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WO2007044653A1 - Systeme et procede de detection de circuits radio utilisant une distorsion d'intermodulation - Google Patents

Systeme et procede de detection de circuits radio utilisant une distorsion d'intermodulation Download PDF

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Publication number
WO2007044653A1
WO2007044653A1 PCT/US2006/039366 US2006039366W WO2007044653A1 WO 2007044653 A1 WO2007044653 A1 WO 2007044653A1 US 2006039366 W US2006039366 W US 2006039366W WO 2007044653 A1 WO2007044653 A1 WO 2007044653A1
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WO
WIPO (PCT)
Prior art keywords
energy
radio unit
frequency spectrum
band
narrow band
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2006/039366
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English (en)
Inventor
Gregory L. Hey-Shipton
Markku I. Salkola
Neil O. Fenzi
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Clearday Inc
Original Assignee
Superconductor Technologies Inc
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Filing date
Publication date
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Publication of WO2007044653A1 publication Critical patent/WO2007044653A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors

Definitions

  • This invention generally relate to systems and methods for locating unknown radio units.
  • radio location techniques are known in the art, many of these techniques require transmission of unique location signals from the target radio unit, or otherwise, some type of communication between the target radio unit and a detection device.
  • radio location techniques require the target radio unit to be turned on and actively transmitting signals.
  • some type of coordination between the target radio unit and the detection device is necessary in prior art radio unit location techniques. In some applications, this may not be possible.
  • a prior art radio unit detection system 10 generally comprises an energy transmission assembly 14 configured for wirelessly transmitting energy to the target radio unit 12 and an energy reception assembly 16 configured for wirelessly receiving reflected energy from the target radio unit 12.
  • the energy transmission assembly 14 includes first and second signal generators 18a, 18b, first and second band-pass filters 20a, 20b respectively coupled to outputs of the first and second signal generators 18a, 18b, and first and second transmit antennas 22a, 22b coupled to the outputs of the first and second band-pass filters 20a, 20b.
  • the energy reception assembly 16 includes a receiving antenna 24, a band-pass filter 26 coupled to the output of the receiving antenna 24, a signal detector 28 coupled to the output of the band-pass filter 26, and a signal processor 30 coupled to the output of the signal detector 28.
  • the first and second signal generators 18a, 18b which may take the form of conventional oscillators, respectively generate sinusoidal signals having closely spaced frequencies ft, f 2 .
  • the signals can either be pulsed or continuous-wave (CW).
  • the first and second band-pass filters 20a, 20b respectively have center frequencies equal to frequencies fi, f 2 and have very narrow bandwidths, thereby removing any frequency components from the signals generated by the signal generators 18a, 18b outside of the frequencies fi, f 2 that may otherwise disguise the intermodulation energy reflected from the target radio unit 12.
  • energy having discrete fundamental tones centered at frequencies ft, f 2 is wirelessly transmitted from the respective first and second transmitting antennas 22a, 22b to the target radio unit 12.
  • a combiner may be used to combine the energy output from the band-pass filters 22a, 22b, in which case, the resulting energy can be wirelessly transmitted from a single antenna.
  • the target radio unit 12 comprises a receiving antenna 72 and receiver circuitry 74 coupled to the output of the target radio unit 12. A portion of the energy transmitted by the system 10 is received by the receiving antenna 72 and enters the receiver circuitry 74 where a portion of the received energy is reflected from the receiver circuitry 74 and re-radiated to the energy reception assembly 16 via the antenna 24.
  • the non-linear components within the receiver circuitry 74 mix the closely spaced fundamental tones in the energy, resulting in intermodulation distortion within the frequency band. In particular, lower-order spurious tones centered at frequencies away from the fundamental tones are created, as illustrated in Fig. 2.
  • the lower-order intermodulation tones of interest are the odd-order tones (3 rd , 5 th , 7 th , etc.), since they occur close to the fundamental tones.
  • the 3 rd order tones i.e., those centered at frequencies equal to 2fi-f 2 and 2f 2 -fi
  • the energy reflected by the target radio unit 12 contains the fundamental tones, along with lower-order intermodulation tones.
  • the third band-pass filter 26 is very selective (i.e., has a small bandwidth relative to the fundamental frequencies f 1 ( f 2 ) and has a center frequency coinciding with the frequency at which one of the lower-order intermodulation tones is centered — preferably one of the 3 rd order tones; for example, the intermodulation tone centered at frequency 2f 2 -fi .
