DETECTION OF ULTRA WIDE BAND SIGNAL

Abstract

A device for the detection of an ultra wide band signal, including a signal reception circuit, a signal divider circuit to divide the received signal into several frequency sub-bands, a circuit to determine the amplitude and duration of the received signal in each frequency sub-band, a circuit to compare the amplitude of the signal received in each frequency sub-band with an amplitude threshold, a circuit to compare the duration of the signal received in each frequency sub-band with a time threshold, and a decision circuit that determines that the received signal is of the ultra wide band type if the amplitude of the signal received in each frequency sub-band is higher than the amplitude threshold and if the duration of the signal received in each frequency sub-band is less than the time threshold.

Claims

1-9. (canceled)

10. A device for the detection of an ultra wide band signal, comprising: a signal reception circuit, a signal divider circuit to divide the received signal into several frequency sub-bands, a circuit to determine the amplitude and duration of the signal received in each frequency sub-band, a circuit to compare the amplitude of the signal received in each frequency sub-band with an amplitude threshold, a circuit to compare the duration of the signal received in each frequency sub-band with a time threshold, and a decision circuit that determines that the received signal is of the ultra wide band type if the amplitude of the signal received in each frequency sub-band is higher than the amplitude threshold and if the duration of the signal received in each frequency sub-band is less than the time threshold.

11. The device for the detection of an ultra wide band signal according to claim 10, wherein an alarm circuit to signal that the received signal is of the ultra wide band type.

12. The device for the detection of an ultra wide band signal according to claim 10, wherein a circuit to store the detected ultra wide band type signal.

13. The device for the detection of an ultra wide band signal according to claim 10, wherein a circuit to determine the envelope of the signal received in each frequency sub-band.

14. The device for the detection of an ultra wide band signal according to claim 10, wherein it is adapted to implement a learning phase during which detected ultra wide band type signals are stored as reference signals.

15. The device for the detection of an ultra wide band signal according to claim 14, wherein the decision circuit is adapted to compare a detected ultra wide band type signal with the reference signals.

16. A method of detecting an ultra wide band signal, comprising: reception of the signal, division of the received signal into several frequency sub-bands, determination of the amplitude and duration of the signal received in each frequency sub-band, comparison of the amplitude of the signal received in each frequency sub-band with an amplitude threshold, comparison of the duration of the signal received in each frequency sub-band with a time threshold, and decision to determine that the received signal is of the ultra wide band type if the amplitude of the signal received in each frequency sub-band is higher than the amplitude threshold and if the duration of the signal received in each frequency sub-band is less than the time threshold.

17. A computer program containing instructions for execution of the steps in the method according to claim 16 when said program is executed by a computer.

18. A storage medium that can be read by a computer, in which a computer program is stored containing instructions for execution of the steps in the method according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other characteristics and advantages will become clear after reading the following description of a preferred embodiment given as a non-limitative example, described with reference to the figures in which:

[0036] FIGS. 1a, 1b and 1c represent examples of ultra wide band signals to be detected,

[0037] FIG. 2 represents an ultra wide band signal detection device according to one embodiment of the invention,

[0038] FIG. 3 represents an ultra wide band signal detection method according to one embodiment of the invention,

[0039] FIG. 4 represents a learning phase of the ultra wide band signal detection method according to one embodiment of the invention,

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

[0040] FIGS. 1a and 1b represent examples of signals to be detected. They are radio frequency signals, for which the amplitude in electric field as a function of time is shown. The signals to be detected are ultra wide band signals for which the shape in time is either bipolar (FIG. 1a), in other words they have a positive alternation and a negative alternation, or they are mono polar (FIG. 1b), in other words they have only a positive alternation.

[0041] In both cases, the rise time Tm is of the order of 0.1 nanosecond and the mean duration Td is of the order of 10 nanoseconds. The amplitude Emax of the ultra wide band signal can vary from a few V/m to several tens of kV/m, depending on the power of the signal source and the distance between the signal source and the detector.

