WO2003044560A1 - Procede de traitement d'un signal radar a ondes entretenues interrompues avec modulation de frequence (fmicw) - Google Patents

Procede de traitement d'un signal radar a ondes entretenues interrompues avec modulation de frequence (fmicw) Download PDF

Info

Publication number
WO2003044560A1
WO2003044560A1 PCT/FI2002/000900 FI0200900W WO03044560A1 WO 2003044560 A1 WO2003044560 A1 WO 2003044560A1 FI 0200900 W FI0200900 W FI 0200900W WO 03044560 A1 WO03044560 A1 WO 03044560A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
frequency
timeslots
fmicw
gated
Prior art date
Application number
PCT/FI2002/000900
Other languages
English (en)
Inventor
Pentti Karhunen
Jarkko Korte
Original Assignee
Vaisala Oyj
Lilja, Aki
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Vaisala Oyj, Lilja, Aki filed Critical Vaisala Oyj
Priority to AU2002338986A priority Critical patent/AU2002338986A1/en
Publication of WO2003044560A1 publication Critical patent/WO2003044560A1/fr

Links

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
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal

Definitions

  • the invention relates to a method according to the preamble of claim 1 for processing a Frequency Modulated Interrupted Continuous Wave (FMICW) radar signal.
  • FMICW Frequency Modulated Interrupted Continuous Wave
  • the invention is related to radar systems utilizing frequency-modulated interrupted continuous wave modulation (FMICW).
  • FMICW frequency-modulated interrupted continuous wave modulation
  • This modulation method is sometimes referred also as interrupted FMCW, or IFMCW.
  • the invention is suited for situations in which FMICW radar signal is used to search for targets, either discrete or continuous, in a continuous range of distances, or to track several targets at various distances.
  • FMICW radar is a radar employing a pulsed frequency sweep (see, for example,
  • this kind of radar method comprises the following steps.
  • a signal with a frequency changing over a set bandwidth is generated.
  • This signal is gated on and off with a predetermined frequency (f g ) thereby forming on-timeslots and off-timeslots.
  • This gated signal is sent to a desired target with help of a transmitter and an antenna.
  • the reflected or back-scattered signal is received during the off-timeslots of the gated signal, and desired properties from the received signal is detected and gathered during the off-timeslots of the gated signal.
  • FIG. 2 Illustrated in Figure 2 is the time-frequency plot after mixing the received signal with transmitted one. The mixing may happen in one step (homodyne) or several steps via intermediate frequencies (heterodyne).
  • Three exemplary radar returns are shown: one matching the pulse modulation frequency, 3000 meters, one return that is significantly closer than the matching distance, and one return that is further away from the radar than the pulse modulation matching distance.
  • These three targets can be regarded as part of a geophysical scattering density targets, or as multiple point targets in a seeker or tracking radar.
  • Illustrated in Figure 1 are the transmitted signal and the returns from 3 heights, 1200, 3000, and 4200 meters.
  • the return from 1200 meters is delayed 8 ⁇ s w.r.t. the transmission, and the return from 3000 meters is delayed 20 ⁇ s w.r.t. the transmission.
  • the return from 4200 meters is delayed 28 ⁇ s.
  • the signal is allowed to go into the receiver only during periods of no transmission.
  • the baseband signal is formed by mixing the received signal with the no-transmission parts of the frequency sweep. As a result, the baseband return of the system from the three heights, 1200 meters, 3000 meters, and 4200 meters are obtained. The returns from these heights are illustrated in Figure 2.
  • the frequency sweep described in Figure 1 is continuous in phase throughout the full 5 ms cycle.
  • the fragments of 1.6 kHz (corresponding to 1200 meters), 4.0 kHz (corresponding to 3000 meters) and 5.6 kHz (corresponding to 4200 meters) signals shown in Figure 2 will also exhibit continuous phase throughout the frequency sweep, given the fact that the 5 ms sweep is much smaller in time than the decorrelation time of the scatterers in the volume studied.
  • each of the fragments in each of the frequencies in Figure 2 creates a sinusoidal signature that is broken in time.
  • the intermittent 1.6 kHz signal will have time to generate 8 cycles of intermittently broken sinusoid during the 5 ms sweep, the 4 kHz signal 20 cycles and the 5.6 kHz signal 28 cycles. These sinusoids get summed in the receiver, producing a voltage that contains various intermittent frequency components relating to various heights.
  • a time series of 125 points (if one sample is taken during one RX interval) is generated.
  • the various frequencies in this time series are separated by means of a Fourier transform.
  • the 8 th , 20 th , and 28 th sample in this Fourier transform correspond to the heights 1200, 3000 and 4200 meters.
