Automated Antenna Controller

Our Team Sam Bryan – Team Leader Electrical Engineer LCD Hardware LCD Software Power Calculations Brandon Gray Electrical Engineer Hardware Prototyping Frequency Counting RF Coupler Jacob Edwards Computer Engineer LCD Software Frequency Counting Motor Control Software Ashley Stough Electrical Engineer Motor Control Hardware Frequency Counting Hardware Dr. Raymond Winton Academic Advisor Sponsor

Outline ProblemProblem SolutionSolution ConstraintsConstraints –Technical –Practical Special ConcernsSpecial Concerns –Manufacturability –Economics System OverviewSystem Overview Subsystem TestingSubsystem Testing System TestingSystem Testing GoalsGoals

What is the Automated Antenna Controller? –Microprocessor controlled version of MFJ Enterprises, Inc.’s user-managed loop antenna controller –Used with MFJ-1786 and MFJ-1788 Super Hi-Q Loop Antennas [1]

What is the Automated Antenna Controller? (cont’d) Unit controls a motor attached to a variable plate capacitor which adds capacitance to the impedance of the loadUnit controls a motor attached to a variable plate capacitor which adds capacitance to the impedance of the load Standing Wave Ratio (SWR)Standing Wave Ratio (SWR) –Ratio of power or impedance: Power reflected to source versus power transmitted from sourcePower reflected to source versus power transmitted from source Load impedance against source impedanceLoad impedance against source impedance

Problems with Existing Controller Operation is Time ConsumingOperation is Time Consuming Unit is Difficult to OperateUnit is Difficult to Operate Meter is Difficult to Read AccuratelyMeter is Difficult to Read Accurately Inaccurately controlledInaccurately controlled [2]

Solution Use microcontroller to allow more accurate tuningUse microcontroller to allow more accurate tuning Automate the tuning process to avoid user errorAutomate the tuning process to avoid user error Utilize digital display to allow easier output for userUtilize digital display to allow easier output for user

Technical Constraints NameConstraint Frequency Frequency must measure and display between 7 and 30MHz ± 30kHz. Standing Wave Ratio A maximum of 3:1 SWR must be achieved. Connector RF connection must be an SO-239 style connector. RF Power Forward and reflected power must be measured and displayed accurately to ± 1W. Power Supply Power supply must be the MFJ-1312D AC adapter.

Health and Safety Enclose the controllerEnclose the controller –Prevent electric shock –Prevent burns from hot components –Prevent RF burns

Economics: Manufacturing Cost Parts must already be in stock at MFJParts must already be in stock at MFJ –Reduces number of parts ordered –Limits design options

Visual System Overview

Testing Subsystem TestingSubsystem Testing –SWR and Power Measurement –Frequency Measurement –Antenna Tuning Circuit –Display System TestingSystem Testing

SWR and Power Measurement

[6]

Power Measurements Voltage from RF Coupler to ADC input

Power Measurements

SWR Measurements

Frequency Measurement

D Flip-Flop Input D Flip-Flop Output D Flip-Flop Input/128 = D Flip-Flop Output

Antenna Tuning Circuit H-Bridge Variable Capacitor

Antenna Tuning Circuit PWM Input H-Bridge Output Fast Tune and Slow Tune No feedback from MotorNo feedback from Motor Tune Down the Antenna to the lower limitTune Down the Antenna to the lower limit

Display Frequency SWRSWR Forward / Reflected PowerForward / Reflected Power

System Testing Testing with the Dummy LoadTesting with the Dummy Load Testing with the Loop AntennaTesting with the Loop Antenna

Prototype Performance Technical Constraint Constraint Met Frequency must measure and display between 7 and 30MHz ± 30kHz. Yes A maximum of 3:1 SWR must be achieved. Yes RF connection must be an SO- 239 style connector. Yes Forward and reflected power must be measured and displayed accurately to ± 1W. Yes Power supply must be the MFJ- 1312D AC adapter. Yes

Design II Goals Analog SWR/Power MeterAnalog SWR/Power Meter User Interface ButtonsUser Interface Buttons Capacitor Limitation SensingCapacitor Limitation Sensing PCB DesignPCB Design Product PackagingProduct Packaging

References [1] [Online]. Accessed: September 29, [2] [Online]. Accessed: September 27, [3]MFJ Enterprises, INC., MFJ Super Hi-Q Loop Antenna: Model MFJ 1786/1788 Instruction Manual, [4] 8f2520-i%20sp.JPG. [Online]. Accessed: September 30, [5] “PIC18F2420/2520/4420/4520 Datasheet”, Microchip Technology Inc. pg 326. [6] Owen Duffy 1995, 2006[Online]. Accessed: October 6, [6] Owen Duffy 1995, 2006 [Online]. Accessed: October 6, 2009.

Questions?