APPARATUS FOR PROTECTING AGAINST RADIOWAVE TRANSMISSION FROM A MOBILE COMMUNICATION DEVICE

Abstract: The present invention provides an apparatus for protecting an electronic apparatus against the transmission of radio waves from a nearby mobile communication apparatus. The apparatus comprises a plurality of radio wave generators for generating inhibiting waves transmitted to the mobile communication apparatus in order to block transmissions from the same. The invention further includes means for sweeping the frequency of the plurality of radio wave generators in different frequency ranges adjusted to cover all frequency ranges of the communication apparatuses.

Description: DESCRIPTION APPARATUS FOR PROTECTING AGAINST RADIOWAVE TRANSMISSION FROM A MOBILE COMMUNICATION DEVICE Technical Field The present invention relates to an apparatus for shielding radio wave transmitted from or to a mobile communication device, and more particularly to an apparatus for shielding electric and electronic devices from an external radio wave having been transmitted from or to a mobile communication device. Background Art As mobile communication devices such as mobile telephones and pagers so called "pocket bell" have recently and widely been used, there has been raised a serious problem about malfunctions of medical equipments or implantable medical devices such as pacemakers due to electromagnetic waves transmitted from the mobile communication devices. Further, it should be hesitated to use such mobile communication devices in museums, movie theaters and playhouses to avoid any trouble to peoples around the user. In the above circumstances, it had been required to develop an apparatus or system for shielding electric and electronic devices from an external radio wave having been transmitted from a mobile communication device. Accordingly, it is an object of the present invention to provide an apparatus or system for shielding electric and electronic devices from an external radio wave having been transmitted from a mobile communication device. The above and other objects, features and advantages of the present invention will be apparent from the following descriptions. Disclosure of Invention The present invention provides an apparatus for shielding an electric or electronic device from external radio waves used for communication devices to prevent the electric or electronic device from showing any malfunction. The apparatus comprises a plurality of radio wave generators for generating a plurality of shielding-purpose radio waves separately and irradiating the shielding-purpose radio waves to the external radio waves, wherein the plurality of radio wave generators further include means for sweeping in frequency of the plurality of shielding-purpose radio waves in frequency ranges which are different from each other and are adjusted to cover ranges, within which frequencies of all of the external radio waves fall, so that when frequency of the shielding-purpose radio wave corresponds to frequency of the external radio wave, the external radio wave is cut off by the shielding-purpose radio wave. It is preferable that the plurality of shielding-purpose radio waves are swept in a time-period shorter than a critical time-period during which the communication devices are required to continuously receive the external radio waves for allowing the communication devices to be operated or activated. It is also preferable that the electric or electronic device is a medical instrument installed in a hospital. It is also preferable that the electric or electronic device is an implantable medical device. It is also preferable that the sweeping means comprises a signal generator for generating a signal which varies in voltage level periodically and proportionally, and a plurality of variable capacitance elements connected to the signal generator for receipt of the signal. The variable capacitance elements has different capacitances from each other which vary in accordance with the periodical and proportional variation in voltage level of the signal received. The number of the variable capacitance elements is the same as the plurality of radio wave generators. It is also preferable that the signal generator comprises a triangle wave signal generator. It is also preferable that the signal generator comprises a sawtooth wave signal generator. It is also preferable that the variable capacitance elements comprises a variable capacitance diode. It is also preferable that each of the radio wave generators comprises a radio-frequency oscillator connected to the variable capacitance element for generating a radio-frequency signal which is swept in frequency in accordance with variation in capacitance of the variable capacitance element, and an antenna connected to the radio-frequency oscillator for receiving the radio-frequency signal sweeping in frequency from the radio-frequency oscillator and irradiating a radio wave which is swept in frequency. A buffer amplifier may be provided between the radio- frequency oscillator and the antenna in each of the radio wave generators. Brief Description of Drawings A preferred embodiment according to the present invention will be described with reference to the accompanying drawing. FIG. 1 is a block diagram illustrative of a novel apparatus for shielding electric and electronic devices from an external radio wave having been transmitted from a mobile communication device in a preferred embodiment according to the present invention. Best Mode for carrying Out the Invention A preferred embodiment according to the present invention will be described with reference to FIG. 1. A novel