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"We fabricated a hybrid antenna that consists of a logarithmic spiral and loop antenna. The antenna was designed to detect electromagnetic (EM) noise and be broadband in the range of 1 MHz to 1 GHz. This style of antenna can be located in buildings and passageways in inaccessible areas for the purpose of shielding integrity surveillance and life cycle shielding degradation monitoring, and can be used as permanent fixtures that detect critical threshold levels of unwanted EM radiation. The antenna structures were modeled with the FEKO EM numerical code and were also experimentally characterized in the laboratory. The measurements compare well with the predictions from the modeling. This report presents the detailed results of the design, and the FEKO analysis and the measured results."
Contents
List of Figures iv
List of Tables iv
1. Objective 1
2. Approach 1
3. Design Goals 1
4. Log Spiral Fabrication 3
5. Log Spiral Results 4
5.1 Modeled 4
5.2 Measured 6
5.2.1 Balun 6
5.2.2 Experimental Test Results 7
6. Loop Antenna Results 10
7. Conclusions 11
7.1 Future Work 11
8. References 13
Distribution List 14
List of Figures
Figure 1. A use for the low profile hybrid antenna 3
Figure 2. Modeled log spiral antenna, with approximately 4000 method of moment elements 4
Figure 3. Fabricated log spiral antenna 4
Figure 4. Modeled antenna gain for ideal and 50 Q. source 5
Figure 5. Modeled input impedance magnitude 5
Figure 6. Modeled complex input impedance of log spiral antenna 6
Figure 7. Balun attached to log spiral feed 6
Figure 8. Design of wideband balun 7
Figure 9. Measured gain of log spiral antenna, with and without balun 7
Figure 10. Measured gain of log spiral antenna, expanded linear scale 8
Figure 1 1 . Input impedance of log spiral antenna, with and without balun 8
Figure 12. Reflection coefficient of log spiral antenna, with and without balun 9
Figure 13. Simulated and measured gains of the log spiral antenna 9
Figure 14. Hybrid log spiral with loop antenna 10
Figure 15. Modeled and measured gains of loop antenna 11
Figure 16. Skin depth versus frequency for various metals 12
List of Tables
Table 1. Mean simulated and measured gains in frequency region of interest 9
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