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
  • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
  • G01S13/0209—Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• • 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
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
  • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
• • 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
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
  • G01S7/28—Details of pulse systems
  • G01S7/282—Transmitters
• • 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
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
  • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
  • G01S2013/9314—Parking operations

Definitions

• Broadband radar and modulator in particular for switching microwave waves over a very short time
• the present invention relates to an ultra wideband radar. It also relates to a modulator, in particular for switching microwave waves over a very short duration. It applies in particular to aid in the parking of motor vehicles. More generally, it is applicable for all applications which require high-resolution radar detection at a distance at low cost.
• Parking assistance typically requires detection ranges of the order of a few meters, two meters for example, and a resolution of a few centimeters, five to ten centimeters for example.
• a known solution consists in using acoustic sensors. Several acoustic sensors are thus placed at the rear of the vehicle, four for example, and the distance from an obstacle is then conventionally determined by a triangularization method from the measurements produced by each of the sensors.
• a first drawback is that an acoustic sensor does not work, or works very badly, if the wearer's movements are sudden or rapid, because of the turbulence produced.
• Another drawback comes from the limited scope, which can prevent in particular a multifunctional use.
• the acoustic sensors must always be mounted in an apparent manner so as to be directly opposite the obstacle to be detected. This results in a change in the exterior appearance of vehicles, often deemed undesirable by car manufacturers.
• these sensors are subject to external degradation caused by weather conditions, rain for example, but also by acts of vandalism. In addition, they do not work in all weathers and are particularly disturbed by the impact of water drops on the sensor in the presence of rain.
• Radar sensors make it possible to overcome all these drawbacks. However, a cost problem remains to be overcome, compatible with the use of mass consumption such as the automobile sector for example.
• these radars pose interference problems with other microwave systems in service, such as GPS for example.
• the radar must transmit by means of a carrier wave of sufficiently high frequency.
• This carrier can for example have a frequency of the order of 24 Ghz or even being in the millimeter range.
• the sensor must have a wide operating frequency band, in particular because of the short distance from the radar to the target, which is typically only one to two meters, and the discrimination power necessary for the intended application. It is then possible to carry out frequency or phase modulation over a very wide frequency band.
• An object of the invention is to allow the realization of a broadband radar at very low cost.
• the subject of the invention is a radar comprising a modulator modulating a microwave carrier wave, this modulator comprising:
• the microwave wave enters on one input of the mixer and the modulation signal enters on the other input of the mixer, the output signal of the mixer being supplied to the radar transmission means.
• the modulation signal may be impulse and of very short duration.
• a local oscillator operating as a free oscillator, provides the microwave wave to be modulated.
• the invention also relates to a microwave modulator, capable in particular of supplying pulses of very short duration economically.
• the invention has in particular the other main advantages that it makes it possible to obtain a radar of very high level of integration, having moreover the possibility of being multifunctional.
• a microwave switch or modulator according to the invention can carry out all types of modulation and can in particular modulate optical waves.
• FIG. 1 illustrates by a block diagram a known embodiment, according to the prior art, of a pulse radar. It includes a local oscillator 1 providing the carrier wave. This carrier wave passes through a switch 2 before being transmitted by a transmitting antenna 3. When the switch 2 is open, no signal is transmitted. The duration of a transmitted pulse 4 is determined by the closing time of the switch. This pulse 4 modulates the carrier wave. Still in a conventional manner, the reception signals are received by a reception antenna 5. The received signal attacks the input of a microwave mixer 6, the other input of this mixer being attacked by a signal from the local oscillator via a coupler 7 to obtain a demodulated signal at the output of the mixer, where the carrier is suppressed.
• Switch 2 is for example a PIN diode or an FET transistor. These components do not make it possible to obtain a pulse 4 of width less than about 10 nanoseconds, and are therefore far from allowing widths less than one nanosecond. Furthermore, at such pulse durations, the shape of the pulse is of very poor quality. It is far from being perfectly square and therefore does not pass the entire desired frequency band. In addition, the switching edges must be steep. However, too steep fronts disturb the local oscillator 1 upstream. A radar as illustrated in FIG. 1 can therefore only with difficulty operate over a wide frequency band and not economically.
• FIG. 2 illustrates by a block diagram an exemplary embodiment of a radar according to the invention. It is for example a radar with modulation amplitude or phase.
