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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
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 .......................... 14
IV. Practical Integration ......................................................................................... 16
V. Conclusion ......................................................................................................... 18
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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 ........................................................................... 11
FIGURE 8
THE DIMENSIONAL DRAWING OF CIRCULATOR ......................................................... 12
FIGURE 9
THE CIRCUIT USED IN LOW NOISE AMPLIFIER CHIP ................................................... 13
FIGURE 10
THE PCB OF LOW NOISE AMPLIFIER .................................................................... 13
FIGURE 11
THE ACTURAL CHIP OF LAUCHPAD WHICH STANDS FOR MICRO-CONTROLLER ............... 14
FIGURE 12
THE MODEL OF LAUNCHPAD WITH 40 PINS AND EXTRA VCC AND GND OUTPUT ......... 15
FIGURE 13 THE INTEGRATED PCBS OF POWER AMPLIFIER WITH LOW-NOISE AMPLIFIER (LEFT)
AND RF GENERATOR WITH POWER AMPLIFIER (RIGHT). ..................................................... 16
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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.
~3~
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 nearfield 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 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.
~4~
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 microcontroller via power attenuator, low-noise amplifier, and power amplifier. The
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.
~5~
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
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.
~6~
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)

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
~7~
Detailed Description
Figure 2 the circuit of Radio Frequency (RF) Generator chip

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 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
~8~
Figure 3 Characteristic Curve of Port TUNING
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.
Figure 4
the PCB of RF Generator
B. Power Amplifier: SKY65028-70LF
Features
 Wideband frequency range: 250–2700MHz
 Highlinearity:OIP3>40dBmandP1dB>24dBm
 High efficiency: PAE48%
 High gain: 20dB
 Single DC supply, 3Vor5V
Description
Skyworks SKY65028-70LF is a high
performance,
ultra-wideband
linear
amplifier with superior output power,
linearity, and efficiency. The device is
Figure 5
fabricated using Skyworks high reliability
~9~
the Characteristic Curve of Adjacent Channel
Leakage Ratio.
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 TransEuropean Trunked Radio (TETRA) transceivers, multi-band (GSM, AMPS, PCS, DCS)
handsets, and many other wireless applications
Figure 6
the Circuit of Power Amplifier
~ 10 ~
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.
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.
Figure 7
C. Circulator: SFC2040A
Features
 FREQUENCY: 2-4 GHZ
 IMPEDANCE: 50 OHMS
~ 11 ~
the PCB of Power Amplifier
 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 threeport 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
Figure 8
the Dimensional Drawing of Circulator
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.
E. Low Noise Amplifier: SKY65080-70LF
Features
 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
~ 12 ~
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.
Figure 9
the Circuit Used in Low Noise Amplifier Chip
PCB
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
Figure 10
~ 13 ~
the PCB of Low Noise Amplifier
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 LaunchPad
Features
 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
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.
~ 14 ~
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.
Figure 12

the Model of LaunchPad with 40 Pins and Extra Vcc and GND Output
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
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.
~ 15 ~
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.
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 LowNoise 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.
~ 16 ~
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.
~ 17 ~
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.
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
~ 18 ~
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.
~ 19 ~