1. EFFECTS OF MUTUAL COUPLING AND DIRECTIVITY ON DOA ESTIMATION USING MUSIC LOPAMUDRA KUNDU & ZHE ZHANG

2. Outline of the Presentation  What is DOA?  MUSIC  Parameter study:  Signal-to-noise ratio (SNR)  Inter-element spacing  Mutual coupling  Directivity  Why DOA?  Applications  Scopes of future work

3. Direction of Arrival (DOA) Estimation  Estimation of direction finding signals in the form of electromagnetic/acoustic waves impinging on a sensor or antenna array.  High resolution DOA can resolve closely spaced frequencies.  Most popular technique is “Subspace method”  Used for locating and tracking signal sources in both military and civilian communications.

4. 4 Multiple Signal Classification (MUSIC)  Steering vectors:  Data model of M signals incident on an array of N elements: Where, k=1,…,K (number of snapshots)  Correlation matrix of x: A: signal correlation matrix σ 2 : noise variance 1 2 N Antenna array d M signals ΦnΦn

5. MUSIC (contd.)  Eigen value decomposition of R  Since (signal subspace) ⊥ (noise subspace), DOAs are the peak locations of MUSIC power spectrum signal subspace noise subspace M N-MM v vHvH

6. Parameters Affecting the Performance of MUSIC  Signal-to-Noise Ratio (SNR)  Inter-element Spacing  Mutual Coupling  Antenna Directivity

7. Normalized Power Spectrum For Different SNR Levels (AWGN)  Simulation Parameters:  Array size=5 (ULA)  Element Spacing=  Number of Signals=2  AOA= 20 ⁰ and 80 ⁰  Number of Snapshots=3  Conclusion:  Broad peaks for SNR<15 dB.  Sharp peaks at SNR ≥ 15 dB and both the signal directions are estimated correctly.

8. Normalized Power Spectrum For Various Inter-Element Spacing (No Coupling)  Simulation Parameters:  Array size=5 (ULA)  SNR level=30 dB (AWGN)  Number of Signals=2  AOA=20 ⁰ and 80 ⁰  Number of Snapshots=3  Conclusion:  Broad peaks for d<0.5.  Sharp peaks at d ≥0.5 and both the signal directions are estimated correctly.

9. Normalized Power Spectrum in the Presence of Mutual Coupling  Simulation Parameters:  Array size=5 (ULA)  SNR level=50 dB  Number of Signals=3 (LP)  AOA=20 ⁰, 50 ⁰ and 80 ⁰  Number of Snapshots=10  Conclusion:  Broad peaks for d<0.5.  Sharp peaks at d ≥ 0.5 and all the three signal directions are estimated correctly.

10. Comparison Between NEC Simulation and MALTLAB Simulation  Simulation Parameters:  Array size=5 (ULA)  SNR level=50 dB  Number of Signals=3 (LP)  AOA=20 ⁰, 50 ⁰ and 80 ⁰  Number of Snapshots=10  Conclusion:  The algorithm works better for no coupling scenario.  Mutual coupling degrades the direction estimation efficiency considerably for same spacing.

11. Directivity of Antenna  DOA estimation is related not only with the mutual coupling, but also with the directivity of the antennas.  Isotropic antenna: radiates uniformly in all directions.  Directional antenna: radiates more efficiently in some directions than others. Steering vector would be modified by the gain of directional antenna  Goal is to compare the performance of isotropic antenna arrays and directional antenna arrays in DOA estimation.

12. Structure of Antenna arrays in NEC Isotropic Directional

13. Simulation Result for Isotropic Array  Analysis:  Incident signals at 3 angles : 20 ⁰, 50 ⁰ and 80 ⁰  All 3 signals are detected accurately.  Isotropic array could detect all the incident signals simultaneously.

14. Simulation Result for Directional Array  Analysis:  Incident signals at 3 angles: 20 ⁰, 50 ⁰ and 90 ⁰.  Only incoming signal at 90 ⁰ is detected.  Directional array could only detect the signals that fall within the range of its main beam position.  The gain of directional antenna may make the result more accurate.

15. Why DOA: Applications DOA ESTIMATION radar Sonar Seismic Exploration Electronic Surveillance Wireless Communication

16. Applications Involving Coupling and Directivity  Applications involving mutual coupling: MIMO system with closely spaced antennas.  Applications involving directivity: Indoor environment with intensive multipath effect and interferences.

17. Scopes of Future Work  Other types of arrays and antennas.  Effects of other parameters like polarization, antenna gain, delay and ground effects.

18. THANK YOU!