Antenna Systems & Technology - Spring 2014 - (Page 14)

FEATURE ARTICLE Recent Progress on Plasma Antennas Dr. Theodore Anderson - Haleakala Research and Development, Inc. During the past two years, much progress has been made on plasma antennas. Co-site and parasitic interference has been shown to be greatly reduced or eliminated using plasma antennas. High frequency plasma antennas have been shown to transmit and receive through low frequency plasma antennas. VSWR has been shown to be reconfigurable and can be reconfigured to give excellent matching. Smart plasma antennas have been developed and built which steer the antenna beam 360° in the azimuthal direction and 180° in the vertical direction. New pulsing techniques have been developed to significantly lower the energy requirements of the plasma antenna and this continues to lower the energy requirements. New numerical techniques have been developed to solve plasma antenna problems theoretically. Plasma antennas have more degrees of freedom then metal antennas making their applications have enormous possibilities. Plasma antennas use partially or fully ionized gas as the conducting medium instead of metal to create an antenna. Haleakala Research and Development, Inc. has built and tested plasma antennas from 30 MHz to 50 GHz. At the higher frequencies, plasma antennas have lower thermal noise than metal antennas and the thermal noise of plasma antennas decreases with the operating frequency of the plasma antenna making them ideal for satellite antennas. Plasma satellite antennas can be made conformal with a surface and give the performance of a parabolic dish antenna. This is true because beam steering and focusing can be done by varying the plasma density from one tube of plasma compared to the next. With this design, plasma satellite antennas can be operated in the reflective or refractive mode. High powered plasma antennas have been built as possible directed energy applications. Alexeff and Anderson and[1],[2] Anderson and Alexeff[3] have done theory, experiments, and have built prototype plasma antennas. Anderson[4] wrote a comprehensive book on plasma antennas. Plasma antennas are a type of metamaterial antenna.[5] Introduction on Reducing or Eliminating Co-Site Interfrence Using Plasma Antennas Co-site interference and/or parasitic interference are greatly reduced using plasma antennas because the plasma antennas not in use can be turned off with the plasma being extinguished. Metal cannot be extinguished so interference of one metal antenna with another metal antenna nearby is a problem which can be solved or greatly mitigated by using plasma antennas. Higher frequency plasma antennas can transmit and receive through lower frequency plasma antennas. Higher frequency plasma antenna arrays can transmit and receive through lower frequency plasma antenna arrays. Therefore, you need not even have to turn off (extinguish) plasma antennas to eliminate or reduce mutual interference. One aspect of the test results we performed which are important and useful for co-site interference mitigation indicates that a plasma antenna's best operating frequency can be "tuned" by varying plasma current. Testing similar to these can be used 14 Antenna Systems & Technology Spring 2014 Figure 1. Transfer curve for the following conditions: Transmitter antenna is a 19 inch vertical metal dipole antenna. The receiver antenna is a 46-inch vertical metal dipole antenna. The network analyzer span is 0.3 MHz to 500 MHz, and there is 10 dBm/div. Figure 2. Transfer curve for the following conditions: The transmitter antenna is a 19 inch vertical metal dipole antenna, The receiver antenna is a 46 inch plasma antenna with 60 mA DC drive current. The network analyzer span of 0.3 MHz to 500 MHz. There is10 dBm/div. Note the reduction in co-site interference as indicated by the received signal above 300 MHz, compared with the metal antenna receiver. www.AntennasOnline.com http://www.AntennasOnline.com

Table of Contents for the Digital Edition of Antenna Systems & Technology - Spring 2014

Editor’s Choice
What's So Exciting About the Future of M2M? Everything
Antenna Design for LTE Enabled Tablets
Recent Progress on Plasma Antennas
Guest Column: Don't Let Your Choice of Tool Hinder Your Cable and Antenna Testing
Antennas
Components/Subsystems
Short-Range Wireless
Software / System Design
Test & Measurement
Industry News
Marketplace

Antenna Systems & Technology - Spring 2014