EP2191294A2 - Adaptive calculation of pulse compression filter coefficients for a radar signal - Google Patents

Adaptive calculation of pulse compression filter coefficients for a radar signal

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Publication number
EP2191294A2
EP2191294A2 EP08801241A EP08801241A EP2191294A2 EP 2191294 A2 EP2191294 A2 EP 2191294A2 EP 08801241 A EP08801241 A EP 08801241A EP 08801241 A EP08801241 A EP 08801241A EP 2191294 A2 EP2191294 A2 EP 2191294A2
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EP
European Patent Office
Prior art keywords
pulse compression
filter
signal
received signal
filter coefficients
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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EP08801241A
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German (de)
French (fr)
Inventor
Franz-Xaver Hofele
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Hensoldt Sensors GmbH
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EADS Deutschland GmbH
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Publication of EP2191294A2 publication Critical patent/EP2191294A2/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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/288—Coherent receivers
    • G01S7/2883—Coherent receivers using FFT processing

Definitions

  • the invention relates to a method according to the features of the preamble of the current claim 1.
  • the PK filter coefficients should be optimized and adapted to specific components of the signal processing, such as filters used. A signal that has passed through an entire signal processing chain has in some cases other properties than a theoretical signal. The PK filter should therefore not be optimized for an ideal theoretical transmission signal, but adapted to a - according to the signal processing - filtered received signal adapted (adapted). 2. The PK filter should not be optimized to the usually preferred Doppler zero position but to a specific Doppler frequency. This can be about in a PC application that takes place after the Doppler processing at the respective filter outputs. 3. The PK filter should be optimized for transmitter shortcomings. These can be caused, for example, by the C operation of the power amplifier. The transmitter amplifies completely from a certain signal amplitude and the signal goes into saturation. Also, based on the passage of such a transmitter in C mode, the signal receives partly different properties than a theoretical signal.
  • the PK filter conventional type can be adapted only to the transmitter behavior of a frequency. However, if during a certain time window the signal does not change appreciably with respect to the PK, an online calculation of the PK filter coefficients for this time window could adaptively optimize the PK image adaptively.
  • the calculation of the PK filter coefficients in its conventional manner in which once-calculated coefficients of the PK filter are fixedly implemented during the operation of the radar system, takes place according to an iteration algorithm.
  • a corresponding period of time must be set for the calculation of the filter coefficients.
  • some experience in dealing with pulse compression is necessary in order to be able to model the desired compressed pulse, especially for truly complex-valued signals. Only when this modeling has been carried out carefully, effective PK side-lobe suppression can be achieved. Consequently, it is almost impossible to implement this algorithm as automatism, without sufficient monitoring. Therefore, this conventional iteration algorithm is rather unsuitable for the adaptive on-line calculation of the PK filter coefficients.
  • the object of the invention is to provide a method with which the disadvantages of the prior art can be eliminated.
  • pulse compression filter coefficients for a received signal of a radar system are adaptively calculated, the received signal being evaluated with the aid of a complex pulse compression mismatch filter and a pulse compression filter coefficient set h (t) being calculated for an ideal theoretical received signal s (t).
  • a transformed set of pulse compression filter coefficients H opt (f) for the complex pulse compression -Mismatch filter H opt (f) are calculated according to the following rule where S (f): the Fourier transform of an undistorted received signal s (t), S v (f): the Fourier transform of a distorted received signal s v (t), Sv * (f): the complex conjugate of S v ( f) H (f): the Fourier transform of the pulse compression mismatch filter h (t).
  • s (t), h (t), H op t (f) are to be understood as vectors.
  • Such an algorithm for optimizing (adapting) the PK filter coefficients to the present received signal has the following form:
  • the conventional iteration algorithm is used to calculate PK filter coefficients in order to calculate a PK mismatched filter h (t) for an ideal theoretical received signal s (t), that is to say for an "unadulterated" received signal, such that a PK output signal g (t) results in a sufficiently high sidelobe distance.
  • S (f), H (f) and G (f) are the transfer functions of s (t), h (t) and g (t).
