RADAR DETECTION DEVICE

Abstract

A radar measuring device including at least: a circuit for generating a radar signal RF.sub.IN(t); an emitting antenna; an injection-locked oscillator; a first power divider comprising an input coupled to an output of the circuit for generating the radar signal RF.sub.IN(t), a first output coupled to the emitting antenna, and a second output to an input of the injection-locked oscillator which is configured to be locked over a portion of an effective band B of the radar signal RF.sub.IN(t); a receiving antenna intended to receive a reflected radar signal RF.sub.IN_REFL(t); a mixer comprising a first input coupled to the receiving antenna, a second input coupled to an output of the injection-locked oscillator, and an output coupled to an input to a signal processing circuit.

Claims

1. A radar measuring device including at least: a circuit for generating a radar signal RF.sub.IN(t); an emitting antenna; an injection-locked oscillator; a first power divider comprising an input coupled to an output of the circuit for generating the radar signal RF.sub.IN(t), a first output coupled to the emitting antenna, and a second output coupled to an input of the injection-locked oscillator which is configured to be locked over a portion of an effective band B of the radar signal RF.sub.IN(t); a receiving antenna intended to receive a reflected radar signal RF.sub.IN_REFL(t); a mixer comprising a first input coupled to the receiving antenna, a second input coupled to an output of the injection-locked oscillator; a signal processing circuit an input of which being coupled to an output of the mixer and configured to provide a signal which is representative of a distance between the receiving antenna and at least one reflector onto which the radar signal RF.sub.IN(t) is reflected.

2. The radar measuring device according to claim 1, wherein the circuit for generating the radar signal RF.sub.IN(t) is configured to generate the radar signal RF.sub.IN(t) corresponding to: a frequency-modulated periodic signal over at least one portion T.sub.rampe of a period T of said signal, corresponding, over said at least one portion T.sub.rampe of the period T, to a sinusoidal signal whose frequency varies linearly in the effective band B and whose amplitude alternates between a first value and a second value different from the first value, or a train of pulses whose frequency modulation is defined by the time position of the beginning of each pulse, by the relative phase-shift of the signal at the beginning of each pulse and by the width of each pulse.

3. The radar measuring device according to claim 2, wherein the radar signal RF.sub.IN(t) corresponding to a pulse train is such that: ${\mathrm{RF}}_{\mathrm{IN}\left(t\right)}=\underset{n=1}{\overset{n_{\max }}{.Math.}}.Math.\left(\frac{t-t_{\mathrm{start}}\left(n\right)-\frac{T\left(n\right)}{4}}{\frac{T\left(n\right)}{2}}\right).Math.e^{j2\pi f_a\left(t-t_{\mathrm{start}}\left(n\right)\right)},n\in \left\{1,\mathrm{.Math.},n_{\max }\right\}$ with f.sub.a corresponding to the frequency of the carrier of the radar signal RF.sub.IN(t);
T(n)=t.sub.start(n+1)−t.sub.start(n), and which corresponds to the duration of a n.sup.th pulse of the radar signal RF.sub.IN(t); $t_{\mathrm{start}}\left(n\right)=\frac{f_{\mathrm{in}}^{\prime }{T}_{\mathrm{rampe}}}{B_{\mathrm{in}}}\left(-1+\sqrt{1+\frac{2B_{\mathrm{in}}}{f_{\mathrm{in}}^{\mathrm{\prime 2}}{T}_{\mathrm{rampe}}}\left(n-1\right)}\right),n\in \left\{1,\mathrm{.Math.},n_{\max }\right\},$ and which corresponds to the starting time of each n.sup.th pulse of the radar signal radar RF.sub.IN(t); f.sub.in′ corresponding to the fundamental frequency of the modulating signal when n=1; n.sub.max corresponding to the number of pulses in the radar signal RF.sub.IN(t) over the effective band B.

4. The radar measuring device according to claim 1, further including a control circuit of the injection-locked oscillator configured to modify, at each period of the radar signal RF.sub.IN(t), the locking frequency band of the injection-locked oscillator such that, over several successive periods of the radar signal RF.sub.IN(t), the locking frequency bands of the injection-locked oscillator cover, together, the effective band B.

5. The radar measuring device according to claim 1, wherein the signal processing circuit is configured to implement: a band-pass filtering of the signal delivered at the output of the mixer, then an analog-to-digital conversion of the signal obtained after the implementation of the band-pass filtering, then a processing of the signal obtained after the implementation of the analog-to-digital conversion, keeping only portions of this signal during which the injection-locked oscillator is locked over a portion of the effective band B, then a discrete Fourier transform of the signal obtained after the implementation of the processing keeping only portions of the signal during which the injection-locked oscillator is locked over a portion of the effective band B.