  • multiple band-pass filters e.g., two band-pass filters
  • the center frequency for one of the filters may be 2f 2 -fi
  • the center frequency for the other filter may be 2f r f 2 .
  • the center frequency of the band-reject filter(s) 36 may be selected to coincide with the frequencies at which any order of tones are centered.
  • the receiving antenna 24 receives the energy reflected from the target radio unit 12, and the band-pass filter 26 filters the received energy to isolate the selected lower-order intermodulation tone or tones.
  • the signal detector 28 detects the level (e.g., power level) of energy output by the band-pass filter 26 (i.e., the power level of the selected lower-order intermodulation tone), and the signal processor 30 detects the presence of the target radio unit 12 based on this measured level.
  • the target radio unit 12 is detected.
  • this technique generally works well for detecting radio units, it requires duplicative circuitry (i.e., two signal generators, two band-pass filters, and two antennas) for wirelessly transmitting the two-tone energy. As a result, this prior art technique does not lend itself well to applications where miniaturization is required or desired.
  • a method of remotely detecting a radio unit comprises generating energy distributed in a frequency spectrum.
  • the energy may, for example, take the form of a single pulse or a pulse train.
  • the energy has an envelope in the frequency spectrum shaped in accordance with a sine function.
  • the method further comprises rejecting a portion of the generated energy (e.g., at a depth of at least below -4OdB relative to a peak of the energy) within a narrow range of the frequency spectrum (e.g., a bandwidth equal to or less than 0.010 times a center of the frequency spectrum).
  • the method further comprises wirelessly transmitting the energy to the radio unit, wherein non-linearities within the radio unit add intermodulation energy within the narrow range of the frequency spectrum, and the energy is reflected from the radio unit.
  • the method further comprises receiving the reflected energy.
  • the radio unit is powered off when the energy is wirelessly transmitted to the radio unit.
  • the method further comprises detecting the energy within the narrow range of the frequency spectrum, and detecting a presence of the radio unit based on the detected energy.
  • the location of the radio unit may be determined based on the received energy, e.g., by using pulsed time of arrival techniques.
  • the reflected energy contains a code identifying the radio unit, in which case, the method may further comprise detecting the code within the received energy.
  • a system for remotely detecting a radio unit comprises a signal generator (e.g., a pulse generator) configured for generating energy.
  • the energy has an envelope in the frequency spectrum shaped in accordance with a sine function.
  • the system further comprises a narrow band-reject filter coupled to an output of the signal generator.
  • the narrow band-reject filter may, e.g., reject energy at least below -4OdB relative to a peak of the energy, and may have a bandwidth equal to or less than 0.010 times a center of the frequency spectrum.
  • the system further comprises at least one antenna coupled to an output of the narrow band-reject filter for wirelessly transmitting the energy to the radio unit. Non-linearities within the radio unit add intermodulation energy within the narrow range of the frequency spectrum, and the energy is reflected from the radio unit.
  • the system further comprises a narrow band-pass filter coupled to an output of the antenna(s), wherein the narrow band-reject filter and narrow band-pass filter have substantially coincident center frequencies. For example, if the energy has an envelope shaped in accordance with a sine function, the center frequencies of the narrow band-reject filter and narrow band-pass filter may be located within a null of the sine function.
  • the system further comprises a signal detector coupled to an output of the band-pass filter, and a signal processor coupled to an output of the signal detector for detecting a presence of the radio unit. In an optional embodiment, the signal processor is configured for determining a location of the radio unit.
  • the reflected energy contains a code identifying the radio unit, in which case, the signal processor may detect the code within the received energy.
  • FIG. 1 is a block diagram of a prior art radio unit detection system
  • Fig. 2 is a diagram showing the distribution of energy generated by the prior art system of Fig. 1 and reflected from the radio unit
  • FIG. 3 is a block diagram of a radio unit detection system arranged in accordance with an embodiment of the inventions;
  • Fig. 4 is a diagram showing the distribution of energy generated by a signal generator of the system of Fig. 3;
  • Fig. 5 is a plot of intermodulation energy distortion reflected from the radio unit, when active and inactive;
  • Fig. 6 is a diagram showing computed insertion loss outputs of a band- reject filter and band-pass filter utilized in the system of Fig. 3;
  • Figs. 7a-7c are diagrams showing the distribution of notched energy output by a band-reject filter of the system of Fig. 3;
  • Figs. 8a-8b are diagrams showing computed intermodulation power as a function of various parameters of a band-reject filter used in the system of Fig. 3;
  • Fig. 9 is a diagram showing the computed energy reflected from a nonlinear target compared to a linear target in response to the notched energy transmitted by the system of Fig. 3;
  • Fig. 10 is a diagram showing the power spectrum of one coherent pulsed waveform
  • Fig. 11 is a diagram showing the power spectrum of another coherent pulsed waveform
  • Fig. 12 is a diagram showing the power spectrum of still anther coherent pulsed waveform
  • Fig. 13 is a diagram showing the power spectrum of yet another coherent pulsed waveform
  • Fig. 14 is a block diagram of a radio unit detection system arranged in accordance with another embodiment of the inventions.