  • an adaptive optimal PK filter hopt (t) to be calculated online is searched for-whatever-"falsified," that is, signal distortion-prone receive signal s v (t), which can change during the radar operation such that after the PK a PK output results, which has a high quality PK output in the form of a high sidelobe distance, and: h opt (t) should be able to be calculated online, ie fast and without a monitoring mechanism.
  • the same and with respect to the main to sidelobel ratio (HNV) sufficiently good
  • Output signal arise, as in the PK filtering of the "unadulterated" received signal s (t), ie g (t).
  • Fig. 3 circuit of a radar with a component having the invention.
  • the starting point is an example of a well-known in the art pulse compression code, the binary code of the 13er Barker code. It is a real-valued signal with the coding (+ stands for +1 and - for -1) + + + + + + + + + _ + _ +. This Signal or this coding represents in the above formulas the "unadulterated" signal s (t).
  • a length 37 PK mismatched filter was calculated at s (t).
  • This PK filter which is represented by (1) in Fig. 1, represents h (t) in the above formulas.
  • This PK filter h (t) provides the PK output g (t), the magnitude of which is represented by (1) in FIG. 2, and a high peak-to-peak ratio (HNV) of FIG 42.3 dB.
  • HNV peak-to-peak ratio
  • the signal s v (t) which does not consist of 13 but instead of 14 sub-pulses according to the coding + + + + + + + + - + + _ + _ as s), is present as a "corrupted" signal.
  • a PK-MMF h opt (t) should be found so that s v (t) gives the same PK-output g (t) at pulse compression with h opt (t) as the PK of s (t) with h ( t).
  • FIG. 3 illustrates, with reference to a schematic representation of a radar system, how an online calculation of the PK filter coefficients according to the invention can be achieved.
  • a signal sample is taken at predetermined time intervals after the signal processing in the branch of the signal generation.
  • the signal conditioning essentially consists of the actual signal generation, mixers, preamplifiers and Power amplifier (bottom view in Fig. 3).
  • a signal sample is coupled out and fed to the receiving path during the dead time (upper illustration in FIG. 3) of the pulse.
  • the signal sample passes through the relevant components of the signal processing in the reception train, which is usually a bandwidth-determining antialiasing filter and necessary mixers.
  • the resulting signal sample corresponds to the expected received pulse before the PK. This is then used for the online calculation according to the above formula (the theoretical signal and its associated PK filter are already available) and in this way the pulse compression filter adapted from time to time to the present waveform (adapted).
  • H m S (J) - H (J). s; (J)

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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)
  • Amplifiers (AREA)

Abstract

The invention relates to a method for adaptively calculating pulse compression filter coefficients for a receive signals of a radar system, said receive signal being evaluated using a complex pulse compression mismatch filter. In said method, a set h(t) of pulse compression filter coefficients for a pulse compression mismatch filter is calculated for an ideal theoretical receive signal s(t) in such a way that a pulse compression output signal is obtained that has a desired main lobe/sidelobe ratio. For a distorted receive signal, a transformed set of pulse compression filter coefficients Hopt(f) for the complex pulse compression mismatch filter Hopt(f) is calculated according to the following formula (I), wherein S(f) represents a Fourier transform of an undistorted receive signal s(t), Sv(f) represents the Fourier transform of a distorted receive signal sv(t), Sv*(f) represents the complex conjugate of Sv(f), and H(f) represents the Fourier transform of the pulse compression mismatch filter h(t).

Description

Adaptive Berechnung von Pulskompressions-Filterkoeffizienten für ein Radarsignal Adaptive calculation of pulse compression filter coefficients for a radar signal
Die Erfindung betrifft ein Verfahren gemäß den Merkmalen des Oberbegriffs des geltenden Anspruchs 1.The invention relates to a method according to the features of the preamble of the current claim 1.
Aus DE 42 30 558 A1 ist eine iterative Berechnung der Pulskompressions (PK) - Filterkoeffizienten bekannt, welche im allgemeinen auf ein ideales theoretisches Signal (Binärcode, Barkercode, Lineare Frequenzmodulation, Nichtlineare Frequenzmodulation, Polyphasencode) angepasst ist. Die über dieses Iterationsverfahren berechneten PK-Filterkoeffizienten sind hierbei fest implementiert worden.From DE 42 30 558 A1 an iterative calculation of the pulse compression (PK) filter coefficients is known, which is generally adapted to an ideal theoretical signal (binary code, bar code, linear frequency modulation, non-linear frequency modulation, polyphase code). The PK filter coefficients calculated using this iteration method have been firmly implemented.
