Download Automated Antenna Controller

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
Dr. Raymond Winton
Academic Advisor
Jacob Edwards
Computer Engineer
LCD Software
Frequency Counting
Motor Control Software
Sponsor
Ashley Stough
Electrical Engineer
Motor Control Hardware
Frequency Counting
Hardware
Outline
• Problem
• Solution
• Constraints
– Technical
– Practical
• Special Concerns
– Manufacturability
– Economics
•
•
•
•
System Overview
Subsystem Testing
System Testing
Goals
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 load
• Standing Wave Ratio (SWR)
– Ratio of power or impedance:
• Power reflected to source versus power transmitted
from source
• Load impedance against source impedance
Problems with Existing Controller
•
•
•
•
Operation is Time Consuming
Unit is Difficult to Operate
Meter is Difficult to Read Accurately
Inaccurately controlled
[2]
Solution
• Use microcontroller to allow more accurate
tuning
• Automate the tuning process to avoid user
error
• Utilize digital display to allow easier output
for user
Technical Constraints
Name
Constraint
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 controller
– Prevent electric shock
– Prevent burns from hot components
– Prevent RF burns
Economics: Manufacturing Cost
• Parts must already be in stock at MFJ
– Reduces number of parts ordered
– Limits design options
Visual System Overview
Testing
• Subsystem Testing
– SWR and Power Measurement
– Frequency Measurement
– Antenna Tuning Circuit
– Display
• System Testing
SWR and Power Measurement
SWR and Power Measurement
[6]
Power Measurements
Voltage from RF Coupler to ADC input
Power Measurements
Coupler Voltages Vs. Power Inputs
2.5
Voltage Reading
2
7MHz
1.5
10MHz
14MHz
18MHz
1
21MHz
24MHz
28MHz
0.5
0
100
90
80
70
60
50
40
Power Inputs
30
20
10
0
SWR Measurements
Frequency Measurement
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
• Fast
Tune and Slow Tune
•No feedback from Motor
•Tune Down the Antenna to the lower limit
PWM Input
H-Bridge Output
Display
• Frequency
•SWR
•Forward / Reflected Power
System Testing
• Testing with the Dummy Load
• Testing 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 SO239 style connector.
Yes
Forward and reflected power
must be measured and
displayed accurately to ± 1W.
Yes
Power supply must be the MFJ1312D AC adapter.
Yes
Design II Goals
•
•
•
•
•
Analog SWR/Power Meter
User Interface Buttons
Capacitor Limitation Sensing
PCB Design
Product Packaging
References
[1]http://www.mfjenterprises.com/Product.php?productid=MFJ1786.[Online]. Accessed: September 29, 2009.
[2]http://www.mfjenterprises.com/catalog/Pages_061-080.pdf [Online].
Accessed: September 27, 2009.
[3]MFJ Enterprises, INC., MFJ Super Hi-Q Loop Antenna: Model MFJ
1786/1788 Instruction Manual, 1997.
[4]http://media.digikey.com/photos/Microchip%20Tech%20Photos/pic1
8f2520-i%20sp.JPG. [Online]. Accessed: September 30, 2009.
[5] “PIC18F2420/2520/4420/4520 Datasheet”, 2008. Microchip
Technology Inc. pg 326.
[6]http://vk1od.net/transmissionline/VSWR/VSWRMeter.htm. Owen
Duffy 1995, 2006 [Online]. Accessed: October 6, 2009.
Questions?