WO2009092393A1 - Single shot complementary code radar ( sscc radar) with qpsk modulation - Google Patents

Single shot complementary code radar ( sscc radar) with qpsk modulation Download PDF

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Publication number
WO2009092393A1
WO2009092393A1 PCT/EP2008/000480 EP2008000480W WO2009092393A1 WO 2009092393 A1 WO2009092393 A1 WO 2009092393A1 EP 2008000480 W EP2008000480 W EP 2008000480W WO 2009092393 A1 WO2009092393 A1 WO 2009092393A1
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WIPO (PCT)
Prior art keywords
pulse
radar
complementary
qpsk
phase
Prior art date
Application number
PCT/EP2008/000480
Other languages
French (fr)
Inventor
Achille Emanuele Zirizzotti
Cesidio Bianchi
James Arokiasamy Baskaradas
Original Assignee
Achille Emanuele Zirizzotti
Cesidio Bianchi
James Arokiasamy Baskaradas
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.)
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Application filed by Achille Emanuele Zirizzotti, Cesidio Bianchi, James Arokiasamy Baskaradas filed Critical Achille Emanuele Zirizzotti
Priority to PCT/EP2008/000480 priority Critical patent/WO2009092393A1/en
Publication of WO2009092393A1 publication Critical patent/WO2009092393A1/en

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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
    • G01S13/02—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
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
    • G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
    • G01S13/284—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses
    • G01S13/288—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using coded pulses phase modulated

Definitions

  • the present invention relates to a phase coded technique applied to pulse compression radar system in particular, complementary code radar.
  • phase coded radar the transmitted pulse, is subdivided into a number N of subpulses of equal duration and each subpulse has a particular phase, selected in accordance with a given binary code sequence.
  • the most widely used phase coded pulse employ two phase (0°, 180°), called bi-phase code, consists of a sequence of Os and 1s.
  • the phase of the transmitted signal alternates between the two phases in accordance with the sequence of elements, Os and 1s.
  • the received echoes are processed using digital or analog systems.
  • an analog to digital conversion of received signal is achieved at the output of the analog chain of the receiver and the echoes are processed digitally using a correlation function between the received signal and the transmitted code (as reference the pending Italian patent n. RM20004A000641).
  • a proper matched filter analog correlator
  • the output is given by the autocorrelation function of the input code.
  • Both the systems provide, practically, the correlation of the received signal furnishing as mathematical output a main lobe corresponding to the target reflection.
  • the correlation process also generates side lobes that affect the target recognition. In order to eliminate side lobes complementary bi-phase codes are used.
  • the complementary code or Golay is a sequence of two or more pair of code sequences of the same length N whose aperiodic autocorrelation function that have side lobes equal in amplitude but opposite in sign.
  • the sum of the two correlation function has a peak of 2N level and a side lobe PatXML 2/6 sscc radar
  • phase coherence of the two echo signals must be maintained.
  • the phase coherence is necessary to obtain the perfect matching of the sum of the two correlations.
  • targets and the radar are in relative motion the phase coherence, in the time interval between the two emitted pulse, can be lost , affecting the side lobes cancellation in the correlation process.
  • Many radar techniques have been applied to solve the problem of side lobes cancellation as reference the United States patent n. 4353067.
  • the object of the present invention is to obtain the side lobe cancellation in a complementary code radar using only one transmitted pulse (single shot).
  • the two codes that constitute the complementary are combined together in a single transmitted pulse and consequently in each of the echoes pulses of the targets in the received signal. In this way there is no problem on time coincidence of the two coded pulse and the phase coherence is always maintained.
  • This objective is achieved by the QPSK modulation and demodulation technique.
  • QPSK modulation is possible to combine two complementary codes in a single transmitted pulse.
  • the two codes are phase coded using 4 different phases.
  • the received signal is QPSK demodulated to obtain two separate code sequences allowing the target peak detection and the side lobes cancellation of the received echoes.
  • Figure 1 represents the block diagram of a simplified QPSK modulator used to illustrate one way of carrying out the single pulse generations from the two complementary codes and the sine wave carrier signal.
  • Figure 2 is the broad block diagram of a simplified QPSK demodulator and matched filter section used to illustrate one way of carrying out the two coded signals separation from the single received trace and their process to obtain the target detection and the side lobes cancellation.
  • Figure 3 is a graphical representation of the principal demodulator block's outputs to illustrate the signals behaviour.
  • Figure 1 is a simplified circuit diagram of the QPSK modulator scheme used to generate the transmitted pulse.
  • the carrier sine wave signal 1, used as reference signal, is fed to a 90° phase shifter block 2 and to the input of the mixer 3.
  • phase can change as show in Table 1. All the possible bit values of the two codes can have a phase representation of the output pulse.
  • FIG. 2 is a simplified circuit diagram of the QPSK demodulator scheme and matched filter section used to obtain the two aperiodic autocorrelations.
  • the received signal 11, from the receiver stages of the radar, is applied both to the in-phase mixers input 12 and in quadrature mixers input 13.
  • the Local Oscillator (LO) signal 14 is applied to the 90° phase shifter block 15 to obtain the LO signal of the quadrature mixer 13 and connected to the LO input of the in-phase mixer 12.
  • the Local oscillator has the same frequency of the carrier signal 1 , in this way the input frequency spectrum has moved in base band for simplicity.
  • the in-phase mixer 12 output and the quadrature mixer 13 output are connected to low pass filters to remove unwanted harmonics components.
  • the in-phase filter output 16 and in quadrature filter output 17 can be processed in standard way here sketched with matched filters A and B and sum blocks.
  • FIG. 3 In Figure 3 is shown plots of the signals of the main blocks of scheme, in particular the plot 21 is the received radar trace 11 showing a QPSK coded echo signal.
  • the low pass filter outputs 16 and 17 are shown in the simulated signal plots 22 and 23, here the detected complementary codes are clearly visible.
  • the output of the matched filters 18 and 19 are shown in plot 24 and 25, the side lobes are visible close to the main received peaks and finally on the plot 26 the side lobe cancellation results after the sum operation.
  • Another way for caring out the invention is the use of digital process achieved by an analog to digital conversion of the low pass filter outputs and implementing the correlation process digitally with the used codes.
  • Phase code radar systems that exploit pulse compression especially airborne and satellite radar system where the targets or radar are in relative rapid motion.