Mit diesem Verfahren ist es nicht möglich, auf Signaländerungen und somit auf Signalunzulänglichkeiten, die während des Radarbetriebs auftreten, zu reagieren und diese für ein qualitativ hochwertiges Pulskompressionsbild zu kompensieren. Mit diesen auftretenden Signaländerungen bzw. Signalunzulänglichkeiten sind gewisse reproduzierbare, also in ihrem Verhalten immer gleichartig wiederkehrend auftretende Ab- Wandlungen des Signals gemeint. Im Folgenden werden für diese Signal- Modifikationen einige Möglichkeiten aufgezeigt:With this method, it is not possible to respond to signal changes and thus to signal deficiencies that occur during radar operation and to compensate them for a high-quality pulse compression image. With these occurring signal changes or signal inadequacies certain reproducible, ie always behaving in their behavior recurring occurring Ab- transformations of the signal meant. In the following, some possibilities are shown for these signal modifications:
1. Die PK-Filterkoeffizienten sollen auf bestimmte Komponenten der Signalverarbeitung, also etwa auf verwendete Filter optimiert und angepaßt sein. Ein Sig- nal, das eine ganze Signalverarbeitungskette durchlaufen hat, besitzt zum Teil andere Eigenschaften als ein theoretisches Signal. Das PK-Filter soll daher nicht auf ein ideales theoretisches Sendesignal optimiert sein, sondern auf ein - gemäß der Signalverarbeitung - gefiltertes Empfangssignal angepaßt (adaptiert) sein. 2. Das PK-Filter soll nicht auf die üblicherweise bevorzugte Doppler-Null-Lage, sondern auf eine spezielle Dopplerfrequenz optimiert werden. Dies kann etwa bei einer PK Anwendung finden, die nach der Dopplerverarbeitung an den je- weilgen Filterausgängen stattfindet. 3. Das PK-Filter soll auf Senderunzulänglichkeiten optimiert sein. Diese können beispielsweise durch den C-Betrieb des Leistungsverstärkers verursacht werden. Dabei verstärkt der Sender ab einer bestimmten Signalamplitude vollständig und das Signal geht in die Sättigung. Auch anhand des Durchlaufens eines solchen Senders im C-Betrieb erhält das Signal teilweise andere Eigenschaften als ein theoretisches Signal.1. The PK filter coefficients should be optimized and adapted to specific components of the signal processing, such as filters used. A signal that has passed through an entire signal processing chain has in some cases other properties than a theoretical signal. The PK filter should therefore not be optimized for an ideal theoretical transmission signal, but adapted to a - according to the signal processing - filtered received signal adapted (adapted). 2. The PK filter should not be optimized to the usually preferred Doppler zero position but to a specific Doppler frequency. This can be about in a PC application that takes place after the Doppler processing at the respective filter outputs. 3. The PK filter should be optimized for transmitter shortcomings. These can be caused, for example, by the C operation of the power amplifier. The transmitter amplifies completely from a certain signal amplitude and the signal goes into saturation. Also, based on the passage of such a transmitter in C mode, the signal receives partly different properties than a theoretical signal.
4. Verallgemeinerung auf allgemein mögliche Signalmodifikationen:ln Punkt 3 genügt es nicht, das Senderverhalten genau zu studieren und dann die PK- Filterkoeffizienten darauf anzupassen. Vielmehr ist das Senderverhalten auch von der Frequenzagilität des Radars abhängig, d.h der Sender verhält sich bei höheren Frequenzen unterschiedlich als bei tieferen Frequenzen, was deutlich merkliche Unterschiede im PK-BiId zur Folge hat.4. Generalization to General Signal Modifications: In point 3, it is not enough to study the transmitter behavior accurately and then adapt the PK filter coefficients to it. Rather, the transmitter behavior is also dependent on the frequency agility of the radar, that is, the transmitter behaves differently at higher frequencies than at lower frequencies, which has significantly noticeable differences in PK image result.
