Methods for detecting the flight path of projectiles
View Patent ↗Methods for detecting the flight path of projectiles involve a sequence of N target detections that include detecting the measured velocities and azimuthal angle bearings of the projectile along the flight path of the projectile by Doppler radar at the times tn, wherein n=1 . . . N, and determining the flight path and the direction of motion of the projectile are from these measurements. The measurements are adapted in a first nonlinear parameter fit to an analytical relationship of the time curve of the radial velocity of the projectile while the projectile passes through the detection range of the radar and so that the absolute projectile velocity, minimum distance of the project flight path from the radar, time at which the projectile passes the point having the minimum distance, flight path direction in azimuth, and flight path direction in elevation can be estimated.
1. A method for the detection of the trajectory of projectiles, comprising:
recording, by a continuous wave Doppler radar that is configured for both bearing indication and speed measurement, a series of N target detections at points in time t n with n=1. . . N with measured speeds v rad (t n ) and azimuthal angle bearings α(t n ) of the projectile along the trajectory of the projectile, wherein the continuous wave Doppler radar comprises a plurality of transmission/reception modules for different spatial angle sectors;
determining a trajectory and direction of motion of the projectile based on the measured speeds v rad (t n ) and azimuthal angle bearings α(t n ) of the projectile along the trajectory of the projectile, wherein said determining the trajectory and direction of motion of the projectile comprises:
estimating absolute projectile speed v 0 , minimum distance of projectile trajectory from the radar d, and estimated point in time t d at which the projectile passes a point at a minimum distance d by adapting the speed measurements v rad (t n ) in a first non-linear parameter fit to an analytical relationship of a time profile of the measured radial speed v rad (t) of the projectile when passing through the detection region of the radar,
estimating a trajectory direction in azimuth α 0 by adapting, in a second non-linear parameter fit, the measured azimuthal angle bearings α(t n ) to an analytical relationship of a time profile of the angular direction in azimuth α(t), and
determining an azimuth direction of the point α d at the minimum distance of the projectile trajectory from the continuous wave Doppler radar by interpolating the series of the measured azimuthal angle bearings α(t n ) at a point in time t=t d
wherein a transmission antenna of at least one of the plurality of transmission/reception modules includes two antennas having a vertical angular offset and transmitting simultaneously with different frequencies f Tx1 and f Tx2 =f Tx1 +Δf, wherein the frequency difference Δf is from 100 Hz to 100 kHz.
2. The method as claimed in claim 1 , wherein an additional series of N angular bearings of the projectile in elevation ε(t n ) along the trajectory of the projectile is recorded, a trajectory direction in elevation ε 0 is estimated by adapting the measurements in a third non-linear parameter fit to an analytical relationship of the time profile of an angular direction in elevation ε(t), and determining the azimuth direction of a point ε d at the minimum distance of the projectile trajectory from the continuous wave Doppler radar by interpolation of the series of measurement values ε(t n ) at the point in time t=t d .
3. The method as claimed in claim 1 , wherein the azimuthal angle bearings are measured using a amplitude monopulse or phase monopulse.
4. The method as claimed in claim 1 , wherein directionally selective antenna patterns are generated using digital beam forming.
5. The method as claimed in claim 1 , a transmission signal of the continuous wave Doppler radar is subjected to a sinusoidal frequency modulation, wherein a frequency range is analyzed for a second harmonic of the modulation signal in a radar receiver.
6. The method as claimed in claim 1 , further comprising:
band pass sampling a received signal to digitize the received signal.
7. The method as claimed in claim 6 , further comprising:
integrating the received signal using FFT blocks with different lengths to extend coherent integration time in Doppler processing.
8. The method as claimed in claim 7 , wherein prior to the integration of the received signal, a hypothetical correction of a profile of the received signal is performed by multiplication with a set of linear frequency chirps of different ramp gradient and time duration.
9. The method as claimed in claim 1 , wherein a working frequency of the continuous wave Doppler radar is in a K u band or K band.
10. The method as claimed in 1 , wherein a working frequency of the continuous wave Doppler radar is in a S band or C band.