Automated Wideband Antenna Testing System for Outdoor Use
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Automated Wideband Antenna Testing System for Outdoor Use. Company Sponsor: MegaWave Corporation Company Contact: Deliang Wu Faculty Advisor: Rajeev Bansal Group Members: Emanuel Merulla (EE) Christopher Mouta (Comp Eng.) Peter Lofaro (EE). Background Introduction Problem Statement

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Automated Wideband Antenna Testing System for Outdoor Use

Company Sponsor: MegaWave Corporation

Company Contact: Deliang Wu

Faculty Advisor: Rajeev Bansal

Group Members:

Emanuel Merulla (EE)

Christopher Mouta (Comp Eng.)

Peter Lofaro (EE)


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Background

Introduction

Problem Statement

Project Specifications

Proposed Solution

Components Comparisons

Final Decision of Components

Software Design

Antenna Design

Budget

Timeline

Questions

Overview


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Company Background

MegaWave Corporation

  • Located in Boylston, MA.

  • Founded in 1994.

  • Develops antennas for radio and television communications technologies.

  • Customer base includes DARPA, U.S. Army, NASA, DOT, U.S. Navy, SOCOM.

  • Research areas include development of genetically optimized antennas, direction finding antennas, and detection of portable electronic devices on-board aircraft.


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Project Introduction

Antenna Background:

  • At MegaWave, in order to test how well an antenna can transmit and receive, they measure antenna radiation patterns.

  • Antenna radiation is a graphical depiction of the field strength that is transmitted or received by the antenna.

    • Radiation strength is measured as gain in units of dB (decibels).

  • Antenna gain is the ratio of the intensity of an antenna's radiation pattern to the intensity of radiation of a reference antenna.

  • Common types of antennas include: monopole, dipole, Yagi, microstrip, loop, and phased array antennas.



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Directional Antenna Radiation

Azimuth Radiation pattern


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Problem Statement

  • Currently, antenna under test must be rotated manually to desired position.

  • Measurements are taken manually from network analyzer.

    • The network analyzer will be explained later in the presentation.

  • This process must be repeated for all data points.

  • More points = More work = More time


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Project Specifications

  • Environmental and Physical:

    • Testing system will be used outdoors (MegaWave parking lot).

    • System will only be used in fair weather conditions (no rain/snow).

    • Entire system should fit through front door (98” x 29”) using a cart system.

    • System should be able to be moved by one person.

    • Rotator should be able to rotate 200+ pounds. 


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Project Specifications cont.

Wide Band Antennas

  • The antennas must have a VSWR of less than 3:1

    • VSWR-voltage standing wave ratio. This tells you how much power will be reflected at the input of the antenna

  • The gain of the antennas are TBD.

    • Antennas with directional patterns are preferred above 500MHz

  • These Antennas must be tested thoroughly to obtain the gain within the frequency band


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Proposed Solution

  • Create centralized PC interface for antenna testing.

  • PC controlled antenna rotator

  • Automated network analyzer setup

  • Automated data retrieval from said analyzer

  • Design and build 2 different Antennas for use in project

    • (30MHz-200MHz)

    • (1.3GHz-3GHz)

  • Buy off-the-shelf rotator and controller



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Network Analyzer

Network Analyzers measure complex impedances, VSWR, losses or gains in devices. It measures the gain of an antenna by radiating from a source antenna from port 2 and measures the gain from the antenna under test from port 1.


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Antenna Rotators

  • For this project we require an off the shelf rotator that could handle a 200lb load.

  • These are two of the rotators that we researched:

Lintech 300 Series Rotator

Prosistel PST-641D


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Antenna Rotator Comparisons

Lintech Rotator

Positive

  • All purpose rotator

  • Has built-in indexing table

  • High gear ratio

  • Low torque requirements

  • Compatible with any standard stepper motor

    Negative

  • More expensive

  • Requires stepper motor for motion

Prosistel Rotator

Positive

  • Inexpensive

  • Comes with motor

  • Designed specifically for antennas

    Negative

  • Limited software compatibility

    (not compatible with VB or Labview)

  • Only couples with limited types of antennas

  • Requires fabrication of table and stand

  • Company is located overseas


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Motion Control System

Motion Group

SID 2.0

NI PCI-7342

Applied Motion Si3540


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Motion Control Comparison

  • NI PCI-7342

  • Positive

  • Can be configured as either stepper or dc motor controller

  • Interfaces with Labview

  • Product and software support from same company

  • Negative

  • Incompatible with Visual basic

  • More expensive

  • Not compatible with laptops

  • 2 axes (only need 1)

  • NI does not sell steppers

Applied Motion Si3540

Positive

  • Includes motion controller and stepper motor driver.

  • Compatible with any standard stepper motor

  • Includes power supplies and RS-232 serial interface

  • Simple software included

    Negative

  • Incompatible with Labview and Visual Basic

  • Very expensive

Motion Group SID 2.0

Positive

  • Integrated package

  • Includes intelligent motion controller, stepper motor and translator/driver

  • Includes power supplies and RS-232 serial interface

  • Inexpensive

  • Easily interfaces with Visual Basic

    Negative

  • Incompatible with Labview


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Software

  • We need software that controls both the network analyzer and the motion controller system.

  • Our software choices for the whole project were narrowed down to either Visual basic or Labview due to the GPIB standard connection compatibilities.


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Software Comparison

Labview

Positive

  • Program can be run standalone with Labview runtime engine(free)

  • Supported by other OS’s

  • GPIB driver set includes Labview specific libraries

  • Widely used in industry

    Negative

  • Development environment is expensive($1195)

  • No previous knowledge of language

  • Not supported by many motion controllers

  • Code not revisable without expensive development environment

Visual Basic

Positive

  • Simple interface design

  • Inexpensive($100)

  • GPIB driver set include VB specific libraries

  • Previous knowledge of language

  • MegaWave preferred

    Negative

  • Not supported by many motion controllers

  • Not easily portable between OS’s


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Visual Basic Design Process

  • Network analyzer flow chart for testing

  • HP8753A HP-IB reference guide

  • NI488.2 software package with VB libraries

  • GPIB command testing through NI Measurement and Automation software

  • 488.2 VB command implementation into first sample test program


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Wireless Transceivers

  • Wireless transceivers were provided by MegaWave.

    • Digital Wireless Hopnet 1500 transceivers

    • Operate at 2.4GHz

    • Will be tested to ensure no interference with gain test

    • RS232 connection


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Wireless Transceivers Testing

  • Transceivers use CSMA for transmission

  • Transceivers will communicate for our required range (30 feet)

  • Data was successfully transmitted and received from each unit at a baud rate of 115 kbps

  • CSMA protocol transmits data by sending random pulses throughout the 2.40 – 2.48 GHz range

    • Pulses occur less frequently when both transceivers are idle

    • Measurements will be taken when transceivers are idle

    • We believe that these random pulses will be averaged out by the network analyzer when it obtains measurements

  • Further testing will be done with a wired connection in place of the wireless transceivers

    • Results from wired and wireless measurements will be compared


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RS232

Antenna Testing System Diagram

Source Antenna

Antenna Under Test

~ 30 feet

Network Analyzer

Wireless Transceiver

RS232

Port 1

Port 2

Stepper Motor

Rotator Table

Stepper Motor Controller

Wireless Transceiver

GPIB





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