  • the system described herein is configured for detecting the presence of a target radio unit. As with prior art systems, this system relies on the inherent non- linearities in electronic circuitry to detect the target radio unit. Unlike the prior art systems, the system described herein wirelessly transmits energy as a single signal having a "notched" frequency spectrum to the target radio unit, where such non- linearities create intermodulation distortion that adds energy within the notch. The energy reflected from the radio unit can then be received and the energy within the notch measured to detect the presence of the radio unit.
  • the system described herein only transmits one signal to the radio unit, the number and/or size of the components can be reduced, thereby lending itself well to miniaturization, and therefore, airborne use.
  • a system can be mounted on any suitable platform, such as an aircraft, piloted or un-piloted.
  • the system 50 generally comprises an energy transmission assembly 54 configured for wirelessly transmitting energy to the target radio unit 52 and an energy reception assembly 56 configured for wirelessly receiving reflected energy from the target radio unit 52.
  • the energy transmission assembly 54 includes a signal generator 58, a band-reject filter 60 coupled to the output of the signal generator 58, and a transmit antenna 62 coupled to the output of the band-reject filter 60.
  • the energy reception assembly 56 includes a receiving antenna 64, a band-pass filter 66 coupled to the output of the receiving antenna 64, a signal detector 68 coupled to the output of the band-pass filter 66, and a signal processor 70 coupled to the output of the signal detector 68.
  • the energy transmission assembly 54 and energy reception assembly 56 are shown as being bistatic (i.e., separate transmitting and receiving antennas are used to transmit and receive energy), they may alternatively be monostatic (i.e., a common antenna is used for transmitting and receiving energy). In the case of a monostatic arrangement, a transmit/receive switch or circulator (not shown) is preferably used, so that the transmitted energy does not damage or confuse the components of the energy reception assembly 16.
  • the transmitting antenna 62 and receiving antenna 64 may be steerable or fixed with equal or unequal horizontal and vertical plane field patterns and may utilize synthetic aperture techniques to improve spatial resolution.
  • the signal generator 58 generates a single-tone pulse by, e.g., amplitude modulating a single tone centered on frequency f 0 (e.g., a sinusoid having a frequency f 0 ) by a rectangular function.
  • a single tone centered on frequency f 0 e.g., a sinusoid having a frequency f 0
  • a rectangular function e.g., a sinusoid having a frequency f 0
  • other pulse shapes that deviate from an ideal rectangular shape can be used. As shown in Fig.
  • the energy of a single-tone pulse is distributed within a frequency spectrum as a sin(x)/x (sine) function (only the main and first two upper and lower side lobes are shown) centered on the frequency f 0 of the tone, with the main lobe having a bandwidth equal to 2/(T*f 0 ), where T is the width of the single- tone pulse in seconds, and the frequency f being normalized to the center frequency
  • the band-reject filter 60 has a relative narrow bandwidth that removes a notch-shaped portion of energy from the single-tone pulse in the frequency spectrum.
  • a band-reject filter that can be used with the system 50 is a low-loss dielectric resonating filter described in U.S. Patent No. 4,862,122.
  • a commercial embodiment of a band-reject filter that can be used with the system 50 is available from K&L Microwave, Inc., located at 2250 Northwood Drive, Salisbury, Maryland 21801 , as part number WSN-00030.
  • energy distributed in accordance with a notched sine function is wirelessly transmitted from the transmitting antenna 62 to the target radio unit 52.
  • a portion of the energy transmitted by the system 10 is received by the receiving antenna 72 and enters the receiver circuitry 74 where a portion of the received energy is reflected from the receiver circuitry 74 and re-radiated to the energy reception assembly 56 via the antenna 64.
