Cost-effective method for determining a pulse response of a high-resolution, band-limited radar channel
First Claim
1. A method for determining a complex impulse response of a high-resolution, band-limited radar channel in a radar station transmitting a binary phase-coded expanded transmitted pulse a(t), the method includingreceiving a complex vector signal e,expanding the transmitted pulse a(t) with respect to bandwidth using a binary complex vector spread code c of length N and a chip duration Tc, from the received signal e;
- superimposing a complex vector additive interference signal n;
performing in a time range covering M range gates of interest according to the spread code c; and
modifying the linear optimum estimation by determining a linear optimum unbiased estimation pulse response xMOS of the band-limited radar channel according to
space="preserve" listing-type="equation">x.sub.MOS =A.sub.E.sup.-1 e,where the step of determining further comprisesforming a complex matrix AE by widening of the rectangular matrix represented by the complex scalar components ci of the spread code c to form a quadratic matrix that circulates to the right,forming an inverse estimation matrix AE-1 of the matrix AE, andmultiplying the inverse estimation matrix by the sampled received signal e and to modify the linear, optimum estimation in the channel estimator.
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Abstract
For less expensive estimation the impulse response xMOS of a high-resolution, band-limited radar channel in a radar station operating with an expanded transmitted pulse a(t), from a received signal e, over which a correlated or uncorrelated additive interference signal n can be superimposed, with the use of knowledge about the spread code c and the use of a channel estimator with which a so-called linear, optimum unbiased estimation of the radar channel impulse response xMOS is performed in a time range covering M range gates of interest, the linear, optimum estimation in the unbiased channel estimator is modified in such a way that the pulse response xMOS of the band-limited radar channel is determined according to the basic principle of a multiplication of the sampled received signal e and an inverse estimation matrix AE-1. The matrix AE is formed by the extension of the rectangular matrix represented by the components ci of the spread code c to form a quadratic matrix that circulates to the right, that is, the modified, optimum unbiased estimation:
x.sub.MOS =A.sub.E.sup.-1 e
applies for a radar channel.
23 Citations
19 Claims
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1. A method for determining a complex impulse response of a high-resolution, band-limited radar channel in a radar station transmitting a binary phase-coded expanded transmitted pulse a(t), the method including
receiving a complex vector signal e, expanding the transmitted pulse a(t) with respect to bandwidth using a binary complex vector spread code c of length N and a chip duration Tc, from the received signal e; -
superimposing a complex vector additive interference signal n; performing in a time range covering M range gates of interest according to the spread code c; and modifying the linear optimum estimation by determining a linear optimum unbiased estimation pulse response xMOS of the band-limited radar channel according to
space="preserve" listing-type="equation">x.sub.MOS =A.sub.E.sup.-1 e,where the step of determining further comprises forming a complex matrix AE by widening of the rectangular matrix represented by the complex scalar components ci of the spread code c to form a quadratic matrix that circulates to the right, forming an inverse estimation matrix AE-1 of the matrix AE, and multiplying the inverse estimation matrix by the sampled received signal e and to modify the linear, optimum estimation in the channel estimator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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10. The method according to claim 1, comprising
providing a microprocessor or a digital signal processor (DSP) whose internal word lengths are significantly greater than a word length me or mM, where me /bit is a quantization word length of the samples of the received signal e, and mM /bit is a finite word length of the elements of the estimation matrix, and using the microprocessor or digital signal processor as a digital computing unit for channel estimation. -
11. The method according to claim 1, including
establishing an optimum value of a process gain that can be attained through coherent integration by the product fdmax · - Tr where fdmax is a maximum Doppler shift and Tr is a pulse repetition frequency.
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12. The method according to claim 1, wherein the radar station is a modular short-range radar (NR) network.
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13. The method according to claim 12, including application of Sensitivity Time Control (STC) by providing an amplifier unit including means for changing amplification over time through a control voltage provided in a receiver such that the control voltage, stored with respect to its course over time, is selected such that an influence of radio-field damping is compensated, and the analog received signal e(t) is amplified to a compensated analog received signal ek (t) as a function of the stored control voltage.
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14. The method according to claim 13, wherein, after being digitized, analog received signals ek (t) subjected to STC amplification regulation are supplied as digital received signals ek to a compensation device (29) in which the influence of the previous STC amplification is compensated again.
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15. The method according to claim 12, including use of a binary code for the spread code and, consequently, of a corresponding binary-coded, phase-shift keying modulation of the transmitted pulses.
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16. The method according to claim 15, including a step of selecting the spread code c to achieve a virtually constant course of the magnitude |A(f)| of the spectrum according to an equation ##EQU23## such that degradation of the signal-to-noise ratio is as low as possible.
- 17. The method according to claim 12, wherein the vector signal e is an analog received signal e(t) and time signal quadrature components eI (t) and eQ (t) of the analog received signal e(t) are formed in a receiver, are sampled at a sampling frequency fc =1/Tc of the spread code, and samples ei are subsequently subjected to a quantization
- space="preserve" listing-type="equation">Q(e.sub.i)=w.sub.i =w.sub.Ii +w.sub.Qi, i=1 . . . M+N-1.
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18. The method according to claim 12, comprising
providing a microprocessor or a digital signal processor (DSP) whose internal word lengths are significantly greater than a word length me or mM, where me /bit is a quantization word length of the samples of the received signal e, and mM /bit is a finite word length of the elements of the estimation matrix, and using the microprocessor or digital signal processor as a digital computing unit for channel estimation. -
19. The method according to claim 12, including
establishing an optimum value of a process gain that can be attained through coherent integration by the product fdmax · - Tr where fdmax is a maximum Doppler shift and Tr is a pulse repetition period.
Specification