Das PK-Filter herkömmlicher Art kann nur auf das Senderverhalten einer Frequenz angepasst werden. Wenn jedoch während eines bestimmten Zeitfensters sich das Signal bezüglich der PK nicht merklich ändert, so könnte eine Online-Berechnung der PK-Filterkoeffizienten für dieses Zeitfenster das PK-BiId in adaptiver Weise wesentlich optimieren.The PK filter conventional type can be adapted only to the transmitter behavior of a frequency. However, if during a certain time window the signal does not change appreciably with respect to the PK, an online calculation of the PK filter coefficients for this time window could adaptively optimize the PK image adaptively.
Die Berechnung der PK-Filterkoeffizienten in seiner herkömmlichen Art, bei der ein- mal berechnete Koeffizienten des PK-Filters während des Betriebs der Radaranlage fest implementiert sind, erfolgt nach einem Iterationsalgorithmus. Aufgrund der Iteration ist einerseits eine entsprechende Zeitdauer für die Berechnung der Filterkoeffizienten anzusetzen. Andererseits ist eine gewisse Erfahrung im Umgang mit Pulskompression notwendig, um den gewünschten komprimierten Puls speziell bei echt kom- plexwertigen Signalen modellieren zu können. Nur wenn diese Modellierung sorgfältig ausgeführt wurde, ist eine effektive PK-Nebenzipfelunterdrückung zu erreichen. Folglich ist es fast unmöglich, diesen Algorithmus als Automatismus zu implementieren, ohne ihn ausreichend zu überwachen. Daher ist dieser herkömmliche Iterationsalgorithmus für die adaptive Online-Berechnung der PK-Filterkoeffizienten eher ungeeig- net.The calculation of the PK filter coefficients in its conventional manner, in which once-calculated coefficients of the PK filter are fixedly implemented during the operation of the radar system, takes place according to an iteration algorithm. On the one hand, due to the iteration, a corresponding period of time must be set for the calculation of the filter coefficients. On the other hand, some experience in dealing with pulse compression is necessary in order to be able to model the desired compressed pulse, especially for truly complex-valued signals. Only when this modeling has been carried out carefully, effective PK side-lobe suppression can be achieved. Consequently, it is almost impossible to implement this algorithm as automatism, without sufficient monitoring. Therefore, this conventional iteration algorithm is rather unsuitable for the adaptive on-line calculation of the PK filter coefficients.
Aufgabe der Erfindung ist es, ein Verfahren anzugeben, mit welchem die Nachteile des Standes der Technik beseitigt werden können.The object of the invention is to provide a method with which the disadvantages of the prior art can be eliminated.
Die Aufgabe wird mit den Merkmalen des Verfahrens gemäß dem Patentanspruch 1 gelöst. Vorteilhafte Ausführungen der Erfindung sind Gegenstand von Unteransprüchen.The object is achieved with the features of the method according to claim 1. Advantageous embodiments of the invention are the subject of dependent claims.
Erfindungsgemäß werden Pulskompressions-Filterkoeffizienten für ein Empfangssig- nal einer Radaranlage adaptiv berechnet, wobei das Empfangssignal mit Hilfe eines komplexen Pulskompressions-Mismatch-Filters ausgewertet wird und wobei für ein ideales theoretisches Empfangssignal s(t) ein Pulskompressions-Filterkoeffizienten- Satz h(t) für ein Pulskompressions-Mismatch-Filter so berechnet wird, dass ein Pulskompressions-Ausgangssignal mit einem gewünschten Haupt- zu Nebenzipfel- Verhältnis resultiert und wobei für ein verzerrtes Empfangssignal ein transformierter Satz von Pulskompressions-Filterkoeffizienten Hopt(f) für das komplexe Pulskompres- sions-Mismatch-Filter Hopt(f) entsprechend folgender Vorschrift berechnet werden wobei S(f) : die Fourier-Transformierte eines unverzerrten Empfangssignals s(t), Sv(f): die Fourier-Transformierte eines verzerrten Empfangssignal sv(t), Sv*(f): die komplex konjugierte von Sv(f), H(f): die Fourier-Transformierte des Pulskompressions-Mismatch- Filters h(t).According to the invention, pulse compression filter coefficients for a received signal of a radar system are adaptively calculated, the received signal being evaluated with the aid of a complex pulse compression mismatch filter and a pulse compression filter coefficient set h (t) being calculated for an ideal theoretical received signal s (t). is calculated for a pulse compression mismatch filter such that a pulse compression output signal results in a desired major to minor lobe ratio, and wherein for a distorted receive signal, a transformed set of pulse compression filter coefficients H opt (f) for the complex pulse compression -Mismatch filter H opt (f) are calculated according to the following rule where S (f): the Fourier transform of an undistorted received signal s (t), S v (f): the Fourier transform of a distorted received signal s v (t), Sv * (f): the complex conjugate of S v ( f) H (f): the Fourier transform of the pulse compression mismatch filter h (t).
