INCREASING the number of antennas on mobile phones will dramatically improve
reception and reduce the number of blind spots in buildings, say US researchers.
One of the most serious sources of interference is caused by signals bouncing
off several buildings
(see 鈥淩adio blast鈥�).
This will be even more of a problem with the
next generation of phones鈥攚here more users will share the same frequency
band.
Multiple antennas coupled with sophisticated signal processing can eliminate
most of this interference, says Michael Zoltowski, professor of electrical and
computer engineering at Purdue University in Lafayette, Indiana. He is due to
present his findings this week at an Institute of Electrical and Electronics
Engineers鈥� meeting on signal processing in Pocono Manor, Pennsylvania.
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The principle behind multiple antennas is analogous to the way humans process
sound. 鈥淚f we had a single ear we鈥檇 have no idea where the sound came from,鈥�
says Zoltowski. With two ears humans can locate sounds and tune into them.
Similarly, two antennas 鈥減rovide the ability to discriminate one signal relative
to another. You can extract one and reject the other. You cannot do it with one
antenna,鈥� he says.
Zoltowski鈥檚 team has shown that two antennas can cut reception errors to 1
per cent of the current rate. Meanwhile, engineers at Texas Instruments have
shown that a prototype phone with two antennas can overcome 鈥渂lind鈥� spots in
buildings.