Method and arrangement for detecting moving objects with a radar

• US 7,576,688 B2
• Filed: 02/20/2006
• Issued: 08/18/2009
• Est. Priority Date: 02/21/2005
• Status: Expired due to Fees

• Current Assignee: Meliorcomp Oy
• Original Assignee: Eigenor Oy
• Inventors: Lehtinen, Markku Sakari
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US11/884,720
• Publication Number:
  US 20090009385A1
• Time in Patent Office: 1,275 Days
• Field of Search: 342/90, 342 95- 97, 342/107, 342113-115, 342139-140, 342/162, 342/189, 342/192, 342194-196
• US Class Current: 342/196
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26

Abstract

Moving objects are detected with a radar by collecting samples of a received signal over an integration period. The terms of a match function contain a product of a sample of said received signal and a delayed-in-time, Doppler-shifted replica of a transmission and depend on parameters that describe an object that caused a reflection of the transmission. The most probable values of the parameters are found by maximizing the match function through Fourier transforming a vector consisting of terms of the match function. Those of said products that contain a non-zero contribution of said delayed-in-time, Doppler-shifted replica of a transmission are actually computed while the others of said products are zero Only non-zero blocks of the products count as final terms to the vector to be Fourier transformed that have nonzero value while intermittent blocks that have zero value are left out. The most probable values of the parameters are those that result from Fourier transforming the vector consisting of the final terms.

Claims

1. A method for detecting moving objects with a radar, comprising:

receiving reflections of a pulsed radar transmission, said reflections constituting a received signal,

collecting samples of the received signal over an integration period,

forming a match function, the terms of which contain a product of a sample of said received signal and a delayed-in-time, Doppler-shifted replica of a transmission and depend on parameters that describe an object that caused a reflection of the transmission, and

finding most probable values of the parameters by maximizing the match function through Fourier transforming a vector consisting of terms of the match function;

characterized in that in order to compose the vector to be Fourier transformed it comprises;

computing those of said products that contain a non-zero contribution of said delayed-in-time, Doppler-shifted replica of a transmission, and letting others of said products be zero, thus forming preliminary terms of the vector to be Fourier transformed,

forming blocks of said preliminary terms,

taking those of said blocks as final terms to the vector to be Fourier transformed that have nonzero value, by preserving the mutual order of said nonzero-valued blocks but leaving out intermittent blocks that have zero value, and

outputting, as said most probable values of the parameters, those values that result from Fourier transforming the vector consisting of said final terms.

2. A method according to claim 1, characterized in that said forming of blocks of said preliminary terms comprises decimating a vector consisting of said preliminary terms, by summing together groups of consecutive preliminary terms.

3. A method according to claim 2, characterized in that it comprises:

taking an acceleration factor of a group of preliminary terms to be constant within said group of preliminary terms,

summing non-constant parts of said group of preliminary terms and

multiplying the summed non-constant parts of said group of preliminary terms by said acceleration factor.

4. A method according to claim 1, characterized in that it comprises receiving a transmission sample signal multiplexed in time with said reflections of a pulsed radar transmission, and using said transmission sample signal to represent said delayed-in-time, Doppler-shifted replica of a transmission.

5. A method according to claim 1, characterized in that it comprises receiving reflections of a pulsed radar transmission used for other radar measurement than said detection of moving objects, thus piggy-backing the detection of moving objects onto said other radar measurement.

6. A method according to claim 5, characterized in that it comprises detecting space debris objects by receiving reflections of pulsed radar transmissions used for scientific research of the Earth'"'"'s ionosphere.

