Communications: directive radio wave systems and devices (e.g. – Determining direction – With frequency or phase steering
Reexamination Certificate
1999-10-08
2001-09-04
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Determining direction
With frequency or phase steering
C342S041000, C342S067000, C342S081000, C342S083000, C342S158000, C342S372000, C342S377000
Reexamination Certificate
active
06285312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a control arrangement designed for controlling radar transmissions for a system of antennas with mutually different broadside directions, disposed on a moving platform.
The invention furthermore relates to a method for allocating a radar transmission, requested for transmission within a future time window to an antenna from a system of antennas with mutually different broadside directions, disposed on a moving platform.
2. Discussion of the Background
Control arrangements of this type are in particular used for controlling radar transmissions for systems of phased array antenna faces, which collectively constitute a multi-surface phased array antenna system. The antennas may be used for both transmitting and reception purposes. The control arrangement is generally continuously supplied with requests generated by an external request generator for realizing a radar transmission within a certain future time window.
An example of an arrangement for controlling radar transmissions for a multi-face phased array radar system is known from the European patent application EP-A-0.440.200. The control arrangement disclosed in this patent contains a number of track computers which, by means of several PRT (Pulse Repetition Time) timing computers, request the generation of transmitter pulses. These requests are supplied to a scheduler which arranges the radar transmissions in time and, per radar transmission, assigns an antenna surface.
The drawback of this prior art control arrangement is its unsatisfactory performance in case the antenna system is mounted on a moving platform, for instance on a ship, and a radar transmission is requested for transmission at a moment or time window that is so far in the future that the ship's motion come into play. In the meantime, the transmit direction of the requested radar transmission with respect to a selected antenna face may have changed in an adverse sense owing to the ship's roll, pitch and yaw, which makes it expedient to allocate the requested radar transmission to another antenna face whose position with respect to the transmit direction of the radar transmission is more favourable.
SUMMARY OF THE INVENTION
The control arrangement according to the invention obviates said drawback and is thereto characterized in that the control arrangement incorporates angle prediction means, designed to predict an angular position of a coordinate system connected to the moving platform with respect to a reference coordinate system.
The method according to the invention is thereto characterized in that during the allocation of a radar transmission to the antenna, use is made of a predicted angular position of a coordinate system connected to the moving platform with respect to a reference coordinate system.
The reference coordinate system preferably comprises the north-horizontal coordinate system so that the predicted angular position has an unambiguous reference. The coordinate system connected to the moving platform may be connected to the ship's hull or to any other object rigidly mounted to the ship, such as one of the antenna faces. As such, it constitutes a ship-fixed coordinate system.
The angular position of the ship-fixed coordinate system is preferably predicted by an adaptive prediction filter. The ship's roll, pitch and yaw have a limited frequency spectrum owing to which the corresponding angular positions are of a certain predictable nature. By making the prediction filter adaptive, it is, under changing circumstances such as a different sea state, still possible to generate an adequate prediction of the desired angles.
For allocating the requests for radar transmissions to an antenna face, the control unit can be provided with an antenna selector, connected to the prediction filter. An advantageous embodiment is then characterized in that the antenna selector is designed to select the antenna that, within the future time window and throughout the longest time span, realizes the smallest predicted off-broadside angle with the transmit direction of the radar transmission. The consequent advantage is then that the antenna gain is optimal and the side-lobe level remains low.
An alternative embodiment is characterized in that the control arrangement is designed to allocate, to each transmitting antenna, a sector within which radar transmissions may take place and that the antenna selector is designed to select a transmitting antenna if a transmit direction of the radar transmission at a future point in time falls within the sector of this transmitting antenna. The sector allocated to each transmitting antenna shall preferably be contiguous to the sector of an adjacent antenna so that on the one hand, no two antennas are receive the same radar transmission and on the other hand, radar transmission is always possible. By varying the extent of an antenna sector, it is furthermore possible to either increase or reduce the chance of a transmission being allocated to this antenna.
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“Target tracking in the presence of ECM: a filter design tool”, Rago, C.; Mahra, R.K., System Theory, 1997, Proceedings of the Twenty-Ninth Southeastern Symposium on, 1997, pp. 514-518.*
“The problem of time in phased array radar”, Billam, E.R., Radar 97 (Conf. Publ. No. 449), pp: 563-575.*
“Revisit calculation and waveform control for a multifunction radar”, Watson, G.A.; Blair, W.D., Decision and Control, 1993, Proceedings of the 32nd IEEE Conference on, 1993, pp: 456-460 vol. 1.*
“Benchmark Problem For Beam Pointing Control Of Phased Array Radar Against Maneuvering Targets”, Blair, W.D.; Watson, G.A.; Roffman, S.A., American Control Conference, 1994, vol. 2, pp: 2071-2075.*
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Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sotomayor John B.
Thales Nederland B.V.
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