Im Weiteren sind s(t), h(t), Hopt(f) als Vektoren zu verstehen.In the following, s (t), h (t), H op t (f) are to be understood as vectors.
Ein derartiger Algorithmus zur Optimierung bzw. Anpassung (Adaptierung) der PK- Filterkoeffizienten auf das vorliegende Empfangssignal hat folgende Gestalt:Such an algorithm for optimizing (adapting) the PK filter coefficients to the present received signal has the following form:
Ausgegangen wird vom herkömmlichen Iterationsalgorithmus zur Berechnung von PK-Filterkoeffizienten, um für ein ideales theoretisches Empfangssignal s(t), also für ein "unverfälschtes" Empfangssignal, ein PK-Mismatched-Filter h(t) zu berechnen so, dass ein PK-Ausgangssignal g(t) mit genügend hohem Nebenzipfel-Abstand resultiert. Mit anderen Worten: die Größen s(t), h(t) und g(t) der FormelThe conventional iteration algorithm is used to calculate PK filter coefficients in order to calculate a PK mismatched filter h (t) for an ideal theoretical received signal s (t), that is to say for an "unadulterated" received signal, such that a PK output signal g (t) results in a sufficiently high sidelobe distance. In other words, the quantities s (t), h (t) and g (t) of the formula
s(t) * h(t) = g(t) (1 )s (t) * h (t) = g (t) (1)
im Zeitbereich sind bekannt.in the time domain are known.
Dasselbe gilt dann für obige Formel im FrequenzbereichThe same applies to the above formula in the frequency domain
S(f) H(f) = G(f) (2)S (f) H (f) = G (f) (2)
wobei S(f), H(f) und G(f) die Übertragungsfunktionen von s(t), h(t) und g(t) sind.where S (f), H (f) and G (f) are the transfer functions of s (t), h (t) and g (t).
Gemäß der Erfindung wird zu einem - wie auch immer - "verfälschten", also mit Signalverzerrungen behafteten Empfangssignal sv(t), welches sich während des Radar- betriebe ändern kann, ein online zu berechnendes adaptives optimales PK-Filter hopt(t) gesucht so, dass nach der PK ein PK-Ausgangssignal resultiert, das ein qualitativ hochwertiges PK-Ausgangssignal in Form eines hohen Nebenzipfel-Abstand aufweist und: hopt(t) sollte online, d.h. schnell und ohne einen Überwachungsmechanismus, berechnet werden können. Aus dem "verfälschten" (verzerrten) Signal sv(t) und dem gesuchten optimalen PK- Filter hopt(t) soll via PK dasselbe (und im Bezug auf das Haupt-zu Nebenzipfel- Verhältnis (HNV) genügend gute) PK-Ausgangssignal entstehen, wie bei der PK- Filterung des "unverfälschten" Empfangssignals s(t), also g(t).According to the invention, an adaptive optimal PK filter hopt (t) to be calculated online is searched for-whatever-"falsified," that is, signal distortion-prone receive signal s v (t), which can change during the radar operation such that after the PK a PK output results, which has a high quality PK output in the form of a high sidelobe distance, and: h opt (t) should be able to be calculated online, ie fast and without a monitoring mechanism. From the "distorted" (distorted) signal s v (t) and the sought-after optimal PK filter h opt (t), the same (and with respect to the main to sidelobel ratio (HNV) sufficiently good) should be determined via PK. Output signal arise, as in the PK filtering of the "unadulterated" received signal s (t), ie g (t).
