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FINAL CDR G17

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					 Wireless MP3 FM Transmitter
Group 17
Anh Huynh
Kwitae Kim
Jung Suh

EEL 4915 Senior Design II
Dr. Richie
Spring 2003


                 *Self-sponsored Project
               Overview

Intro - Anh
Transmitter - Jung
Circuit Design - Kwitae
Prototype Design & Assembly – Anh
Circuit Testing - Kwitae
Summary - Anh
Introduction
Anh Huynh
               Project Description
 Wireless MP3 FM transmitter is a
  device that will enable MP3 audio
  playback through any FM stereo
  receiver.

 Device will transmit any MP3 audio
  output to any FM stereo located
  within the operating range.

 Allows the user to listen to MP3
  music through higher quality speakers
  vs standard computer speakers.
             Project Motivations

 Popularity of MP3 audio format
 Low cost
 Versatile
 Easy to use
 No programming needed
 Practical Use
 Stereo Output
 Portable Unit
              Project Objectives
 Variable transmitter frequency
 Reasonable user range
 FM stereo transmission
 Compact
 Light weight
 Wireless data transmission
 Low voltage & current consumption
 Reliable
 Durable
 User-friendly
               Design Approach

 Theory




Research    Re-evaluation




Analysis
               Failure                                  End Product



Prototype


              Success       Testing   Troubleshooting   Final Prototype
                 General Diagram


            3.5mm Stereo Cable               FM Transmission



MP3 Audio                        MP3 Tx                         Receiver
Source

                                                               Music

                                   User
                             (Enjoying the music)
                   Block Diagram

Audio Input   Pre-emphasis   MPX Modulator      FM Modulator



                               Buffer Amp        Carrier Osc



                             Freq. Multiplier     BA1404

                                RF Amp


                                Antenna            Receiver
             Reasons for FM Tx
Wireless FM link between the PC and home stereo
FM Tx allows:
  A flexible product
  Requires no line of sight by receiver
  Plug-n-Play, no software required
FM scheme:
  Popular method of audio transmission
  Inexpensive transmitters
  Compatible with existing technology
                        Features
 3.5mm stereo plug compatible with most audio devices (PC,
  Laptop, MP3 Stereo, Portable MP3 player)
 Easy to tune to your home or portable FM radio
 Listen to your favorite MP3 music in full-stereo sound
 Works with most MP3 players
 Operates using DC adapter or 9V Battery
 On/Off switch to conserve battery life
 Additional audio jack to connect to more audio outputs
 Clear case to view components & quality workmanship
                  Specifications
 Variable frequency range: 88 – 98 MHz
 Voltage Source: 9V DC adapter or Battery
 Battery life approximately 8 hrs
 Device dimensions: 6.5” x 5” x 2”
 Weight: Less than 1 lbs.
 Transmission Range: 30 m (unobstructed)
 Input Jack: 3.5mm stereo plug
 Construction cost < $100
                User Benefits
Eliminate need to buy costly computer speakers
Multipurpose use
Extends MP3 audio playback capabilities
Compatible with home stereos
Portable
MP3 playback in stereo sound
Compact space-saving design
                 How to Use

Easy, plug-and-play device
Turn on MP3 audio source, Tx, Rx
Connect audio source to transmitter using
 audio cable
Tune intended receiver to preset Tx frequency
Play audio source
Listen to music & enjoy
               FCC Compliant
According to
 Title 47 - Telecommunication
 Chapter I - Federal Communications Commission
 Part 15 - Radio Frequency Devices
 Subpart C - Intentional Radiators
 Section 15.239 - Operation in the band 88 - 108MHz

Yes, Transmitter is FCC Compliant
Transmitter (I/C)
     by Jung Suh
        Transmitter Chip Requirements
 Has to be stereo transmitter (stereo modulation)

 Appropriate in-built systems
  (Multiplexer, Filters, RF Amplifier, Crystal
 Oscillator)

 Easy interfacing with other components

 Cost issue
    Under $20 range
              Chip Comparison - 1
 BA1404                         MC2833
   Made by Rohm Corp.             Made by Motorola
   Stereo FM Transmitter          Stereo FM Transmitter
   Pro                            Pro
     requires low voltage           very low drain current
     requires few external          requires few external
      components                      components
   Con                            Con
     RF oscillator is little        high voltage required
      unstable (some times
      it drifted)
             Chip Comparison - 2
 NJM2035
   Made by New Japan
   Radio Corp.
   Stereo FM Transmitter
   Pro
     requires low voltage
     requires few external
      components
   Con
     Low voltage gain
                    Technical Comparison -1

Parameters                          BA1404                                            MC2833

                Symbol    Limits    Min   Typical   Max    Unit   Symbol    Limits    Min   Typical   Max    Unit




  Operating     Topr     -25/+75     -       -       -    °C      Topr     -30/+75     -       -       -    °C
   Temp.


