دانشگاه صنعتي اصفهان دانشكده برق و كامپيوتر

1. دانشگاه صنعتي اصفهان دانشكده برق و كامپيوتر Various Beamformer Structures Suitable For Smart Antennas ارائه کننده: آرش میرزایی (8523754) ارائه مقاله تحقيقي در درس “ SDR ” مدرس: دکتر جواد امیدی نيمسال بهار 1386-1385

2. What Will We See? • Introduction • Signal model • Various beamformers • Comparison • Comparison in presence of look direction errors

3. Introduction • Output If and then

4. Introduction Output power: So if x(t): stationary & zero-mean Then where

5. Output components If Then Output components power then SNR Or where Introduction

6. Signal Model • Delay due to origin: • Delay in linear array:

7. Signal Model • The signal induced on the reference element due to the kth source: • the signal induced on the lth element due to the kth source: • the total signal induced due to all M directional sources and background noise on the lth element: • so

8. Steering Vector Representation • steering vector associated with the kth source: • Signal vector: • Output: • array correlation matrix when directional sources are uncorrelated:

9. Conventional Beamformer • also known as the delay-and-sum beamformer • S0 denoting the steering vector in the look direction, the array weights are given by: • Source in look direction: • Random noise environment:

10. Conventional Beamformer • Directional interference: where • ρ depends on the array geometry and the direction of the interference relative to the look direction. • So if no interference then:

11. Conventional Beamformer

12. Null Steering Beamformer • Is used to cancel a plane wave arriving from a known direction. • S0 : the steering vector in the direction. • S1, …, Sk : k steering vectors associated with k directions. • So • Using matrix notation, this becomes where and • for k=L-1 else

13. Optimal Beamformer • No require acknowledge of directions and power levels of interference. • Maximize the output SNR. • The weights are the solution of: • The weights are: • When no directional interference, then optimal : conventional and • If one directional interference and then output SNR

14. Optimization Using Reference Signal • Minimize mean squared error between the array output and the reference signal ξ(w). • For minimizing • So where

15. Beam Space Processor • Main beam: • Interference beam: and • Output: • Output power:

16. Beam Space Processor • No signal in interference beam So • Signal power independent of w. • Maximizing SNR with minimizing output power:

17. Postbeamformer Interference Canceler (PIC) • Signal beamformer: and • Interference beamformer: • Output: • Output power:

18. PIC With Conventional Interference Beamformer • Interference beamformer weights: • So:

19. PIC With Orthogonal Interference Beamformer • Interference beamformer weights: • where • So • No signal suppressing.

20. PIC With Improved Interference Beamformer • Full suppression of the interference. • So • And • Signal power and noise power at the output are independent of interference power. Output signal power • When & when , depend on

21. Comparison • Comparison of Normalized Signal Power, Interference Power, Uncorrelated Noise Power and SNR at the Output of the Optimal PIC Forming Interference Beam with CIB, OIB and IIB, ,

22. Comparison • Uncorrelated noise power: • in PIC using OIB Pn> • in PIC using IIB depend on if then Pn> else Pn< for ,Pn=

23. Comparison ESP With PIC In The Presence Of Look Direction Error

24. THANK YOU. ANY QUESTION?