6. The radar measuring device according to claim 1, including: several injection-locked oscillators; several first power dividers configured to apply the radar signal RF.sub.IN(t) on the emitting antenna and on an input of each of the injection-locked oscillators; several mixers each comprising a second input coupled to an output of one of the injection-locked oscillators and an output coupled to an input of the signal processing circuit; one or several second power divider(s) configured to apply the reflected radar signal RF.sub.IN_REFL(t) on a first input of each of the mixers.

7. The radar measuring device according to claim 6, wherein the signal processing circuit is configured to implement: a band-pass filtering of each of the signals delivered at the output of the mixers, then an analog-to-digital conversion of each of the signals obtained after the implementation of the filtering, then a processing of the signals obtained after the implementation of the analog-to-digital conversion, keeping only portions of each of these signals during which each of the injection-locked oscillators is locked over a portion of the effective band B, then a discrete Fourier transform of a signal obtained after the implementation of the processing keeping only portions of each of the signals during which each of the injection-locked oscillators is locked over a portion of the effective band B.

8. The radar measuring device according to claim 6, wherein each of the injection-locked oscillators is configured such that its locking frequency band is different from that of the other injection-locked oscillators and that the locking frequency bands of the injection-locked oscillators cover, together, the effective band B.

9. The radar measuring device according to claim 6, further including a control circuit of each of the injection-locked oscillators configured to modify, at each period of the radar signal RF.sub.IN(t), the locking frequency band of each of the injection-locked oscillators such that, over several periods of the radar signal RF.sub.IN(t), the locking frequency bands of the injection-locked oscillators include, together, the effective band B.

10. The radar measuring device according to claim 9, wherein the injection-locked oscillators are configured to be successively or simultaneously locked over different portions of the effective band B.

11. The radar measuring device according to claim 4, wherein: the control circuit is configured to apply, at the input of the injection-locked oscillator or of each of the injection-locked oscillators, a control voltage whose value determines a central frequency f.sub.c of a locking frequency band of the injection-locked oscillator or of each of the injection-locked oscillators, and/or the control circuit is configured to modify the values of switched capacitances of at least one resonator in the injection-locked oscillator or in each of the injection-locked oscillators.

12. The radar measuring device according to claim 9, wherein: the control circuit is configured to apply, at the input of the injection-locked oscillator or of each of the injection-locked oscillators, a control voltage whose value determines a central frequency f.sub.c of a locking frequency band of the injection-locked oscillator or of each of the injection-locked oscillators, and/or the control circuit is configured to modify the values of switched capacitances of at least one resonator in the injection-locked oscillator or in each of the injection-locked oscillators.

13. The radar measuring device according to claim 1, further including at least one power amplifier disposed between the emitting antenna and the first power divider(s).

14. The radar measuring device according to claim 1, further including at least one low-noise amplifier interposed between the receiving antenna and the mixer or, when the radar measuring device includes several second power dividers, between the receiving antenna and the second power dividers.

15. The radar measuring device according to claim 1, wherein the signal processing circuit (120) is configured to carry out a compensation of a phase-shift between the radar signal RF.sub.IN(t) and the signal(s) delivered at the output of the injection-locked oscillator(s).

16. The radar measuring device according to claim 15, further including a controllable feedback circuit configured, in a configuration of measuring the phase-shift between the radar signal RF.sub.IN(t) and the signal(s) delivered at the output of the injection-locked oscillator(s), to directly connect the first output of the first power divider of one of the first power dividers to the first input of the mixer or of each of the mixers, and wherein the signal processing signal is configured to perform a measurement of the phase-shift between the radar signal RF.sub.IN(t) and the or each of the signals delivered at the output of the injection-locked oscillator(s), then the phase-shift compensation using the performed phase-shift measurement(s).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present invention will be better understood upon reading the description of embodiments provided for purely indicative and non-limiting purposes with reference to the appended drawings wherein:

[0062] FIG. 1 schematically shows a radar measuring device according to a first embodiment;

[0063] FIG. 2 shows a first example of a radar signal RF.sub.IN(t) generated in a radar measuring device;

[0064] FIG. 3 shows the spectrum of the first example of the radar signal RF.sub.IN(t) when the latter is of the pulse-type and does not include any spectral overlap;

[0065] FIG. 4 shows the evolution in the time domain of the instantaneous frequency of the first example of the radar signal RF.sub.IN(t) when the latter is of the pulse-type and does not include any spectral overlap;

[0066] FIG. 5 shows the spectrum of the first example of the radar signal RF.sub.IN(t) when the latter is of the pulse-type and includes a spectral overlap;

[0067] FIG. 6 shows the evolution in the time domain of the instantaneous frequency of the first example of the radar signal RF.sub.IN(t) when the latter is of the pulse-type and includes a spectral overlap;

[0068] FIGS. 7 and 8 show, each, the evolution in the time domain of the instantaneous frequency of a second example of a FMCW-type radar signal RF.sub.IN(t) generated in the radar measuring device;

[0069] FIG. 9 shows the spectrum of the second example of the radar signal RF.sub.IN(t);

[0070] FIG. 10 shows several signals of the radar measuring device according to the first embodiment;

[0071] FIG. 11 shows an example of a signal obtained at the output of the signal processing circuit of the radar measuring device;

[0072] FIG. 12 schematically shows a radar measuring device according to a second embodiment;

[0073] FIG. 13 shows several signals of the radar measuring device according to the second embodiment;

[0074] FIG. 14 schematically shows a radar measuring device according to a third embodiment;

[0075] FIG. 15 shows several signals of the radar measuring device according to the third embodiment.