  • the receiver is, as is preferably the case, a receiver capable of separating the in-phase and quadrature components in the base-band, the corresponding Fourier transform will be complex and the frequencies extracted in the given example are negative.
  • FMICW Frequency Modulated Interrupted Continuous Wave
  • the goal of the invention is accomplished by detecting and/or processing only a desired portion of the off-timeslot during each off-timeslot of the gated signal in order to obtain information from a desired distance only and in order to minimize the noise of the signal.
  • the method according to the invention is characterized by what is stated in the characterizing part of claim 1.
  • the invention offers significant benefits over conventional techniques.
  • the invention improves the detection capability of an FMICW radar outside the distance that matches the pulsing period.
  • it will improve the usability of the FMICW technique for detecting continuous profiles of volume scatterers, which is the case in weather radars, wind profilers, and other geophysical radars.
  • It will also improve the usability of FMICW in seeker radars and reduce the need for pulse frequency scanning, because a larger distance range is detectable with one realization of pulsing frequency.
  • Figure 1 shows a frequency/time graph of the principle of the FMICW-modulation.
  • Figure 2 shows another frequency/time graph of the principle of the FMICW- modulation.
  • Figure 3 is a frequency/time graph of the principle of the invention.
  • Figure 4 is a multiple graph presentation of the signals obtained by the invention.
  • Figure 5 is another multiple graph presentation of the signals obtained by the invention.
  • FMICW frequency-modulated interrupted continuous wave modulation
  • signal from different heights in the FMICW system consists of intermittent frequency components.
  • the intermittence is dictated by the pulsing parameters and the height in question. If one sample per pulse is taken, integrated over the reception period, the sample will contain noise and the signals from the various heights. Let us look at one, the first, of the reception periods in more detail.
  • each frequency component in the signal after integration will contain a signal contribution and a noise contribution.
  • the signal contribution results from the integrated voltage over the duration of each line shown in Figure 3.
  • the noise content in that frequency bin will correspond to the integration over the whole 20 ⁇ s period. While the signal contribution to the signal will remain coherent over several pulses, the noise contribution will not, and the noise will thus have an adverse effect to the signal via disturbing the phase and the voltage of the actual, wanted signal.
  • Figure 4 upmost row of plots, shows the time domain signal of a (simulated) target at
  • the right-hand plot shows the result of using a 5000-point fast
  • the signal-to-noise ratio for this target and method is 15.9 dB, measured over the resolved bandwidth of 200 Hz. It occurs at the 1.6 kHz baseband frequency, at the 8 th frequency bin, which corresponds to the 8 th height bin, 1200 meters.
  • the signal consists of 20 zeroes, corresponding to the transmission time during which the receiver is blanked, followed by 20 samples of signal and noise, followed by 20 zeroes, etc (see also Figure 5).
  • the time unit in left column of plots in Figure 4 is 1 ⁇ s
  • the frequency unit in the right column of plots is 1 MHz.
  • the blanking is achieved in the digital domain, making complete nulling of the transmission-time signal possible.
  • the 1-MHz bandwidth is larger than the pulse repetition frequency, 25 kHz, resulting in replicas of the signal ⁇ 25 kHz from the centermost frequencies.
  • FIG 4 middle row of plots shows the effect of integrating over the period of 20 ⁇ s, the full reception time, and using a 125-point fast Fourier transform to extract the different range components from the signal.
  • the length of the Fourier transform was decreased without loss in signal-to-noise ratio, which is now 15.7 dB.
  • the pulsing effect is not anymore shown due to decreased Nyquist frequency in the baseband.
  • the integration has been realized as a sum of values over each of the reception periods, resulting in increased voltage amplitudes. It is noteworthy that the signal studied here, 1200 meters, corresponds to a rotating phasor that turns less than 5 degrees during one reception period. It is thus possible to sum all the samples from the reception period without losing significantly signal voltage due to summing rotating phasors.
  • Figure 4 shows the effect of integrating according to this invention.
  • a discrete Fourier transform which can also be implemented as using only one of the output components of the fast Fourier transform, is used to extract the frequency component corresponding to 1200-meter range.
  • an integrated signal instead of using the full reception-time integrated signal, an integrated signal in which the integration time has been matched with the two-way delay between the transmission and the said target's echo reception is used. In this case, only the 8 first samples are integrated during each reception period to produce the time series shown in the left plot in the last row.