apparatus in accordance with the present invention is capable of irradiating a weak radio wave or electromagnetic wave having the same frequency as the radio wave used for the mobile communication device for shielding the mobile communication devices from the radio wave at close range, for example, within 2-3 meters, so that the mobile communication device is prevented from transmitting or receiving the radio wave. A triangle wave generator 10 is provided which is capable of generating a triangle wave signal. The triangle wave generator 10 is capable of controlling a frequency and an amplitude of the triangle wave signal to be generated. A power source 12 is provided which is connected to the triangle wave generator 10 for supplying a power to the triangle wave generator 10. The apparatus has three parallel radio wave generators, for example, first, second and third radio wave generators which are capable of generating first, second and third radio waves respectively which are swept in frequency in first, second and third sweeping ranges. The first, second and third sweeping ranges are different from each other. The first, second and third radio wave generators are connected to the triangle wave generator 10 in parallel to each other for receipt of the triangle wave signal generated by the triangle wave generator 10 in order to generate the first, second and third radio waves which are swept in accordance with the periodical variations in voltage level of the triangle wave signals. The first, second and third radio wave generators are also connected to the power source 12 in parallel to each other for receiving the powers therefrom separately. The first radio wave generator comprises the following elements. A first variable capacitance diode 20 is provided which is connected to the triangle wave generator 10 for receiving the generated triangle wave signal from the triangle wave generator 10. The triangle wave signal periodically varies in voltage level. The capacitance of the first variable capacitance diode 20 is varied in accordance with the periodical variation in voltage level of the triangle wave signal. Namely, the triangle wave signal proportionally increases in voltage level in an initial half of each period and then proportionally decreases in voltage level in the last half of that period. Since the capacitance of the variable capacitance diode 20 depends upon the voltage level of the triangle wave signal, the capacitance of the variable capacitance diode 20 periodically varies in accordance with the proportional and periodical variations in voltage level of the triangle wave signal. A first radio frequency oscillator 22 is provided which is connected to the first variable capacitance diode 20 for generating a first radio frequency signal which varies in frequency in accordance with the varying capacitance of the first variable capacitance diode 20. Namely, the frequency of the radio frequency signal depends upon the capacitance of the first variable capacitance diode 20. Thus, the radio frequency signal generated by the first radio frequency oscillator 22 varies in frequency in accordance with the periodical variation in capacitance of the first variable capacitance diode 20. This means that the radio frequency signal generated by the first radio frequency oscillator 22 is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. A first buffer amplifier 24 is provided which is connected to the first radio frequency oscillator 22 for amplifying the first radio frequency signal which having been varying in frequency proportionally to the periodical variation in capacitance of the first variable capacitance diode 20. The first buffer amplifier 24 also serves to ensure the stability of the radio frequency signal. The radio frequency signal amplified by the first buffer amplifier 24 is also swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. A first antenna 26 is provided which is connected to the first buffer amplifier 24 for receiving the amplified radio frequency signal which is swept in frequency and irradiating a first radio wave which is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. A first width of sweeping in frequency of the first radio wave irradiated from the first antenna 26 depends upon the amplitude of the triangle wave signal generated by the triangle wave signal generator 10. A first time-period of sweeping in frequency of the first radio wave irradiated from the first antenna 26 is defined by the time-period of the triangle wave signal generated by the triangle wave signal generator 10. This means that the first radio wave generator is capable of controlling both the first width and the first time-period of sweeping in frequency of the first radio wave irradiated from the first antenna 26. The second radio wave generator comprises the following elements. A second variable capacitance diode 30 is provided which is connected to the triangle wave generator 10 for receiving the generated triangle wave signal from the triangle wave generator 10. The triangle wave signal periodically varies in voltage level. The capacitance of the second variable capacitance diode 30 varies in accordance with the periodical variation in voltage level of the triangle wave signal. However, the capacitance of the second variable capacitance diode 30 is different form the capacitance of the first variable capacitance diode 20. Namely, the triangle wave signal proportionally increases in voltage level in the initial half of each time period and then proportionally decreases in voltage level in the last half of the each time period. Since the capacity of the variable capacitance