[0076] Identical, similar or equivalent portions of the different figures described hereinafter bear the same reference numerals so as to facilitate switching from one figure to another.

[0077] The different portions shown in the figures are not necessarily according to a uniform scale, to make the figures more readable.

[0078] The different possibilities (variants and embodiments) should not be understood as exclusive of each other and could be combined together.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

[0079] A radar measuring device 100 according to a first embodiment is described hereinbelow in connection with FIG. 1.

[0080] The device 100 includes a circuit 102 for generating a radar signal RF.sub.IN(t).

[0081] According to a first embodiment, the radar signal RF.sub.IN(t) generated by the circuit 102 corresponds to a signal with a train of pulses coherently modulated. An example of such a pulse signal is shown, in the time domain, in FIG. 2, and is expressed by the following relationship:

[00004]${\mathrm{RF}}_{\mathrm{IN}\left(t\right)}=\underset{n=1}{\overset{n_{\max }}{.Math.}}.Math.\left(\frac{t-t_{\mathrm{start}}\left(n\right)-\frac{T\left(n\right)}{4}}{\frac{T\left(n\right)}{2}}\right).Math.e^{j2\pi f_a\left(t-t_{\mathrm{start}}\left(n\right)\right)},n\in \left\{1,\mathrm{.Math.},n_{\max }\right\}$

[0082] In the equation hereinabove: [0083] n.sub.max corresponds to the number of pulses of the radar signal RF.sub.IN(t) for the instantaneous frequency of the signal RF.sub.IN(t) to vary over the entire effective band B of the radar signal RF.sub.IN(t); [0084] t.sub.start(n) corresponds to the start time point of an n.sup.th pulse of the signal RF.sub.IN(t); [0085] f.sub.a corresponds to the frequency of the carrier of the radar signal RF.sub.IN(t); [0086] T(n) corresponds to the duration of an n.sup.th pulse of the radar signal RF.sub.IN(t).

[0087] The parameter t.sub.start(n) is expressed by the following relationship:

[00005]$t_{\mathrm{start}}\left(n\right)=\frac{f_{\mathrm{in}}^{\prime }{T}_{\mathrm{rampe}}}{B_{\mathrm{in}}}\left(-1+\sqrt{1+\frac{2B_{\mathrm{in}}}{f_{\mathrm{in}}^{\mathrm{\prime 2}}{T}_{\mathrm{rampe}}}\left(n-1\right)}\right),n\in \left\{1,\mathrm{.Math.},n_{\max }\right\}$

[0088] In the equation hereinabove, f.sub.in′ corresponds to the fundamental frequency of the beginning of the ramp, i.e. when n=1, of the low-band signal or modulating signal, and T.sub.rampe corresponds to the duration with which the instantaneous frequency of the signal RF.sub.IN(t) varies over the entire effective band B. The value of f.sub.in′ is equal to 1/T(1).

[0089] The parameter T(n) is expressed by the following relationship:

T(n)=t.sub.start(n+1)−t.sub.start(n), n.Math.{1, . . . , n.sub.max}

[0090] In FIG. 2, examples of T(n) and t.sub.start(n) for different values of n are shown. In addition, in the example of FIG. 2, n.sub.max=15.

[00006]$f_{\mathrm{in}}^{\prime }<\frac{B.f_a}{f_{\mathrm{in}}^{\prime }},$

[0091] When the signal RF.sub.IN(t) is such that it does not includes any spectral overlap over the duration T.sub.rampe. The spectrum of such a signal RF.sub.IN(t), with f.sub.a=60 GHZ, is shown in FIG. 3, and the evolution in the time domain of the instantaneous frequency of this signal RF.sub.IN(t), over a duration equal to T.sub.rampe, is shown in FIG. 4. In this case, the radar signal RF.sub.IN(t) corresponds to an alternating multi-band signal, i.e. it will simultaneously cover, throughout the duration T.sub.rampe, several frequency bands whose values does not overlap, or do not straddle on each other, and which define the effective band B of the radar signal RF.sub.IN(t).

