Wideband RF detection

1. A method, comprising:

transmitting a signal from a plurality of transmit positions along a drive path;

receiving reflections of the transmitted signal at a plurality of receive positions along the drive path;

forming a signature of a structure based on arrival angles of the reflections at each of the receive positions;

inferring an interior of the structure based on the signal; and

comparing the signature to other signatures to detect internal changes within the structure.

2. The method of claim 1 , wherein the signature includes the arrival angles of the reflections at each of the receive positions with respect to a distance along the drive path of a corresponding transmit position and a corresponding receive position of each of the reflections.

3. The method of claim 1 , wherein each arrival angle of each of the reflections is computed in accordance with the following equation

cos

⁢

⁢

θ

=

-

sgn

⁡

(

x

)

1

+

R

2

/

x

2

,



x



≥

d

2

wherein θ is an arrival angle of a particular reflection, x is an x-axis location of a corresponding receive position, d is a distance along the drive path between the corresponding transmit position and the corresponding receive position for the particular reflection along the x-axis range, and R is a distance along the y-axis from the drive path to a reflection point of the particular reflection.

4. The method of claim 1 , wherein the signature includes an intensity of the received reflections at each of the receive positions along the drive path.

5. The method of claim 1 , wherein the signature includes a path delay of the received reflections at each of the receive positions along the drive path with respect to transmit times of corresponding transmit signals.

6. The method of claim 1 , further comprising:

representing the signature as a display of the arrival angles of the reflections at each of the receive positions with respect to a distance along the drive path of a corresponding transmit position and a corresponding receive position of each of the reflections at each of the receive positions along the drive path, with coloring to indicate a path delay of the received reflections, the path delay in respect to transmit times of corresponding transmit signals.

7. The method of claim 6 , wherein an intensity of the coloring indicates an intensity of the received reflections at each of the receive positions along the drive path.

8. The method of claim 6 , wherein a path loss is based on the arrival angle of the received reflections, the path loss being a difference between an intensity of the transmitted signal and an intensity of the received reflections.

9. The method of claim 1 , further comprising:

performing beamforming along the drive path to derive the received reflections for the signature.

10. The method of claim 9 , further comprising:

distributing the arrival angles of the received reflections across a plurality of bins of a column of a matrix for each corresponding transmit/receive position pair, the bins being filled with a complex path amplitude of the reflections, each column of the matrix corresponding to a single transmit/receive position pair.

11. The method of claim 1 , further comprising:

storing the signature as a reference file.

12. The method of claim 1 , wherein the inferring the interior of the structure includes matching trajectories of the arrival angles of the reflections to identify corners within the structure.

13. The method of claim 1 , wherein the transmitted signal is a wideband RF probe signal.

14. The method of claim 1 , wherein the arrival angles are computed in a two-dimensional coordinate system.

15. The method of claim 1 , wherein the arrival angles are computed in a three-dimensional coordinate system.