MSD I: WKS 8-10 Preliminary TEST plan Sub …edge.rit.edu/edge/P12311/public/P12311 Detailed Design... · Web viewNext the angle of incidence from the normal, that the wave will impact

KGCOE MSD Technical Review AgendaMeeting Purpose:

1. Overview of Project2. Confirm Engineering Specifications and Customer Needs3. Review Concepts4. Propose a Design Approach and Confirm its Functionality

Materials to be Reviewed:

1. Project Overview2. Antenna3. Control System4. LabVIEW

Meeting Date: November 04, 2011

Meeting Location: 3119

Meeting time: 1:00-2:30pm

Timeline:

Meeting Timeline

Start time Topic of Review Required Attendees

1:00 Project Overview1:15 Bill of Materials, Test Plan1:30 Chamber1:45 Control System2:00 LabVIEW2:15 LabVIEW Demo

1P12311 RF Anechoic Chamber


Senior Design Project Data Sheet

Project Description

Project Background: An Anechoic Chamber is a testing chamber that simulates far field situations for antenna and transceiver arrangements. A receive antenna is placed on a rotating platform while the radiation pattern and gain are measured using a spectrum analyzer to enable testing of future antenna and transceiver devices.

Problem Statement: Design an Anechoic Chamber for Bluetooth frequency which measures the antenna pattern of the receive antenna and transceiver devices. The receive antenna must be able to rotate 180°. Design three different microstrip antennas to test in the chamber. Chamber is to be used by future senior design teams to test their projects.

Objectives/Scope: 1. Build an anechoic chamber 2. Determine anechoic chamber dimensions 3. Design an antenna stand to rotate the receive

antenna up to 360° 4. Design a motor control system to rotate the

platform a given amount 5. Design three antennas with various purposes to

test in the chamber 6. Characterize chamber performance 7. Perform trade-off analysis

Deliverables: Completed Anechoic Chamber for the 2-3GHz

frequency range Three antennas to be used to test chamber Rotating receive antenna platform capable of

rotating 360° Instruction manual featuring step-by-step instruction

on use of chamber Calculations, drawings, sketches Characterize chamber

Expected Project Benefits: Basis for testing future Senior Design

projects Verification of integrity of parts

Core Team Members: Lucas McKeehan Sheldon Palmer Danielle Walters

Strategy & Approach

Assumptions & Constraints: 1. Space: Chamber must be built in the given

space. If it does not meet specs at that size, another place must be allotted for chamber location.

2. Budget: Must examine cost vs. efficiency trade-off. Try to find the cheapest materials to get the project done.

3. Frequency: Chamber must be adequate for the Bluetooth, Zigbe, Wifi, and wireless devices in the given frequency range (2.4GHz)

Issues & Risks: Must learn how chamber functions before

designing one Complete calculations to ensure chamber

size will meet far field requirements Chamber size will not fit available space Scope of project is too large for time given Project goes over budget Chamber must be usable with no RF

background

Project # Project Name Project Track Project Family

P12311 RF Anechoic Chamber Autonomous Systems and Controls Track NA

Start Term Team Guide Project Sponsor Doc. Revision 20111 Professor Slack Dr. Venkataraman 2

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MSD Project Risk Assessment

ID Risk Item Effect Cause

Lik

elih

ood

Seve

rity

Impo

rtan

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Action to Minimize Risk Owner

