Cavity length determination apparatus

• US 9,645,233 B2
• Filed: 10/31/2013
• Issued: 05/09/2017
• Est. Priority Date: 03/17/2010
• Status: Active Grant

• Current Assignee: Kenneth J. Hintz
• Original Assignee: Kenneth J. Hintz
• Inventors: Hintz, Kenneth J
• Primary Examiner(s): Sotomayor, John B
• Application Number:
  US14/068,165
• Publication Number:
  US 20160223660A1
• Time in Patent Office: 1,286 Days
• Field of Search: 342196, 342 90, 342192, 342193
• CPC Class Codes: F41G 3/147 based on detection of a firing weapon
• CPC Class Codes: G01S 13/347 using more than one modulation frequency
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 5/0278 involving statistical or probabilistic considerations G01S5/0252, G01S5/0294 take precedence

Abstract

Embodiments include an apparatus comprising a frequency selective electromagnetic receiver and a signal analyzing module. The frequency selective electromagnetic receiver is configured to receive a reradiating electromagnetic signal resulting from a cavity induced modulation phenomenon occurring within cavit(ies). The signal analyzing module is configured to: determine a power spectral density of the reradiating electromagnetic signal. Frequencies are observed at which the amplitude modulation of the power spectral density peaks. A cavity length is determined employing the frequencies of the power spectral density peaks.

Claims

1. An apparatus comprising:

a) a frequency selective electromagnetic receiver configured to receive a reradiating electromagnetic signal resulting from a cavity induced modulation phenomenon occurring within at least one cavity; and

b) a signal analyzing module configured to;

i) determine a power spectral density of the reradiating electromagnetic signal;

ii) observe frequencies at which the amplitude modulation of the power spectral density peaks; and

iii) determine a cavity length employing an integer relationship of the frequencies of the power spectral density peaks.

2. The apparatus according to claim 1, wherein the signal analyzing module is further configured to:

a) compute at least one cavity detecting statistic of the reradiating electromagnetic signal; and

b) generate a notification when the at least one cavity detecting statistic exceeds a threshold.

3. The apparatus according to claim 1, wherein the signal analyzing module is further configured to generate a value corresponding to the cavity length.

4. The apparatus according to claim 1, wherein the cavity induced modulation phenomenon results from an interaction of at least one irradiating signal with the at least one cavity, said at least one irradiating signal including at least two frequency components.

5. The apparatus according to claim 2, wherein the threshold includes a multi-variable function.

6. The apparatus according to claim 2, wherein the threshold includes at least one value.

7. The apparatus according to claim 2, wherein at least one of the at least one cavity detecting statistic is an autocorrelation function.

8. The apparatus according to claim 7, wherein the autocorrelation function is a Fourier transform of the power spectral density of the reradiating electromagnetic signal.

9. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is further configured to receive the reradiating electromagnetic signal comprising a randomized spectral component.

10. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is further configured to receive the reradiating electromagnetic signal resulting from a spread spectrum irradiating signal.

11. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is further configured to receive the reradiating electromagnetic signal radiated from at least two non co-located radiators.

12. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is further configured to receive at least one irradiating signal radiated from a location spatially distinct from the signal receiver.

13. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is further configured to receive at least one reradiating electromagnetic signal above a cavity dependent cutoff frequency.

14. The apparatus according to claim 1, wherein the cavity is a weapon bore.

15. The apparatus according to claim 1, wherein the apparatus is further configured to determine at least one of the following:

a) an azimuth bearing from the cavity to the apparatus;

b) an elevation bearing from the cavity to the apparatus; and

c) a combination of the above.

16. The apparatus according to claim 1, wherein the frequency selective electromagnetic receiver is configured to simultaneously receive at least two selected frequencies.

17. The apparatus according to claim 2, wherein the threshold is dynamically determined based on at least one of the at least one cavity detecting statistic.

18. The apparatus according to claim 2, wherein at least one of the at least one cavity detecting statistic is used to guide a projectile to the cavity.

19. The apparatus according to claim 2, wherein at least one of the at least one cavity detecting statistic is used to aim a weapon in the direction of the cavity.

20. The apparatus according to claim 1, wherein the signal analyzing module uses the cavity length to determine a weapon type.