  • the non-linear components within the receiver circuitry 74 results in intermodulation distortion that redistributes energy within the notch. That is, the energy is redistributed in the frequency spectrum due to the variable impedance (i.e., both resistance and reactance) of the receiver circuitry (or alternatively the transmitter circuitry) of the target radio unit primarily through amplitude and phase modulation.
  • a target radio unit could be a T5620 Talkabout FRS/GMRS Radio, manufactured by Motorola, Inc.
  • the non-linear device is a semiconductor (e.g., diodes and/or transistors) located behind a band-pass filter of the receiver circuitry of the target radio unit.
  • the target radio unit will only produce a non-linear response when the energy is coupled to the receiver circuitry by an antenna of the radio unit and then passed through the band-pass filter of the receiver circuitry.
  • the level of the reflected intermodulation energy is much lower when the target radio unit 52 is inactive.
  • a T5620 Talkabout FRS/GMRS radio unit was characterized using a two- tone, 3 rd order intermodulation generation measurement system similar to that shown in Fig. 1, with the exception that the signals were measured directly from the antenna port of the radio unit— rather than radiated.
  • the fundamental input tones were centered at 465 MHz and 466 MHz, which generated 3 rd order intermodulation tones centered at 464 MHz and 467 MHz.
  • the power level of the fundamental input tones, and average power level of the resulting 3 rd order intermodulation tones were measured and plotted for both powered-on (active) and powered-off (dormant) cases, as shown in Fig. 5. Note that at an input power of -7 dBm, the power level of the reflected 3 rd order tones are independent of the state of the target radio unit. Significantly, coupling between the system 50 and other non-linear devices will be much lower (due to the absence of an appropriate antenna and filter); hence, energy reflected from the target radio unit 52 will dominate.
  • the reflected energy is distributed in a frequency spectrum as a sine function having a notch at least partially filled in with intermodulation energy.
  • the band-pass filter 66 has a center frequency that coincides with the center frequency of the notch (i.e., the center frequency of the band-reject filter 60), and is very selective (i.e., has a small bandwidth relative to the fundamental frequency f 0 ; e.g., equal to or less than 0.010 times, and preferably equal to or less than 0.002 times, the fundamental frequency f 0 ) in order to maximize rejection of the energy outside the bandwidth rejected by the band-reject filter 60.
  • the band-pass filter 66 preferably has a low loss in order to maximize the sensitivity as the intermodulation energy detection process.
  • a commercial embodiment of a band-pass filter that can be used with the system 50 is available from Superconductor Technologies, Inc., 460 Ward Drive, Santa Barbara, CA 93111 under the name SuperLink®.
  • the receiving antenna 64 receives the energy reflected from the target radio unit 52, and the band-pass filter 66 filters the received energy to isolate the notch within the energy.
  • the signal detector 68 detects the level (e.g., power level) of energy output by the band-pass filter 66 (i.e., the power level of the energy in the notch), and the signal processor 70 detects the presence of the target radio unit 52 based on this measured level.
  • the band-reject filter 60 and band-pass filter 66 are preferably designed in coordination with each other, and as previously discussed above, both should be as highly selective as possible to maximize detection of the intermodulation energy.
  • Fig. 6 illustrates an example of a computer generated response for the rejection characteristics of both the band-pass filter 66 and band-reject filter 60, which have been modeled with 8 resonators.
  • the center frequency of both the band-reject filter 60 and band-pass filter 66 is 450 MHz, and the pass band of the band-pass filter 66 is approximately one-half the stop band of the band-reject filter 60.
  • the band responses of the filters cross at a very low level — approximately at - 8OdB, so that the signal processor 30 can differentiate the intermodulation energy from background and clutter energy.
  • the center frequency of the band-reject filter 60 may be selected to locate the notch relative to the center frequency f 0 of the single-tone pulse in a manner that optimizes the non-linear response of the target radio unit 52.
  • the center frequency of the band-reject filter 60 may be coincident with the center frequency f 0 of the single-tone pulse or may be displaced from the center frequency f 0 by a frequency df from f 0 .
  • the width of the single-tone pulse T is also selected to maximize the energy in the receiver circuitry 74 of the target radio unit 52 and for other operational requirements (e.g., range, peak pulsed power, size, weight, etc.). In addition, care must be taken when selecting the bandwidth of the band- reject filter 60.