1 Team runs out of time Project is not completed

Poor Project Planning 2 3 6 Create a Schedule Team

2 Parts Arrive Late Schedule is delayed Unreliable Vendor 1 1 1

Constant Communication with

vendorTeam

3Technology requires a

lot of technical knowledge for upkeep

Teams will not be able to easily use chamber to test their products

Choice of technology 2 1 2 Research easiest

technology usable Team

4 Requirements change during project

Project will not be able to change in

timeRedesign required 1 2 2 Verify deliverables

with customer

Team, Guide,

Customer

5 Teammates do not do assigned work

Team will need to do the work of the

teammate

Laziness/ not enough time/ over

ambitious expectations

3 1 3 Ask for help from team when needed

Team, Guide

6 Teammates do not arrive prepared

Team will be delayed and work will be postponed

Laziness/ not enough time/ over

ambitious expectations

3 1 3

Assign tasks that have a high

likelihood of being completed

Team

7 Miscommunication among teammates

Will lead to confusion and

could hurt project

Poor communication 3 1 3

Make sure to explain every detail/ ask

questionsTeam

8 Inability to contact the customer or guide

May miss vital information and

requirements


Keep constant information flow with the customer and guide, weekly

meetings

Team, Guide,

Customer

9 Customer needs not clear

Lead to solving an issue that doesn’t

exist

Poor communication 2 2 4 Set up meetings and

communicate oftenTeam,

Customer

10 Arguments between teammates

Will hurt team morale and cause conflict between

members


Have group focused and group leader

awareTeam

12 Project scope too large Project not completed on time

Project improperly scoped 3 3 9

Project scope assignment

completed week 1

Team, Guide

13 Parts ordered too late Schedule is delayed

Long lead parts not identified and

ordered on time1 2 2

Long lead parts identified and

orderedTeam

14 Design doesn’t meet needs

Project failure/ customer unhappy

Improper needs flow down to

Engineering Specs2 3 6

Systems Design Review includes

discussion of Needs to Specs flow down

Team

15Design not executed to

Engineering Specs2 3 6

Detailed Design Review includes verification of

Engineering Specs (Calculations)

Team

16 Necessary technology Concept cannot be Inadequate concept 2 3 6 Concept selection Team,


not available for budget allocated built assessment includes technology

availability criterion Guide

17 Project goes over budget

Project will not be completed Poor planning 3 3 9

Cheapest solutions and materials will be

researchedTeam

18 Setup is too difficult Customer will not use it Poor design 3 2 6

Make user interface as easy as possible/ create instruction

manual

Team

19Spectrum Analyzer

does not interface with Labview

Product will not be usable in

systemPoor planning 1 1 1

Spectrum Analyzer compatibility will be

researched before being bought

Team

20 Reflecting signals within chamber

Inaccurate test results

Poor design/ lack of absorbent

material1 1 1

Place more absorbing material at points

with high reflection/ run tests

Team

21 RF leakage from door seal

Inaccurate test results Poor planning 1 1 1

Use smooth metal on metal contacts/ if there is leakage,

document the amount

Team

22 Motor arm shaft reflects signal

Reflected signals cause inaccurate

test resultsPoor design 1 1 1 Cover arm with

absorbing material Team

23Data is not collected in the correct time

frameInaccurate results

Poor communication

between Labview and

Microcontroller

2 1 2Make sure there is

good communication, test for accuracy

Team

24 User error System does not operate correctly

Lack of training/ tool understanding 3 3 9

Write instruction manual with step-by-step instructions for

proper usage

Team

25Chamber does not simulate Far Field

conditions

Customer need not met Poor calculation 2 3 6

Calculations/ tests to ensure far field

conditions hold upTeam

26 Poor precision of motor rotation

Measurements will not be a smooth curve

Poor part choice 2 2 4Research motor

characteristics before buying

Team

27 Size of chamber insufficient

Measurements incorrect Poor design

Calculations proving chamber size requirement

completed before design

Team


Revi

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P12311 RF Anechoic ChamberPreliminary Test Plan

MSD I: WKS 8-10 Preliminary TEST plan Sub-Systems/ Functions/ Features\

Major Sub-Systems/ Features/ Function

1. Chamber

2. Rotation Control

3. Instrumentation Calibration

4. Data Display

5. DUT


Required Tests

Engr. Spec.