  • Eight-sample integration was chosen for this DFT, because it matches the amount of time at the beginning of the reception period with target-scattered signal. This can be seen in Figure 3, only the 8 first microseconds in the reception period contain scattered signal from the target at 1200 meters. The amount of noise in this time series is less than the noise in the previous time series, because the last 12 samples has been omitted in the integration, and the noise in those samples does not contribute to the output of the 8- point integrator. The signal itself remains intact, because all the information from that range has been used, as shown in Figure 3.
  • the signal-to-noise ratio resulting from partial reception time integration for this exemplary case is 19.5 dB, 3.8 dB higher than the SNR for the fully integrated reception period.
  • the essence of the invention described herein is to construct several digital integrators, preferably by accumulating a sum continuously, and use a variable integration time for each range.
  • 150-meter range would be detected by using 1 -point integration, i.e., the first sample, of each reception period with a DFT that resolves the first non-zero frequency from the 125-point time series consisting of said first samples.
  • 300-meter range would be detected by using 2-point integration, i.e., the first two samples summed, of each reception period, and subjecting the resulting 125-point time series to a DFT that resolves the second non-zero frequency component from the 125- point time series.
  • This scheme is continued up to the pulse matching height, 3000 meters in this case, for which the full 20-point integration result is used with a DFT resolving the non-zero frequency component.
  • the 12 last samples during each of the 1-MHz sampled 20 ⁇ s reception period are used in conjunction with a DFT extracting the 28 th non-zero frequency component from the time series.
  • One preferred embodiment of the present invention would be to use a DSP or FPGA system to compute the range-resolved signals, using cumulative sum accumulator at a high-enough frequency to resolve the transmitted waveform and multiplying the contents of said accumulator with complex weights that correspond to the DFT coefficient for that pulse and that range.
  • the output of the multiplication would be input into another complex sum accumulator for each range, and the contents of those accumulators would be read at the end of each sweep. These values are the complex voltages corresponding to each height for that sweep.
  • the DFT accumulators are nulled at the end of each sweep, and the integrator accumulators are nulled at the beginning of each reception period.
  • a DFT to the range-matched subset of the original 1-MHz samples. This is useful in cases where targets at ranges commensurate with the sweep repetition period are detected. For example, in the exemplary case shown in this document, targets at several hundred kilometers would get damped if the summing integrator was used. This is due to summing complex voltages with a rotating phasor over a time in which the phasor rotates significantly. Thus, in the case of targets for away from the radar, the preferred method is to use a matched subset of the original samples as an input to a long DFT. In these cases summing the digital samples would result in loss of some of the signal amplitude due to summing a significantly rotating phasor.
  • a typical device in accordance with the invention comprises following elements:
  • a wide-bandwidth sampling system (connected to an analog-to-digital converter), ii) a digital logic that produces more than one sum of samples per reception period of one FMICW pulse, iii) a computing system that uses more than one time series, consisting of the said sums of samples, as input to DFTs or FFTs to extract one or more frequency components per time series, corresponding to same number of ranges.
  • each sum of samples and the frequency component extracted in the DFT or FFT is matched to correspond to the same radar range.
  • wide-bandwidth refers to a sampling bandwidth that is sufficient to resolve the transmitted bandwidth of the radar.
  • integration system in accordance with the invention may comprise the following elements: i) a wide-bandwidth sampling system, ii) a digital logic that produces more than one subset of samples per reception period of one FMICW pulse, iii) a computing system that uses zero-padded time series, consisting of the said subsets of samples, as input to DFTs or FFTs to extract one or more frequency components per time series, corresponding to same number of ranges.
  • the length of each continuous subset of sample per reception period, and the frequency component extracted in the DFT and FFT, is matched to correspond to the same radar range.
  • a typical duty cycle for the gating is 50%, in accordance with the invention the duty cycle can vary in a range of 10-90%.

