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

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. 2

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˚ E H S 3

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˚ Simulation - Total Error RMS 1.43 Measurements - Total Error RMS

Theoretical Background The 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 5

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

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

Dipoles Simulation Electric and magnetic dipoles – far field (incident wave response). Electric dipole far field radiation (E θ ) Rectangular loop far field radiation (E φ ) 8

Dipoles Simulation Slotted Dipole – far field (incident wave response). Electric dipole far field radiation (E θ ) Slot far field radiation (E φ ) 9

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

Combined Simulation – DF analysis Simulation results – 6 dipoles in the TEM CELL  7.12E-06 |Ex|  5.02E-09 |Ey|  4.63E-04 |Ez|  2.35E-06 |Hx|  5.19E-02 |Hy|  1.03E-07 |Hz| 2.39E-05|Sx| 1.09E-09|Sy| 1.45E-07|Sz| Sx Hy Ez AngleExpected Simulation result Phi Theta00.34 X E H Y Z 11 z x y

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

DF Results and Noise Analysis Error in RMSPhiThetaAbs Dipole and Loop Slotted Dipole 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. 13

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 Input Output/ Termination 14

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 S 21 is measured. 15

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 16

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) 17

Measurements Results and Comparison to Simulation Error – RMSError - θError - φθφγβα Total Error-RMS 1.43Simulation -Total Error-RMS 18

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 19

References [1]C. Balanis, Antenna theory: Wiley New York, [2] C. Balanis, Modern Antenna Handbook: Wiley New York, [3]A. Nehorai and E. Paldi, "Vector sensor processing for electromagnetic source localization," in Signals, Systems and computers, [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. 20

Thank You For Your Attention Questions ??? 21

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

Project Methodology Simulation Production and Measurements Analysis Electric and magnetic dipoles basic simulation in different realizations Detailed simulation of selected realization including feed Calculation and simulation of the TEM- cell for match evaluation Simulation of the dipoles in the cell and DF calculations Production of the TEM- cell and S-parameters measurements for match evaluation Production of one element of the antenna – electric and magnetic dipole Measurement of the electric and magnetic dipole response in the TEM-cell in different orientation DF calculation and comparison with the simulation results 23

Project Methodology Simulation Production and Measurements Analysis Electric and magnetic dipoles basic simulation Detailed simulation including feed Calculation and simulation - TEM-cell Simulation and DF calculation Production of the TEM- cell and S-parameters measurements Production of electric and magnetic dipole Measurement of the electric and magnetic dipole in the TEM-cell DF calculation 24