diode 30 depends upon the voltage level of the triangle wave signal, the capacitance of the variable capacitance diode 30 periodically varies in accordance with the proportional variations in voltage level of the triangle wave signal. A second radio frequency oscillator 32 is provided which is connected to the second variable capacitance diode 30 for generating a second radio frequency signal with a frequency which varies in accordance with the variable capacitance of the second variable capacitance diode 30. Namely, the frequency of the radio frequency signal depends upon the capacitance of the second variable capacitance diode 30. Since the capacitance of the second variable capacitance diode 30 is different from that of the first variable capacitance diode 20, the first radio frequency signal generated by the second radio frequency oscillator 32 is different in frequency from the second radio frequency signal generated by the first radio frequency. Thus, the radio frequency signal generated by the second radio frequency oscillator 32 varies in frequency in accordance with the periodical variation in capacitance of the second variable capacitance diode 30, however, in the different frequency range from that of the radio frequency signal generated by the first radio frequency oscillator 22. This means that the radio frequency signal generated by the second radio frequency oscillator 32 is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10, however, in the different frequency range from that of the radio frequency signal generated by the first radio frequency oscillator 22. A second buffer amplifier 34 is provided which is connected to the second radio frequency oscillator 32 for amplifying the second radio frequency signal which varies in frequency proportionally to the periodical variation in capacitance of the second variable capacitance diode 30. The frequency of the second radio frequency signal amplified by the second buffer amplifier 34 varies in the different range from that of the variable frequency of the first radio frequency signal amplified by the first buffer amplifier 24. The second buffer amplifier 34 also serves to ensure the stability of the radio frequency signal. The radio frequency signal amplified by the second buffer amplifier 34 is also swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10, however, in the different frequency range from that of the radio frequency signal amplified by the first buffer amplifier 24. A second antenna 36 is provided which is connected to the second buffer amplifier 34 for receiving the amplified radio frequency signal which is swept in frequency and irradiating a second radio wave which is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. A second width of sweeping in frequency of the second radio wave irradiated from the second antenna 36 depends upon the amplitude of the triangle wave signal generated by the triangle wave signal generator 10. A second range of sweeping in frequency of the second radio wave irradiated from the second antenna 36 is different from the first range of sweeping in frequency of the first radio wave irradiated from the first antenna 26. A second time-period of sweeping in frequency of the second radio wave irradiated from the second antenna 36 is defined by the time-period of the triangle wave signal generated by the triangle wave signal generator 10. The second time-period of sweeping in frequency of the second radio wave irradiated from the second antenna 36 is the same as the first time-period of sweeping in frequency of the first radio wave irradiated from the first antenna 26. This means that the second radio wave generator is capable of controlling both the second range and the second time-period of sweeping in frequency of the second radio wave irradiated from the second antenna 36. Since, however, the second variable capacitance diode 30 is different in capacitance from the first variable capacitance diode 20, the second range of sweeping in frequency of the second radio wave irradiated from the second antenna 36 is different from the first range of sweeping in frequency of the first radio wave irradiated from the first antenna 26. The third radio wave generator comprises the following elements. A third variable capacitance diode 40 is provided which is connected to the triangle wave generator 10 for receiving the generated triangle wave signal with the first amplitude and the first frequency. The triangle wave signal periodically varies in voltage level. The capacitance of the third variable capacitance diode 40 varies in accordance with the periodical variation in voltage level of the triangle wave signal. However, the capacitance of the third variable capacitance diode 40 is different form the capacitance of the first variable capacitance diode 20 and also different from the capacitance of the second variable capacitance diode 30. Namely, the triangle wave signal proportionally increases in voltage level in the initial half of each time period and then proportionally decreases in voltage level in the last half of the each time period. Since the capacitance of the variable capacitance diode 40 depends upon the voltage level of the triangle wave signal, the capacitance of the variable capacitance diode 40 periodically varies in accordance with the proportional and periodical variations in voltage level of the triangle wave signal. A third radio frequency oscillator 42 is provided which is connected to the third variable capacitance diode 40 for generating a third radio frequency signal which varies in frequency in accordance with the periodically varying capacitance of the