Abstract

La présente invention concerne un procédé de traitement d'un signal radar à ondes entretenues interrompues avec modulation de fréquence (FMICW). Ce procédé consiste à produire un signal dont la fréquence change sur une largeur de bande déterminée, à commander le signal par porte en modes marche et arrêt à une fréquence prédéterminée (fg), d'où la formation d'intervalles de temps en modes marche et arrêt, à envoyer le signal commandé par porte en direction d'une cible souhaitée à l'aide d'un émetteur et d'une antenne, à recevoir un signal réfléchi pendant les intervalles de temps en mode arrêt du signal commandé par porte, puis à détecter et rassembler des propriétés souhaitées à partir du signal reçu pendant les intervalles de temps en mode arrêt du signal commandé par porte. Selon l'invention, une partie souhaitée de l'intervalle de temps en mode arrêt est détectée et/ou traitée pendant chaque intervalle de temps en mode arrêt du signal commandé par porte en vue d'obtenir des informations à partir d'une distance souhaitée et de réduire le bruit du signal associé à une distance souhaitée.
PCT/FI2002/000900 2001-11-21 2002-11-13 Procede de traitement d'un signal radar a ondes entretenues interrompues avec modulation de frequence (fmicw) WO2003044560A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002338986A AU2002338986A1 (en) 2001-11-21 2002-11-13 Method for processing a frequency modulated interrupted continuous wave (fmicw) radar signal

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20012274A FI110966B (fi) 2001-11-21 2001-11-21 Menetelmä taajuusmoduloidun, katkotun jatkuva-aaltotutkasignaalin (FMICW) käsittelemiseksi
FI20012274 2001-11-21

Publications (1)

Publication Number Publication Date
WO2003044560A1 true WO2003044560A1 (fr) 2003-05-30

Family

ID=8562312

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2002/000900 WO2003044560A1 (fr) 2001-11-21 2002-11-13 Procede de traitement d'un signal radar a ondes entretenues interrompues avec modulation de frequence (fmicw)

Country Status (3)

Country Link
AU (1) AU2002338986A1 (fr)
FI (1) FI110966B (fr)
WO (1) WO2003044560A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003194924A (ja) * 2001-12-25 2003-07-09 Mitsubishi Electric Corp ドップラーレーダー装置
WO2008048318A2 (fr) * 2006-01-05 2008-04-24 M/A-Com, Inc. Appareil duplex temporel et procédé pour des extrémités initiales de capteur radar
ES2298081A1 (es) * 2006-12-05 2008-05-01 Universidad Politecnica De Madrid Tecnica de conmutacion de antena a frecuencia variable para radares de onda continua con una unica antena.
US8410976B2 (en) 2005-10-24 2013-04-02 Mitsubishi Electric Corporation Frequency-modulated interrupted continuous wave radar using pulses derived from a frequency-modulated signal in which the rate of frequency change increases at the boundary of a pulse repetition interval
US8499016B2 (en) 2007-06-07 2013-07-30 Mitsubishi Electric Corporation Determination of sine wave period
CN113383245A (zh) * 2019-02-12 2021-09-10 三菱电机株式会社 雷达装置、观测对象检测方法及车载装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6018309A (en) * 1998-02-20 2000-01-25 Mitsubishi Denki Kabushiki Kaisha Radar data processing method and radar apparatus using the same
JP2000275333A (ja) * 1999-03-24 2000-10-06 Mitsubishi Electric Corp Ｆｍｉｃｗによるレーダ信号処理装置およびｆｍｉｃｗによる距離・速度計測方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6018309A (en) * 1998-02-20 2000-01-25 Mitsubishi Denki Kabushiki Kaisha Radar data processing method and radar apparatus using the same
JP2000275333A (ja) * 1999-03-24 2000-10-06 Mitsubishi Electric Corp Ｆｍｉｃｗによるレーダ信号処理装置およびｆｍｉｃｗによる距離・速度計測方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
KHAN R. ET AL.: "Waveform analysis for high-frequency FMICW radar", IEE PROCEEDINGS F-RADAR AND SIGNAL PROCESSING, vol. 138, no. 5, October 1991 (1991-10-01), pages 411 - 419, XP000321910 *
MCGREGOR J. ET AL.: "Switching system for single antenna opertion of an S-band FMCW radar", IEE PROCEEDINGS-RADAR, SONAR AND NAVIGATION, vol. 141, no. 4, August 1994 (1994-08-01), pages 241 - 248, XP002960545 *
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 13 5 February 2001 (2001-02-05) *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003194924A (ja) * 2001-12-25 2003-07-09 Mitsubishi Electric Corp ドップラーレーダー装置
US8410976B2 (en) 2005-10-24 2013-04-02 Mitsubishi Electric Corporation Frequency-modulated interrupted continuous wave radar using pulses derived from a frequency-modulated signal in which the rate of frequency change increases at the boundary of a pulse repetition interval
WO2008048318A2 (fr) * 2006-01-05 2008-04-24 M/A-Com, Inc. Appareil duplex temporel et procédé pour des extrémités initiales de capteur radar
WO2008048318A3 (fr) * 2006-01-05 2008-07-10 Ma Com Inc Appareil duplex temporel et procédé pour des extrémités initiales de capteur radar
US7791530B2 (en) 2006-01-05 2010-09-07 Autoliv Asp, Inc. Time duplex apparatus and method for radar sensor front-ends
ES2298081A1 (es) * 2006-12-05 2008-05-01 Universidad Politecnica De Madrid Tecnica de conmutacion de antena a frecuencia variable para radares de onda continua con una unica antena.
US8499016B2 (en) 2007-06-07 2013-07-30 Mitsubishi Electric Corporation Determination of sine wave period
CN113383245A (zh) * 2019-02-12 2021-09-10 三菱电机株式会社 雷达装置、观测对象检测方法及车载装置
US20210325531A1 (en) * 2019-02-12 2021-10-21 Mitsubishi Electric Corporation Radar device, observation target detecting method, and in-vehicle device
US11921196B2 (en) * 2019-02-12 2024-03-05 Mitsubishi Electric Corporation Radar device, observation target detecting method, and in-vehicle device
CN113383245B (zh) * 2019-02-12 2024-04-02 三菱电机株式会社 雷达装置、观测对象检测方法及车载装置

