1 / 14

Broadband Antennas

Broadband Antennas. Neal Mansfield Joseph Pete Matthew Robinson Steven Summers. Overview. Typical antennas are designed for a specific narrow band of operation Broadband antennas are designed to operate effectively over a wide range of frequencies Public two-way-radio VHF covers 130-174Mhz

hosea
Télécharger la présentation

Broadband Antennas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Broadband Antennas Neal Mansfield Joseph Pete Matthew Robinson Steven Summers

  2. Overview • Typical antennas are designed for a specific narrow band of operation • Broadband antennas are designed to operate effectively over a wide range of frequencies • Public two-way-radio VHF covers 130-174Mhz • Public two-way-radio UHF 406-512Mhz • The challenge is to create an antenna which can operate in both the VHF and UHF bands

  3. Bandwidth • Definition for center frequency: • Bandwidth can be expressed as a percentage of the center frequency or as a ratio • The percentage is commonly used for small bandwidth antennas: • The ratio is commonly used for large bandwidth antennas:

  4. Broad Spectrum of Types • Helical • Log Periodic • Biconical • Sleeve • Spiral

  5. Biconical Antenna • Types of Biconical • Infinite Biconical • Finite Biconical • Discone • http://www.ik8uif.it/biconical-10ghz.htm

  6. Log Periodic Antenna • The antenna is ideally suited for reception of VHF/UHF point-to-point communication where its directional characteristics can significantly improve rejection of interfering signals. • In professional applications, this antenna is ideally suited for EMC pre-testing, surveillance and monitoring. • The antenna covers a frequency range of 230 to 1600 MHz (a much wider frequency range can be received with reduced gain). • http://www.winradio.com/home/ax31b.htm

  7. Sleeve Antenna • The sleeve antenna is used primarily as a receiving antenna. It is a broadband, vertically polarized, omnidirectional antenna. Its primary uses are in broadcast, ship-to-shore, and ground-to-air communications. Although originally developed for shore stations, there is a modified version for shipboard use. • http://www.tpub.com/inch/32.htm • http://www.emartin.it/it9vky/Risorse/opensleeve.htm

  8. Spiral Antenna http://www.emi.dtu.dk/research/afg/research/gpr/spiral_antenna.html http://www.naapo.org/Argus/docs/990702.htm • The spiral antenna is used primarily as a receiving antenna • Vertically polarized • Frequency Independent • Designed to minimize finite lengths and maximize angular dependence http://www.ece.uiuc.edu/pubs/antenna/slide03.html

  9. Helical Antenna • Directional • Circularly Polarized • Polarization changes with time • Both high gain and wide band http://www.wireless.org.au/~jhecker/helix/helical.html http://helix.remco.tk/

  10. Geometry D= diameter of helix C= circumference of helix Lo= length of one turn = α= pitch angle = S= spacing between turns N= number of turns Lw= length of helix d= diameter of conductor Antenna Theory, Constantine A. Balanis

  11. Normal Mode • Radiation pattern similar to linear dipole • The dimensions of the helix are small compared to the wavelength • Narrow in bandwidth • Radiation efficiency is small • Rarely used Antenna Theory, Constantine A. Balanis

  12. Axial Mode • Circular Polarization • ¾<C/λ<4/3 • C/λ=1:near optimum • S= λ/4 • Half-Power Beam width: 50 x 50 degrees • Directivity: • Typical Gain: 10dB • Bandwidth: 52% • Frequency limit: 100MHZ to 3GHz Antenna Theory, Constantine A. Balanis http://www.mobile.ss.titech.ac.jp/~ken/broadband-antennas.pdf

  13. Helix Applications • Space Telemetry Applications of satellites, space probes, and ballistic missiles • Signals have undergone Faraday rotation • Directional applications

  14. Adaptation of Single Antenna for Multi-band Use.

More Related