#Specification (description) Unit of

Measure

Marginal

ValueComments/Status

S5 Acceptable Frequencies GHz 0.8-3 Sweep Frequency- Look for Level Response

S2 Chamber Dimensions feet 8x8x12 Inspection

S3 Full Wavelength from Tx to Rx lambda 1

S4 Far Field Conditions Test to See if There Are Oscillations in Power

S6, S7

Leakage Into/Out of Chamber dB < -80 Isolation Test

S9 Connection Loss dB/ connection 2 View Part Spec Sheet

S10 Absorption of Material dB/ reflection > 15 Waived Until Enough Foam is in

ChamberS11 DUT Rotation Increment degrees 0.1 Encoder/ Micro ControllerS12 DUT Rotation Amount degrees 180 Encoder/ Observation

S13 Designed Antenna- Reduced Size mm < 15 Simulation Software to Verify

S26 Designed Antenna- Wideband GHz 0.8-3 Frequency Sweep to Transmit in Entire

Range

S14 Designed Antenna- High Gain dB 15 Measure Gain

S17 Calibration dB - Compare Measured Gain to Spec Sheet Gain

Test Equipment

Frequency Generator (0-6GHz)

Spectrum Analyzer

SMA Connector Test Cables

Network Analyzer

Dipole Antenna

PC with LabVIEW

Power Meter



Anechoic Chamber Quiet Zone Calculation(Rectangular Chamber)

The Quiet zone of an anechoic chamber describes a rectangular volume where electromagnetic waves reflected from the walls, floor and ceiling are stated to be below a certain specified minimum. There are two main methods to calculate the quiet zone for a given chamber geometry. The first is a detailed mathematical model, accounting for a volume of reflections converging in the quiet zone, with a power gradient across them for how far inside and outside the HPBW of the antenna the reflection is, and how many times it reflects. The second method is to take the largest factor in this calculation, and estimate based off of it. For the case of a rectangular chamber, the largest factor in the detailed calculation is the wave that only reflects once to reach the receiving antenna. There will be four such waves, two from the sides, one from the ceiling, and one from the floor.

To calculate the quiet zone, first the chamber size must be decided. With the chamber size selected, the size of the absorber cones must be decided. To get a rough estimate of what to select a table for the specific material used must be consulted. If a specific quiet zone is expected, but it requires large cones, the large cones can be placed in key areas (such as the walls where the bounce will take place, and the rear wall behind the DUT). Table 1 was used for the case of the 8x8x12 chamber that will serve as an example for the duration of this paper. For the example chamber the SFC-12 cones will be used. The number denotes the height of the cones. The example chamber will be used at 2-3 GHz, and the reflectivity for this frequency is -40 dB.

Next the angle of incidence from the normal, that the wave will impact the wall must be determined. For a rectangular chamber this is a simple calculation. First the distance between the Tx and Rx antenna must be determined. This is done by determining how far from the ends each antenna will be. For the Tx 10” is selected since this is the length of the example antenna that will be used. For the Rx, 16” is selected, since the cones at the back wall are 12” and the platform requires 4” space to rotate a microstrip DUT. This leaves 9’10” between Tx and Rx:

12’-1’4”-10”=9’10” (1) Once this distance is determined, the height off the chamber floor of the antennas must be

determined. For the example chamber, half way up was selected (4’). Once these two distances are determined, a rectangle can be drawn, for the example chamber this rectangle is 4’x9’10”. The rectangle is then divided by two lines that meet in the middle of the rectangle at the top. These represent the wave reflecting off the chamber wall then hitting the receiving antenna. The angle that is needed is the angle this wave reflection makes with the normal of the chamber wall. It is found by taking the arctangent of the height of the rectangle divided by ½ the length of the rectangle. The result is then subtracted from 90°. For the example chamber the calculation was:

90 °−tan−1 4 '4 ' 10 } =50.9 °¿

¿ (2)

With the angle of incidence calculated, Table 2 can be used to look up the multiplier used to calculate the off incidence reflectivity of the material. For the example chamber 12” cones are 3 wavelengths tall, so the 2 wavelength coefficient .82 and the 4 wavelength coefficient .95 are averaged together for a coefficient of .885. This coefficient is then multiplied with the normal incidence reflectivity of the absorber selected. For the example chamber this works out to:

-40 dB * .885 = -35.4 dB (3)(3) is the adjusted reflectivity.

