PROJECT REPORT

2.1/2.4 GHz Passive SAW Sensor Driver

EENG-491 Senior Design Project

Advisor:

Dr. Tao Zhang

Dr. Michael Colef

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TEAM MEMBER:

YIN XU

SAIDE ZHU

LENING WANG

May 15 2014

2.1/2.4 GHZ PASSIVE SAW SENSOR DRIVER .........................................................1

EXECUTIVE SUMMARY....................................................................................................................3

I. INTRODUCTION............................................................................................................................ 4

II. PREPARATION.............................................................................................................................. 5Division of Work................................................................................................................................................................ 5

Schedule................................................................................................................................................................................ 6

Cost..........................................................................................................................................................................................7

III. SYSTEM DESIGN......................................................................................................................... 7Sensor.....................................................................................................................................................................................7

Design Architecture..........................................................................................................................................................8

IV. COMPONENTS.............................................................................................................................. 9RF Generator: MAX2752EUA+.....................................................................................................................................9

Power Amplifier: SKY65028-70LF..........................................................................................................................11

Circulator: SFC2040A....................................................................................................................................................12

Low Noise Amplifier: SKY65080-70LF.................................................................................................................13

SAW Sensor....................................................................................................................................................................... 14

V. HARDWARE DEVELOPING:.....................................................................................................15PCB 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

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The RF generator...............................................................................................................................................20

The Power Amplifier........................................................................................................................................20

VI. RESULTS...................................................................................................................................... 22Products..............................................................................................................................................................................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.

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When a 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 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

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figure2 Block Diagram

monitor a patient’s vital signs or any other physiological phenomena without using a

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

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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

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

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performance of the oscillator.

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

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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

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

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figure4 the Circuit Used in Low Noise Amplifier Chip

Operating Supply Voltage: 5 V

Supply Current: 75 mA

Low Noise Figure: 2.3 dB

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.

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SAW Sensor

For BTS Power Amplifier applications

Operating Frequency: 2140MHz

Usable bandwidth of 100 MHz

Absolute delay of 450ns

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.

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The simple schematic is shown here:

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:

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figure 6 RF generator

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.

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figure 12 output

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

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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

better to make our products more perfect. We want to make our products in market in

the future.

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