   Storage       Tstg    -50/+125    -       -       -    °C       Tstg    -65/+150    -       -       -    °C
   Temp.


   Power         Vcc        -        -    1.25      2.0    V       Vcc        -              6.0      9.0    V
   Supply


  RF Output     VoRF        -       350   600        -    mVrms   VoRF        -       60     90        -    mVrms
   Voltage


 Input/Output    AV         -       30       37      -     dB      AV         -       27     30        -     dB
     Gain
                    Technical Comparison -2

Parameters                          NJM2035

                Symbol    Limits    Min   Typical   Max    Unit   Symbol   Limits   Min   Typical   Max    Unit




  Operating     Topr     -20/+75     -        -      -    °C      Topr       -       -      -        -    °C
   Temp.


   Storage       Tstg    -40/+125    -        -      -    °C       Tstg      -       -      -        -    °C
   Temp.


   Power         Vcc        -        -     2.0      3.6    V       Vcc       -       -      -        -     V
   Supply


  RF Output     VoRF        -       180   240        -    mVrms   VoRF       -       -      -        -    mVrms
   Voltage


 Input/Output    AV         -       16     20        -     dB      AV        -       -      -        -     dB
     Gain
           Why BA1404 (DIP18) ?
 Equipped with a constant voltage pin
 (variable capacitor that is used to finely adjust the FM
 frequency)

 Low required voltage

 Low power consumption

 More resources available

 Available in DIP18 packages
                      BA1404 Description

 The IC consists of a stereo modulator (creates stereo composite signals), an FM
  modulator (creates FM signals), and an RF amplifier.

 The stereo modulator develops composite signals made up of a MAIN (L+R)
  signal, a SUB (L_R) signal and a pilot (19 KHz) signal using 38 KHz crystal
  oscillators.

 The FM modulator has carriers on the FM broadcast band (88 - 98 MHz).

 The RF amplifier transmits the stereo encoded FM signals and is also a buffer
  for the FM modulator.

 The stereo transmitter is equipped with a constant voltage pin for a variable
  capacitor that is used to finely adjust the FM frequency.
              BA1404 Specifications
 A 38 KHz crystal derived stereo modulation (by crystal
  oscillator)

 Maximum Voltage: 3.8V

 Current Required: typically 3mA

 The transmission frequency is stable because it has a PLL
  Phase-Locked Loop)
BA1404 Specifications – pin out




          Reprint with permission from ROHM
                      Corporation
       BA1404 Specifications
        – pin out description
Pin No.   Pin Name            Description
   1      R-ch audio input    Connects to the pre-emphasis circuit
   2      Input amplifier     Connects to the bypass capacitor
          bypass
   3      GND                 Low frequencies
   4      38 KHz oscillator   Connects to bypass capacitor
          bypass
   5      38 KHz oscillator   Connects to 38 KHz crystal oscillators
   6      38 KHz OSC          Connects to load capacitor of crystal
                              osc.
   7      RF output           Connects to LC resonator
   8      GND                 High frequency
   9      RF oscillator       Connects to bypass capacitor
  10      RF oscillator       Connects to capacitor and LC resonator
  BA1404 Specifications
– pin out description (cont’)
 11   Voltage supply        Connects to variable capacitor

 12   Modulation signal     Connects to bypass capacitor and
         input                 modulated signal source

 13   Pilot signal output   Connects to RC mixer circuit

 14   Multiplexer signal    Connects to RC mixer circuit
         output

 15   Vcc                   Power supply

 16   Multiplexer           Connects to trimpot resistor
         modulator
         balance
 17   Multiplexer           Connects to trimpot resistor
         modulator
         balance
 18   L-ch audio input      Connects to pre-emphasis circuit
BA1404 Dimensions




                                   (Unit: mm)
    Reprint with permission from
        ROHM Corporation
        Chip Operation

