looking forward to finding it match well.
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V. Conclusion
Human body can be treated as a signal generator in some way, we can use the driver
as a signal transceiver, transfer physiological signals to another terminal via specific
communicating methods, where these signals can be processed, then user’s health
condition can be monitored easier, which could be very important for treatments of
chronic diseases.
The prototype we are building on is a small size portable device, which should no
big than a palm. The range of frequency can be adjusted, so user can receive multiple
signals from different SAW sensors with only one driver. Without this innovation,
monitoring multiple physiological signal can also be done yet, but no like this
convenient. For whole body health condition monitoring, a convenient design will be
a big breakthrough on medical treatment.
The frequency we choose is in a range of 2.1 ~ 2.3 GHz, this range is still meets
ISM standard. Because of the high frequency, the SAW sensor can be smaller than the
SAW sensors in 900MHz. Smaller sensor can be more convenient in use, even can be
implanted under the surface of skin, the SAW sensor – one kind of high-integrated
passive sensors which is no need for a power source, once the SAW sensor implanted
under the skin, there won’t need another surgery for recharging batteries of the sensor,
of which the extra expense and pain are eliminated.
The design we have now is still can be improved in the future.
We are using a Launchpad C2000 with a processor TMS320F2820X, the
Launchpad C2000 meets processing frequency requirement and it’s cheap. However,
there is no coaxial cable connector or connector port on board; it will be a little hard
to connect the Launchpad to PCB board which contains Radio Frequency generator
and other components. In the future, we can choose a better MCU board with proper
ports.
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In the design, there will be an antenna used for sending and receiving signals. But
we are not on that stage yet, so we are using a coaxial cable to connect the driver and
sensor. We hope that we can make more efforts on this to make the prototype to be the
same as our original design.
The adjustable frequency range now is still very limited, only a few SAW sensors
can be used to construct a personal area network around this driver in a same time.
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