  • the integrated intermodulation power has been plotted as a function of the fractional bandwidth (VWf 0 ) of the band- reject filter 60 for the cases where the fractional center frequency f BRF /fo of the band- reject filter 60 is 1.01 and 1.008.
  • the optimum bandwidth W for the band-reject filter 60 is approximately 0.0045f 0 .
  • the integrated intermodulation power has been plotted as a function of the fractional center frequency f ⁇ RF/fo Qf the band-reject filter 60 for the cases where the fractional bandwidth VWf 0 of the band-reject filter 60 is 0.002 and 0.004.
  • a computer simulated example showing the energy distribution of a single-tone pulse at the terminals of both a linear target and a nonlinear target was plotted over a frequency spectrum.
  • a pulse train may be utilized to further optimize the system 50, resulting in narrow spectral lines that increase the signal strength of the energy reflected from the target radio unit 52.
  • coherent pulses with appropriate selection of pulse width, pulse repetition frequency, and pulse-to-pulse phasing, will generate concentrations of energy around discrete spectral lines. This property can further be used to optimize the non-linear returns from the target radio unit, while still maintaining the advantage of a single signal generator and associated circuitry.
  • the use of multiple pulses also facilitates coherent pulsed time of arrival techniques in target location, target speed determination, and signal processing. This technique can also be combined with synthetic aperture radar techniques to further facilitate target location.
  • Fig. 10 illustrates a computer generated comparison between the energy of a single-tone pulse and the energy of an infinite sequence of pulses distributed within a frequency spectrum, wherein the power level of the energy in dB is plotted as a function of normalized frequency f/fo.
  • the pulses were created by modulating a sine wave with an ideal rectangular function.
  • the peak power level was equal, and the pulse width T was equal to 100/f 0 .
  • the pulse repetition period T p was twice the pulse width T, and the phase difference between adjacent pulses was 0 degrees.
  • the single-tone pulse is distributed within a frequency spectrum as a sine function in the same manner described above, while the infinite pulse train is distributed as discrete spectral lines having an envelope shaped in accordance with a sine function.
  • Fig. 11 illustrates a computer generated comparison between the energy of a single-tone pulse and the energy of a finite gate of 20 pulses (as would be the case for a moving target radio or platform) distributed within a frequency spectrum, wherein the power level of the energy in dB is plotted as a function of normalized frequency f/f 0 .
  • the pulses were created by modulating a sine wave with an ideal rectangular function.
  • the peak power level was equal
  • the pulse width T was equal to 100/f 0 .
  • the pulse repetition period T p is twice the pulse width T, and the phase difference between adjacent pulses is 0 degrees.
  • the finite pulse train is distributed as discrete spectral lines having an envelope shaped in accordance with a sine function.
  • the use of a finite pulse train results in an increase of energy between the locations of the spectral lines, with the bandwidth of the energy surrounding each spectral line is equal to 2/nT p , where n is the number of pulses, and T p is the pulse repetition period.
  • n is the number of pulses
  • T p is the pulse repetition period.
  • most energy is still concentrated in the narrow range of frequencies adjacent the location of the spectral lines, thereby facilitating the filtering process.
  • the use of a pulse train effectively creates 3-tone energy in the frequency spectrum, which, when incident on a non- linear target, will produce both 2-tone, 3 rd order intermodulation energy, and 3-tone, 3 rd order intermodulation energy in regions of the frequency spectrum equal to 0.99f 0 or 1.01f 0 .
  • the center frequencies F B RF, F B PF of the band-reject filter 60 and band-pass filter 66 may either be equal to 0.99f 0 or 1.01f 0 .
  • two band-reject filters 60 and two band-pass filters 66 may be utilized, in which case, the center frequencies F B RF, F B PF for one matched set of filters may be 0.99f 0 and the center frequencies F B RF, FBPF for the other matched set of filters may be 1.01f 0 .
  • the center frequencies F BRF , F B PF of the band-reject filter 60 and bandpass filter 66 may be selected to coincide with any frequency band where spurious intermodulation energy is expected to reside.
  • the parameters of the pulse train may be selected to facilitate target radio detection.
  • Fig. 12 illustrates a computer generated comparison between the energy of a single-tone pulse and the energy of a finite sequence of 20 pulses distributed within a frequency spectrum, wherein the pulse repetition period T p for the finite pulse train case has been modified to be equal to one and a half times the pulse width T, and the phase difference between adjacent pulses has been modified to be equal to 180 degrees.