[00007]$f_{\mathrm{in}}^{\prime }\ge \frac{B.f_a}{f_{\mathrm{in}}^{\prime }},$

[0092] Conversely, when the signal RF.sub.IN(t) is such that it includes a spectral overlap over the duration T.sub.rampe. The spectrum of such a signal RF.sub.IN(t) is shown in FIG. 5, and the evolution in the time domain of the instantaneous frequency of this signal RF.sub.IN(t), over a duration equal to T.sub.rampe, is shown in FIG. 6. In this case, the radar signal RF.sub.IN(t) corresponds to a simultaneous multi-band signal, i.e. it will simultaneously cover, throughout the duration T.sub.rampe, several frequency bands whose values overlap, or straddle on each other, and which define the effective band B of the radar signal RF.sub.IN(t).

[0093] According to a second embodiment, the radar signal RF.sub.IN(t) generated by the circuit 102 corresponds to a FMCW-type radar signal, i.e. a frequency-modulated periodic signal over at least one portion T.sub.rampe of a period T, corresponding, over said at least one portion T.sub.rampe of the period T, to a sinusoidal signal whose frequency varies linearly in the effective band B and whose amplitude alternates between a first value and a second value different from the first value. In contrast with the previously-described first embodiment, the radar signal RF.sub.IN(t) according to the second embodiment corresponds to a single-band signal, i.e. it will cover, throughout the duration T.sub.rampe, one single frequency band that corresponds to its effective band B.

[0094] The evolution in the time domain of the instantaneous frequency of this second embodiment of the signal RF.sub.IN(t) is shown, in FIG. 7 when T=T.sub.rampe, and in FIG. 8 when T≠T.sub.rampe. The spectrum of such a signal RF.sub.IN(t) is shown in FIG. 9.

[0095] The radar signal RF.sub.IN(t) according to this second embodiment may be expressed by the following relationship:

RF.sub.IN(t)=sin(2πf′.sub.ct+2παt.sup.2) Åt.Math.[0, T.sub.rampe]

[0096] The slope of the radar signal RF.sub.IN(t) is defined by the parameter a representative of the quickness of the frequency excursion of the radar signal over a fixed time. This parameter a is representative of the tangent of the angle formed by the ramp with respect to the time axis, and is expressed in GHz/μs. The higher the value of the parameter a, the quicker the variation of the instantaneous frequency of the signal over the effective band B is obtained (i.e. the shorter T will be) or, for a fixed duration T, the larger the effective band B is. The parameter α is expressed by the relationship α=B/(2T.sub.rampe).

[0097] The frequency f′.sub.c of the signal RF.sub.IN(t) at the beginning of the ramp is expressed by the relationship f′.sub.c=f.sub.c−α. T.sub.rampe, with f.sub.c corresponding to the frequency of the carrier of the radar signal RF.sub.IN(t).

[0098] The radar signal RF.sub.IN(t) delivered at the output of the circuit 102 is sent at the input of a power divider 104. A first output of the power divider 104 is coupled to an input of a power amplifier 106 whose output is coupled to an emitting antenna 108. A second output of the power divider 104 is coupled to an input of an injection-locked oscillator, or ILO, 110. For example, the ILO 110 may be made as described in the document “A 60 GHz UWB impulse radio transmitter with integrated antenna in CMOS65nm SOI technology” of A. Siligaris et al., Silicon Monolithic Integrated Circuits in RF Systems (SiRF), 2011 IEEE 11th Topical Meeting on, pp. 153-156, 17-19 Jan. 2011.

[0099] The device 100 also includes a receiving antenna 112 intended to receive a reflected radar signal RF.sub.IN_REFL(t) which corresponds to the radar signal RF.sub.IN(t) has been emitted by the emitting antenna 108 and reflected on one or several reflector(s). The total duration required by the emitted radar signal RF.sub.IN(t) to reach a reflector, be reflected on the latter and reach the receiving antenna 112 is reflected by a time-shift of the signal RF.sub.IN_REFL(t) with respect to the signal RF.sub.IN(t) that is proportional to the distance separating the reflector from the receiving antenna 112.

[0100] In the example of FIG. 1, two reflectors 114.1 and 114.2 are shown, the reflector 114.1 being closer to the receiving antenna 112 than the reflector 114.2. The delay τ.sub.1 imparted on the radar signal reflected on the first reflector 114.1 is such that

[00008]${\tau }_1=\frac{2R_1}{c},$

with R.sub.1 corresponding to the distance between the first reflector 114.1 and the receiving antenna 112, and c corresponding to the velocity of light in vacuum. The delay τ.sub.2 imparted on the radar signal reflected on the second reflector 114.2 is such that

[00009]${\tau }_2=\frac{2R_2}{c},$

with R.sub.2 corresponding to the distance between the second reflector 114.2 and the receiving antenna 112. In the case shown in FIG. 1, the distances R.sub.1 and R.sub.2 are such that R.sub.2>R.sub.1, and therefore the delays τ.sub.1 and τ.sub.2 are such that τ.sub.2>τ.sub.1.

[0101] The signal RF.sub.IN_REFL(t) is sent at the input of a low-noise amplifier 116 whose output is coupled to a first input of a mixer 118. A second input of the mixer 118 is coupled to an output of the ILO 110. And output of the mixer 118 is coupled to an input of a signal processing circuit 120.

