Flat panel antenna
A flat panel antenna fed by a planar feed array and steered by varactors performs the function of a single beam phased array antenna. This flat panel antenna has a planar array to passively amplify radio frequency (RF) signals, and a transmitarray metasurface having an array of unit cells to steer the antenna's main beam. It uses varactors to dynamically control the phase shift for each unit cell.
1 . A method of steering a beam comprising:
providing a flat feed array;
generating plane waves with the feed array;
providing a metasurface comprising an array of unit cells having varactors, the unit cells configured to steer beams according to capacitance of the varactors;
impinging the plane waves on the metasurface; and
varying the capacitance of the varactors to steer beams resulting from the plane waves.
2 . The method of claim 1 , further comprising the step of separating the flat feed array and the metasurface by a distance on the order of a longest wavelength the steerable antenna is configured to amplify.
3 . The method of claim 2 wherein the step of providing a metasurface further comprises the step of configuring the unit cells in layers separated by a distance on the order of ¼ of the longest wavelength the steerable antenna amplifies.
4 . The method of claim 3 wherein the step of configuring the unit cells in layers provides four layers.
5 . The method of claim 3 wherein each layer includes a substrate and each unit cell includes a conductive overlay on each substrate.
6 . The method of claim 2 wherein the step of controlling varactor capacitances further comprises the step of using a single DAC to control switches attached to the varactors.
7 . The method of claim 1 wherein the step of providing the metasurface comprising an array of unit cells provides four spaced apart layers, each layer including a substrate and each unit cell including a conductive overlay on each substrate.
8 . The method of claim 7 wherein the conductive overlay includes an inner copper ring and an outer copper ring and the varactors is are disposed between the inner copper ring and an outer copper ring.
9 . The method of claim 1 wherein the step of providing a metasurface further comprises the step of configuring the unit cells in layers separated by a distance on the order of ¼ of the longest wavelength the steerable antenna amplifies.
10 . The method of claim 9 wherein the step of configuring the unit cells in layers provides four spaced apart layers.
11 . The method of claim 10 wherein each layer includes a substrate and each unit cell includes a conductive overlay on each substrate.
12 . The method of claim 9 further comprising the step of separating the flat feed array and the metasurface by a distance on the order of a longest wavelength the steerable antenna is configured to amplify.
13 . The method of claim 1 wherein the step of controlling varactor capacitances further comprises the step of using a single DAC to control switches attached to the varactors.
14 . The method of claim 13 wherein the step of configuring the unit cells in layers provides four spaced apart layers.
15 . The method of claim 14 wherein the layers are separated by a distance on the order of ¼ of the longest wavelength the steerable antenna amplifies.
16 . The method of claim 13 wherein each layer includes a substrate and each unit cell includes a conductive overlay on each substrate.
17 . The method of claim 1 further comprising the steps of:
providing a bias layer; and
separately controlling varactor capacitances with the bias layer such that each unit cell independently shifts the phase of electromagnetic waves.
18 . The method of claim 1 further comprising the steps of:
providing a bias layer configured as a patch array with patches including an RF choke having a radial stub and a ¼λ transmission line.