Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/02—Access restriction performed under specific conditions
  • H04W48/04—Access restriction performed under specific conditions based on user or terminal location or mobility data, e.g. moving direction, speed

Definitions

• THIS INVENTION relates to cellular telephone communication.
• it relates to a method of disabling operation of a cellular telephone in a particular zone and to a cellular telephone disabling device.
• a method of disabling operation of a cellular telephone in a particular zone including sweeping an interference signal across a frequency band in which the cellular telephone operates to inhibit communication between the cellular telephone and a base station.
• the method may include generating a source signal; sweeping the source signal across the frequency band in which the cellular telephone operates to provide the interference signal; and transmitting the interference signal in the zone thereby to disable operation of the telephone.
• the source signal generated may be a monotone source signal.
• the frequency band across which the interference signal is swept is the GSM band of about 935 MHz to about 960 MHz.
• a cellular telephone disabling device for disabling a cellular telephone in a particular zone, the device including a signal source for generating a source signal; control means for sweeping the source signal across a frequency band in which the cellular telephone operates to provide an interference signal; and transmitter means operable to transmit the interference signal in the zone thereby to disable operation of the telephone.
• the signal source may include conventional circuitry to generate a monotone source signal.
• the signal source includes temperature compensation means for compensating for the effect of ambient temperature changes on the signal source.
• the signal source may be a voltage controlled oscillator (VCO).
• the control means may be operable to provide a voltage control signal to which the VCO is responsive.
• the control means may include circuitry for generating a sweep control signal, and an adjustable voltage reference for setting a centre frequency of the voltage controlled oscillator.
• the circuitry is oscillator circuitry and the sweep control signal is a sawtooth waveform.
• the control means may include a summing circuit to sum the sweep control signal and the voltage reference.
• the sweep control signal typically has a frequency of about 20 KHz so that the interference signal sweeps across the frequency band in which the cellular telephone operates at a frequency of about 20 KHz.
• the device may include an amplifier for amplifying the interference signal prior to transmission thereof.
• the amplifier may be a conventional amplifier, e.g an HMPX 3002 or the like, adjusted to have a gain of about 30 dB.
• the device may further include a bandpass filter connected intermediate the VCO and the amplifier.
• the bandpass filter typically operates in the range of about 935 MHz to about 960 MHz.
• the device may include a low-pass filter, e.g. a conventional LC filter, connected to an output of the amplifier for attenuating harmonics of the interference signal.
• a low-pass filter e.g. a conventional LC filter
• the low-pass filter has a cutoff frequency of about 1 GHz.
• Figure 1 shows a schematic block diagram of a cellular telephone disabling device in accordance with the invention.
• Figure 2 shows a circuit diagram of the device of Figure 1 .
• reference numeral 10 generally indicates a cellular telephone disabling device for disabling communication between a cellular telephone in a particular zone and a base station.
• the device 1 0 includes a signal source in the form of a voltage controlled oscillator (VCO) 14, a controller 1 6 connected to the VCO 14 and operable to sweep a source signal of the VCO 14 across a frequency band in which the cellular telephone operates.
• VCO voltage controlled oscillator
• the VCO 14 provides an interference signal which is fed into a bandpass filter
• the device 10 further includes transmitter circuitry 20 comprising an amplifier 22, a low-pass filter 24, and an antenna (not shown).
• the signal source is a conventional voltage controlled oscillator 14 and the controller 1 6 is operable in a conventional fashion to provide an output voltage control signal which is fed into the VCO 14 thereby to control the interference signal generated at its output.
• the controller 1 6 includes an adjustable voltage reference 26 which defines a centre frequency of the VCO 14, oscillator circuitry 28 for generating a sweep control signal in the form of a sawtooth wave, and a summing circuit 30.
• the summing circuit 30 sums the output voltage control signal and the output voltage of the voltage reference 26.
• An output of the summing circuit 30, which is fed into the voltage controlled oscillator 14 defines a sweep control signal with a frequency of about 20 KHz thereby to sweep the interference signal through the frequency band in which the cellular telephone operates.
• the frequency band is typically about 935 MHz to about 960 MHz.
• the bandpass filter In order to filter out any unwanted frequencies in the event of the voltage controlled oscillator 14 being faulty, the bandpass filter
• the amplifier 22 is typically a conventional amplifier e.g an HMPX 3002 or the like, adjusted by circuitry 32 to have a gain of about 30 dB.
• An output of the amplifier 22 is fed into the low-pass filter 24 which typically has a cut off frequency of about 1 GHz.
• the power output from the output of the low-pass filter 24 is typically about 20 dBm.
• the power output may be adjusted accordingly by means of the circuitry 32. Further, in various countries or regions throughout the world, the frequency band in which the device 10 operates may vary.
• the oscillator circuitry 28 for generating the sweep control signal includes conventional oscillator circuitry employing operational amplifiers 34, 36 to generate a sawtooth waveform which is fed along line 38 to gain control circuitry 40.
• the sweep control signal is then fed via line 42 to the summing circuit 30.
• the adjustable voltage reference 26 has its output voltage reference adjusted by a variable resistor 44 and fed via line 46 to the summing circuit 30.
• the voltage controlled oscillator 14 includes conventional circuitry and generates the interference signal which is then fed along line 50 into the amplifier 22.
• An output interference signal is fed via the low-pass filter 20 to an antenna system (not shown) which is arranged to have an appropriate radiation pattern dependant upon the application of the device 10.
• the low-pass filter 20 typically has a cutoff frequency of about 1 GHz.
• the voltage controlled oscillator 14 includes temperature compensation means for compensating for deviations in the interference signal due to ambient temperature changes.
• the device 10 is mounted in a particular zone for example a bank or the like where disabling of operation of cellular telephones is required.
• control information in the form of digital data received by the cellular telephone must be error free.
• the interference signal in the form of a single tone which is scanned across the operating frequency band introduces errors in the signal received by the cellular telephone thereby disabling the communication between the cellular telephone and the base station.
• the Applicant believes that as the interference signal is a single tone which is scanned across the cellular telephone frequency band, energy transmitted by the device 10 is confined to a single receive channel thereby effectively to disable operation of a cellular telephone in the selected zone.
• the blocking of cellular communication is achieved with lower output power from the device 10 than would be required if a broad band noise-like jamming signal was to be generated to disable cellular telephone communication.
• the Applicant further believes that by confining the sweep range to the intended blocking band, and if it is swept at a slow enough rate, an additional advantage of reduced incidental blocking of the adjacent frequency spectrum is obtained.

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• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Transmitters (AREA)
• Noise Elimination (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1999
  • 1999-05-12 EP EP99921032A patent/EP1131913A1/de not_active Withdrawn
  • 1999-05-12 WO PCT/IB1999/000860 patent/WO2000030286A1/en not_active Application Discontinuation
  • 1999-05-12 AU AU38406/99A patent/AU3840699A/en not_active Abandoned
  • 1999-05-12 CN CN 99813391 patent/CN1328730A/zh active Pending

Non-Patent Citations (1)

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