Date

12-2011

Degree Name

BS in Electrical Engineering

Department

Electrical Engineering Department

Advisor

Dean Arakaki

Abstract

Radio transmitters and antennas have differing impedances at the output and feedpoint, depending on frequency. Modern antenna tuning methods involve manual or automatic resistance and reactance network adjustment to match transmitter and antenna impedance. This reduces power reflections to the transmitter, but introduces losses and prevents full transmitter power from being radiated at the antenna. This project utilizes a variable length antenna element to tune and match transmitter and antenna impedances, allowing efficient power transfer to the antenna. The antenna length varies from 0 to 30.5 inches. The method involves an RF signal with a maximum power of 2 watts and a standing wave ratio (SWR) analyzer for measuring reflections. An Atmega32 is used to analyze SWR analyzer data and control the motor driver and liquid crystal display (LCD). The motor driver controls antenna extension and retraction. The LCD displays the SWR reading. The tuning process is an automated easy-to-use system for radio operators.