Development of Novel HF Electromagnetic Vector Sensor for Direction Finding Applications

1. E H S θ=80˚ φ=157˚ Department of Electrical and Computer Engineering - BGU Fourth Year Final Project - BGUHF Electromagnetic Vector Sensor Students: Roy Nevo, Yiftach Barash Advisors: Mr. Benny Almog Prof. Reuven Shavit 17.5.2011

2. Challenges and Motivation • Electromagnetic direction finding (DF) is of high priority, both for civilian and military needs. • In the High-Frequency (HF) range (3-30MHz) the common passive DF methods require very large aperture (tens of meters). • Thus, HF DF system is bulky to carry and to set-up. • Small aperture antenna array and elements (in terms of wavelength) that perform DF is required.

3. E H S Project Goals Main Goal: • Using the Poynting theorem to produce a small antenna for HF-DF applications Objectives: • Wideband in the HF region • Simultaneous azimuth and elevation finding • RMS error < 2˚ • Production of the antenna • Test environment for the HF range – The TEM Cell θ=80˚ φ=157˚

4. Project Final Result • The sensor basic element and its feeding circuitry were simulated and produced • TEM-cell test environment was also simulated and produced • The antenna was measured inside the TEM-cell and the total RMS error of the azimuth and elevation estimation was < 2˚

5. Theoretical BackgroundThe Poynting Theorem • Propagating EM plane wave in free space: E-field ┴ H-field ┴ Propagation (Poynting vector). • The Poynting Theorem • From the Cartesian elements of the fields, the propagation direction can be extracted

6. Z H E Y X Z E Y H X Theoretical Background Electric and Magnetic Dipoles • Electric dipole on the Z axis • Response related to Ez • Magnetic dipole on the Z axis • Response related to Hz

7. Simulated Elements • Small Electric Dipole • Small Loop – Magnetic Dipole • Combined element – Slotted Dipole With less coupling and thus, possibly, higher SNR

8. Dipoles Simulation • Electric and magnetic dipoles – far field (incident wave response). Electric dipole far field radiation (Eθ) Rectangular loop far field radiation (Eφ)

9. Dipoles Simulation • Slotted Dipole – far field (incident wave response). Electric dipole far field radiation (Eθ) Slot far field radiation (Eφ)

10. Ey [mV/m] Ez [V/m] Ex [mV/m] Test Environment – The TEM cell • The TEM-cell was matched to have 200Ω impedance • The Electric field orientation in the center is well defined

11. z y Z E Ez Sx Y x Hy H X Combined Simulation – DF analysis • Simulation results – 6 dipoles in the TEM CELL

12. Orientation Index • Polarization=0 • Theta=0 • Phi=0 • Polarization=0 • Theta=0 • Phi=30˚ • Polarization=30˚ • Theta=0 • Phi=0 • Polarization=0 • Theta=30˚ • Phi=0 12

13. DF Results and Noise Analysis • The slotted dipole show better DF result in simulation • For good performance, with no signal processing operations, the signal must be larger than the noise in at least 20dB.

14. The TEM-cell • The TEM-cell was produced from wood (EM “transparent”) and two parallel metal net (EM plate) • From S parameters measurements, the TEM-cell is well matched and perform as parallel plate transmission line Output/ Termination Input

15. Testing System Layout • The antenna is placed on special holders with different angels in the TEM-cell. • The TEM-cell is connected to port 1, the antenna to port 2 of the ENA and S21 is measured.

16. Sensor Element Measurement Results • The elements directional response is as expected ! • In most of the HF range, the signal response in the TEM is larger than the noise in more than 30dB

17. Sensor Element Measurement Results • In the HF range the antenna gain is very small – small antenna-large bandwidth limitation • The DF result on arbitrary angle show good performance up to 20MHz (The magnetic dipole upper limitation)

18. Measurements Results and Comparison to Simulation

19. Conclusion and Future Steps • A novel HF DF antenna was developed and produced • The antenna is very small in terms of wavelength and thus highly mobile • The DF RMS error < 2˚ as was initially specified • Continuous measurements and signal processing algorithm (MUSIC) will be applied in order to further reduce the RMS error

20. References [1] C. Balanis, Antenna theory: Wiley New York, 1997. [2] C. Balanis, Modern Antenna Handbook: Wiley New York, 2008. [3] A. Nehorai and E. Paldi, "Vector sensor processing for electromagnetic source localization," in Signals, Systems and computers, 1991. [4] C. E. Smith and R. A. Fouty, “Circular Polarization in F-M Broadcasting,” Electronics, vol. 21 (September 1948): 103– 107. Application of the slotted cylinder for a circularly polarized omnidirectional antenna.

21. Thank You For Your AttentionQuestions ???

22. The slotted dipole • Simulation results – current density Electric dipole ports generator - J [A/m] Slot ports generator - J [mA/m]

23. Project Methodology Production and Measurements Simulation Analysis DF calculation Electric and magnetic dipoles basic simulation Production of the TEM-cell and S-parameters measurements Detailed simulation including feed Production of electric and magnetic dipole Calculation and simulation - TEM-cell Measurement of the electric and magnetic dipole in the TEM-cell Simulation and DF calculation