Standing Wave Ratio Analyzer

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Standing Wave Ratio Analyzer
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Design Team Members

Team Leader Frank Castillo Email
fac1_at_ece.msstate.edu
Team Member Jose Pvillalta Email
jsp2_at_ece.msstate.edu
Team Member Joey Ford Email jaf1_at_ece.msstate.ed
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Design Team Advisors
Faculty Advisor Dr. John P. Donohoe Electrical
and Computer Engineering Professor
No Photo Available
Industrial Advisor Martin F. Jue President of
MFJ Enterprises Starkville, MS
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Task Assignments
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Abstract

• The team will design an inexpensive Standing
  Wave Ratio Analyzer that will measure the SWR of
  an antenna for any user defined frequency ranging
  from 1.8MHz 56 MHZ. It will also count the
  frequency of a connected signal source. These
  values will be displayed to the user through a
  LCD screen.

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What are Standing Waves?

• A standing wave occurs in regions containing
  electromagnetic waves traveling in opposite
  directions
• The interaction of these oppositely directed
  traveling waves sets up a standing wave pattern
• Standing Wave Forward Wave Reflected Wave
• Ratio of V(max) to V(min) of this Standing Wave
  is known as the Standing Wave Ratio

Forward Wave
Reflected Wave Standing Wave
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Problems with Current Models

• Cost
• Todays Models range from 160 up to 350
• Frequency Tuning Accuracy
• The tuning accuracy of todays models is good for
  smaller ranges but is limited when seeking a
  frequency in the upper frequency ranges.
• Size
• Current models are too large and heavy.

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Technical Design Constraints

• Oscillator Frequency Range
• 1.8MHz 56 MHz
• Frequency Counter Accuracy
• Accuracy to 0.1MHz
• SWR Meter Accuracy
• Accuracy to 0.1
• Voltage Regulation
• 9 15 volts produce 5 volts with 3 accuracy
• Oscillation Tuning Accuracy
• Accuracy to 0.1 MHz

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Oscillator Frequency Range

• Six Range Selections
• 1.8 3.6 MHz
• 3.6 7 MHz
• 7 14 MHz
• 14 21 MHz
• 21 28 MHz
• 28 56 MHz
• Achieve Full Range of
• 1.8 56 MHz while
• Maintaining Accuracy

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Oscillator Tuning Accuracy

• Six Frequency Ranges
• Dual Variable Capacitor
• Tuning
• Coarse Tuning Knob
• Fine tuning Knob

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Practical Design Constraints

• Cost
• 25
• Packaging
• 6 L x 4 W x 1.5 H and no more than 2 pounds
• Power Supply
• Uses 8, AA alkaline batteries or AC adapter
• Connections
• SO-239 coaxial antenna connection and BNC
  frequency counter connection
• Enclosure Rating
• NEMA 1 Enclosure

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Projected Cost
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Prototype Design Components

• Power Supply
• Voltage Regulated 5 volts
• Tuning Circuitry
• Adjusts frequency with variable capacitances
• Oscillator Circuit
• Converts DC into AC signal
• Bridge Circuit
• Measures SWR of antenna

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Prototype Design Components (cont.)

• Microcontroller
• Gathers Data and prepares to display to LCD
• LCD
• Displays SWR to user
• Displays SWR strength of signal to user
• Displays counted frequency and user adjusted
  frequency to user

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Software Interface Design(physical model)
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Block Diagram
Power
User Tuning
Antenna
External Signal
Oscillator
Bridge
Freq. Counter
PIC
LCD Screen
Bar-graph
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Oscillator Circuit
Stabilizes Oscillations at Higher Frequencies
2 VAC with 10 VDC offset
Changes High Impedance Signal to a Low Impedance
Signal
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Oscillator Simulation

• Simulated Oscillator at 5MHz
• Input 2 VAC at 10 VDC offset
• Expected Signal of 2 Volts Oscillating at 5MHz

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Bridge Circuit
Antenna Connection
Differential Voltage
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Bridge Simulation Data

• Measured Differential Voltage Across Bridge
• Different Resistances from short to open circuit

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PIC Characteristics and Pin-out

• Operating Speed of
• DC 20MHz
• Power Saving Sleep Mode
• Low Cost
• Power ON Reset
• Watchdog Timer with its own on-chip RC Oscillator
  for Reliable Operation

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Software

• Count Frequency of Connected Signal
• Supply Pulse Signal to be used by Oscillator
• Prepare Data for LCD
• SWR signal from bridge will be prepared for the
  LCD
• Frequency Measurements from oscillator will be
  prepared for the LCD
• Strength of signal to be produced from SWR
  measurements to be used in the bar-graph

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Hardware Testing

• Voltage Amplitude
• Amplitude across the load must be equal to 1 V
• Voltage Regulation
• Tests ranging from 9v 15 volts
• Frequency Range
• Testing involves testing oscillator output with
  all capacitor adjustments made to circuit
• SWR Measurements
• Tests the bridge for functionality and range
• LCD
• Test LCD for functionality

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Software Testing

• Test frequency Counter for Accuracy
• Test for output to LCD when antenna is connected
• Test for output to LCD when frequency signal is
  connected
• Test SWR bar-graph strength of signal reading

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Summary

• New frequency tuning design will allow for
  easier, faster more accurate adjusting.
• Improved overall accuracy of the SWR analyzer
• Easy read strength of signal bar-graph
• Smaller and Lighter Packaging
• The new model will be less expensive than current
  models.

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Acknowledgements

• Special thanks to the following people
• Mr. Martin F. Jue, president of MFJ Enterprises
• Dr. J. Patrick Donohoe, faculty advisor
• Dr. Picone
• Jordan Goulder

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Questions

• ?