[0102] In the embodiment of FIG. 1, the signal processing circuit 120 includes a filtering circuit 122 performing a band-pass filtering of the signal delivered at the output of the mixer 118. According to one embodiment, the filtering circuit 122 includes several stages with a gain higher than 1 coupled in series and performing together this band-pass filtering. The output of the filtering circuit 122 is coupled to an input of an analog-to-digital converter 124.

[0103] The output of the converter 124 is coupled to the input of a circuit 126 configured to perform a processing of the signal obtained after the implementation of the analog-to-digital conversion in order to keep only portions of this signal during which the ILO 110 is locked over a portion of the effective band B. When the signal RF.sub.IN_REFL(t) received by the receiving antenna 112 is mixed with the signal obtained at the output of the ILO 110, a convolution of the spectra of these two signals takes place. Depending on the considered frequency band, the result of this convolution is: [0104] in the band between 0 and f.sub.in, the result of the selection of the unique band B derived from the ILO 110; [0105] in the band between f.sub.in and +∞, the convolution of the signal delivered at the output of the ILO 110 with other ramps in other bands.

[0106] The frequency f.sub.in corresponds to the maximum frequency deviation between the emitted and received signals, for a given radar range D.sub.max, i.e. f.sub.in=α.T.sub.max=α.D.sub.max/c, with T.sub.max the maximum value of T.

[0107] Then, this portion lying in the band between f.sub.in and +∞, is filtered by an analog filter of the circuit 126 and only the useful portion of the spectrum in the acquisition band is kept.

[0108] This circuit 126 also performs a phase equalisation, or compensation, and a discrete Fourier transform, for example in the form of an FFT, of the processed signal. The phase equalisation is performed by determining the power profile of the phase-shift of the processed signal according to the frequency and by applying the inverse of this profile to the signal. The circuit 126 also performs an amplitude equalisation allowing compensating for the deformation of the amplitude of the signal due to the shape of the spectrum of the envelope signal.

[0109] In this first embodiment, for the ILO 110 to be locked over several portions of the effective band B (which is wider than the locking band of the ILO 110), the device 100 includes a control circuit 128 configured to modify, at each period T of the radar signal RF.sub.IN(t), the locking frequency band of the ILO 110 such that, over several successive periods of the radar signal RF.sub.IN(t), the locking frequency bands of the ILO 110 include, together, the effective band B. To modify the locking frequency band of the ILO 110, the control circuit 128 is configured to apply, on a control input of the ILO 110, a control voltage, called Vctrl, whose value determines the central frequency f.sub.c of the locking frequency band of the ILO 110. Alternatively to or complementarily with the variation of the control voltage Vctrl, the control circuit 128 could be configured to modify the values of switched capacitances, forming together a capacitance with a value C, of a resonator for example an LC-type one, of the ILO 110. For example, the natural oscillation frequency of the ILO 110 can thus be modified in a range that could extend to substantially 30% with respect to its nominal carrier frequency.

[0110] This operation of the device 100 according to the first embodiment and illustrated by FIG. 10 which illustrates several signals of the device 100. The signal V.sub.ctrl, bearing the reference 202, corresponds to the control voltage applied on the ILO 110 and whose value makes the locking frequency band of the ILO 110 vary. The evolution in the time domain of the instantaneous frequency of the radar signal RF.sub.IN(t) is also shown in FIG. 10 and is designated by the reference 204. The reference 206 designates echo signals of the signal RF.sub.IN(t) which are represented in dotted lines. The references 208.1, 208.2 and 208.3 designate the evolution in the time domain of the instantaneous frequency of the signal delivered at the output of the ILO 110 when the latter is locked on the radar signal RF.sub.IN(t) on different locking frequency bands. The variation of the locking band of the ILO 110 is obtained via the parameters (value of the control voltage Vctrl and/or values of switched capacitances) applied by the control circuit 128 on the ILO 110. The reference 210 designates the signal obtained at the output of the filtering circuit 122. The signal designated by the reference 212 corresponds to the signal obtained after the processing applied by the circuit 126 and which is formed by the portions of the signal 210 obtained when the ILO 110 is locked over different portions of the effective band B.

[0111] FIG. 11 shows the signal obtained after the discrete Fourier transform applied by the circuit 126, and which corresponds to the signal delivered at the output of the signal processing circuit 120. The measurement of the two reflectors 114.1, 114.2 on which the signal RF.sub.IN(t) is reflected is clearly visible thanks to the two peaks obtained on this signal and whose value on the abscissa axis corresponds to the distance of each of the reflectors 114.1, 114.2 with respect to the receiving antenna 112 of the device 100.