In Anlehnung an obige Formeln (1 ) und (2) erhält man dann die Formeln Following the formulas (1) and (2) above, the formulas are then obtained
undand
Sv(f) • Hopt(f) = G(f) (4) sv(t) und Sv(f) sind bekannt. Somit ergibt sich aus obigen Formeln (3) und (4), wobei mit Sv *(f) ist der konjugiert komplexe Vektor von Sv(f) gemeint ist, die Übertragungsfunktion Hopt(f) des gesuchten optimalen PK-Filters hopt(t) alsSv (f) • hop t (f) = G (f) (4) s v (t) and S v (f) are known. Thus, it follows from the above formulas (3) and (4), where S v * (f) is the conjugate complex vector of S v (f), the transfer function H o p t (f) of the sought optimal PK Filters h op t (t) as
und die Impulsantwort hopt(t) als IFFT-Resultat (IFFT = inverse Fourier Fransformation) der Übertragungsfunktion Hopt(f). and the impulse response h opt (t) as IFFT result (IFFT = Inverse Fourier Fransformation) of the transfer function H opt (f).
Die Erfindung wird nachfolgend anhand eines Beispiels sowie von Figuren näher er- läutert. Es zeigenThe invention will be explained in more detail below with reference to an example and figures. Show it
Fig. 1 ein Vergleich eines PK-Filters gemäß dem Stand der Technik mit einem PK- Filter gemäß der Erfindung1 shows a comparison of a PK filter according to the prior art with a PK filter according to the invention
Fig. 2 den Verlauf eines gemäß der Erfindung berechneten PK-Ausgangssignals,2 shows the course of a calculated according to the invention PK output signal,
Fig. 3 Schaltung einer Radaranlage mit einer Komponente, welche die Erfindung aufweist.Fig. 3 circuit of a radar with a component having the invention.
Ausgegangen wird beispielhaft von einem in der Fachwelt bekanntesten Pulskompressionscode, den Binärcode des 13er Barkercodes. Er ist ein reellwertiges Signal mit der Codierung (+ steht für +1 und — für — 1 ) + + + + + + + _ + _ + . Dieses Signal bzw. diese Codierung stellt in obigen Formeln das "unverfälschte" Signal s(t) dar.The starting point is an example of a well-known in the art pulse compression code, the binary code of the 13er Barker code. It is a real-valued signal with the coding (+ stands for +1 and - for -1) + + + + + + + _ + _ +. This Signal or this coding represents in the above formulas the "unadulterated" signal s (t).
Mit dem herkömmlichen Iterationsverfahren wurde zu s(t) ein PK-Mismatched-Filter (MMF) der Länge 37 berechnet. Dieses PK-Filter, das in Fig.1 mit (1) dargestellt ist, stellt in obigen Formeln h(t) dar.With the conventional iteration method, a length 37 PK mismatched filter (MMF) was calculated at s (t). This PK filter, which is represented by (1) in Fig. 1, represents h (t) in the above formulas.
Dieses PK-Filter h(t) liefert bei Pulskompression mit s(t) das PK-Ausgangssignal g(t), dessen Betrag in Fig. 2 mit (1 ) dargestellt ist und ein hohes Haupt-zu Nebenzipfel- Verhältnis (HNV) von 42,3 dB aufweist. Außerdem ist in diesem PK-Ausgangssignal ein sehr homogenes Nebenzipfel-Verhalten festzustellen, was für nachfolgende CFAR-Schaltungen recht günstig ist.This PK filter h (t) provides the PK output g (t), the magnitude of which is represented by (1) in FIG. 2, and a high peak-to-peak ratio (HNV) of FIG 42.3 dB. In addition, a very homogeneous sidelobe behavior is observed in this PK output signal, which is quite favorable for subsequent CFAR circuits.
