Patent ID: 6784871
Filing Date: 2004-08-31
Classification: G06F

Abstract:
An ultrasonic security system for personal computer comprising:a nonpiezoelectric plate; at least one transducer-unit consisting of at least one input IDT Ti (i=1, 2, . . . , m) with a construction such that distances between two electrode-fingers are equal, and having an interdigital periodicity P and an overlap length L, at least one output IDT Ri (i=1, 2, . . . m) with a construction such that distances between two electrode-fingers are equal, having the electrode-finger direction slanting to that of said at least one input IDT Ti by an angle &thgr;, and having an interdigital periodicity PN along the orthogonal direction to said electrode-finger direction of said at least one output IDT Ri and an overlap length LP along said electrode-finger direction of said at least one output IDT Ri, a first input piezoelectric substrate, and a first output piezoelectric substrate; a signal analyzer; a second piezoelectric substrate; a coding IDT consisting of interdigital electrode pairs and having a coded pattern; a terminal IDT having the electrode-finger direction parallel to that of said coding IDT; a third piezoelectric substrate; an initial IDT; and a decoding IDT having the same construction pattern as said coding IDT, said nonpiezoelectric plate, said at least one transducer-unit, and said signal analyzer forming a touch-panel section, said second piezoelectric substrate, said coding IDT, and said terminal IDT forming a lock section, said third piezoelectric substrate, said initial IDT, and said decoding IDT forming a key section, said at least one input IDT Ti receiving an input electric signal, exciting a first SAW in said first input piezoelectric substrate by making all the electrode-finger pairs of said at least one input IDT Ti function at the same level, and transmitting said first SAW to said first output piezoelectric substrate along an upper end surface of said nonpiezoelectric plate, said at least one output IDT Ri making all the electrode-finger pairs thereof function at the same level for transducing said first SAW to electric signals Ej (j=32 1, 2, . . . , n), of which the phase delays linearly correlate to SAW propagation lanes Wj (j=1, 2, . . . , n) between said at least one input IDT Ti and said at least one output IDT Ri on said upper end surface of said nonpiezoelectric plate, and detecting one of said electric signals Ej only when touching one of said SAW propagation lanes Wj, said coding IDT receiving said one of said electric signals Ej, and exciting a second SAW based on said coded pattern on said second piezoelectric substrate, said terminal IDT detecting a coded burst-signal corresponding to said coded pattern, said initial IDT receiving said coded burst-signal, and exciting a third SAW on said third piezoelectric substrate, said decoding IDT detecting a pulse if said third SAW correlates to said coded pattern, and said signal analyzer sensing said one of said SAW propagation lanes Wj by means of the phase of said pulse.