While freedom of movement is one of the great advantages of wireless sensors, we have occasionally heard, “I don’t want wireless because when I moved my refrigerator just a few feet from where it was, I lost my sensor.” This is invariably due to the physical environment (metal objects which cause signal attenuation and reflections). The CQ sensor’s high power levels and the use of Spread Spectrum technology all but eliminate this objection.
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 from 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 frequency 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 probability viewpoint, a conventional radio system faces a 1% – 2% chance of signal impairment at any given time due to multipath fading.
Spread spectrum reduces the vulnerability of a radio system to 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.
SmartScan Technologies is involved in offering quality web based monitoring systems and temperature and humidity monitoring systems among more for monitoring critical applications across a variety of market fields.
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