Als "verfälschtes" Signal liege nun beispielhaft das Signal sv(t) vor, welches gegenüber s(t) nicht aus 13 sondern aus 14 Subpulsen gemäß der Codierung + + + + + + — + + _ + _ + besteht. Dazu soll ein PK-MMF hopt(t) gefunden werden so, dass sv(t) bei Pulskompression mit hopt(t) quasi dasselbe PK-Ausgangssignal g(t) ergibt wie die PK von s(t) mit h(t).By way of example, the signal s v (t), which does not consist of 13 but instead of 14 sub-pulses according to the coding + + + + + + - + + _ + _ as s), is present as a "corrupted" signal. For this purpose, a PK-MMF h opt (t) should be found so that s v (t) gives the same PK-output g (t) at pulse compression with h opt (t) as the PK of s (t) with h ( t).
Wird das erfindungsgemäße Verfahren auf die vorliegende Problematik angewendet, so erhält man als hopt(t) das in Fig. 1 mit (2) illustrierte PK-Filter der Länge 64 und daraus abgeleitet das mit (2) gezeichnete PK-Ausgangssignal in Bild 2.If the inventive method applied to the present problem, is obtained as h opt (t) is illustrated in FIG. 1 (2) PK-filter of length 64 and derived from the with (2) drawn PK output signal in Figure 2 ,
Es lässt sich feststellen, dass im Kern des PK-Ergebnisses liegt die Kurve (1 ) exakt auf der Kurve (2) (Fig. 1 ). Lediglich an den Rändern des PK-Bildes tritt die Kurve (2) aufgrund des längeren PK-Filters gegenüber der Kurve (1 ) in Erscheinung. Was also rein theoretisch vorhergesagt wurde, konnte an diesem Beispiel verifiziert werden.It can be stated that at the core of the PK result, the curve (1) lies exactly on the curve (2) (FIG. 1). Only at the edges of the PK image does the curve (2) appear due to the longer PK filter over the curve (1). What was theoretically predicted could be verified by this example.
In Fig. 3 ist anhand einer schematischen Darstellung einer Radaranlage verdeutlicht, wie eine erfindungsgemäße Online-Berechnung der PK-Filterkoeffizienten erreicht werden kann. Dazu wird in vorgebbaren Zeitintervallen eine Signalprobe nach der Signalaufberei- tung im Zweig der Signalerzeugung genommen. Die Signalaufbereitung besteht im Wesentlichen aus der eigentlichen Sigηalgenerierung, Mischer, Vorverstärker und Leistungsverstärker (untere Darstellung in Fig. 3). Nachdem das Signal diese Komponenten der Signalaufbereitung durchlaufen hat, wird eine Signalprobe ausgekoppelt und während der Totzeit (obere Darstellung in Fig. 3) des Pulses dem Empfangs- zug zugeführt. Die Signalprobe durchläuft die maßgebenden Komponenten der Signalverarbeitung im Empfangszug, was in der Regel ein bandbreitenbestimmendes Antialiasing-Filter sowie notwendige Mischer sind. Die dann daraus resultierende Signalprobe entspricht dem zu erwartenden Empfangspuls vor der PK. Diese wird dann für die Online-Berechnung gemäß obenstehender Formel genutzt (das theoretische Signal und sein zugehöriges PK-Filter liegen bereits vor) und auf diese Weise das Pulskompressionsfilter von Zeit zu Zeit an die vorliegende Signalform adaptiert (angepaßt).FIG. 3 illustrates, with reference to a schematic representation of a radar system, how an online calculation of the PK filter coefficients according to the invention can be achieved. For this purpose, a signal sample is taken at predetermined time intervals after the signal processing in the branch of the signal generation. The signal conditioning essentially consists of the actual signal generation, mixers, preamplifiers and Power amplifier (bottom view in Fig. 3). After the signal has passed through these components of the signal conditioning, a signal sample is coupled out and fed to the receiving path during the dead time (upper illustration in FIG. 3) of the pulse. The signal sample passes through the relevant components of the signal processing in the reception train, which is usually a bandwidth-determining antialiasing filter and necessary mixers. The resulting signal sample corresponds to the expected received pulse before the PK. This is then used for the online calculation according to the above formula (the theoretical signal and its associated PK filter are already available) and in this way the pulse compression filter adapted from time to time to the present waveform (adapted).