• the modulation pulse 4 is not produced by a switch, but by means of a microwave mixer 21 and a reference pulse 22.
• the latter is for example supplied by a digital circuit 23.
• Current digital circuits are indeed capable of providing very short pulses, less than a nanosecond in particular, for example of the order of 500 picoseconds.
• the shape of the pulses supplied is for example square.
• the radar also comprises at least one local oscillator 1, which functions as a free oscillator, that is to say an uncontrolled one. It also includes a transmitting antenna 3 and reception circuits 5, 6.
• a first input of the mixer 21 receives the signal supplied by the oscillator 1.
• the second input of this mixer receives the reference pulse 22.
• the mixture of the latter with the carrier creates at the output of the mixer a signal modulated by a pulse which is the image of this reference pulse. That is to say that the modulation pulse 4 has a pulse width and rising and falling edges substantially identical to the width and to the edges of the reference pulse.
• the mixer 21 can have a conventional structure. It can in particular be produced on the basis of diodes or microwave transistors. Given the frequencies involved, it may be necessary to provide an adaptation of the line 24 between the circuit 23 for generating the reference pulse 22 and the mixer 21 to allow in particular the passage of the entire frequency band. In particular, it is preferable that this line 24 is as short as possible.
• the mixer and the pulse generation circuit 23 are produced on the same chip, the same integrated circuit, for example of the MMIC type.
• the signal at the output of the mixer 21 is amplified on transmission by amplification means 25 before attacking the transmission antenna 3.
• the power transmitted is for example of the order of 10 mW, even lower .
• the reception can for example be done as in the case of the radar of FIG. 1, that is to say with a reception antenna 5 connected to an input of a mixer 6 whose other input receives the carrier wave supplied by the local oscillator 1 via a coupler 7.
• This mixer 6 then supplies as output a demodulated signal, image of the pulse emitted and intended for the processing circuits.
• FIGS. 3a and 3b illustrate examples of modulation codes used by a radar according to the invention. It is possible to provide a single pulse transmission, transmitted periodically. However, there may be interference or compatibility issues with other microwave systems in the radar environment. To overcome these problems, the radar according to the invention works, for example, on several pulses during each recurrence period, and in particular on a large number of pulses.
• Figures 3a and 3b illustrate two examples of sequences of pulses used. These sequences are for example pseudo-random, for example according to a Barker code.
• FIG. 3a presents a code varying between 0 and 1.
• this code comprises a series of elementary moments taking the value 0 or 1, the duration of an elementary moment being for example equal to 1ns, or less, for example 500ps .
• the output of the latter does not provide any signal.
• the output of the mixer supplies the product of the carrier by a constant signal, of infinite bandwidth, therefore equal to the carrier.
• the radar does not emit, the signal being zero at the output of the mixer 21.
• Figure 3b presents a code varying between -1 and +1, more precisely taking the values -1 or +1.
• the control of the mixer 21 is offset from the level 0 of the code 0-1 in FIG. 3a.
• the carrier is multiplied by -1, which corresponds to undergoing an offset of ⁇ .
• the carrier is multiplied by 1. In these cases, there is continuous transmission and the average value of the signal transmitted is zero. This can bring an advantage.
• FIG. 4 indeed shows a correlation result with secondary lobes 41 which are approximately 50 dB lower than the correlation peaks 42, and this regardless of the relative position of the sequences of pulses, whether or not there is overlap.
• the code can be a looped polynomial whose periodicity is greater than the round-trip propagation time for a target of maximum range, which in particular avoids ambiguity problems.
• the code used comprises for example 32,768 moments. If we suppose a continuous emission where each moment lasts a nanosecond, 1 ns, by taking the value -1 or 1 in a pseudo-random way, the total duration of the complete emission of the code is 32768 times 1 ns, that is to say approximately 32 ⁇ s , which corresponds to the repetition frequency.
• the ambiguity distance here is of the order of 4.9 km, very largely sufficient for the applications in question, which have a maximum range of a few meters to a few tens of meters.
• a long code makes it possible to work at lower peak power, which brings a better output and can also make it possible to save the amplification of the transmitted power. This makes it possible, for example, to save the amplifier 25 at the output of the mixer 21.
• FIG. 5 shows an embodiment comprising two reception mixers 61, 62.
• a circuit 63 placed on the input channel of one of the two mixers 61 dephases by ⁇ / 2 the signal coming from the oscillator 1.
• the signal reception drives each of these two mixers, their outputs are connected to the processing circuits.
• a mixer I, Q is thus obtained.
• This embodiment is particularly suitable for coding the pulses transmitted according to FIG. 3b, that is to say varying between -1 and +1.
• the modulation mixer 21 is off-center with respect to level 0 as indicated above.
• the control of the receiving mixer 6 must also be shifted. There is then the risk of the presence of uncontrolled microwave leaks. Using two mixers can help prevent these leaks.
• FIG. 6 shows an embodiment of a radar according to the invention in which the circuit 23 which generates the modulation pulses also comprises the circuits for processing the reception signals after demodulation, that is to say the code received .
