Nonreciprocal reflectarray antennas based on time-modulated unit-cells
The disclosed embodiments relate to the design of a system that implements a reflectarray antenna. The system includes a time-modulated metasurface, which is configured to act as a planar reflector for an electromagnetic wave that is radiated by a feeder into free space at an operation frequency f 0 . The time-modulated metasurface includes time-modulated unit-cells that provide a nonlinear conversion between f 0 and another desired frequency f d . The system also includes a phase-delay mechanism, which adjusts a phase delay by acting on a phase applied to a modulation frequency f m that modulates each unit-cell. The nonlinear conversion and the phase-delay mechanism operate collectively to facilitate angle-independent nonreciprocity by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
1. A reflectarray antenna, comprising:
a time-modulated metasurface configured to act as a planar reflector for an electromagnetic wave, which is radiated by a feeder into free space at an operation frequency f 0 , wherein:
the time-modulated metasurface includes time-modulated unit-cells that provide a nonlinear conversion between f 0 and another desired frequency f d ; and
each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor; and
a phase-delay mechanism, which adjusts a phase delay by acting on a phase applied to a modulation frequency f m , that modulates each unit-cell.
2. The reflectarray antenna of claim 1 , wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity during transmission and reception by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
3. The reflectarray antenna of claim 1 , wherein the nonlinear conversion and the phase-delay mechanism facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
4. The reflectarray antenna of claim 1 , wherein the nonlinear conversion and the phase-delay mechanism facilitate transmitting a signal in one direction and receiving a signal from another direction.
5. The reflectarray antenna of claim 1 , wherein the modulation frequency f m for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
6. The reflectarray antenna of claim 1 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
7. The reflectarray antenna of claim 6 , wherein a capacitance value of the time-modulated capacitor varies with time according to the function C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
8. The reflectarray antenna of claim 1 , wherein each of the time-modulated unit-cells further comprises:
a patch antenna located on a top substrate, which acts as an interface element with free space;
a plurality of slots located on a bottom substrate; and
a short-circuited substrate-integrated waveguide (SIW), which hosts a varactor in a shunt configuration, wherein the varactor is located approximately λ/4 away from a short-circuit in the SIW thereby implementing a tunable resonator, wherein during operation of the reflectarray antenna, incoming power from the patch antenna is coupled through the plurality of slots to the short-circuited SIW.
9. The reflectarray antenna of claim 1 , further comprising the feeder, which radiates the wave into free space at the frequency f 0 .
10. A method for operating a reflectarray antenna, comprising:
receiving an electromagnetic wave, which was radiated by a feeder into free space at an operation frequency f 0 ; and
using the reflectarray antenna to reflect the electromagnetic wave, wherein the reflectarray antenna comprises a time-modulated metasurface, which is configured to act as a planar reflector for the electromagnetic wave;
wherein while reflecting the electromagnetic wave, the time-modulated metasurface uses time-modulated unit-cells to provide a nonlinear conversion between f 0 and another desired frequency f d , and uses a phase-delay mechanism to adjust a phase applied to a modulation frequency f m , that modulates each unit-cell; and
wherein each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor.
11. The method of claim 10 , wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity in transmission and reception by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
12. The method of claim 10 , wherein the nonlinear conversion and the phase-delay mechanism facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
13. The method of claim 10 , wherein the nonlinear conversion and the phase-delay mechanism facilitate transmitting a signal in one direction and receiving a signal from another direction.
14. The method of claim 10 , wherein the modulation frequency f m for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
15. The method of claim 10 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
16. The method of claim 15 , wherein a capacitance value of the time-modulated capacitor varies with time as C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
17. A system that includes a reflectarray antenna, comprising:
a housing;
a computer system mounted to the housing; and
the reflectarray antenna mounted to the housing, which comprises,
a time-modulated metasurface configured to act as a planar reflector for an electromagnetic wave, which is radiated by a feeder into free space at an operation frequency f 0 , wherein:
the time-modulated metasurface includes time-modulated unit-cells that provide a nonlinear conversion between f 0 and another desired frequency f d , and
each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor; and
a phase-delay mechanism that adjusts a phase delay by acting on a phase applied to a modulation frequency f m , that modulates each unit-cell.
18. The system of claim 17 , wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
19. The system of claim 17 , wherein the nonlinear conversion and the phase-delay mechanism facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
20. The system of claim 17 , wherein the nonlinear conversion and the phase-delay mechanism facilitate transmitting a signal in one direction and receiving a signal from another direction.
21. The system of claim 17 , wherein the modulation frequency f m for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
22. The system of claim 17 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
23. The system of claim 22 , wherein a capacitance value of the time-modulated capacitor varies with time as C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
24. The system of claim 22 , wherein each of the time-modulated unit-cells comprises:
a patch antenna located on a top substrate, which acts as an interface element with free space;
a plurality of slots located on a bottom substrate; and
a short-circuited substrate-integrated waveguide (SIW), which hosts a varactor in a shunt configuration, wherein the varactor is located approximately λ/4 away from a short-circuit in the SIW thereby implementing a tunable resonator, wherein during operation of the reflectarray antenna, incoming power from the patch antenna is coupled through the plurality of slots to the short-circuited SIW.
