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PROJECT REPORT
2.1/2.4 GHz Passive SAW Sensor Driver
EENG-491 Senior Design Project
Advisor:
Dr. Tao Zhang
Dr. Michael Colef
TEAM MEMBER:
YIN XU
SAIDE ZHU
LENING WANG
May 15 2014
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2.1/2.4 GH Z PASSIVE SAW SENSOR DRIVER ......................................................... 1
EXECUTIVE SUMMARY .................................................................................................................... 3
I. INTRODUCTION ............................................................................................................................. 4
II. PREPARATION ............................................................................................................................... 5
Division of Work .................................................................................................................................................................... 5
Schedule ..................................................................................................................................................................................... 6
Cost............................................................................................................................................................................................... 7
III. SYSTEM DESIGN .......................................................................................................................... 7
Sensor ......................................................................................................................................................................................... 7
Design Architecture.............................................................................................................................................................. 8
IV. COMPONENTS ............................................................................................................................... 9
RF Generator: MAX2752EUA+ ........................................................................................................................................ 9
Power Amplifier: SKY65028-70LF............................................................................................................................. 11
Circulator: SFC2040A ....................................................................................................................................................... 12
Low Noise Amplifier: SKY65080-70LF .................................................................................................................... 13
SAW Sensor ........................................................................................................................................................................... 14
V. HARDWARE DEVELOPING: ......................................................................................................15
PCB Design: ........................................................................................................................................................................... 15
Process of design(2.1 GHz): .......................................................................................................................................... 16
Sending Part: ........................................................................................................................................................... 17
Receiving Part:........................................................................................................................................................ 18
Switch Between 2.1 GHz and 2.4 GHz....................................................................................................................... 20
The RF generator .................................................................................................................................................. 20
The Power Amplifier ........................................................................................................................................... 20
VI. RESULTS .......................................................................................................................................22
Products .................................................................................................................................................................................. 22
Testing data:.......................................................................................................................................................................... 23
Future developing: ............................................................................................................................................................. 24
VII. CONCLUSION: ............................................................................................................................24
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Executive Summary
A wireless sensor may be the key to cope with the booming demand for convenience
and humanity of patients and nurses/doctors. The integration of these technologies
with medical sensors could be a great improvement over currently used wired sensors.
The surface acoustic sensor transduces an input electrical signal into a mechanical
wave, which unlike an electrical signal, can be easily influenced by physical
phenomena. The device then transduces this wave back into an electrical signal.
Changes in amplitude, phase, frequency, or time-delay between the input and output
electrical signals can be used to measure the presence of the desired phenomenon.
At the time SAW sensor is working, 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 body 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 light back. It will points out the abnormal conditions if the state of human
body is out of a normal range.
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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.
A wireless sensor may be the key to cope with the booming demand for
convenience and humanity of patients and nurses/doctors. The integration of these
technologies with medical sensors could be a great improvement over currently used
wired sensors. The device then transduces this wave back into an electrical signal.
Changes in amplitude, phase, frequency, or time-delay between the input and output
electrical signals can be used to measure the presence of the desired phenomenon.
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
short for Surface Acoustic Wave. The advantages of using a SAW sensor are that they
are small in size and also there is no need for a common power supply.
When a SAW sensor is working, the reader sends a pulse at a specific frequency.
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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. When light is pointed onto a mirror, it will then reflect a light back. It will
points out the abnormal conditions if the state of human body is out of a normal
range.
II. Preparation
Division of Work
Lening Wang(Group Leader) is responsible for researching, schematics and PCB
design, assembling, testing, writing and presentation.
Yin Xu is responsible for researching, system design and check, assembling, testing,
writing and presentation.
Saide Zhu is responsible for researching, components check and order, assembling,
testing, writing and presentation.
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Schedule
Fall 2013
Setup our project; Study the fundamental knowledge of PCB
design
Spring 2014
Week 1-3
Check the availability of all the components
Week 4
Study the software of PCB design and set up the final solution for
our project
Week 5-6
Design the schematics of our PCB boards
Week 7-8
Finish the first version of our PCB boards
Week 10-12
Check and correct all the mistakes; approved by our advisor
Week 13
Re-check all the components and send our design to the
manufactory
Week 14-15
Write papers and prepare for the presentation
Week 16-17
Get the PCB boards; assembling and test; final presentation
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Cost
figure1 cost
III. System Design
Sensor
Today, SAW sensor components are implemented in almost every color TV set, in
personal mobile communication systems, in RF remote control systems, etc.
And our design is for medical use. These sensors what we use can be easily placed on
the surface of the skin or implanted under the skin in various parts of the body. These
sensors are passive, which means they do not power supply, so it can continuously
monitor a patient’s vital signs or any other physiological phenomena without using a
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battery.
When a SAW sensor is installed, the reader sends a pulse at a 2.1/2.4 GHz 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.
So, as we known, when the physical conditions are abnormal, for example, our body
temperature increase, it will cause a different pulse and a different time delay. Our
drive will quickly evaluate the date it receives and tell us if the patient’s condition is
in a normal range.
Design Architecture
figure2 Block Diagram
Our design is actually divided into three parts. All these left part we can call it Radio
interrogation, it does the job of requesting, responding and evaluation. Radio
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interrogation (or sensor readout) summarizes RF request, RF response, its reception
and evaluation of measured, the circulator is the communication part, it works as
transmit / receive switcher. And the last part is the sensor. It can detect the condition
of patient.
IV. Components
RF Generator: MAX2752EUA+
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.

