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

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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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