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

What Will We See? Introduction

Signal model

Various beamformers

Comparison

Comparison in presence of look direction errors

Introduction Output

If

and

then

IntroductionOutput power:

So

if x(t): stationary & zero-mean

Then where

Introduction Output components

If

Then

Output components power

then

SNR

Or where

Signal Model Delay due to origin:

Delay in linear array:

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

Steering Vector Representation steering vector associated with the kth source:

Signal vector:

Output:

array correlation matrix when directional sources are uncorrelated:

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:

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:

Conventional Beamformer

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

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

Optimization Using Reference Signal

Minimize mean squared error between the array output and the reference signal ξ(w).

For minimizing

So where

Beam Space Processor Main beam:

Interference beam:

and

Output:

Output power:

Beam Space Processor No signal in interference beamSo

Signal power independent of w.

Maximizing SNR with minimizing output power:

Postbeamformer Interference Canceler (PIC)

Signal beamformer:and

Interference beamformer:

Output:

Output power:

PIC With Conventional Interference Beamformer

Interference beamformer weights:

So:

PIC With Orthogonal Interference Beamformer

Interference beamformer weights:

where

So

No signal suppressing.

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

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, ,

Comparison Uncorrelated noise power: in PIC using OIB Pn> in PIC using IIB depend on

if then Pn>else Pn< for ,Pn=

Comparison ESP With PIC In The Presence Of Look Direction Error