Circular Transmitting/Receiving Radar Array

Malihe Zarre Dooghabadi

Nanoelectronics group, Department of Informatics June 8th, 2010

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Outline

● introduction● Beamformer array

● Circuit description● Circular array

● Modeling ● MATLAB simulation results

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introduction● Beamformnig:

● Transmitting array: delaying transmitted waves to reach at focal point simultaneously.

● Receiving array: delaying received waves to have constructive interference at the desired direction.

● Beam pattern depends on:

● Array geometry

– 1D structure → 2D image

– 2D structure : rectangular, circular, … → 3D image● Number of elements

– The more element the higher main-lobe peak and more side-lobe● Element weight

– Set the location of nulls at the beam pattern ● Element spacing

–Beam width / λ/D in Narrow-band array and / c.T/D in UWB array

– The larger element spacing the narrower beam (Narrow-band array : element spacing > one

wavelength → grating lobe)

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Pulse Generator

Thr.

DAC

LNA

Sampler

Counter

Sampler

Counter

Read out circuit

Output

τ τ

τ1

τ2

Trigger

Input

Antenna_RX

Antenna_TXCalibration_Circuit

tune τ2 to set the focal point

tune τ1 to set the range

τ set the depth resolutionnumber of τ set the depth of sampling

sweep the Vth

Vth1

x1=range x2=range+deptht2=range/c t2=(range+depth)/c

Beamformer Circuit

Vth2

R=c.τ/2

x

Y

Z

Focal point on (x,y,z)

X

Y

Dr TX1/RX1

TX2/RX2

TX3/RX3

TX4/RX4

TX5/RX5

TX6/RX6

TX7/RX7

TX8/RX8

Circular Transmitting/Receiving Array

∙ A uniform Transmitting/Receiving Circular array with element spacing of D.

∙ Antenna polarization should be considered to have constructive interference.

∙ 8 transmitted signals are delayed to reach on point (x,y,z) simultaneously.

∙ Each receiver with "n" delay element of τ has a sampling frame with length of “n.τ.c/2”.

∙ All receivers are delayed in a way that their frame at their center point crossed each other on focal point.

∙ All data from 8 receivers are processed in the software to construct a 3D image.

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Modeling

● Friis equation :

● Pt / Pr : Transmitted/Received power

● Gt / Gt : Transmitted/Received Antenna gain

● λ : wavelength and, R : distance

● Simulation:● FCC constraint ● transmitted pulse is a multiplication of sinusoidal waveform with

Gaussian pulse● Ominidirectional antenna● 8 elements

● Element spacing of 10 cm → radius is 13 cm

Pr

Pt=Gr⋅Gr

4R2

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MATLAB Simulation Result (1)● Focal point on (0 cm, 0 cm, 50 cm)

● Received power at the depth of 50 cm in XY plane

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MATLAB Simulation Result (2)● Focal point on (0 cm, 0 cm, 50 cm)

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MATLAB Simulation Result (3)● Focusing on center line→radiation pattern and

resolution is the same at X and Y direction

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MATLAB Simulation Result (4)● Focal point on (20 cm, 0 cm, 50 cm)

● Received power at the depth of 50 cm in XY plane

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MATLAB Simulation Result (5)

● Focal point on (20 cm, 0 cm, 50 cm)

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MATLAB Simulation Result (6)● Focusing off center →different radiation pattern and resolution at

X and Y direction