7. A method according to claim 1, characterized in that it comprises maximizing the match function

$\mathrm{MF}$

( R j , v k , a ) = 

∑

n = 0 N - 1 ⁢

( z n ⁢

x _ n - j ⁢

exp ⁡

( - ⅈ

α

d ⁢

n 2 ) ) ⁢

exp ⁡

( - ⅈ

⁢

⁢

kn N ) 



x 

by Fourier transforming a vector w″

obtained from the vector

w_n=z_nx_n-jexp(−

iα

_dn²)

by decimating and only preserving non-zero blocks resulting from said decimating;

wherein R_j denotes a j;

th radial range bin,

v_k denotes a k;

th radial velocity bin,

a denotes the radial acceleration of a reflecting object,

z_n is the n;

th sample of a received signal z,

x_n-j is the complex conjugate of the n-j;

th sample of a transmission signal x,

i is the imaginary unit,

α

_d is the normalized Doppler drift caused by a reflecting object moving with radial acceleration,

n is a summing index,

k is a velocity index,

N is the number of samples taken of the received signal during an integration period and

∥

x∥

is the square root of transmission sample energy.

14. A computer program product comprising machine-readable instructions that, when executed in a computer, implement the method of claim 1.

8. A signal processing apparatus for processing received signals in a radar system, comprising:

an input adapted to receive samples collected of a received signal over an integration period, and

a scanner adapted to form a match function, the terms of which contain a product of a sample of said received signal and a delayed-in-time, Doppler-shifted replica of a transmission and depend on parameters that describe an object that caused a reflection of the transmission, said scanner being additionally adapted to find most probable values of the parameters by maximizing the match function through Fourier transforming a vector consisting of terms of the match function;

characterized in that;

the scanner is adapted to compute those of said products that contain a non-zero contribution of said delayed-in-time, Doppler-shifted replica of a transmission, and to let others of said products be zero, in order to form preliminary terms of the vector to be Fourier transformed,

the scanner is adapted to form blocks of said preliminary terms,

the scanner is adapted to condense a vector consisting of said blocks by pre-serving the mutual order of nonzero-valued blocks but leaving out intermittent blocks that have zero value, in order to produce a condensed vector and

the scanner is adapted to output, as said most probable values of the parameters, those values that result from Fourier transforming the condensed vector.

9. A signal processing apparatus according to claim 8, characterized in that the scanner is adapted to compare said most probable values of the parameters to a threshold and to store such outputted most probable values that exceed said threshold as a hit.

10. A signal processing apparatus according to claim 9, characterized in that it comprises an even archiver adapted to combine to an event the hits that appear to correspond to a single target passing through a radar beam.

11. A signal processing apparatus according to claim 10, characterized in that it comprises an analyzer adapted to compute final target parameters by calling the scanner (422) to rescan data of an event (601) with maximal time and range resolution and by making a fits to a time series of parameter values resulting from such rescanning.

12. A radar system for detecting remote moving objects, comprising:

a radar receiver adapted to receive reflections of a pulsed radar transmission and to produce a received signal,

a sampler and sample collector adapted to collect samples of the received signal over an integration period,

a processing unit adapted to form a match function, the terms of which contain a product of a sample of said received signal and a delayed-in-time, Doppler-shifted replica of a transmission and depend on parameters that describe an object that caused a reflection of the transmission, and adapted to find most probable values of the parameters through maximisation of the match function through Fourier transforming a vector consisting of terms of the match function;

characterized in that;

the processing unit is adapted to compute those of said products that contain a non-zero contribution of said delayed-in-time, Doppler-shifted replica of a transmission, and to let others of said products be zero, to form preliminary terms of the vector to be Fourier transformed,

the processing unit is adapted to form blocks of said preliminary terms,

the processing unit is adapted to take those of said blocks as final terms to the vector to be Fourier transformed that have nonzero value, through preserving the mutual order of said nonzero-valued blocks but leaving out intermittent blocks that have zero value, and

the radar system comprises an output adapted to output, as said most probable values of the parameters, those values that result from Fourier transforming the vector consisting of said final terms.

13. A radar system according to claim 12, characterized in that it comprises a radar transmitter adapted to transmit said pulsed radar transmissions.