third variable capacitance diode 40. Namely, the frequency of the radio frequency signal depends on the capacitance of the third variable capacitance diode 40. Since the capacitance of the third variable capacitance diode 40 is different from that of the first variable capacitance diode 20 and also different from that of the second variable capacitance diode 30, the third radio frequency signal generated by the third radio frequency oscillator 42 is different in frequency from the second radio frequency signal generated by the second radio frequency oscillator 32 and also different in frequency from the first radio frequency signal generated by the first radio frequency oscillator 22. Thus, the radio frequency signal generated by the third radio frequency oscillator 42 varies in frequency proportionally to the periodical variation in capacitance of the third variable capacitance diode 40. The radio frequency signal generated by the third radio frequency oscillator 42 varies in frequency in the different range from that of the radio frequency signal generated by the first radio frequency oscillator 22 and also different range from that of the radio frequency signal generated by the second radio frequency oscillator 32. This means that the radio frequency signal generated by the third radio frequency oscillator 42 is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10, however, in the different frequency range from that of the radio frequency signal generated by the first radio frequency oscillator 22 and also from that of the radio frequency signal generated by the second radio frequency oscillator 32. A third buffer amplifier 44 is provided which is connected to the third radio frequency oscillator 42 for amplifying the third radio frequency signal with a variable frequency which varies proportionally to the periodical variation in capacitance of the third variable capacitance diode 40. The periodically varying frequency of the third radio frequency signal amplified by the third buffer amplifier 44 also varies in the different range from that of the periodically varying frequency of the first radio frequency signal amplified by the first buffer amplifier 24 and also from that of the periodically varying frequency of the second radio frequency signal amplified by the second buffer amplifier 34. The third buffer amplifier 44 also serves to ensure the stability of the radio frequency signal. The radio frequency signal amplified by the third buffer amplifier 44 is also swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. However, the radio frequency signal amplified by the third buffer amplifier 44 is swept in frequency in the different range from that of the radio frequency signal amplified by the first buffer amplifier 24 and also from that of the radio frequency signal amplified by the second buffer amplifier 34. A third antenna 46 is provided which is connected to the third buffer amplifier 44 for receiving the amplified radio frequency signal which is swept in frequency and irradiating a third radio wave which is swept in frequency at the same time-period as that of the triangle wave signal generated by the triangle wave generator 10. A third width of sweeping in frequency of the third radio wave irradiated from the third antenna 46 is defined by the amplitude of the triangle wave signal generated by the triangle wave signal generator 10. A third range of sweeping in frequency of the third radio wave irradiated from the third antenna 46 is different from the first range of sweeping in frequency of the first radio wave irradiated from the first antenna 26 and also different from the second range of sweeping in frequency of the second radio wave irradiated from the second antenna 36. A third time-period of sweeping in frequency of the third radio wave irradiated from the third antenna 46 is defined by the time-period of the triangle wave signal generated by the triangle wave signal generator 10. The third time-period of sweeping in frequency of the third radio wave irradiated from the third antenna 46 is the same as the first time-period of sweeping in frequency of the first radio wave irradiated from the first antenna 26 and also is the same as the second time-period of sweeping in frequency of the second radio wave irradiated from the second antenna 36. This means that the third radio wave generator is capable of controlling both the third range and the third time-period of sweeping in frequency of the third radio wave irradiated from the third antenna 46. Since, however, the third variable capacitance diode 40 is different in capacitance from the first variable capacitance diode 20 and also from the second variable capacitance diode 30, the third range of sweeping in frequency of the third radio wave irradiated from the third antenna 46 is different from the first range of sweeping in frequency of the first radio wave irradiated from the first antenna 26 and also different from the second range of sweeping in frequency of the second radio wave irradiated from the second antenna 36. As described above, the first, second and third antennas irradiate the first, second and third radio waves which are swept in frequency at the same time-period as the frequency of the triangle wave signal, however, in the first, second and third frequency ranges which are different from each other. The first frequency range, in which the radio wave irradiated from the first antenna 26 is swept, may be set corresponding to a frequency band, for example, 275 MHz through 322 MHz in which pagers of various types are operable. The second frequency range, in which the radio wave irradiated from the