Patent ID: 6717983
Filing Date: 2004-04-06
Classification: H03H,H04B

Abstract:
An ultrasonic coding modem for digital network communication comprising:a transmitting device consisting of an input terminal, a first piezoelectric substrate, an input IDT consisting of at least three interdigital electrode pairs, and having a coded pattern, a first intermediary IDT, an electrode group consisting of two IDTs and a central IDT between said two IDTs, said input IDT, said first intermediary IDT, and said electrode group being formed on said first piezoelectric substrate, a synchronizing device connected between said first intermediary IDT and one of said two IDTs of said electrode group, an envelope detecting device connected with said central IDT of said electrode group, an output terminal; and a receiving device consisting of a receiving terminal, a second piezoelectric substrate, a second intermediary IDT, an output IDT having a coded pattern in reverse to said input IDT, said second intermediary IDT and said output IDT being formed on said second piezoelectric substrate, and a detecting terminal, said input IDT exciting a SAW on said first piezoelectric substrate only when receiving a pulse (1) of a message digital-signal via said input terminal, said first intermediary IDT detecting a coded burst-signal corresponding to said SAW excited at said input IDT, said two IDTs of said electrode group receiving said coded burst-signal simultaneously, and exciting two SAWs on said first piezoelectric substrate, respectively, said central IDT of said electrode group receiving said two SAWs simultaneously, said envelope detecting device causing a coded digital-signal from said two SAWs, said output terminal delivering said coded digital-signal into a digital network, said second intermediary IDT exciting a SAW on said second piezoelectric substrate only when receiving said coded digital-signal from said digital network via said receiving terminal, said output IDT detecting a decoded pulse (1), if said SAW excited at said second intermediary IDT corresponds to said SAW excited at said input IDT, said detecting terminal delivering an output digital-signal, which is composed of said decoded pulse (1) and no detected pulse (0), and is equivalent to said message digital-signal.