Surveillance apparatus and method
A surveillance apparatus ( 100 ) is provided, said apparatus including a linear sub-array ( 101 ) of N omnidirectional transmitter elements ( 103 ) and a planar sub-array ( 102 ) of M receiver elements ( 104 ). A plurality of the transient elements ( 105 ) are generated by separating out at each of the receivers ( 104 ) the signals transmitted from the antenna elements ( 103 ) of the transmitter sub-array ( 101 ). This allows the geometry of each path (from each transmitter antenna element, to the point being imaged and back to the receiver antenna elements) to be converted to a delay or phase shift to focus on the particular point being imaged. The transient elements ( 105 ) form a cylindrical array ( 106 ) at the mid points between transmitter and receiver sub-arrays. Such a configuration enables a full 360 degrees of cover in azimuth and typically +/−60 degrees in elevation.
1. A surveillance apparatus, said apparatus comprising:
a first array of radar elements;
a second array of radar elements, wherein the first array of radar elements and the second array of radar elements are orthogonal to one another;
a feed network coupled to one or more radar elements of said first array of radar elements;
a processor coupled to one or more radar elements of the second array of radar elements and said feed network, wherein said processor is adapted to synthesise a plurality of transient elements.
2. The apparatus of claim 1 , wherein the first array of radar elements comprises transmitter elements and the second array of radar elements comprises receiver elements.
3. The apparatus of claim 2 , wherein the transmitter elements periodically transmit a plurality of pulses, each pulse having a different signature code allowing the receiver elements to separate out a reflected signal from a plurality of reflected signals for each transmitting element, wherein the plurality of reflected signals are reflected by one or more objects within a region of interest.
4. The apparatus of claim 3 , wherein each signature code comprises a carrier frequency selected from a set of predetermined frequencies.
5. The apparatus of claim 2 , wherein the transmitter elements transmit a plurality of pulses utilizing time division multiplexing (TDM), wherein successive pulses of said plurality of pulses are transmitted at a time delay of sufficient length to allow the receiver elements to separate out a reflected signal from a plurality of reflected signals for each transmitter element, wherein the plurality of reflected signals are reflected by one or more objects within a region of interest.
6. The apparatus of claim 2 , wherein the transmitter elements transmit a plurality of pulses utilizing code division multiplexing scheme, whereby each transmitter element simultaneously transmits a coded pulse of the same frequency allowing the receiver elements to separate out a reflected signal from a plurality of reflected signals for each transmitter element, wherein the plurality of reflected signals are reflected by one or more objects within a region of interest.
7. The apparatus of claim 6 , wherein each pulse of said plurality of pulses is coded with a differing phase modulation or a differing amplitude modulation.
8. The apparatus of claim 2 , wherein the transmitter elements transmit a plurality of pulses in accordance with a frequency division multiplexing (FDM) scheme, wherein each pulse comprises a carrier frequency selected from a set of predetermined frequencies allowing the receiver elements to separate out a reflected signal from a plurality of reflected signals for each transmitter element, wherein the plurality of reflected signals are reflected by one or more objects within a region of interest.
9. The apparatus of claim 8 , wherein the carrier frequencies of the plurality of pulses are cycled incrementally after each transmission, such that each transmitter element transmits a sequence of pulses covering the set of predetermined frequencies.
10. The apparatus of claim 8 , wherein the plurality of pulses are transmitted in accordance with an orthogonal frequency division multiplexing (OFDM) scheme.
11. The apparatus of claim 9 , wherein the transmission of the plurality of pulses is staggered, whereby each transmitter element transmits a pulse having a different carrier frequency than an adjacent transmitter element.
12. The apparatus of claim 11 , wherein the sequence of pulses comprises a number N of frequency steps that is equal to or greater than a number L of transmitter elements in the first array of radar elements, wherein the number L comprises substantially all of the transmitter elements in the first array of radar elements.
13. The apparatus of claim 12 , wherein the receiver elements are arranged such that each receiver element of the second array of radar elements captures L×M×N sequences of pulses, where M is the number of receiver elements in the second array of radar elements.
14. The apparatus of claim 9 , wherein a constant frequency separation is maintained between the carrier frequencies of each pulse.
15. The apparatus of claim 14 , wherein each pulse comprises code compression.
16. The apparatus of claim 15 , wherein the pulse code compression includes step-frequency range compression.
17. The apparatus of claim 1 , wherein the first array of radar elements comprises a linear array of radar elements and the second array of radar elements comprises a planar array of radar elements.
18. The apparatus of claim 1 , wherein the first array of radar elements comprises a planar array of radar elements and the second array of radar elements comprises a linear array of radar elements.
19. The apparatus of claim 17 , wherein the planar array of radar elements defines a closed planar shape selected from at least one of the following: a circle, a square, a rectangle or an octagon.
20. The apparatus of claim 18 , wherein the planar array of radar elements defines a closed planar shape selected from at least one of the following: a circle, a square, a rectangle, or an octagon.
21. The apparatus of claim 17 , wherein the radar elements of the second array of radar elements are positioned adjacent to a perimeter of the planar array of radar elements.
22. The apparatus of claim 21 , wherein the linear array of radar elements is positioned within the perimeter of the planar array of radar elements.
23. The apparatus of claim 22 , wherein the linear array of radar elements is positioned coincident with the centre of the planar array of radar elements.
24. The apparatus of claim 21 , wherein the linear array of radar elements is positioned external to the perimeter of the planar array of radar elements.
25. The apparatus of claim 21 , wherein one or more of the radar elements of the planar array of radar elements are foldable with respect to the linear array of radar elements.
26. The apparatus of claim 24 , wherein the planar array of radar elements comprises a plurality of radial supports hinged at one end to the linear array of radar elements, wherein each radial support comprises at least one receiver element pivotally attached thereto such that when the radial supports are swung upon the hinged end toward the linear array of radar elements, each receiver element pivots to lie substantially flat along a radial support.
27. A surveillance apparatus, said apparatus comprising:
an array of radar transmitting elements that transmit a plurality of pulses;
an array of radar receiving elements that receive a plurality of reflected signals, wherein the plurality of reflected signals are reflected from one or more objects within a region of interest, wherein said array of radar transmitting elements and said array of radar receiving elements are orthogonal to one another;
a feed network coupled to one or more radar transmitting elements of said array of radar transmitting elements; and
a processor coupled to one or more radar receiving elements of the array of radar receiving elements and said feed network, wherein said processor is adapted to generate from said plurality of reflected signals a three dimensional radar image, wherein the three dimensional radar image is based on a plurality of transient elements.
28. A method of conducting surveillance of a region of interest, said method comprising:
transmitting a plurality of pulses from a first array of radar elements toward the region of interest;
receiving by a second array of radar elements a plurality of reflected signals that are reflected form one or more objects in the region of interested, wherein said second array of radar elements is arranged orthogonal to said first array of radar elements; and
processing the transmitted plurality of pulses and the reflected signals to synthesise a plurality of transient elements, wherein each of the transient elements act as a transceiver that is positioned at a mid point between a transmitter element within the first array of radar elements and a receiver element within the second array of radar elements.