[0042] FIG. 1c represents the spectrum of an ultra wide band signal. The frequency coverage of the ultra wide band signal is such that the band ratio RB=Fh/Fb is greater then 10, where Fh is the high frequency of the signal and Fb is the low frequency of the signal. The band ratio RB is even higher than the rise time Tm is low.

[0043] According to one preferred embodiment shown in FIG. 2, the ultra wide band signal detection device according to the invention includes the following elements.

[0044] The ultra wide band signal detection device comprises one or several ultra wide band signal reception antennas 1. For example, it may be a monopole antenna. FIG. 2 shows a single antenna, but the device can include several antennas to make it independent of the direction of the signal to be detected and the orientation of the electric field.

[0045] The output from antenna 1 is connected to the input of a limiter 2 that protects electronic components downstream. The limiter clips the signal received by the antenna 1 above a predetermined threshold. Thus, the limiter 2 produces a limited signal at its output with an amplitude compatible with protection of electronic components downstream.

[0046] The output of the limiter 2 is connected to the input of a power divider 3 that distributes the signal that it receives identically on several parallel channels. In the example shown, the power divider 3 has four outputs, as an example.

[0047] Each output is connected to a respective branch. The branches are similar.

[0048] One branch comprises a respective attenuator 4.sub.1, 4.sub.2, 4.sub.3 and 4.sub.4 that assures that the signal amplitude is compatible with electronic components downstream. The output of each attenuator 4.sub.1, 4.sub.2, 4.sub.3 and 4.sub.4 is connected to the input of a respective passband filter 5.sub.1, 5.sub.2, 5.sub.3 and 5.sub.4.

[0049] Each passband filter 5.sub.1, 5.sub.2, 5.sub.3 and 5.sub.4 divides the spectral content of the signal that it receives into a respective sub-band. The sub-bands are adjacent and the combination of all the sub-bands covers the frequency range of the ultra wide band signal to be detected. For example, filter 5.sub.1 correspond to the 0 to 0.1 GHz sub-band, filter 5.sub.2 corresponds to the 0.1 to 0.5 GHz sub-band, filter 5.sub.3 corresponds to the 0.5 to 1 GHz sub-band and filter 5.sub.4 corresponds to the 1 to 3 GHz sub-band. There can be a small overlap between sub-bands.

[0050] The output of each passband filter 5.sub.1, 5.sub.2, 5.sub.3 and 5.sub.4 is connected to the input of a respective logarithmic amplifier 6.sub.1, 6.sub.2, 6.sub.3, and 6.sub.4 that outputs the signal envelope in a respective sub-band defined by the passband filter 5.sub.1, 5.sub.2, 5.sub.3 and 5.sub.4.

[0051] It should be noted that the response time of logarithmic amplifiers in the lowest frequency bands is compatible with the detection of UWB type signals.

[0052] The output of each logarithmic amplifier 6.sub.1, 6.sub.2, 6.sub.3 and 6.sub.4 is connected to the input to a respective analogue/digital converter 7.sub.1, 7.sub.2, 7.sub.3, and 7.sub.4 that outputs a digital signal representative of the envelope of the signal in a respective sub-band.

[0053] The output of each analogue/digital converter 7.sub.1, 7.sub.2, 7.sub.3 and 7.sub.4 is connected to a respective input of a calculation module 8.

[0054] The calculation module 8 is a programmable microcomputer that has calculation and memory capabilities. For example, it may be an FPGA type component.

[0055] The calculation module 8 receives signals output from analogue/digital converters 7.sub.1, 7.sub.2, 7.sub.3 and 7.sub.4 and determines whether or not the received signal is a UWB signal. To achieve this, the amplitude and duration of the signal received in each frequency sub-band are determined. A signal is detected as being an ultra wide band signal if the amplitudes in each of the frequency sub-bands are high simultaneously and if the total duration of the detected signal is of the order of 10 to 20 nanoseconds. This approach overcomes difficulties related to the rise time of the detection component. The following description gives details of operation of the calculation module 8.