 Stereo Modulator

 FM Modulator

Crystal oscillator

 RF oscillator
               Stereo Modulator
 The R-channel audio is input from pin 1 and the L-
 channel from pin 18.
 Each audio signal is amplified about 37 dB by
 independent amplifiers and output to the multiplexer.
 The 38 kHz crystal oscillator, connected between pin 5
 and pin 6, creates a 38 kHz subcarrier and a 19 kHz pilot
 signal.
 The audio signals and the 38 kHz subcarrier are balanced
 and modulated in the multiplexer.
 The L+R signal and the 38 kHz subcarrier are added to
 create the main carrier, which is output from pin 14.
               FM Modulator
 The composite signal is input from pin 12 to the
 base of the transistor.
 By changing the time constant of the tuning
 circuit in the oscillator, the frequency is
 modulated.
 The oscillation frequency is determined by the
 LC resonator .
 It is possible to change the oscillator frequency
 with DC voltage by using the stable output
 voltage on pin 11 and a variable capacitor
Stereo Modulator - Schematic




          Reprint with permission from
              ROHM Corporation
              Crystal Oscillator

 Use to generate the 38 KHz carrier signal.
 Start-up takes some time after the 38 KHz oscillator
 has been powered up.
 With a recommended load of 10 pF for the crystal
 oscillator, startup time approximately 1.5 sec.
 When the load is 33 pF, startup time is about 1 sec.
                 RF oscillator
 The built-in FM modulator can be operated in the 30~110
  MHz range.
 The RF oscillator frequency drift following power-up of the
  power supply becomes small when the Vcc is low.
 Frequency drift after 5 sec is as follows:

    Vcc (V)                 Drift (kHz)
    1.25                    85
    2                       85
    3                       130
                     Chip Noise

 If beats or noise are present on the output, and the input
 capacitors are in place, the noise may be due to the third or
 higher harmonics from the pilot signal and the subcarrier.

 In addition, high frequency signals are particularly large
 because of the pre-emphasis of high frequency signals.

 Therefore excessive input of 15 KHz frequencies or more
 should be limited before input to the IC.

 We can also connect 1000pF capacitors on pin 1 and 18 to
  ground to prevents the S/N ratio from deteriorating due to
  high frequencies.
Circuit Design
 by Kwitae Kim
              Power supply Design

 Input  9V Wall DC Adapter or 9V Battery

 Output  Regulated and Filtered 6V DC

 Use LED to indicate ON/OFF status

 On board adapter jack
               Design approach

 Often unwanted hum appears on the transmitted signal

 Power supply hum due to poor DC supply filtering

 Need to have almost zero-ripple at the output to prevent the
  “hum” which is caused by the 60 HZ AC line oscillation
                    Power Supply Schematic

                                                                                                        L2
                                                                   C945
                                                                                                        1mH
                                          R2                               R1
V1                                                  2N4124
                                          220ohm
9V
         2 D2       C2                                                    1kohm
                                  C1                                               C3      C6      R4
                                                                                                              C5     C7
     4      1            1000uF   0.1uF                                             1000uF 820pF   100kohm
                                                                                                              10nF   820pF
                                          C4
                                                             LED           D1
         3 1J4B42                          1000uF                          5.1 V
                  Maximum Ratings
              Q1 2N4124 Transistor Data

Symbol     Parameter                        Ratings       Units



VCEO       Collector-Emitter Voltage        25            V



VCBO       Collector-Base Voltage           30            V



VEBO       Emitter-Base Voltage             5             V



IC         Collector Current – Continuous   200           mA



TJ, Tstg   Operating and Storage Junction   -55 to +150   °C
           Temperature Range
                               Electrical Characteristics
                              Q1 2N4124 Transistor Data
Symbol      Parameter                              Test Condition       Minimum   Maximum   Units

BVCEO       Collector-Emitter Breakdown Voltage    IC =1.0mA, IB =0     25                  V



BVCBO       Collector-Base Breakdown Voltage       IC =10µA, IE =0      30                  V


BVEBO       Emitter-Base Breakdown Voltage         IC =10µA, IC =0      5                   V


ICBO        Collector Cut-off Current              VCB =20V, IE =0                50        nA


IEBO        Emitter Cut-off Current                VEB =3V, IC =0                 50        nA


hFE         DC Current Gain                        IC =2.0mA, VCE =1V   120       360
                                                   IC=50mA, VCE=1V      60
VCE (sat)   Collector-Emitter Saturation Voltage   IC =50mA, IB =5mA              0.3       V