Guaranteed Frequency Tuning Range: 2.025GHz ~ 2.165GHz (Zero IF)

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
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figure3 the circuit of Radio Frequency (RF) Generator chip
Description:
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.
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.
The tuning input is typically connected to the output of the PLL loop filter. The
loop filter provides an appropriately low-impedance source. Any excess noise on the
tuning input is directly translated into FM noise, which can degrade the phase-noise
performance of the oscillator.
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Power Amplifier: SKY65028-70LF
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 signalto 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.

Operating Frequency: 250 MHz to 2.7 GHz

Operating Supply Voltage: 5 V

Supply Current: 125 mA

High gain: 20 dB
Description
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.
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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
Circulator: SFC2040A
The circulator transmits an RF signal and switches to receive mode then. After a delay
time, the convolution of the radio request signal and the reflective SAW device's RF
response (burst response, if a burst was transmitted), carrying the information about
the measured, and send it to the evaluation unit.

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
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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.
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.
Low Noise Amplifier: SKY65080-70LF
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.

Operating Frequency: 1.5 GHz to 2.5 GHz

Operating Supply Voltage: 5 V

Supply Current: 75 mA

Low Noise Figure:
2.3 dB
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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.
figure4 the Circuit Used in Low Noise Amplifier Chip
SAW Sensor

For BTS Power Amplifier applications

Operating Frequency: 2140MHz

Usable bandwidth of 100 MHz

Absolute delay of 450ns
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
Low group delay variation

Ceramic Surface Mount Package (SMP)

Hermetic
V. Hardware developing:
PCB Design:
We want to develop our PCB design to reduce the cost of our products. PCB boards
with irregular shapes may cause the high cost of producing. We want to find a better
way to design our PCB boards. Which can make our PCB boards more cheap and
efficiency.
We are going to use two pieces of PCB boards to realize our function to avoid
interference since it is high frequency RF circuits. One of them is to generate and
send signals. The other one is designed to receive signals. Both of the two boards are
connected to the two pins of circulator, whose third pin is connected to Antenna.
The simple schematic is shown here:
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figure5 simple block diagram
Process of design(2.1 GHz):
Before drawing our PCB board, we need to do some preparation because there are no
components in the library of ExpressPCB. We have to draw our own components
using the datasheet of those components.
Here is one of our designed components:
figure 6 RF generator
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Sending Part:
RF generator and Amplifier are put in the sending part of PCB board. RF generator
generates signals that are about 2.1GHz.
The amplified signals are transferred to antenna through the circulator. Then antenna
will send signals to SAW sensor.
figure7 schematic of sending board
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figure8 PCB for sending part
There are 4 pins on the left. The first pin is connected to the ground. RF generator and
amplifier share the 5 volts voltage through the second pin. The third pin is the
connector than can shut down the RF generator. The last pin is the connector where
the voltage is put in. The pin on the right is the output that should be connected to the
circulator.
We decided to use the two layer boards because it can save spaces. Also, we use the
whole bottom layer as the ground layer to reduce the interferences.
Receiving Part:
Amplifier and Low-pass filter are in the receiving part of PCB board. The received
signals will go through the low-pass filter first to remove some noises. Then the
amplifier will amplify the signals. Amplified signals will be sent to be processed.
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figure9 schematic of receiving board
figure10 PCB for receiving part
There are 3 pins on the left. The first pin is connected to 5 volts voltage. The second
pin is the input connected to the circulator. The last pin is connected to the ground.
The pin on the right is the output.
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Switch Between 2.1 GHz and 2.4 GHz
Our PCB boards can be used for both 2.1 GHz and 2.4 GHz SAW sensor drivers. The
only difference is just we need to replace some of the components.
The RF generator
We should change the RF generator from MAX2752EUA+ to MAX2750EUA+. Both
of them work under the same environment but MAX2750EUA+ produces the 2.4
GHz signals while MAX2752EUA+ produces the 2.1 GHz signals.
figure 10 datasheet of RF generator
The Power Amplifier
We do not need to change the power amplifier because its work range covers from 2.1
GHz to 2.4 GHz, the only difference is to replace or drop some components.
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figure 11 datasheet of power amplifier
From the tablet above, we only need to change the value of M1, M2, M5 and M6.
Also, we need to drop M3 and M4 to make our driver work under 2.4 GHz.
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VI. Results
Products
We have assembled two boards, one for the sending part and another for receiving
part.
Here is the pictures of two boards(before being assembled).
Here is the pictures of two boards(after being assembled).
After they connected:
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Testing data:
We have tested both the sending part and receiving part separately. If we do not
connect the sending part, there is no signal being detected. If we connect both the
sending part and receiving part, signals could be detected. This means both the
sending part and receiving part can work.
This is the output from the receiving board, a time-delay could be found in the
picture.
figure 12 output
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Future developing:
We already have our SAW sensor drivers but the products still could be improved.
Our SAW sensor can just be used as testing purpose. The SAW sensor can give an
output which is an 450ns delay to the input. It is very hard to find a high-frequency
SAW sensor. Maybe in the future, we can find a specific SAW sensor which we can
see the difference between input and output more clearly. Also, if we are able to make
the signals more stable, it will be better.
VII. 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 frequency we choose is in a range of 2.1 ~ 2.4 GHz, this range is still
meets ISM standard. Because of the high frequency, the SAW sensor can be
smaller. 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.
We are doing to made a very small driver which will be very convenient of using.
Actually, we have already made the model of our products, however, we can still do
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better to make our products more perfect. We want to make our products in market in
the future.