14 May 2015 Phase response of high to very high frequency metal/anomaly detector
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In this paper the phase response and reflection coefficient notch of a metal/anomaly detector design that operates in the high to very high frequency range is studied. This design uses a high-Q tuned loop antenna for metal/anomaly detection. By measuring the reflection coefficient or voltage standing wave ratio a frequency notch can be detected. Tuning to the optimal location for detector performance can be accomplished by monitoring both the depth of the notch and the phase response. It has been experimentally observed that there are three regions of interest relative to the notch and phase response of the detector. One is at the frequency where the phase response is on a near vertical line of substantial phase shift and the notch is near its deepest depth. The second and third are at slightly higher and lower frequencies, where the slope of the phase shift line is reduced and the notch is still deep, but slightly removed from the frequency of maximum depth. As would be expected, initial experimentation indicates that the region of maximum detection performance, in terms of relative change in phase response, occurs when the phase response is at the center of the near vertical phase shift response near the location of the deepest notch. However, there may be advantages to the other two regions, since the response is more stable and less prone to false alarms. Performance results for various combinations of phase response and notch depth will be shown.
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Daniel C. Heinz, Daniel C. Heinz, Michael L. Brennan, Michael L. Brennan, Michael B. Steer, Michael B. Steer, Adam W. Melber, Adam W. Melber, John T. Cua, John T. Cua, } "Phase response of high to very high frequency metal/anomaly detector", Proc. SPIE 9454, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XX, 94540H (14 May 2015); doi: 10.1117/12.2182083; https://doi.org/10.1117/12.2182083

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