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1 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 2 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 3 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. 4 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. 5 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. 6 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 7 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 8 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 9 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 10 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. 11 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. 12 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 13 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 14 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 15 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: 16 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 17 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 18 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. 19 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. 20 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. 21 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. 22 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: 23 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 24 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 25 better to make our products more perfect. We want to make our products in market in the future.