VBE (sat)   Base-Emitter Saturation Voltage        IC =50mA, IB =5mA              0.95      V
          Transmitter Design

Pre-emphasis Filter
Crystal Oscillator
LC Resonator
RF amplifier
Antenna
BA1404 Application




     Reprint with permission pending from
              ROHM Corporation
  Basic Pre-emphasis filter




H   
                  R2
                R1
                           R2
         1  j * R1 * C1
         Pre Emphasis Filter

High-pass filter                                 C4
                                            C2
                                                             Pin1


Accentuate high            R4
                                            R6



 frequencies                     R5
                                      50%
                                                        C5




Improves SNR,
                    Audio




                                                 C3

 boosts treble                              C1
                                                             Pin18


                                            R3
                            R1

                                 R2                    C6
                                      50%
                             Output Amplifier &
                          Q3 SS9018 Transistor Data

                                         Symbol   Parameter     Ratings   Units


                                         VCBO     Collector-    30        V
                  Power
                                                  Base
                                                  Voltage
                                         VCEO     Collector-    15        V
                                                  Emitter
                  R2                              Voltage
                                         VEBO     Emitter-      5         V
                                                  Base
                               Antenna
                                                  Voltage
                          C2
                                         IC       Collector     50        mA
             R3                                   Current
RFout
                  9018                   PC       Collector     400       mW
        C1                                        Power
                                                  Dissipation
                                         TJ       Junction      150       °C
                                                  Temperature

                                         TSTG     Storage       -55~150   °C
                                                  Temperature
                                  Electrical Characteristics
                                   Q3 SS9018 Transistor
Symbol      Parameter                          Test Condition     Minimum   Type   Maximum   Units

BVCBO       Collector-Base Breakdown Voltage   IC =100µA, IE =0   30                         V



BVCEO       Collector-Emitter Breakdown        IC =1.0mA, IB =0   15                         V
            Voltage

BVEBO       Emitter-Base Breakdown Voltage     IE =100µA, IC =0   5                          V


ICBO        Collector Cut-off Current          VCB =12V, IE =0                     50        nA


hFE         Emitter Cut-off Current            VCE =5V, IC        28        100    198
                                               =1.0mA


VCE (sat)   Collector-Emitter Saturation       IC =10mA, IB                        0.5       V
            Voltage                            =1mA


Cob         Output Capacitance                 VCB =10V, IE =0              1.3    1.7       pF
                                               f=1MHz


fT          Current Gain Bandwidth Product     VCE =5V, IC        700       100              MHz
                                               =5mA
                           Transmitter Circuit
                                                                                                                                              Power
                                                                                                            R4
                                                                                                  C10
                                                   C12          D3               C11




                                            C19
                                                                                       C3
                                C18                             C1               C2
                         C15
                                                   R5                                       C8         L1
                                                               C7                                                 R6               R3
                         R12                        50%
                                       C16                            R1     R2
        R10

              R11
                   50%

Audio
                                                                                                            C20
                                                                     U1                                                                       Ant

                               C17                                                                                                      C23
                         C13
                                                                                                                             R13
                                                                                                                                   Q1
                         R9           C14
        R7                                    C9          C5                                     C21
              R8                                                                  C6
                                                                                                                       C22
                   50%
                                                                          Xtal




                                                                C4
   Antenna Characteristics
Wire antenna
  Low cost
  Variable length
  Widely available
  Easy to install
  Space saver
  Small loss
          Antenna Calculations

1/4 Wavelength
Example: 95MHz Frequency
λ (cm) = c / f
        = 3 x 10 ^10 (cm/s) / 95 x 10 ^ 6 Hz
        ≈ 315.79 cm

Antenna length should be 315.79 / 4 ≈ 78.95 cm
Max. Ant. length at 88MHz ≈ 85 cm
Will Use 85 cm Antenna
            Transmitter Power

Tx Pwr = 3V * 3mA
Tx Pwr = 9 mW
9mW ≈ 31m transmission distance
  Which meets requirements
                            Circuit Formulas
  DC Analysis                        AC Analysis
VB 
           R2
                   VCC              RIN(base)  β(RE 1  r' e)
         R1  R 2
                                     RIN  R 1 || R 2 || RIN(base)
VE  VB  0.7
                                     ROUT  (RC || r' c)
            VE
IE                   IC                        RC
       ( RE1  RE 2)                 AV 
                                             (RE 1  r' c)
VC  VCC  ( IC  RC )
                                             IC
                                      Ai       β
                                             IB
VCE  VC  VE
                  Additional Formulas
Parallel Resonant Circuit   Wire