[0112] Since the radar signal RF.sub.IN(t) has its frequency that varies over time, this frequency variation induces phase-shift conditions that are also variable over time. This evolution of the phase-shift in the locking band of the ILO 110 is therefore characterised to perform the post-calibration of this subsequent phase-calibration of the measurement of the radar signal. For this purpose, the device 100 may include a controllable feedback circuit (not shown in FIG. 1) configured, in a configuration of measuring the phase-shift between the radar signal RF.sub.IN(t) and the signal delivered at the output of the ILO 110, to directly connect the first output of the power divider 104 to the first input of the mixer 118. In this phase-shift measurement configuration, the signal processing circuit 120 performs a measurement of the phase-shift between the radar signal RF.sub.IN(t) and the signal delivered at the output of the ILO 110, then, during an operation of the device 100 in a radar measurement configuration where the feedback circuit does not connect the first output of the power divider 104 to the first input of the mixer 118, a compensation of the phase-shift between the radar signal RF.sub.IN(t) and the signal delivered at the output of the ILO 110 using the phase-shift measurement performed beforehand. Alternatively, it is possible that the device 100 does not include such a feedback circuit and the phase-shift between the radar signal RF.sub.IN(t) and the signal delivered at the output of the ILO 110 is measured in a low-frequency portion of the signal applied at the input of the signal processing circuit 120 and which corresponds to a leakage due to the coupling between the emission portion of the radar signal RF.sub.IN(t) and the reception portion of the reflected radar signal RF.sub.IN_REFL(t) of the device 100.

[0113] In this first embodiment, the locking frequency band of the ILO 110 is dynamically modified thanks to the modification of the value of the control voltage Vctrl and/or of the variable capacitance C of the resonator of the ILO 110 over several periods T of the signal RF.sub.IN(t). Hence, this first embodiment enables the device 100 to operate over a wide effective band B, yet with some duration of acquisition of the reflected radar signal RF.sub.IN_REFL(t) to cover the entire effective band B because the device 100 includes only one single ILO 110 to scan this effective band B.

[0114] In this first embodiment, it is possible to perform a relative change of the carrier frequency Δf of the ILO 110 up to Δf/fc=5%, with fc corresponding to the central frequency of the effective band B, and thus scan the entire effective band B by locking the ILO 110 on several portions of the effective band B. Thus, considering a locking frequency band of the ILO 110 centred around the frequency 1.2 GHz, the device 110 is capable of acquiring a radar signal over a relative frequency band that exceeds 5% of the effective band B. For example, with an ILO 110 that could be locked over a frequency band of 1.2 GHz, and with a radar signal RF.sub.IN(t) with an effective band B equal to 3.6 GHz ranging from 59.4 GHz to 63 GHz, the ILO 110 will be controlled so as to be locked over three different locking frequency bands with three offsets of its carrier frequency with the frequencies f.sub.c equal to 60 GHZ, 61.2 GHz and 62.4 GHz, and thus cover the entire effective band B with this single ILO 110. In this case, the device 100 forms a radar receiver with a relative band equal to 6%.

[0115] With this first embodiment, while considering that the radar signal RF.sub.IN(t) generated by the circuit 102 corresponds to a signal with a train of pulses coherently modulated, with or without a spectral overlap, having a central frequency f.sub.c equal to 60 GHz, that the ILO 110 could be locked over a frequency band lower than or equal to 1.2 GHz and that the ILO 110 is controlled to be locked over four different locking frequency bands by offsetting its carrier frequency, the spatial resolution ΔR that could be obtained is larger than 3.6 cm, and the acquisition duration is in the range of 1 μs. The maximum effective band B that could be obtained with the device 100 according to the first embodiment is 4.2 GHz.

[0116] Another advantage of the radar measuring device according to this first embodiment is that its electric consumption is reduced because of the use of one single frequency channel, one single ILO, and one single baseband route of the analog-to-digital converter.

[0117] A device 100 according to a second embodiment is described hereinbelow in connection with FIG. 12.

[0118] In comparison with the first embodiment, the device 100 according to this second embodiment includes m ILOs 110.1-110.m, with m an integer greater than 1. In FIG. 12, two ILOs bearing the references 110.1 and 110.m are shown.

[0119] The device 100 according to this second embodiment also includes m power dividers 104, called first power dividers, configured to apply the radar signal RF.sub.IN(t) on the emitting antenna 108 (through the power amplifier in the embodiment of FIG. 12) and on an input of each of the ILOs 110.1-110.m. In FIG. 12, two first power dividers 104.1 and 104.m are shown.

[0120] In the embodiment shown in FIG. 12, the input of the power divider 104.1 is coupled to the output of the circuit 102, a first output of the power divider 104.1 is coupled to the input of the power amplifier 106 and a second output of the power divider 104.1 is coupled to the input of the power divider 104.m. A first output of the power divider 104.m is coupled to the input of the ILO 110.1 and a second output of the power divider 104.m is coupled to the input of the ILO 110.m. Alternatively, the first power dividers 104.1-104.m and the ILOs 110.1-110.m may be coupled in a manner different from the example shown in FIG. 12.