Also Published As

Publication number Publication date
FI110966B (fi) 2003-04-30
AU2002338986A1 (en) 2003-06-10
FI20012274A0 (fi) 2001-11-21

Similar Documents

Publication Publication Date Title
Jankiraman Design of multi-frequency CW radars
US4241347A (en) PRC/FM CW Radar system
US5646623A (en) Coherent, frequency multiplexed radar
US4992797A (en) Method of detection and identification of one or more remote objects
US4527161A (en) 3D Imaging with stepped frequency waveforms and monopulse processing
US5977905A (en) Target detection method and device for wideband unambiguous pulse Doppler radar
Song et al. The velocity and range detection using the 2D-FFT scheme for automotive radars
CA2513883A1 (fr) Technique d'integration non coherente de cibles a vitesses ambigues
CN1154162A (zh) 减轻脉冲多普勒雷达中距离一多普勒模糊的设备和方法
US5235338A (en) Moving target detection through range cell migration radar
Huo et al. High resolution range profile analysis based on multicarrier phase-coded waveforms of OFDM radar
WO2020218925A1 (fr) Traitement de signaux radar pour radar fmcw
WO2003044560A1 (fr) Procede de traitement d'un signal radar a ondes entretenues interrompues avec modulation de frequence (fmicw)
Hague Target resolution properties of the multi-tone sinusoidal frequency modulatedwaveform
Gill et al. The ambiguity function of the step frequency radar signal processor
Frazer et al. Wigner-Ville analysis of HF radar measurement of an accelerating target
Malanowski et al. Noise vs. deterministic waveform radar—Possibilities and limitations
US3987443A (en) Radar
WO2003044559A1 (fr) Procede pour utiliser un signal radar a onde entretenues interrompues a modulation de frequence (fmicw) afin d'effectuer une detection geophysique a distance
Kahlert et al. Stepped-Frequency PMCW-Radar Modulation Scheme for Automotive Applications
CN101097255A (zh) 谱线增强式脉冲多卜勒雷达回波信号预处理器
Liao et al. A novel motion compensation method for random frequency hopping radar
Liao et al. A range profile synthesis method for random frequency hopping radar and comparison with experiments
Zhou et al. Range/Doppler ambiguity elimination in high-frequency chirp radars
RU2099735C1 (ru) Устройство распознавания летательных аппаратов

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ OM PH PL PT RO RU SC SD SE SG SI SK SL TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR IE IT LU MC NL PT SE SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP