Patent ID: 8699542
Filing Date: 2014-04-15
Classification: H04K

Abstract:
1. An information leakage prevention apparatus which generates, based on an image signal generated by an information processing apparatus, a leakage prevention signal for preventing leakage of image information from an unwanted electromagnetic wave containing a signal component of the image signal, comprising: a basic clock generation unit that generates a basic clock signal that has a carrier frequency of the image information leaked from the unwanted electromagnetic wave or a harmonic frequency of the carrier frequency and synchronizes with a horizontal sync signal or vertical sync signal contained in the image signal; a spread spectrum modulation unit that generates a spread spectrum clock signal by performing spread spectrum clocking processing for the basic clock signal; a modulation pattern generation unit that outputs, as a modulation pattern signal, a PN (Pseudo Noise) code having sign bit data synchronized with each pulse of the spread spectrum clock signal, and resets a repetition period of the PN code based on the horizontal sync signal; a modulated clock generation unit that generates a modulated clock signal by modulating the spread spectrum clock signal in accordance with the modulation pattern signal; and an output amplification unit that amplifies the modulated clock signal to generate the leakage prevention signal, wherein, said basic clock generation unit generates, as the basic clock signal, a plurality of individual basic clock signals of frequencies having neither an integer multiple relationship nor an integer fraction relationship, sets each including said spread spectrum modulation unit, said modulation pattern generation unit, and said modulated clock generation unit are juxtaposed for the respective individual basic clock signals, each of said modulation pattern generation units generates an individual spread spectrum clock signal by performing spread spectrum clocking processing for the individual basic clock signal, each of said modulation pattern generation units outputs, as an individual modulation pattern signal, a PN (Pseudo Noise) code having sign bit data synchronized with each pulse of the individual spread spectrum clock signal, and resets the repetition period of the PN code based on the horizontal sync signal, each of said modulated clock generation units generates an individual modulated clock signal by modulating the individual spread spectrum clock signal in accordance with the individual modulation pattern signal, the information leakage prevention apparatus further comprises an output synthesis unit that generates a synthesized modulated clock signal by synthesizing the individual modulated clock signals, and said output amplification unit amplifies the synthesized modulated clock signal to generate the leakage prevention signal.