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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

A pulse compressed radar system that uses a single pulse for complementary code to achieve the side lobe cancellation providing time and frequency (therefore phase) coincidence. The codes are QPSK modulated (or in higher order of PSK modulation) in the transmitted pulse and QPSK demodulated (or in higher order of PSK demodulation) in the received target echoes of the radar trace. The trace is processed in accordance with complementary code theory.

Description

PatXML 1/6 sscc radar
Description
SINGLE SHOT COMPLEMENTARY CODE RADAR (SSCC RADAR) WITH QPSK MODULATION
Technical
[0001] The present invention relates to a phase coded technique applied to pulse compression radar system in particular, complementary code radar.
Background Art
[0002] In a pulse compression radar, to increase the detection capability, a relatively long coded pulse is transmitted and to maintain the range resolution capability of a narrow pulse system, the received echo must be processed.
[0003] In phase coded radar, the transmitted pulse, is subdivided into a number N of subpulses of equal duration and each subpulse has a particular phase, selected in accordance with a given binary code sequence. The most widely used phase coded pulse employ two phase (0°, 180°), called bi-phase code, consists of a sequence of Os and 1s. The phase of the transmitted signal alternates between the two phases in accordance with the sequence of elements, Os and 1s.
[0004] The received echoes are processed using digital or analog systems. In the digital systems an analog to digital conversion of received signal is achieved at the output of the analog chain of the receiver and the echoes are processed digitally using a correlation function between the received signal and the transmitted code (as reference the pending Italian patent n. RM20004A000641). In analog systems, a proper matched filter (analog correlator) is used and the output is given by the autocorrelation function of the input code. Both the systems provide, practically, the correlation of the received signal furnishing as mathematical output a main lobe corresponding to the target reflection. The correlation process also generates side lobes that affect the target recognition. In order to eliminate side lobes complementary bi-phase codes are used.
[0005] The complementary code or Golay is a sequence of two or more pair of code sequences of the same length N whose aperiodic autocorrelation function that have side lobes equal in amplitude but opposite in sign. The sum of the two correlation function has a peak of 2N level and a side lobe PatXML 2/6 sscc radar
level of zero. The method most often used employs a couple of code that are alternatively transmitted and the received signal is processed completing the cycle summing the two separate correlation output in order to minimize the side lobes levels. Reference is made to a publication entitled "Complementary Series" published in 1961 by M. J. E. Golay in Trans. Inform. Theory, IT-7 pages 82- 87 for a more a detailed explanation.
[0006] In many radar applications really the usefulness of the complementary code is limited of the fundamental problem to obtain two separate frequency and time sequences.
[0007] To obtain the side lobes cancellation, time and frequency coincidence
(phase coherence) of the two echo signals must be maintained. In fact the phase coherence is necessary to obtain the perfect matching of the sum of the two correlations. When targets and the radar are in relative motion the phase coherence, in the time interval between the two emitted pulse, can be lost , affecting the side lobes cancellation in the correlation process. Many radar techniques have been applied to solve the problem of side lobes cancellation as reference the United States patent n. 4353067.
Disclosure of Invention
[0008] The object of the present invention is to obtain the side lobe cancellation in a complementary code radar using only one transmitted pulse (single shot). The two codes that constitute the complementary are combined together in a single transmitted pulse and consequently in each of the echoes pulses of the targets in the received signal. In this way there is no problem on time coincidence of the two coded pulse and the phase coherence is always maintained.
[0009] This objective is achieved by the QPSK modulation and demodulation technique. In particular using a QPSK modulation is possible to combine two complementary codes in a single transmitted pulse. The two codes are phase coded using 4 different phases.
