Measuring angular variation of target strength for simple geometric objects
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Measuring Angular Variation of Target Strength for Simple Geometric Objects. CDR Ed Tucholski US Naval Academy Annapolis, MD. Reflected Wave. Object. Transmitter/ Receiver. Original Wave. Distance r. Drawing Source: Wikipedia. Active Sonar Equations.

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Measuring Angular Variation of Target Strength for Simple Geometric Objects

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Measuring angular variation of target strength for simple geometric objects

Measuring Angular Variation of Target Strength for Simple Geometric Objects

CDR Ed Tucholski

US Naval Academy

Annapolis, MD


Active sonar equations

Reflected Wave

Object

Transmitter/

Receiver

Original Wave

Distance r

Drawing Source: Wikipedia

Active Sonar Equations

Function of geometry and scattering direction

Noise Limited Case

Reverberation Limited Case


Target strength

Target Strength

The reflected intensity (pressure) is dependent on the reflection, diffraction, and interference of sound scattered off the object.

Target Strength is highly dependent on the scattering angle.

The teaching point of this demonstration is to show the angular dependence.

For simplicity, we will measure


Apparatus

Filter

Pre-Amp

Target

1.15 cm

0.8 cm

Transducers

and Positioning System

Envelope Detector

Motor

Controller

Signal

Generator

40 kHz

25 kHz

O-scope

O-scope

Apparatus

  • Data Acquisition

    • Serial to USB

    • TekVisa

    • Excel

Transducers


Measuring angular variation of target strength for simple geometric objects

-

+

IN914 Diodes

LM741

Operational Amplifier

Envelope Detector


Square plate

a

Data

Theory

Square Plate


Circular plate

a

Data

Theory

Circular Plate


Cylinder

Data

Theory

Cylinder

L


Cylinder 360 o target strength

Cylinder 360o Target Strength


Target strength is a decibel

Target Strength is a Decibel


Demonstration

Demonstration


Settings

Wavetek Model 29

Sine 40.04 kHz

18.1 V p-p

SR560

Source A, AC Coupled

6 dB/oct band pass, 10k-100k HZ

Low Noise

Gain = 20

Scope 1

Ch 1 10 V/div

Ch 2 50 mV/div

t = 10.0 ms

Scope 2

Ch 2 100 mV/div

t = 4.00 s

VXM-1

72 s/rev

Settings


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