دانشگاه صنعتي اصفهان دانشكده برق و كامپيوتر
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Transcript of دانشگاه صنعتي اصفهان دانشكده برق و كامپيوتر
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اصفهان صنعتي دانشگاهكامپيوتر و برق دانشكده
Various Beamformer Structures Suitable For
Smart Antennas
: کننده ارائه( 8523754آرشمیرزایی )
درس در تحقيقي مقاله ارائه “ SDR”
امیدی: جواد دکتر مدرسبهار 1385-1386نيمسال
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What Will We See? Introduction
Signal model
Various beamformers
Comparison
Comparison in presence of look direction errors
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Introduction Output
If
and
then
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IntroductionOutput power:
So
if x(t): stationary & zero-mean
Then where
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Introduction Output components
If
Then
Output components power
then
SNR
Or where
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Signal Model Delay due to origin:
Delay in linear array:
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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
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Steering Vector Representation steering vector associated with the kth source:
Signal vector:
Output:
array correlation matrix when directional sources are uncorrelated:
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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:
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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:
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Conventional Beamformer
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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
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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
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Optimization Using Reference Signal
Minimize mean squared error between the array output and the reference signal ξ(w).
For minimizing
So where
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Beam Space Processor Main beam:
Interference beam:
and
Output:
Output power:
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Beam Space Processor No signal in interference beamSo
Signal power independent of w.
Maximizing SNR with minimizing output power:
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Postbeamformer Interference Canceler (PIC)
Signal beamformer:and
Interference beamformer:
Output:
Output power:
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PIC With Conventional Interference Beamformer
Interference beamformer weights:
So:
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PIC With Orthogonal Interference Beamformer
Interference beamformer weights:
where
So
No signal suppressing.
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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
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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, ,
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Comparison Uncorrelated noise power: in PIC using OIB Pn> in PIC using IIB depend on
if then Pn>else Pn< for ,Pn=
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Comparison ESP With PIC In The Presence Of Look Direction Error
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