                            Basic Pre-emphasis Filter




                              H   
                                                R2
                                              R1
                                                         R2
                                       1  j * R1 * C1
Prototype Design & Assembly
       By Anh Huynh
                      Components list
              Components                          Values
                R10, R7                            27K
                R12, R9                            62K
                   R4                              330
                 R3, R6                            270
                   R1                             4.7K
                   R2                             130K
                   R13                             10K
                R11, R8                     10K (Potentiometer)
                   R5                      100K (Potentiometer)
C3, C5, C13, C14, C15,C16, C20, C22, C23         0.001F
                  C2                                220pF
                  C6                                 24pF
               C7, C11                            0.0047F
                 C10                               0.01F
                  C8                                 33pF
               C4, C21                               15pF
                 C19                                390pF
           C1, C9, C17, C18                       10F/16V
                 C12                             470F/16V
                  L1                       Adjustable Inductor coil
                  Q1                       TO-92 Transistor (9018)
                  D3                                 2.7V
                  U1                               BA1404
Parts Used
       Initial Prototype

Top View
       Initial Prototype

Bottom View
Component Layout
              P-Cad Layout




RED = Top Layer     Green = Bottom Layer
            PCB Layout




Top Layer                Bottom Layer
             Final Prototype
 Top View
                Final Prototype
 Bottow View
              Final Prototype
 Side View
Circuit Testing
By Kwitae Kim
Input Voltage
INPUT LEFT-CHANNEL
INPUT RIGHT-CHANNEL
CARRIER SIGNAL
PILOT SIGNAL
MPX OUT
MPX W/ PILOT SIGNAL
OUTPUT SIGNAL
                              Testing Data

Parameters               Theoretical Values                   Tested Values
                Symbol       Average          Unit   Symbol     Average       Unit

Input Voltage                   9              V                  9.22         V


BA 1404                         3             mA                  1.98        mA
Current
Consumption

BA 1404          Vcc            3              V      Vcc         2.91         V
Voltage
             Complications

Weak signal of the receiver input
Variable inductor difficult to tune
Several components very sensitive to external
 interference
Excess noise on the transmitted signal
            Solution to Noise
Current Solutions Implemented
  Re-adjust the variable inductor
  Re-adjust the variable resistor
  Check proper voltage input
  Mount the components on a PCB

Additional Solution
  Shield components from external interference
Summary
  Anh
                              100




                                0
                               10
                               20
                               30
                               40
                               50
                               60
                               70
                               80
                               90
           Part acquisition




      Power Supply Design




      PCB Layout & Milling




            Circuit Design




Prototype & Case Assembly
                                                    Work Division




Presentation/Documentation
                                              Anh
                                       Jung
                              Kwitae
                                      Milestone
                               Oct Nov Dec   Jan Feb 1-15 Feb 16-28 Mar 1-15 Mar 15-31 Apr 1-16 17-Apr Apr 18-28
Research
Design
Parts Acquisition
Assembling Initial Prototype
PCB Design
PCB Milling
Assembling Final Prototype
Testing and Debugging
Presentation Preparation
Final Presentation
Final Document
      Current Progress

100

98                       Parts Acquired
                         Power Supply Design
96
                         Circuit Design
94                       Initial Prototype
                         PCB Layout & Milling
92
                         Testing & Analysis
90                       Final Prototype
                         Final Presentation
88
                         Final Documentation
86                       Overall Progress

84
                               Budget
Item                              Estimated cost   Actual cost

PC Board                          $5               $4

Integrated Circuit(BA1404)        $8               $7

Electronic Components              $55             $35
(Resistors, Capacitors, Inductors,
& etc.)
Stereo Jacks, plugs, Antenna      $15              $10

Miscellaneous                     $15              $20

Total                             $98              $86

Under Budget                                       $ 12
         Objectives Completed

Milled PCB
Assembled final prototype
Final prototype fully functional
Completed testing and analysis
Completed final presentation
Working on final documentation
              Final Words

Final prototype complete
Met or exceeded
 specifications
Fully operational
Works as intended
Please Stand By For A Brief
           Demo

				
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