[0121] The device 100 according to the second embodiment also includes several mixers 118.1-118.m each comprising a second input coupled to an output of one of the ILOs 110.1-110.m and an output coupled to an input of the signal processing circuit 120. This device 100 also includes m-1 second power dividers 130.1-130.(m-1) configured to apply the reflected radar signal RF.sub.IN_REFL(t) on a second input of each of the mixers 118.1-118.m. In the embodiment shown in FIG. 12, one single second power divider 130.1 is shown, the latter comprising an input coupled to the output of the low-noise amplifier 116, a first output coupled to the first input of the mixer 118.1 and a second output coupled to the first input of the mixer 118.m.

[0122] In the embodiment shown in FIG. 12, the signal processing circuit 120 includes m inputs each conveying the output signal of one of the mixers 118.1-118.m in a filtering circuit 122 and an analog-to-digital converter 124 dedicated to this signal. The outputs of all analog-to-digital converters 124 are coupled to inputs of the circuit 126.

[0123] In this second embodiment, the radar signal RF.sub.IN(t) is therefore applied at the input of each ILO 110.1-110.m in an independent manner. Each of the ILOs 110.1-110.m will replicate on its output the emitted radar signal RF.sub.IN(t) only in the locking band specific to each of the ILOs 110.1-110.m and which is defined by the properties of the resonator of the ILO and of the value of the control voltage applied thereon. Each of the ILOs 110.1-110.m therefore filters the radar signal RF.sub.IN(t) in its frequency band of interest. Afterwards, after having mixed the output signal of each of the ILOs 110.1-110.m with the reflected radar signal RF.sub.IN_REFL(t) and thus frequency transposed the reflected radar signal RF.sub.IN_REFL(t) in the locking frequency band of each ILO, low-frequency signals are obtained from which information on the distance and relative velocity of the reflector(s) opposite the receiving antenna 112 of the radar measuring device 100 are obtained. Thus, considering the reception of several frequency bands by different ILOs allows using a radar signal RF.sub.IN(t) whose effective band B is larger while keeping a shorter reception duration than is the case in the first embodiment.

[0124] Like in the first embodiment, the radar signal RF.sub.IN(t) used in the device 100 according to this second embodiment could correspond to one of the signals described before in connection with FIGS. 2 to 9. When the radar signal RF.sub.IN(t) corresponds to the previously-described pulse signal and including a spectral overlap over the duration T.sub.rampe, it is possible to use each of the ILOs 110.1-110.m so as to maximise its locking time over a ramp duration T.sub.rampe.

[0125] In this second embodiment, the circuit 120 may be configured to implement: [0126] a band-pass filtering of each of the signals delivered at the output of the mixers 118.1-118.m, then [0127] an analog-to-digital conversion of each of the signals obtained after the implementation of the filtering, then [0128] a processing of the signals obtained after the implementation of the analog-to-digital conversion, keeping only portions of each of these signals during which each of the injection-locked oscillators is locked over a portion of the effective band B, then [0129] a discrete Fourier transform of the signal obtained after the implementation of the previous processing.

[0130] The signal obtained at the output of the discrete Fourier transform is representative of the distance between the receiving antenna 112 and the reflector(s) on which the radar signal RF.sub.IN(t) has been reflected.

[0131] In this second embodiment, each of the ILOs 110.1-110.m is configured such that its locking frequency band is different from those of the other ILOs 110.1-110.m and that the locking frequency bands of the ILOs 110.1-110.m cover, together, the effective band B. Each of the ILOs 110.1-110.m is configured to be successively locked over a sub-band of the effective band B. In addition, in this second embodiment, the parameters (values of the control voltage Vctrl and of the switched capacitances of the resonator) of each of the ILOs 110.1-110.m are constant, which means that the locking band of each of the ILOs 110.1-110.m does not vary and is the same for each period T of the radar signal RF.sub.IN(t) (in contrast with the first embodiment wherein the locking band of the ILO 110 is different over several periods T of the radar signal RF.sub.IN(t)).

[0132] This operation of the device 100 according to the second embodiment is illustrated by FIG. 13 which illustrates several signals of the device 100 when the latter includes three ILOs 110.1-110.3. Like in FIG. 10 described before in connection with the first embodiment, the evolution in the time domain of the instantaneous frequency of the radar signal RF.sub.IN(t) is designated by the reference 204. The reference 206 designates echo signals of the signal RF.sub.IN(t). Each of the references 208.1, 208.2 and 208.3 respectively designates the evolution in the time domain of the instantaneous frequency of the signal delivered at the output of one of the ILOs 110.1-110.3 when the latter is locked on the radar signal RF.sub.IN(t). The references 210.1, 210.2 and 210.3 designate the signals obtained at the output of each of the filtering circuits 122. The signal designated by the reference 212 corresponds to the signal obtained after the preprocessing applied by the circuit 126 and which is formed by the portions of the signals 210.1-210.3 obtained when each of the ILOs 110.1-110.3 is locked over a portion of the effective band B.

