Cell Phone Controlled House Automation by XXK7mr


									                                                                            Keshav Bansal
                                                                                Tyler Rossi
                                                                              Daniel Hvala
                                                                           Project Proposal
                                                                               Feb. 7, 2007

                      Near-Field Communications
I.     Introduction

        Near Field Communication Technology or NFC is a short-range wireless
technology similar to the famous Bluetooth technology. It can be used for short range
transfer of information. As the demands for new and improved wireless communication
technologies are increasing, NFC provides unique advantages over other available
wireless technologies. In this project we will design a near-field transmitter and receiver
ands try to send data from one computer to another.

           Due to the rapid spatial decay of the field strength the system offers
              unique advantages of frequency reuse and less adjacent channel
              interference. Therefore, multiple devices in a small area can communicate
              with each other using the same transmitters and receivers.
           The receiver can be either active or passive. In passive mode it derives its
              operating power from the electromagnetic field generated by the
              transmitter. In this way the information can be sent to the places where it
              is hard to power the devices, such as within human body.


              The system will operate at a frequency of 13.56 MHz.
              The bit rate of up to 424 kbps is possible in this design.
              The operating distance can be up to 1 meter.
              No special software needs to be installed on either of the two computers to
               send data from one to the other.
              The same frequency can be used and tunable transmitters and receivers are
               not required.
              It can be used implement any task that can be performed by Bluetooth.
II. Design:

              Figure 1.1 Block Diagram of Communication System

                                                      Local                          Loop

                Digital to
 Digital        Analogue           Low Pass Filter
 Data In                                             Mixer
                                                                  Power Amplifier

                      Figure 1.2 Block diagram of Transmitter
           Loop                                                Local

                                                                                             Analogue to Digital
                         Band Pass                                         Low Pass Filter
                                                                                                 Converter         Digital
   Low Noise Amplifier                  Low Noise Amplifier

                                     Figure 1.3 Block Diagram of Receiver

Block Description

1). Transmitter: The function of the transmitter is to convert the digital signal received
from the computer into an analog message signal, modulate a carrier signal with this
message signal, and transmit the modulated signal to the receiver using the antenna.

        Digital to Analog Converter (D/A): The digital data from the computer can be
         converted into an analog message signal using and a digital to analog converter.
        Low-Pass Filter (LPF): The low-pass filters out the message signal making it a
         finite bandwidth signal.
        Local Oscillator: It generates the carrier signal with desired carrier frequency.
        Mixer: Modulates the carrier signal produced by oscillator with the message
        Power Amplifier: Amplifies the modulated signal to increase its power before
         wireless transfer of the modulated carrier.
        Loop Antenna: Since our communication system used near-field RF coupling, a
         loop antenna will be used for transmission of the wireless signal.

2). Receiver: The functions of the receiver are to catch the signal sent from the
transmitter, demodulate this signal to get the required message signal, convert this analog
message signal into a digital signal, and send the digital signal to the PC.

        Loop Antenna: A loop antenna similar to one used in the transmitter will be
         used to receive the transmitted signal.
        Low Noise Amplifier (LNA): This component amplifies the received signal
         while keeping the noise in the signal fairly low. The amplification of the received
         signal is necessary as the signal has very low voltage amplitude.
        Band Pass Filter (BPF): The band pass filter attenuates the noise signals picked
         up by the antenna, without affecting the desired signal sent by the transmitter.
       Local Oscillator: This component is similar to one used in the transmitter. It
        produces the carrier signal which is required to demodulate the received signal.
       Mixer and Low Pass Filter (LPF): Demodulates the received signal by
        multiplying it with the locally generated carrier and then low-passing the output to
        get the original message signal.
       Analog to Digital Converter (A/D): Converts the analog message signal into a
        digital signal that can be read by a computer.

    PC Interface: The transmitter and the receiver can be connected to the PC through its
    serial port. Either a different circuit need to be designed to connect transmitter and
    receiver to the serial port or to keep things simple we can use already available line
    drivers and receivers. MAX232A can be easily used for this purpose.

Performance Requirements

       Communication range of at least 1 meter
       Bit rate of at least 212 kbps

III. Verification

Testing Procedures

The transmitter and the receiver can be easily divided into different modules. Some of the
modules will brought directly from the store (e.g. A/D converter, D/A converter), while
others would be designed (e.g. Local Oscillator, Mixer, Filters, Amplifiers). The best way
to test our project will be to first test each individual part separately. Therefore, oscillator
will be tested if it can oscillate at required frequency, filters will be tested if they have
right center frequency and bandwidth, the A/D and D/A converters will be tested to see if
they sample and reconstruct data at the required speed etc. After making sure that each
module works by itself, we will try connecting two modules together and see if they give
the expected output. This procedure will be continued until all the modules are connected

Tolerance Analysis

The carrier frequency is an important variable that can have a large effect on the
performance of the design. The antennas and the communication channel will react
differently to different carrier frequencies. We will be using a carrier frequency of 13.56
MHz. The oscillators used in the transmitter and receiver may vary slightly on the order
of 1%.
The orientation of the antennas is another important factor that will affect design
performance. The antenna can be coupled in several different ways and the radius of the
loop is variable.

We will attempt to operate the entire system at 9V + .5V. This way the system can be
operated off of a standard 9V battery.

IV. Cost and Schedule

Cost Analysis


   ($50/hour)(150 hours)(3 people)(2.5) = $56,250

         Part                              Cost     Quantity   Total
         Local Oscillator                  $15      5          $75
         Low Noise Amplifier               $5       5          $25
         Power Amplifier                   $5       3          $15
         D/A Converter                     $5       3          $15
         A/D Converter                     $5       3          $15
         Low Pass and Band Pass Filters    $5       8          $40
         Mixer                             $10      6          $60
         MAX232A                           $5.00    4          $20
         Passive Components (capacitors,   $0.10    100        $10
         resistors, diodes, etc.)
         Serial Port Connecter             $3       4          $12
         Circuit Boards                    $4.00    2          $8
         Bread Board                       $10      2          $20
         Copper Wire                       $4       1          $4

         Total:                                                $319

Total Project Cost = $56,250 + $319 = $56,569

Keshav-Oscillators and mixers
Dan-Filters and computer interface
All-Antennas, A/D and D/A converters

Task                                                     Target
Background research on system requirements               02/12/2007

All - P-Spice calculations for all individual modules     02/19/2007
and have the circuit diagrams mapped out and buy all
the necessary components.
Test A/D and D/A converters, build loop antennas
Test antenna range
Make sure design meets FCC regulations
Keshav – Check if oscillator works at desired             02/26/2007
frequency and see if mixer gives the expected output.
Tyler – check the power levels on the amplifiers
Dan – Test the filters by sending a signal and see how
the signal is affected
All – start putting together individual models for the 03/05/2007
transmitter on a breadboard and make necessary
Then design PCB for final transmitter circuit
Have working transmitter, agree on receiver               03/12/2007
modulation to be used and start working on individual
receiver modules.
Try to synchronize the transmitter and the serial port of
the computer
Spring Break (work individually on modules)               03/19/2007

Have initial construction of transmitter and receiver    03/26/2007
completed and see how the system performs.
Mock-up Demos
Have transmitter and receiver working and see how the 04/02/2007
signal is modified during transmission.
Initial testing attempt to optimize operation parameters 04/09/2007
Test and troubleshoot bugs                               04/16/2007
Presentations                                            04/23/2007
Check out and final papers due                           04/30/2007

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