[0010] For each combination of bits of the two complementary codes there are one phase shift level (see Table 1 as reference). In this way the two code can be transmitted simultaneously in a single radar pulse. PatXML 3/6 sscc radar
[0011] In a similar way in analog or digital systems, the received signal is QPSK demodulated to obtain two separate code sequences allowing the target peak detection and the side lobes cancellation of the received echoes.
[0012] Afterwards using higher order of PSK modulation (for the transmitter) and demodulation (for the receiver) is possible to code (decode) 2 or more couple of complementary codes. This will increase the complexity of the radar system increasing the side lobe cancellation probability.
[0013] Further developments of the invention are the subject-matter of the dependent claims.
Brief Description of Drawings
[0014] Figure 1 represents the block diagram of a simplified QPSK modulator used to illustrate one way of carrying out the single pulse generations from the two complementary codes and the sine wave carrier signal.
[0015] Figure 2 is the broad block diagram of a simplified QPSK demodulator and matched filter section used to illustrate one way of carrying out the two coded signals separation from the single received trace and their process to obtain the target detection and the side lobes cancellation.
[0016] Figure 3 is a graphical representation of the principal demodulator block's outputs to illustrate the signals behaviour.
Best Mode for Carrying Out the Invention
[0017] The invention is elucidated by reference to an embodiment in conjunction with Figure 1. Figure 2 and Figure 3.
[0018] Figure 1 is a simplified circuit diagram of the QPSK modulator scheme used to generate the transmitted pulse. The carrier sine wave signal 1, used as reference signal, is fed to a 90° phase shifter block 2 and to the input of the mixer 3.
[0019] These two signals in phase and quadrature with respect to signal 1, are used as input of the two mixers, in-phase mixer 3 and in quadrature mixer 4. The first complementary code 5 is the second input of the in-phase mixer 3. The second complementary code 6 has been applied to the second input of the in quadrature mixer 4. The two mixer outputs, in phase 7 and in quadrature 8, are summed , using the block 9, to obtain the phase modulated pulse signal 10. Depending on the two code values the output PatXML 4/6 sscc radar
phase can change as show in Table 1. All the possible bit values of the two codes can have a phase representation of the output pulse.
Table 1
Figure imgf000005_0001
[0020] Figure 2 is a simplified circuit diagram of the QPSK demodulator scheme and matched filter section used to obtain the two aperiodic autocorrelations. The received signal 11, from the receiver stages of the radar, is applied both to the in-phase mixers input 12 and in quadrature mixers input 13. The Local Oscillator (LO) signal 14 is applied to the 90° phase shifter block 15 to obtain the LO signal of the quadrature mixer 13 and connected to the LO input of the in-phase mixer 12. Here the Local oscillator has the same frequency of the carrier signal 1 , in this way the input frequency spectrum has moved in base band for simplicity. The in-phase mixer 12 output and the quadrature mixer 13 output are connected to low pass filters to remove unwanted harmonics components. The in-phase filter output 16 and in quadrature filter output 17 can be processed in standard way here sketched with matched filters A and B and sum blocks.
[0021] In Figure 3 is shown plots of the signals of the main blocks of scheme, in particular the plot 21 is the received radar trace 11 showing a QPSK coded echo signal.
[0022] The low pass filter outputs 16 and 17 are shown in the simulated signal plots 22 and 23, here the detected complementary codes are clearly visible. The output of the matched filters 18 and 19 are shown in plot 24 and 25, the side lobes are visible close to the main received peaks and finally on the plot 26 the side lobe cancellation results after the sum operation.
Mode(s) for Carrying Out the Invention PatXML 5/6 sscc radar
[0023] Another way for caring out the invention is the use of digital process achieved by an analog to digital conversion of the low pass filter outputs and implementing the correlation process digitally with the used codes.
Industrial Applicability
[0024] Phase code radar systems that exploit pulse compression especially airborne and satellite radar system where the targets or radar are in relative rapid motion.