second antenna 36 is swept, may be set corresponding to a different frequency band, for example, 800 MHz through 940 MHz in which mobile telephones of various types are operable. The third frequency range, in which the radio wave irradiated from the third antenna 46 is swept, may be set corresponding to a further different frequency band, for example, 1.4 GHz through 1.95 GHz in which mobile telephones of the remaining various types are operable. The above described novel apparatus is capable of shielding the electric and electronic devices from any external radio waves for the various pagers and the various mobile telephones. The radio wave transmitted to the pagers and mobile telephones can be cut off by the irradiation of the radio wave having the same frequency. The radio wave irradiated from the first antenna 26 and swept in the range of 275 MHz through 322 MHz can cut off the transmission of the radio wave with any frequency in the range of 275 MHz through 322 MHz. The pagers are operated to call a person only when the pagers could receive the radio wave continuously for a predetermined time-period. This means that if the radio wave transmitted to the pagers is once cut by irradiation of the radio wave transmitted from the first antenna 26 during the above predetermined time- period, then the pagers is not operated to call the person. In order to prevent the pagers to be operated to call persons, it is required to cut off the radio wave transmitted to the pagers by the irradiation of the radio wave transmitted from the first antenna 26 during the above predetermined time- period. Since the radio wave transmitted to the pagers can be cut off by irradiation of the radio wave having the same frequency, it is required that the radio wave irradiated from the first antenna 26 is swept in frequency in the range of 275 MHz through 322 MHz, however, within a shorter time- period than the above predetermined time-period. The radio wave irradiated from the first antenna 26 can cut off the radio wave transmitted to the pagers when the correspondence in frequency between the both radio waves is obtained during the above predetermined time-period thereby to prevent the pagers to be operated to call the person. If the pagers are set to be operated to call persons when the pagers could not receive the radio wave continuously for 1/10,000 seconds, then the radio wave irradiated from the first antenna 26 is swept in a shorter time period than 1/10,000 seconds, for example, at a frequency of 9 kHz. Namely, the time period of sweeping in frequency of the radio wave irradiated from the first antenna 26 depends on the frequency of the triangle wave signal generated by the triangle wave signal generator 10, for which reason the frequency of the triangle wave signal generated by the triangle wave signal generator 10 is so set that the sweeping time period or frequency is at 9 kHz. In order to prevent the mobile telephone to be operated to call persons, it is required to cut off the radio wave transmitted to the mobile telephone by the irradiation of the radio wave transmitted from the second antenna 36 during the above predetermined time-period. Since the radio wave transmitted to the mobile telephone can be cut off by irradiation of the radio wave having the same frequency, it is required that the radio wave irradiated from the second antenna 36 is swept in frequency in the range of 800 MHz through 940 MHz within a time-period shorter than the above predetermined time-period, for example, at a frequency of 9kHz. Further, in order to prevent the mobile telephone to be operated to call persons, it is required to cut off the radio wave transmitted to the mobile telephone by the irradiation of the radio wave transmitted from the third antenna 46 during the above predetermined time-period. Since the radio wave transmitted to the mobile telephone can be cut off by irradiation of the radio wave having the same frequency, it is required that the radio wave irradiated from the third antenna 46 is swept in frequency in the range of 1.4 GHz through 1.95 GHz within a time-period shorter than the above predetermined time-period, for example, at a frequency of 9kHz. As described above, the above novel apparatus in accordance with the present invention is capable of irradiating a weak radio wave or electromagnetic wave having the same frequency as the radio wave used for the mobile communication device for shielding the mobile communication devices from the radio wave at close range, for example, within 2-3 meters, so that the mobile communication device is prevented from transmitting or receiving the radio wave. As a modification, it is possible to use, in place of the triangle wave signal generator, a saw-tooth wave generator for seeping the radio wave in frequency. As a further modification, it is also possible to change the number of sets of the radio wave generator which comprises the variable capacitance diode, the radio-frequency oscillator, the buffer amplifier and the antenna. The above apparatus may comprise two or four sets of the radio wave generators. Each frequency range in which the radio waves transmitted from the antennas are swept may be adjusted to the various uses. Whereas modifications of the present invention will no doubt be apparent to a person having ordinary skill in the art, to which the invention pertains, it is understood that embodiments as shown and described by way of illustrations are by no means intended to be considered in a limiting sense. Accordingly, it is to be intended to cover by claims all modifications which fall within the spirit and scope of the present invention.

