In Dec. 2007, Huahui Wang of Wheeling, Ill. filed an application for MMSE-DFE equalization with antenna diversity for mobile DTV. Last week, a patent was granted—number 8045610--to protect his invention.
This patent application was filed before the ATSC Mobile DTV standard was proposed. The methods described--using two antennas a half a wavelength apart, each with its own channel equalizer and MMSE-DFE equalization--would allow mobile DTV reception of traditional ATSC signals.
The patent describes its solution to the problem of mobile DTV reception this way:
"A promising solution to such problems is to employ antenna diversity at the receiver. Theoretically, as long as two antennas are separated by more than half a wavelength, the channel characteristics of the two paths are independent. Hence, the probability of concurrent deep fades is small. When one channel fades, accurate symbol decisions can still be obtained from the other channel, so that the update process can continue without divergence. Thus, system performance is significantly improved with joint operation of the multiple antennas."
Wang further stated that antenna diversity in an equalizer is proposed for effectively receiving 8-VSB ATSC signals. He proposed using a "double-threshold" switching scheme in combination with the multiple antenna branches, with the weaker signals being received via some of the antennas being excluded from the equalization process.
While this technology was developed for mobile applications, it appears it could also be useful for indoor antennas in an environment where signal levels and multipath change as people move about the room. The required separation between antennas makes it unsuitable for most hand-held devices.