  • the pulse train with these parameters effectively creates 2-tone energy in the frequency spectrum, which behaves much like the two-tone energy of Fig. 2, which, when incident on a non-linear target, will produce 2-tone, 3 rd order intermodulation energy in regions of the frequency spectrum centered about f 0 + 1/T and f 0 -1/T.
  • the center frequencies FBRF, FBPF of the band-reject filter 60 and band-pass filter 66 may either be equal to f 0 + 1/T or fo -1/T, or alternatively, if two band-reject filters 60 and two band-pass filters 66 are utilized, equal to both fo + 1/T and fo -1/T.
  • Fig. 13 illustrates a computer generated comparison between the energy of a single-tone pulse and the energy of a finite sequence of 20 pulses distributed within a frequency spectrum, wherein the pulse repetition period T p for the finite pulse train case has been modified to be equal to five times the pulse width T.
  • the pulse train with these parameters effectively creates 9-tone energy in the frequency spectrum, which, when incident on a non-linear target, will produce 2- tone, 3 rd order intermodulation energy in many regions of the frequency spectrum.
  • RFID radio frequency identification
  • a radio unit in the form of a RFID tag 80 can be detected with a RFID detection system 50', which is similar to the system 50 illustrated in Fig. 3, with the exceptions noted below.
  • the RFID tag 80 includes an antenna 82, a detector 84, an encoder 86, a switch 88, a non-linear device 90, and an amplifier 92.
  • the antenna 82 is configured for wirelessly receiving a portion of the notched energy transmitted from the system 50'.
  • the detector 84 is configured for detecting the receipt of the energy and optionally activating the encoder 86.
  • the non-linear device 90 which may be one or more diodes and/or transistors, creates intermodulation distortion that adds energy within the notch of the transmitted energy.
  • the encoder 86 encodes the energy with an identification code by alternately connecting and disconnecting the non-linear device 90 from the remaining circuitry, thereby amplitude modulating the intermodulation energy.
  • the amplifier 92 which takes the form of a tank circuit having a capacitor and inductor, amplifies the energy, which is then wirelessly transmitted from the antenna 82.
  • the RFID tag 80 may be powered by the energy incident on the antenna 82 or a battery (not shown).
  • the modified system 50' wirelessly receives and processes the energy from the RFID tag 80 in the same manner that the system 50 receives and processes the energy from the radio unit 52, with the exception that the signal processor detects the identification code in the energy within the notch of the frequency spectrum.
  • the signal processor detects the identification code in the energy within the notch of the frequency spectrum.
  • the energy transmitted from the system 50 interferes with the energy transmitted from the RFID.
  • no entity, other than the one in control of the system 50 will be able to detect the presence of the RFID tag 80.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

L'invention concerne un procédé et des systèmes de détection d'unités radio. Le procédé comporte les étapes consistant à: produire de l'énergie répartie dans un spectre de fréquences, et rejeter une partie de l'énergie produite dans une plage étroite dudit spectre; transmettre sans fil l'énergie vers l'unité radio, les non-linéarités présentes dans l'unité radio ajoutant de l'énergie d'intermodulation dans la plage étroite du spectre de fréquences; faire en sorte que l'énergie reçue sans fil soit réfléchie par l'unité radio; détecter ensuite cette énergie dans la plage étroite dudit spectre; détecter la présence de l'unité radio sur la base de l'énergie détectée.
PCT/US2006/039366 2005-10-07 2006-10-06 Systeme et procede de detection de circuits radio utilisant une distorsion d'intermodulation Ceased WO2007044653A1 (fr)

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US8831593B2 (en) 2011-09-15 2014-09-09 Andrew Wireless Systems Gmbh Configuration sub-system for telecommunication systems
US9036486B2 (en) 2011-09-16 2015-05-19 Andrew Wireless Systems Gmbh Integrated intermodulation detection sub-system for telecommunications systems
US9398464B2 (en) 2011-07-11 2016-07-19 Commscope Technologies Llc Base station router for distributed antenna systems
US9894623B2 (en) 2012-09-14 2018-02-13 Andrew Wireless Systems Gmbh Uplink path integrity detection in distributed antenna systems
US9913147B2 (en) 2012-10-05 2018-03-06 Andrew Wireless Systems Gmbh Capacity optimization sub-system for distributed antenna system
CN109922709A (zh) * 2017-05-18 2019-06-21 伊卡尔芬兰有限公司 用于测量眼睛的生理参数的仪器和方法

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