25. The system of claim 17 , wherein the system comprises a satellite.
26. The system of claim 17 , wherein the system comprises a radar system.
27. A reflectarray antenna, comprising:
a time-modulated metasurface configured to act as a planar reflector for an electromagnetic wave, which is radiated by a feeder into free space at an operation frequency f 0 , wherein the time-modulated metasurface includes time-modulated unit-cells that provide a nonlinear conversion between f 0 and another desired frequency f d ; and
a phase-delay mechanism, which adjusts a phase delay by acting on a phase applied to a modulation frequency f m , that modulates each unit-cell;
wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity during transmission and reception by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
28. The reflectarray antenna of claim 27 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
29. The reflectarray antenna of claim 27 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate transmitting a signal in one direction and receiving a signal from another direction.
30. The reflectarray antenna of claim 27 , wherein the modulation frequency f m , for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
31. The reflectarray antenna of claim 27 , wherein each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor.
32. The reflectarray antenna of claim 31 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
33. The reflectarray antenna of claim 32 , wherein a capacitance value of the time-modulated capacitor varies with time according to the function C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
34. The reflectarray antenna of claim 31 , wherein each of the time-modulated unit-cells further comprises:
a patch antenna located on a top substrate, which acts as an interface element with free space;
a plurality of slots located on a bottom substrate; and
a short-circuited substrate-integrated waveguide (SIW), which hosts a varactor in a shunt configuration, wherein the varactor is located approximately λ/4 away from a short-circuit in the SIW thereby implementing a tunable resonator, wherein during operation of the reflectarray antenna, incoming power from the patch antenna is coupled through the plurality of slots to the short-circuited SIW.
35. The reflectarray antenna of claim 27 , further comprising the feeder, which radiates the wave into free space at the frequency f 0 .
36. A method for operating a reflectarray antenna, comprising:
receiving an electromagnetic wave, which was radiated by a feeder into free space at an operation frequency f 0 ; and
using the reflectarray antenna to reflect the electromagnetic wave, wherein the reflectarray antenna comprises a time-modulated metasurface, which is configured to act as a planar reflector for the electromagnetic wave;
wherein while reflecting the electromagnetic wave, the time-modulated metasurface uses time-modulated unit-cells to provide a nonlinear conversion between f 0 and another desired frequency f d , and uses a phase-delay mechanism to adjust a phase applied to a modulation frequency f m , that modulates each unit-cell; and
wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity in transmission and reception by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
37. The method of claim 36 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
38. The method of claim 36 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate transmitting a signal in one direction and receiving a signal from another direction.
39. The method of claim 36 , wherein the modulation frequency f m for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
40. The method of claim 36 , wherein each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor.
41. The method of claim 40 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
42. The method of claim 41 , wherein a capacitance value of the time-modulated capacitor varies with time as C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
43. A system that includes a reflectarray antenna, comprising:
a housing;
a computer system mounted to the housing; and
the reflectarray antenna mounted to the housing, the reflectarray antenna comprising:
a time-modulated metasurface configured to act as a planar reflector for an electromagnetic wave, which is radiated by a feeder into free space at an operation frequency f 0 , wherein the time-modulated metasurface includes time-modulated unit-cells that provide a nonlinear conversion between f 0 and another desired frequency f d , and
a phase-delay mechanism that adjusts a phase delay by acting on a phase applied to a modulation frequency f m that modulates each unit-cell;
wherein the nonlinear conversion and the phase-delay mechanism facilitate angle-independent nonreciprocity by imposing different phase gradients during up-conversion and down-conversion processes, and by preventing generation of certain propagative harmonics due to total internal reflection.
44. The system of claim 43 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate full control of shape and direction of a generated beam during the up-conversion process by imposing a configurable phase gradient.
45. The system of claim 43 , wherein the nonlinear conversion and the phase-delay mechanism further facilitate transmitting a signal in one direction and receiving a signal from another direction.
46. The system of claim 43 , wherein the modulation frequency f m , for the time-modulated unit-cells is more than one order of magnitude smaller than the operation frequency f 0 .
47. The system of claim 43 , wherein each of the time-modulated unit-cells comprises a resonator with an incorporated time-modulated capacitor.
48. The system of claim 47 , wherein the phase-delay mechanism controls the time-modulated capacitor in each of the time-modulated unit-cells by using a time-varying harmonic signal having frequency ω m =2πf m and phase φ m .
49. The system of claim 47 , wherein a capacitance value of the time-modulated capacitor varies with time as C p (t)=C 0 [1+Δ m cos(ω m t+φ m )], wherein C 0 is an average capacitance value and Δ m is a modulation index 0<Δ m <1.
50. The system of claim 47 , wherein each of the time-modulated unit-cells comprises:
a patch antenna located on a top substrate, which acts as an interface element with free space;
a plurality of slots located on a bottom substrate; and
a short-circuited substrate-integrated waveguide (SIW), which hosts a varactor in a shunt configuration, wherein the varactor is located approximately λ/4 away from a short-circuit in the SIW thereby implementing a tunable resonator, wherein during operation of the reflectarray antenna, incoming power from the patch antenna is coupled through the plurality of slots to the short-circuited SIW.
51. The system of claim 43 , wherein the system comprises a satellite.
52. The system of claim 43 , wherein the system comprises a radar system.