Murata Electronics North America DNT500FP Manual Do Utilizador
www.RFM.com
Technical support +1.800.704.6079
Page 6 of 58
©2008 by RF Monolithics, Inc.
E-mail: tech sup@rfm.com
DNT900 - 11/05/08
1.0 Introduction
The DNT500 series transceivers provide highly reliable wireless connectivity for either point-to-point or
point-to-multipoint applications. Frequency hopping spread spectrum (FHSS) technology ensures maxi-
mum resistance to multipath fading and robustness in the presence of interfering signals, while operation
in the 900 MHz ISM band allows license-free use in the US, Canada, Australia and New Zealand. The
DNT500 supports all standard serial data rates for host communications from 1.2 to 460.8 kb/s. On-board
data buffering and an error-correcting air protocol provide smooth data flow and simplify the task of inte-
gration with existing applications. Key DNT500 features include:
point-to-multipoint applications. Frequency hopping spread spectrum (FHSS) technology ensures maxi-
mum resistance to multipath fading and robustness in the presence of interfering signals, while operation
in the 900 MHz ISM band allows license-free use in the US, Canada, Australia and New Zealand. The
DNT500 supports all standard serial data rates for host communications from 1.2 to 460.8 kb/s. On-board
data buffering and an error-correcting air protocol provide smooth data flow and simplify the task of inte-
gration with existing applications. Key DNT500 features include:
•
Multipath fading resistant frequency hop-
ping technology with up to 50 frequency
channels (902 to 928 MHz).
ping technology with up to 50 frequency
channels (902 to 928 MHz).
•
Support for point-to-point or point-to-
multipoint applications.
multipoint applications.
•
FCC 15.247 certified for license-free
operation.
operation.
•
40 mile plus range with omni-directional
antennas (antenna height dependent).
antennas (antenna height dependent).
•
Transparent ARQ protocol with data
buffering ensures data integrity
buffering ensures data integrity
1.1 Why Spread Spectrum?
•
Selectable 1, 10, 100, 250, 500 or 1000 mW
transmit power with a firmware interlock of
85 mW maximum for 500 kb/s operation.
85 mW maximum for 500 kb/s operation.
•
Optional AES encryption provides
protection to eavesdropping
•
Nonvolatile memory stores DNT500 configu-
ration when powered off
•
Dynamic TDMA slot assignment that maxi-
mizes throughput.
•
Simple serial interface handles both data and
control at up to 460.8 kb/s
A radio channel can be very hostile, corrupted by noise, path loss and interfering transmissions from
other radios. Even in an interference-free environment, radio performance faces serious degradation
through a phenomenon known as multipath fading. Multipath fading results when two or more reflected
rays of the transmitted signal arrive at the receiving antenna with opposing phases, thereby partially or
completely canceling the signal. This problem is particularly prevalent in indoor installations. In the fre-
quency domain, a multipath fade can be described as a frequency-selective notch that shifts in location
and intensity over time as reflections change due to motion of the radio or objects within its range. At any
given time, multipath fades will typically occupy 1% - 2% of the band. From a probabilistic viewpoint, a
conventional radio system faces a 1% - 2% chance of signal impairment at any given time due to multi-
path fading.
other radios. Even in an interference-free environment, radio performance faces serious degradation
through a phenomenon known as multipath fading. Multipath fading results when two or more reflected
rays of the transmitted signal arrive at the receiving antenna with opposing phases, thereby partially or
completely canceling the signal. This problem is particularly prevalent in indoor installations. In the fre-
quency domain, a multipath fade can be described as a frequency-selective notch that shifts in location
and intensity over time as reflections change due to motion of the radio or objects within its range. At any
given time, multipath fades will typically occupy 1% - 2% of the band. From a probabilistic viewpoint, a
conventional radio system faces a 1% - 2% chance of signal impairment at any given time due to multi-
path fading.
Spread spectrum reduces the vulnerability of a radio system to interference from both multipath fading
and jammers by distributing the transmitted signal over a larger region of the frequency band than would
otherwise be necessary to send the information. This allows the signal to be reconstructed even though
part of it may be lost or corrupted in transmission.
and jammers by distributing the transmitted signal over a larger region of the frequency band than would
otherwise be necessary to send the information. This allows the signal to be reconstructed even though
part of it may be lost or corrupted in transmission.