Single-frequency dynamic metasurface microwave imaging systems and methods of use

Abstract

A single frequency, or very narrow frequency band, microwave imaging system is described herein. A microwave imaging system can include an array transmitter; an array receiver; and a computing device that receives signals detected from the array receiver, transforms the signals received by the array receiver into independent spatial measurements, constructs an image using the independent spatial measurements, and outputs a reconstructed image. The array transmitter and the array receiver may each have a plurality of independently controllable metasurface resonant elements.

1 . A microwave imaging system comprising:
 an array transmitter;   an array receiver; and   a computing device that receives signals detected from the array receiver, transforms the signals received by the array receiver into independent spatial measurements, constructs an image using the independent spatial measurements, and outputs a reconstructed image.   
     
     
         2 . The system of  claim 1 , wherein the computing device transforms the signals received by the array into independent spatial measurements by:
 emulating a particular radiation pattern in which a single element is operating at a time to generate an independent spatial measurement that when combined, correspond to a received signal.   
     
     
         3 . The system of  claim 1 , wherein the computing device transforms the signals received by the array into independent spatial measurements by:
 performing a singular value decomposition inversion to sampled raw data of the signals detected from the array receiver.   
     
     
         4 . The system of  claim 3 , further comprising a sampling device that samples the signals detected from the array receiver and generates the sampled raw data in a form of a complex number for each transmission pattern transmitted by the array transmitter and received at the array receiver. 
     
     
         5 . The system of  claim 1 , wherein the array transmitter comprises a plurality of independently controllable metasurface resonant elements and the array receiver comprises a plurality of independently controllable metasurface resonant elements. 
     
     
         6 . The system of  claim 5 , wherein a size of each element of the plurality of independently controllable metasurface resonant elements is subwavelength and a spacing between each element of the plurality of independently controllable metasurface resonant elements is subwavelength. 
     
     
         7 . The system of  claim 6 , wherein the plurality of independently controllable metasurface resonant elements each comprise at least one tunable component. 
     
     
         8 . The system of  claim 7 , further comprising a control circuitry coupled to each of the tunable components of the plurality of independently controllable metasurface resonant elements. 
     
     
         9 . The system of  claim 1 , wherein the array transmitter is a phased array and the array receiver is a phased array. 
     
     
         10 . A method comprising:
 dynamically controlling a tuning of radiation patterns of an array transmitter and an array receiver;   receiving a signal corresponding to each of the radiation patterns generated by the array transmitter;   transforming the signals received by the array receiver into independent spatial measurements;   constructing an image using the independent spatial measurements; and   outputting the image.   
     
     
         11 . The method of  claim 10 , wherein dynamically controlling the tuning of the radiation patterns comprises:
 generating a plurality of radiation patterns, where for each radiation pattern, the generating of the radiation pattern comprises:
 controlling circuitry to create a radiation pattern by adjusting each element to be on or off, or adjusting the phase and/or amplitude of the elements. 
   
     
     
         12 . The method of  claim 10 , wherein receiving a signal corresponding to each of the radiation patterns generated by the array transmitter comprises:
 sampling the signal to generate a complex number for each of the radiation patterns.   
     
     
         13 . The method of  claim 10 , wherein transforming the signals comprises emulating a particular radiation pattern in which a single element is operating at a time to generate an independent spatial measurement that when combined, correspond to the received signal. 
     
     
         14 . The method of  claim 13 , wherein the total number of independent spatial measurements is equal to a total number of independently controllable metasurface resonant elements within the array transmitter multiplied by a total number of independently controllable metasurface resonant elements within the array receiver. 
     
     
         15 . The method of  claim 10 , wherein the constructing of the image using the independent spatial measurements comprises applying a Range Migration Algorithm (RMA). 
     
     
         16 . The method of  claim 15 , wherein the applying of the RMA comprises performing a Fast Fourier Transform. 
     
     
         17 . The method of  claim 10 , further comprising applying a single-frequency microwave signal to the array transmitter. 
     
     
         18 . The method of  claim 10 , further comprising applying a small bandwidth microwave signal to the array transmitter. 
     
     
         19 . A microwave imaging system comprising:
 an array transmitter comprising a plurality of independently controllable metasurface elements;   an array receiver comprising a plurality of independently controllable metasurface elements;   a sampler that samples each signal detected from signals received via the array receiver, each signal corresponding to a radiation pattern of a plurality of radiation patterns output from the array transmitter; and   a computing device that performs an image reconstruction algorithm on output of the sampler.   
     
     
         20 . The microwave imaging system of  claim 19 , wherein the computing device performs the image reconstruction algorithm by:
 inputting a collection of complex numbers output from the sampler into a matrix equation and then solving the matrix equation.