[0056] The output from calculation module 8 is connected to an alarm module 9. The calculation module 8 transmits an information signal to the alarm module 9 if the signal received by the detection device is of the UWB type. The alarm module 9 then issues an alarm that may be audible and/or visual. The alarm can also be an electric signal containing warning information that is sent to a remote processing system.

[0057] FIG. 3 shows the operation of the ultra wide band signal detection device, in the form of a flowchart comprising steps E1 to E5.

[0058] Step E1 is the reception of a signal S by the antenna 1.

[0059] The next step E2 is division of the received signal S into several frequency sub-bands. The sub-bands are adjacent and the combination of all the sub-bands covers the frequency range of the ultra wide band signal to be detected. For example, the signal is divided into four frequency sub-bands SB1, SB2, SB3 and SB4.

[0060] In the next step E3, the divided signal envelope is determined for each sub-band.

[0061] The next step E4 is a comparison of the signal amplitude in each sub-band with a respective predetermined amplitude threshold SA1, SA2, SA3 and SA4, and a comparison of the total duration of the detected signal with a predetermined time threshold ST. The time threshold is the same for all sub-bands and may for example be equal to 10 nanoseconds.

[0062] If the amplitude of the signal detected in each sub-band is greater than the amplitude threshold SA and if the total duration of the detected signal is less than the time threshold ST, then the detected signal S is identified as being of the ultra wide band type.

[0063] Preferably, a detected UWB signal is also compared with reference UWB signals stored in the calculation module 8. These reference UWB signals are determined during a learning phase that will be described below. They form signals typical of the normal electromagnetic environment of the device. If the detected signal is similar to a reference UWB signal, it is not considered to be an alarm generator.

[0064] The comparison is made on a number of criteria, for example the measured amplitude in each sub-band, the duration, the repetition ratio, and the event time and date. A user will preferably be able to configure all or at least some of these criteria.

[0065] Error margins can also be configured by the user, and are taken into account for each comparison made.

[0066] If the detected signals are repetitive events, the minimum, maximum and average amplitudes and durations and any other statistic that can be deduced from them (standard deviation, etc.) can be used.

[0067] Comparison and/or discrimination criteria can be formed from the envelope: slope of the first rising front, decay time, decay shape. The calculation module determines these data from the recorded envelope. Several of these criteria may be necessary. Criteria are valid for all sub-bands.

[0068] In all cases, the characteristics of the detected UWB signal are recorded so that a log of the electromagnetic environment of the detection device can be created.

[0069] The next step E5 is to send an alarm when the detected signal S is identified as being of the ultra wide band type, and if applicable, different from the reference signals in the previous step. The alarm is emitted by the alarm module 9. It may be an audible and/or visible alarm. The alarm can also be an electric signal containing warning information that is sent to a remote processing system.

[0070] FIG. 4 shows a learning phase of the ultra wide band signal detection device, in the form of a flowchart comprising steps E10 to E11.

[0071] Learning takes place when the device is started for the first time. It may also be necessary occasionally during use of the detection device.

[0072] Step E10 records signals detected in each frequency sub-band for a predetermined duration that may vary from several seconds to several hours. This is done using steps E1 to E4 described above. If UWB signals are detected during the learning phase, it is considered that they form part of the normal electromagnetic environment of the device. They are reference signals.

[0073] The next step E11 stores the characteristics of reference signals in the calculation module 8.

[0074] The characteristics stored are characteristics that will be used in the subsequent comparison step E4.

[0075] Preferably, several UWB signal detectors are used in an installation to be monitored. Detectors are then located at sufficient intervals from each other, for example about ten metres, and are perfectly synchronised by their calculation modules. As a variant, synchronisation is also possible using a GPS chip capable of giving a good time reference. The GPS chip is a complementary component connected to or integrated into the calculation module 8.