Vor der Pulskompression PK wird die Signalprobe sv(t) in die Komponente "Erfin- düng" eingespeist. Die Übertragungsfunktionen S(f) und H(f) sind dort bereits abgelegt. Es wird dann nach obiger FormelBefore the pulse compression PK, the signal sample s v (t) is fed into the component "invention". The transfer functions S (f) and H (f) are already stored there. It will then according to the above formula
H m = S(J) - H(J) . s ; (J) H m = S (J) - H (J). s; (J)
11 opt U ) I „ , fΛ I 2 11 opt U) I ", fΛ I 2
\ \U) \ (5) \ \ U) \ (5)
und mit IFFT das Online-PK-Filter hopt(t) berechnet und für eine adaptive PK genutzt. and calculated with IFFT the online PK filter h opt (t) and used for an adaptive PK.

Claims

Patentansprüche claims
1. Verfahren zur adaptiven Berechnung von Pulskompressions-Filterkoeffizienten für ein Empfangssignal einer Radaranlage, welches mit Hilfe eines komplexen Pulskompressions-Mismatch-Filters ausgewertet wird, wobei für ein ideales theoretisches Empfangssignal s(t) eine Pulskompressions-Filterkoeffizienten-Matrix h(t) für ein Pulskompressions-Mismatch-Filter so berechnet wird, dass ein Pulskompressions-Ausgangssignal mit einem gewünschten Haupt- zu Nebenzipfel-Verhältnis resultiert, dadurch gekennzeichnet, dass für ein verzerrtes Empfangssignal die Pulskompressions-Filterkoeffizienten- Matrix Hopt(f) für das komplexe Pulskompressions-Mismatch-Filter Hopt(f) ent- sprechend folgender Vorschrift berechnet werden wobei1. A method for adaptively calculating pulse compression filter coefficients for a received signal of a radar system, which is evaluated by means of a complex pulse compression mismatch filter, wherein for an ideal theoretical received signal s (t) a pulse compression filter coefficient matrix h (t) for a pulse compression mismatch filter is calculated such that a pulse compression output signal results with a desired main to secondary lobe ratio, characterized in that, for a distorted received signal, the pulse compression filter coefficient matrix H opt (f) for the complex pulse compression Mismatch filter H op t (f) can be calculated according to the following procedure in which
S(f) : die Fourier-Transformierte eines unverzerrten Empfangssignals s(t), Sv(f): die Fourier-Transformierte eines verzerrten Empfangssignal sv(t), Sv *(f): die komplex konjugierte von Sv(f),S (f): the Fourier transform of an undistorted received signal s (t), S v (f): the Fourier transform of a distorted received signal s v (t), S v * (f): the complex conjugate of S v ( f)
H(f): die Fourier-Transformierte des Pulskompressions-Mismatch- Filters h(t).H (f): the Fourier transform of the pulse compression mismatch filter h (t).
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass das Pulskompressions-Mismatch-Filter als Transversal-Filter ausgebildet ist 2. The method according to claim 1, characterized in that the pulse compression mismatch filter is designed as a transversal filter
3. Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass ein Sendesignal der Radaranlage ausgekoppelt wird und während der Totzeit der Radaranlage als Signalprobe für ein verzerrtes Empfangssignal in den Empfangszweig der Radaranlage eingekoppelt wird und nach Durchlaufen einer Signalaufbereitung einer Komponente zugeführt wird, in welcher die Pulskompres- sions-Filterkoeffizienten-Matrix Hopt(f) für das komplexe Pulskompressions- Mismatch-Filter berechnet wird. 3. The method according to any one of the preceding claims, characterized in that a transmission signal of the radar system is coupled and coupled during the dead time of the radar system as a signal sample for a distorted received signal in the reception branch of the radar system and is supplied after passing through a signal processing of a component in which the pulse compression filter coefficient matrix H opt (f) is calculated for the complex pulse compression mismatch filter.
EP08801241A 2007-09-01 2008-09-01 Adaptive calculation of pulse compression filter coefficients for a radar signal Ceased EP2191294A2 (en)

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