Claims

PatXML 6/6 sscc radarClaims
1. A method of detecting targets echo using a complementary code radar comprising the step of: transmitting complementary code pair only in one pulse; the transmitted pulse is QPSK modulated in this way the carrier of the pulse signal can have 4 different phases allowing, the codification of two complementary codes inside a single pulsed signal; receiving a complementary coded echoes of said pulse from said targets and using a QPSK demodulating receiver, separating two complementary coded signal trace, and processing them in analog matched filters or digital correlation process
2. A method according to claim 1 transmitting two or more couple of complementary codes only in one pulse of the pulse compressed radar; the transmitted pulse is modulated in higher order of PSK modulation and separating the different phased echo using a higher order of PSK demodulator and processing them in analog matched filters or digital correlation process.
3. An apparatus according to the claim 1 comprising: a QPSK modulator for generating the transmitted pulse using a couple of complementary codes; a transmitter for transmitting the said phase coded pulse; a receiver for receiving the targets echoes of said transmitted pulse; a QPSK demodulator for separating the said received echoes; a signal processing section.
4. An apparatus according to the claim 2 comprising: a higher order of PSK modulator for generating the transmitted pulse using two or more couple of complementary codes; a transmitter for transmitting the said phase coded pulse; a receiver for receiving the targets echoes of said transmitted pulse; a higher order of PSK demodulator for separating the said received echoes; a signal processing section.
PCT/EP2008/000480 2008-01-23 2008-01-23 Single shot complementary code radar ( sscc radar) with qpsk modulation WO2009092393A1 (en)

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Cited By (5)

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WO2012029242A1 (en) * 2010-09-02 2012-03-08 パナソニック株式会社 Radar device
CN103562744A (en) * 2011-08-12 2014-02-05 松下电器产业株式会社 Radar apparatus
WO2014129142A1 (en) * 2013-02-21 2014-08-28 パナソニック株式会社 Radar system
WO2014147941A1 (en) * 2013-03-21 2014-09-25 パナソニック株式会社 Radar device
US9535156B2 (en) 2013-03-15 2017-01-03 Src, Inc. Passive listening pulse adaptive sidelobe canceller

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WO2006099934A1 (en) * 2005-03-23 2006-09-28 Reinhart Rudershausen Circuit arrangement and method for receiving specially designed coded signals
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US4353067A (en) * 1980-08-29 1982-10-05 Westinghouse Electric Corp. Method of reducing side lobes of complementary coded pulses in a coherent pulse compression doppler radar receiving system
DE10104022A1 (en) * 2001-01-31 2002-08-01 Bosch Gmbh Robert Radar device and method for coding a radar device
WO2006099934A1 (en) * 2005-03-23 2006-09-28 Reinhart Rudershausen Circuit arrangement and method for receiving specially designed coded signals
WO2007120225A2 (en) * 2005-12-06 2007-10-25 Trustees Of Princeton University Instantaneous radar polarimetry

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US9213091B2 (en) 2010-09-02 2015-12-15 Panasonic Intellectual Property Management Co., Ltd. Radar device
US20130135140A1 (en) * 2010-09-02 2013-05-30 Panasonic Corporation Radar device
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WO2012029242A1 (en) * 2010-09-02 2012-03-08 パナソニック株式会社 Radar device
JP2012052964A (en) * 2010-09-02 2012-03-15 Panasonic Corp Radar apparatus
EP2743721A1 (en) * 2011-08-12 2014-06-18 Panasonic Corporation Radar apparatus
CN103562744A (en) * 2011-08-12 2014-02-05 松下电器产业株式会社 Radar apparatus
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US9513365B2 (en) 2013-02-21 2016-12-06 Panasonic Corporation Radar system
US9535156B2 (en) 2013-03-15 2017-01-03 Src, Inc. Passive listening pulse adaptive sidelobe canceller
WO2014147941A1 (en) * 2013-03-21 2014-09-25 パナソニック株式会社 Radar device
JPWO2014147941A1 (en) * 2013-03-21 2017-02-16 パナソニック株式会社 Radar equipment
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