• the output of the mixer 6, or the outputs of the mixers 61, 62 are connected to the input of this circuit 23.
• the circuit 23 is therefore a digital modulation and correlation circuit which generates coded pulses 22 intended for the mixer of modulation 21 on transmission and which includes the processing circuits, in particular for the detection of a target.
• FIG. 7 presents, by a block diagram, the functions of the modulation and correlation circuit 23.
• This circuit therefore generates the code pulses 22 in a conventional manner, for example by means of a shift register. These pulses are directed at output S to supply the mixer 21 on transmission and to supply an internal circuit 71 which is for example a programmable delay line. The output of this delay line is connected to the input of a multiplier 72 which multiplies the code shifted by the code received, supplied by the mixers 61, 62. The multiplier 72 multiplies these binary values with each other.
• the result of the multiplication is integrated by integration means 73. The latter sum the bits of the multiplication result.
• the integration means add this bit to the previous ones.
• the output of the integration means is connected to the input of a comparator 74 to be compared to a threshold.
• the result of the comparison defines the correlation between the code received and the code shifted, that is to say determines the presence or not of the target in the monitored distance box.
• the delay made by the delay line 71 on the transmitted code corresponds to this given distance box. If the result of the integration is greater than the threshold, the circuit 23 deduces therefrom the presence of the target in the distance box.
• the radar according to the invention does not examine all the distance boxes simultaneously. For example, if we consider a maximum range of two meters for a distance resolution of 10 cm, or 20 distance boxes, examining the 20 distance boxes requires performing 20 correlations like the one described above. Due to the short range, all distance boxes are not monitored simultaneously but periodically.
• the radar starts for example by treating the 20 th range bin and the 19 th and so on. When a target is detected in a distance box, the radar tracks this target.
• a processor not shown, integrated in the modulation and correlation circuit 23, processes the results of the comparison, and also manages the order of processing of the distance boxes, in particular by programming the delays effected by the delay line.
• FIG. 6 shows a radar comprising, in addition to the antennas 3, 5, four components in integrated circuit.
• a first component is the local oscillator 1.
• a second component 100 contains the modulation mixer 21 and for example the transmission amplifier 25.
• a third component 101 comprises the two mixer (s) 61, 62 as well as for example that amplifier 26.
• a fourth component is the modulation and correlation circuit 23.
• the latter is for example in technology known under the name of ECL Fast or in technology known under the name of BICMOS.
• the other components are, for example, in Asga (Gallium Arsenide) technology.
• Asga Gallium Arsenide
• the antennas 3, 5 are for example made up of printed networks of the patch or "patch" type.
• these antennas are not very directive and can therefore radiate over a wide space.
• the antennas can also, for example, be of the resonant dipole type.
• a radar according to FIG. 6 is very compact and compact. Furthermore, it can be produced at very low cost and in particular in large series. Indeed, the components used are economical. In particular, they can be produced at very low cost in the form of specific integrated circuits of the ASIC type.
• the modulation pulses 4 can be very narrow, less than 1 ns, or even reach 500 ps or less. Thus a pulse radar according to the invention can work up to frequency bands which reach 2 GHz.
• a radar according to the invention can also do Doppler detection.
• Other types of modulation than pulses can also be produced, thanks to the mixer 21 placed in the transmission circuit, coupled to the circuit 23 generating modulation signals.
• a microwave switch as produced by the association of the mixer 21 and the circuit 23, as a pulse generator 22, can of course be used for radar applications, but also for applications involving optical waves.
• this switch can modulate optical waves, associated with opto-electronic coupling means.
• opto-electronic component At the input, the component ensures a transition from the optics to the microwave, and the output component does the opposite.
• the other input of the mixer is of course always coupled to the output of the means 23 for generating pulses 22.
• These same means can supply other modulation signals than pulse signals.
• the switch then functions as a modulator which can carry out all types of modulations.
• the means 23 for generating pulses or modulation signals can be integrated in the same circuit, for example of the MMIC type.
• a radar according to the invention can be applied for all fields requiring a very large operating frequency band. It is very economical and has a very high level of integration. It also has the possibility of being multifunctional. Finally, the microwave switch or modulator that it uses can carry out all types of modulations and can in particular modulate optical waves.

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

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• 2000
  • 2000-12-15 FR FR0016414A patent/FR2818385B1/fr not_active Expired - Lifetime
• 2001
  • 2001-12-11 US US10/450,045 patent/US7161526B2/en not_active Expired - Lifetime
  • 2001-12-11 EP EP01270783A patent/EP1344086A1/de not_active Withdrawn
  • 2001-12-11 JP JP2002549989A patent/JP2004515789A/ja active Pending
  • 2001-12-11 WO PCT/FR2001/003927 patent/WO2002048735A1/fr not_active Application Discontinuation
• 2003
  • 2003-06-12 NO NO20032672A patent/NO20032672L/no not_active Application Discontinuation

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