Metamaterial system endowing object with adjustable radar profile (track one)
View Patent ↗Vehicles with adjustable metamaterial systems, integrated on the outside or inside of their non-conductive fuselage, have the ability to control their radar cross section dynamically for the purposes of evading detection or spoofing their size by looking larger or more numerous. The frequency response of a metamaterial system can be obtained by combining the RF properties of the individual metamaterial layers that comprise it. A first metamaterial layer that can controllably switch between transmissive and reflection in a relevant frequency band and a second absorptive layer results in a controllable radar cross-section with the ability of controlling the amplitude of the reflected radar pulse. The first layer can be modulated with a repetitive waveform to change the phase of a reflected wave that results in a doppler shift in frequency. The frequency of the modulation can result in a change in range, velocity, or combinations of both. The waveform used can also create a linear change of phase or can be made pseudorandom to create decoy targets that appear to move with random ranges and velocities as detected by a radar. The metamaterial layers can also have a separate passband for allowable communications, navigations, or for other wireless uses within the vehicle. The passband itself can also be switchable or tunable to allow for multiple passband frequencies.
1 . A method for making adjustable a radar profile of an object, the method comprising:
integrating into the object a set of metamaterial structures including a first metamaterial structure having an exterior surface defining an outer surface of the object and configured to be controllably reflective so as to operate, in a first mode wherein the outer surface is reflective at an external radar frequency f1 so as to cause reflection of an RF radar wave at frequency f1, incident on the object, and in a second mode wherein the outer surface is transmissive;
coupling a waveform generator to the set of metamaterial structures including the first metamaterial structure; and
configuring the waveform generator to cause a corresponding temporal variation in reflectivity of the first metamaterial structure with a resulting phase change in the reflected RF radar wave and a change in doppler shift associated with the reflected RF radar wave and therefore modification of the radar profile of the object by operating in a mode selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile in both range and velocity of the object;
(c) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object;
(d) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(e) combinations of the foregoing;
wherein operation of the waveform generator causes the corresponding temporal variation in reflectivity of the first metamaterial structure having the exterior surface that defines the outer surface of the object so as to produce the phase change of the reflected RF radar wave and the change in doppler shift of the reflected RF radar wave and therefore an adjustment of the radar profile of the object.
2 . A method according to claim 1 , wherein the mode is selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile in both range and velocity of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object;
(c) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(d) combinations of the foregoing.
3 . A method according to claim 1 , wherein the mode is selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object;
(c) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(d) combinations of the foregoing.
4 . A method according to claim 1 , wherein the mode is selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile in both range and velocity of the object;
(c) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(d) combinations of the foregoing.
5 . A method according to claim 1 , wherein the waveform generator is configured to operate in a set of modes selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile in both range and velocity of the object;
(c) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object; and
(d) combinations of the foregoing.
6 . A method according to claim 1 , further comprising configuring the waveform generator further to modulate the reflection of the RF radar wave as a means of encoding information in digital communications.
7 . A method according to claim 1 , further comprising configuring the waveform generator to operate in a mode selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object;
(b) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(c) combinations of the foregoing.
8 . A method according to claim 1 , further comprising configuring the waveform generator to operate in a mode selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a pseudorandom binary sequence waveform at a set of frequencies for providing a set of radar decoys having a set of different ranges and velocities as compared to those of the object; and
(c) combinations of the foregoing.
9 . A method according to claim 1 , further comprising configuring the waveform generator to operate in a mode selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile in both range and velocity of the object; and
(c) combinations of the foregoing.
10 . A method according to claim 1 , further comprising configuring the waveform generator to operate in a mode selected from the group consisting of:
(a) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a range of the object;
(b) generating a repetitive waveform at a set of frequencies for providing a change of the radar profile only in a velocity of the object; and
(c) combinations of the foregoing.
11 . A method for making adjustable a radar profile of an object, the method comprising:
integrating into the object a set of metamaterial structures including (i) a first metamaterial structure having an exterior surface defining an outer surface of the object and configured, with respect to a radar wave at frequency f1 incident on the object, to be controllably reflective; and (ii) a second metamaterial structure having an exterior surface configured, with respect to the radar wave at frequency f1 incident on the object, to be absorptive;
wherein integrating includes overlaying the first metamaterial structure on the second metamaterial structure; and
coupling a control signal generator, to apply an adjustable signal to the set of metamaterial structures including the first metamaterial structure, so as to apply thereto an adjustable signal, and configuring the control signal generator to cause the exterior surface of the first metamaterial structure to operate in a transparent mode and to control an extent of transmissivity thereof, at the radar frequency f1, in combination with absorption by exterior surface of the second metamaterial structure, so as to endow the object with a customized radar cross-section that is potentially larger, or smaller, than that of the object without the metamaterial system, or to render the object invisible to radar;
wherein operation of the control signal generator to apply the adjustable signal produces an adjustment in the extent of transmissivity of the first metamaterial structure and a corresponding adjustment in absorption by the second metamaterial structure and therefore a corresponding adjustment of the radar profile of the object.
12 . A method according to claim 11 , wherein integrating includes supporting communications through both the first and the second metamaterial structures, while still functioning as a radar reflector at frequency f1, by the exterior surfaces of the first and second metamaterial structures being configured to be transmissive at a frequency different from f1.
13 . A method according to claim 12 , wherein supporting communications further includes allowing for multiple communication channels by the exterior surfaces of the first and second metamaterial structures being electronically configured to be transmissive at a plurality of non-radar frequencies.
14 . A method according to claim 12 , wherein integrating into the object includes incorporating the set of metamaterial structures into a vehicle.
15 . A method according to claim 13 , wherein allowing for multiple communication channels further includes providing flexibility in communication and radar operation by any given one of the plurality of transmissive frequencies being user selectable.
16 . A method according to claim 13 , wherein allowing for multiple communication channels further includes allowing for precise adjustment of the communication and radar operation by any given one of the plurality of transmissive frequencies being tunable.
17 . A method according to claim 13 , wherein integrating into the object includes incorporating the set of metamaterial structures into a vehicle.
18 . A method according to claim 15 , wherein integrating into the object includes incorporating the set of metamaterial structures into a vehicle.
19 . A method according to claim 16 , wherein integrating into the object includes incorporating the set of metamaterial structures into a vehicle.
20 . A method according to claim 11 , wherein integrating into the object includes incorporating the set of metamaterial structures into a vehicle.