Claims: CLAIMS 1. An apparatus for shielding an electric or electronic device from external radio waves used for communication devices to prevent said electric or electronic device from showing any malfunction, said apparatus comprising a plurality of radio wave generators for generating a plurality of shielding-purpose radio waves separately and irradiating said shielding- purpose radio waves to said external radio waves, wherein said plurality of radio wave generators further include means for sweeping in frequency of said plurality of shielding-purpose radio waves in frequency ranges which are different from each other and are adjusted to cover ranges, within which frequencies of all of said external radio waves fall, so that when frequency of said shielding-purpose radio wave corresponds to frequency of said external radio wave, said external radio wave is cut off by said shielding-purpose radio wave. 2. The apparatus as claimed in claim 1, wherein said plurality of shielding-purpose radio waves are swept in a time-period shorter than a critical time-period during which said communication devices are required to continuously receive said external radio waves for allowing said communication devices to be operated or activated. 3. The apparatus as claimed in claim 1, wherein said electric or electronic device is a medical instrument installed in a hospital. 4. The apparatus as claimed in claim 1, wherein said electric or electronic device is an implantable medical device. 5. The apparatus as claimed in claim 1, wherein said sweeping means comprises : a signal generator for generating a signal which varies in voltage level periodically and proportionally ; and a plurality of variable capacitance elements connected to said signal generator for receipt of said signal, said variable capacitance elements having different capacitances from each other which vary in accordance with said periodical and proportional variation in voltage level of said signal received, and the number of said variable capacitance elements being the same as said plurality of radio wave generators. 6. The apparatus as claimed in claim 5, wherein said signal generator comprises a triangle wave signal generator. 7. The apparatus as claimed in claim 5, wherein said signal generator comprises a saw-tooth wave signal generator. 8. The apparatus as claimed in claim 5, wherein said variable capacitance elements comprises a variable capacitance diode. 9. The apparatus as claimed in claim 5, wherein each of said radio wave generators comprises : a radio-frequency oscillator connected to said variable capacitance element for generating a radio-frequency signal which is swept in frequency in accordance with variation in capacitance of said variable capacitance element ; and an antenna connected to said radio-frequency oscillator for receiving said radio-frequency signal sweeping in frequency from said radio-frequency oscillator and irradiating a radio wave which is swept in frequency. 10. The apparatus as claimed in claim 9, further comprising a buffer amplifier provided between said radio-frequency oscillator and said antenna in each of said radio wave generators.

Inventors: MAEDA YOICHI, MAEDA, YOICHI
Applicants: MAEDA YOICHI, NIKKO KK, TAKAFUJI YASUTANE, MAEDA, YOICHI, NIKKO CO., LTD., TAKAFUJI, YASUTANE
Application year: 1997
Main classification: H04K3
IPC codes: H04B7, H04K3