Intrusion detection

1. A method for intrusion detection, comprising:

transmitting a direct sequence spread spectrum (DSSS) signal, wherein the signal includes a chipping sequence formed from multiple chips and wherein a chip length is a time between each of the chips and the chip length determines a time period corresponding to a phase delay;

receiving a reflected DSSS signal from a target, via a receiver;

determining the phase delay by correlating the reflected DSSS signal and the transmitted DSSS signal based upon comparison of the chipping sequences of the reflected DSSS signal and the transmitted DSSS signal;

determining a distance to the target based on the phase delay between the reflected DSSS signal and the transmitted DSSS signal; and

determining a location of the target based on an azimuth of the reflected DSSS signal and the distance to the target, wherein the azimuth of the reflected DSSS signal is an angle at which the receiver receives the reflected DSSS signal.

2. The method of claim 1 , wherein the method includes:

generating a replica of a code used to modulate a frequency of the transmitted DSSS signal; and

correlating the chipping sequence between a reflection of the code used to modulate the frequency of the transmitted DSSS signal and the replica of the code used to modulate the frequency of the transmitted DSSS signal.

3. The method of claim 2 , wherein the method includes:

transmitting the DSSS signal with a transmitter;

receiving the reflected DSSS signal with the receiver; and

generating the replica of the code used to modulate the frequency of the transmitted DSSS signal with the receiver.

4. The method of claim 2 , wherein the method includes determining the phase delay based on the correlation of the chipping sequence between the reflection of the code used to modulate the frequency of the transmitted DSSS signal and the replica of the code used to modulate the frequency of the transmitted DSSS signal.

5. The method of claim 4 , wherein the method includes calculating a time delay between the transmitted DSSS signal and the reflected DSSS signal based on the phase delay between the transmitted DSSS signal and the reflected DSSS signal.

6. The method of claim 1 , wherein the method includes:

determining the azimuth of the reflected DSSS signal; and

determining a speed of the target based on the azimuth of the reflected DSSS signal and the distance to the target.

7. The method of claim 6 , wherein the method includes:

receiving the reflected DSSS signal from the target at a multi-antenna receiver;

comparing the reflected DSSS signal received at each of the multiple antennas; and

determining the azimuth of the reflected DSSS signal from the comparison of the reflected DSSS signals.

8. The method of claim 1 , wherein the method includes:

determining a position of the target based on the azimuth of the reflected DSSS signal and the distance to the target;

sending a notification to an imaging device, wherein the notification includes the position of the target; and

recording the target with the imaging device, based on the position of the target.

9. The method of claim 1 , wherein the method includes determining a size of the target based on an amplitude signature of the reflected DSSS signal and a radial extent of the reflected DSSS signal.

10. The method of claim 1 , wherein the method includes determining a type of target based on the size of the target and the speed of the target.

11. A machine-readable non-transitory medium storing instructions for intrusion detection, the instructions executable by a machine to cause the machine to:

transmit a first direct sequence spread spectrum (DSSS) signal from a first point and a second DSSS signal from a second point, wherein each of the first DSSS signal and the second DSSS signal include a chipping sequence formed from multiple chips and wherein a chip length is a time between each of the chips and the chip length determines a first time period corresponding to a first phase delay and a second time period corresponding to a second phase delay;

receive a reflection of the first DSSS signal from a target at the first point and a reflection of the second DSSS signal from the target at the second point;

determine the first phase delay between the reflection of the first DSSS signal and the first transmitted DSSS signal based upon comparison of the chipping sequences of the reflected first DSSS signal and the transmitted first DSSS signal and the second phase delay between the reflection of the second DSSS signal and the second transmitted DSSS signal based upon comparison of the chipping sequences of the reflected second DSSS signal and the transmitted second DSSS signal;

determine a position of the target based on the first and second phase delay and a distance between the first and second point; and

determine an azimuth of the target based on the first and second point.

12. The medium of claim 11 , wherein the instructions are executable by the machine to store the position of the target at a first time and a second time.

13. The medium of claim 11 , wherein the instructions are executable by the machine to determine a speed of the target based on the position of the target at the first time and the position of the target at the second time.

14. The medium of claim 11 , wherein the instructions are executable by the machine to display the position of the target on a user interface.

15. The medium of claim 11 , wherein the instructions are executable by the machine to transmit the first DSSS signal and the second DSSS signal at an industrial, scientific, and medical radio band.

16. A system for intrusion detection, the system comprising a processing resource in communication with a non-transitory computer-readable medium, wherein the computer-readable medium contains a set of instructions and wherein the processing resource is designed to execute the set of instructions to:

transmit a direct sequence spread spectrum (DSSS) signal with a transmitter, wherein the signal includes a chipping sequence formed from multiple chips and wherein a chip length is a time between each of the chips and the chip length determines a time corresponding to a phase delay;

receive a reflected DSSS signal from a target with a receiver;

generate a replica of the transmitted DSSS signal;

determine the phase delay between the replica of the transmitted DSSS signal and the reflected DSSS signal based upon comparison of the chipping sequences of the reflected DSSS signal and the replica of the transmitted DSSS signal, and an azimuth of the reflected DSSS signal; and

determine a position of the target based on the phase delay and the azimuth of the reflected DSSS signal, wherein the azimuth of the reflected DSSS signal is an angle at which the receiver receives the reflected DSSS signal.

17. The system of claim 16 , wherein the instructions are executable to determine a distance to the target from a point where the DSSS signal is received.

18. The system of claim 16 , wherein the DSSS signal is transmitted by the transmitter in a direction away from the receiver.

19. The system of claim 16 , wherein the instructions are executable to determine a propagation delay of the transmitted DSSS signal as a function of the phase delay and a period of the transmitted DSSS signal.

20. The system of claim 19 , wherein the instructions are executable to determine the distance to the target as a function of the speed of light and the propagation delay.