[0133] In this second embodiment, the value of m, i.e. the number of ILOs, is preferably comprised between 2 and 4, because an excessively large number of power dividers 104.1-104.m would lead to applying at the input of the ILOs 110.1-110.m signals with an amplitude that is too low for the ILOs 110.1-110.m to be able to be locked at the frequency of these signals.

[0134] With this second embodiment, considering that the radar signal RF.sub.IN(t) generated by the circuit 102 corresponds to a signal with a train of coherently modulated pulses having a central frequency f.sub.c equal to 60 GHz and which does not include any spectral overlap, that each of the ILOs 110.1-110.m could be locked over a frequency band lower than or equal to 1.2 GHz and that the device 100 includes at most four ILOs, the spatial resolution ΔR that could be obtained is larger than 12.5 cm, the obtained acquisition duration is in the range of 250 ns and the maximum effective band B that could be obtained is 1.2 GHz. When the radar signal RF.sub.IN(t) includes a spectral overlap, the spatial resolution ΔR that could be obtained is larger than 3.1 cm, the obtained acquisition duration is in the range of 1 μs and the maximum effective band B that could be obtained is 4.8 GHz.

[0135] A device 100 according to a third embodiment is described hereinbelow in connection with FIG. 14.

[0136] This device 100 according to the third embodiment includes all of the elements of the device 100 according to the previously-described second embodiment. The difference between the device 100 according to the third embodiment and that according to the second embodiment is that the parameters (values of the control voltage Vctrl and/or of the switched capacitances of the resonator) of each of the ILOs 110.1-110.m are not constant and are adjusted by the control circuit 128, the locking band of each of the ILOs 110.1-110.m varying over several periods T of the radar signal RF.sub.IN(t), like in the first embodiment.

[0137] This operation of the device 100 according to the third embodiment is illustrated by FIG. 15 which illustrates several signals of the device 100 when the latter includes three ILOs 110.1-110.3. Like in the previously-described FIGS. 10 and 13, the evolution in the time domain of the instantaneous frequency of the radar signal RF.sub.IN(t) is designated by the reference 204. The reference 206 designates echo signals of the signal RF.sub.IN(t). Each of the references 208.1, 208.2 and 208.3 respectively designates the evolution in the time domain of the instantaneous frequency of the signal delivered at the output of one of the ILOs 110.1-110.3 when the latter is locked on the radar signal RF.sub.IN(t). In the example shown in this FIG. 15, each of the ILOs 110.1-110.3 is locked over a first sub-band of the effective band B during a first period T of the radar signal RF.sub.IN(t), and is locked over a second sub-band of the effective band B, different from the first sub-band, during a second period T of the radar signal RF.sub.IN(t). Thus, over these two periods of the radar signal RF.sub.IN(t), the entirety of the effective band B is covered by the locking sub-bands of the ILOs of the device 100. The references 210.1, 210.2 and 210.3 designate the signals obtained at the output of each of the filtering circuits 122. The signal designated by the reference 212 corresponds to the signal obtained after the preprocessing applied by the circuit 126 and which is formed by the portions of the signals 210.1-210.3 obtained when each of the ILOs 110.1-110.3 is locked over a portion of the effective band B.

[0138] Like in the second embodiment, the value of m, i.e. the number of ILOs, of the device 100 according to this third embodiment is preferably comprised between 2 and 4. Furthermore, the number of sub-bands over which each ILO 110 is intended to be locked is comprised for example between 2 and 16.

[0139] As example, the device 100 according to this third embodiment allows exploiting a radar signal RF.sub.IN(t) whose effective band B will range from 59 GHz to 65 GHz, enabling the radar device 100 to have a resolution equal to 2.5 cm when each of the ILOs 110.1-110.3 covers two distinct sub-bands extending over two distinct periods T of the radar signal RF.sub.IN(t). It is possible to cover a larger frequency band by increasing the number of periods over which the locking band of each ILO varies. With this third embodiment, considering that the radar signal RF.sub.IN(t) generated by the circuit 102 corresponds to a signal with a train of coherently-modulated pulses, with or without a spectral overlap, having a central frequency f.sub.c equal to 60 GHz, that each of the ILOs 110.1-110.n could be locked over a frequency band lower than or equal to 1.2 GHz and that the device 100 includes at most four ILOs, the spatial resolution AR that could be obtained will be larger than 0.78 cm, and the acquisition duration will be in the range of 4 μs. The maximum effective band B that could be obtained with the device 100 according to the first embodiment is 19.2 GHz.

[0140] In all of the previously-described embodiments, it is possible that the ILO(s) of the device 100 is/are used to scan the entire effective band B of the radar signal RF.sub.IN(t), or only one portion of this effective band B.