NT132 System Overview
© 1999, AXCESS
TM
Inc.
750.001.003
Revised June 1999
17
Antennas
Because the Tags receive and transmit at different frequencies,
different antennas are used for each leg of the communication.
Antenna construction is related to the wavelength (or fraction thereof)
of its design frequency. Antennas designed for the Ultra High
Frequency spectrum (to receive the transmit signal from the Tag) can
be quite short. Antennas designed for Very Low Frequencies (to
transmit the wake-up signal to the Tags) must be quite long. The
transmitting antenna is a loop and the receiving antenna is a dipole.
Types of Antennas
For interior use, antennas can be inconspicuously mounted – for
example, hidden in a false ceiling or disguised as a common picture
frame. Also, depending on type of installation, the transmitting
antenna and receiving antenna may be combined into a single
enclosure or may be built as separate units.
Road Loop and Dipole Antennas
The Road Loop and Dipole Antennas are used for identifying Tags in
vehicles. The Road Loop Antenna is installed in the road surface and
sends out wake-up signals. The Dipole Antenna is separate from the
Road Loop Antenna and is mounted so that it can receive
transmissions from the Tags.
Bar Antenna
The Bar Antenna has both transmitting and receiving antennas
enclosed in a box that is approximately 2 feet long, 5 inches wide and
1 inch thick. It can be inconspicuously mounted above or next to a
door or above the ceiling tiles.
Swing Frame Antenna
The Swing Frame Antenna has both transmitting and receiving
antennas built into its frame. The antenna enclosure is designed as a
picture frame so that it may be mounted unobtrusively on walls.