MP Antenna introduces multipath interference-resistant antenna
MP Antenna unveiled at the recent International Wireless Communications Expo (IWCE 2010) in Las Vegas, the Mobius, a device that overcomes multipath interference and polarization issues that plague other antennas and result in signal losses of varying degrees, both inside and outside buildings.
The Mobius eliminates the signal loss that occurs when a radio signal is refracted by obstructions inside buildings because it uses three antennas of different lengths, which creates spatial diversity, according to its inventor, Dr. Jack Nilsson, the company’s chief science officer. The theory is that if one antenna is a dead spot — because the refracted signal shot past it — one of the other two will be a hot spot.
A refracted signal also will lose its vertical polarization, so Nilsson designed the Mobius to also perform with horizontal polarization. “You greatly increase the probability that in any particular location of that walkie-talkie, you’re going to have a useable signal that’s going to make it to the walkie-talkie, if you’re producing it both vertically and horizontally,” Nilsson said.
To test his theory, MP Antenna conducted an exercise at an Abercrombie and Fitch complex in New Albany, Ohio, that consists of 18 buildings that cover about 1 million square feet. The complex also has an underground tunnel to evacuate employees in weather emergencies, such as tornados. The tunnel is 15 feet underground and features an L shape measuring 350 feet by 250 feet.
According to Brian Gaul, the company’s sales manager, a local fire chief entered the tunnel carrying his portable radio; the apparatus positioned outside the building that housed the tunnel had a mobile radio that retransmitted the tower signal into the building using a conventional, vertically polarized antenna. “As soon as he walked downstairs, he lost signal,” Gaul said.
When the conventional antenna was swapped out for a Mobius, the fire chief was able to receive a radio signal from the apparatus’ mobile the entire length of the tunnel, in both directions, Gaul said.
The effect works in the inverse, as the Mobius enables mobile radios to receive a signal regardless of whether they are “in a valley or behind tall buildings,” Gaul said.
According to Nilsson, “It’s like when you’re driving and listening to FM radio and you come to a stop light and the signal goes away completely. That’s called flutter. So what do you do? You creep forward a couple of feet and the signal is fine again.”
At an emergency response incident, apparatus can’t be continuously repositioned in order to pick up the signal from the tower. Again, Nilsson designed the Mobius with multiple antennas that not only are of different lengths but also are positioned at different angles so that the device is able to pick up the tower signal regardless of topology and obstructions.
“You can’t move the antenna, so you have to think three-dimensionally,” he said. “When flutter occurs, our technology stabilizes the signal.”
The company, which is located in North Ridgeville, Ohio, conducted a test with the nearby Cleveland Heights (Ohio) Fire Department. Using a conventional antenna, the apparatus’ mobile radio lost contact with the tower at roughly 2.7 miles from the site. “We were still in Cleveland Heights, and we lost reception,” Gaul said. “The obstructions were enough, and the topology changed enough, that the signal was blocked.”
However, once the Mobius was attached, Gaul said the apparatus traveled another couple of miles to adjoining Shaker Heights, Ohio, “but the signal remained loud and clear, despite the fact that there were obstructions everywhere.”