Next, the transmitting antenna’s radiation pattern is analyzed. 90° minus the angle of incidence calculated previously is the angle from the normal of the Tx antenna that the wave leaves from. Looking at the radiation pattern from the Tx antenna, the angle from Tx’ing normal is located, then the power at


that angle is read out. This power is subtracted from the maximum power of the antenna. This value (in dB) is the how much less powerful the wave is when it reflects off the wall. This number (positive) is subtracted into the adjusted reflectivity (negative) to quantify the effect of a less powerful wave interfering at the Rx DUT. For the example chamber and Tx antenna, the power difference at the angle from transmitting normal was found to be __ dB so the new adjusted reflectivity is:

-35.4 dB - __ dB=_dB (4)The last value needed to calculate the quiet zone is a random phase correction. The waves

reflecting off the chamber walls will be converging at the Rx DUT with random phases. This will cause some random cancellation of the main transmitted beam in the quiet zone. Therefore an industry standard value of -6 dB is subtracted from the adjusted reflectivity (negative) thus decreasing the magnitude of the reflectivity. In the example chamber this works out to be:

__ dB – (-6 dB) = __ dB. (5)This is the quiet zone reflectivity for the chamber being analyzed.


Chamber Size

Absorber Height

Distance Tx-Rx

Angle of Incidence

Angle from Tx Normal

Absorber Reflectivity

Absorber Coefficient at incidence

Effective Reflectivity

Quiet Zone

4x4x8 flat 6'8" 59° 31° -15 .31 -4.65 4x4x8 8” 6'2” 57º 33º -35 .7 -24.5 4x4x8 12” 5'10” 55.6° 34.4º -40 .8 -32 6x6x12 8” 10'2” 59.5º 30.5º -35 .66 -23.1 6x6x12 12” 9'10” 58.6º 31.4º -40 .705 -28.2 8x8x12 12” 9’10” 50.9º 39.1º -40 .885 -35.4 8x8x12 24” 8'10” 47.8 42.2° -50 .999 -50

Table 3: Sample calculations for various chamber sizes (no Tx antenna selected so calculations could not be completed.)

Required Absorber


Antenna Selection


Antenna Type Model # Feed GainHorizonal

AngleVertical Angle

F M dB Degrees Degrees in cm in cm in cmf1 f2

1 Standard Gain Horn 3160-03 - 1.7 2.6 16.3 27 27 25.25 64.1 13.6 35 25.3 64.12 Octave Horn 3161-02 - 2 4 17.5 22 22 9.12 23.2 13.6 35 23.4 59.33 Parabolic Grid HG2415G 36.99 52.99 Feedhorn 2.4 2.5 15 16 21 15.7 40 11.8 30 10.4 26.34 Parabolic Grid HG2419G 47.99 59.99 Feedhorn 2.4 2.5 19 12 16 23.6 60 15.7 40 10.4 26.35 Backfire Dish HG2414G 35.99 - - 2.4 2.5 14 25 25 (10.25) (26) - -6 Parabolic Grid HG915G 73.99 84.99 - 0.87 0.96 15 30 19 23.5 60 39.3 1007 Circular Parabolic Grid HG918G 327.99 - - 0.89 0.96 18 16.5 16.5 (47.2) (120) - -8 Parabolic Grid HG8915EG 69.99 - - 0.824 0.96 15 18 30 23.62 60 35.43 90

5510.00

Freq Range

GHz

Price Height (Diameter)

Width Depth

3745.00

Effective Aperture

Website

m m feet m feetf1 f2

0.72901 0.17647 0.11538 6.02316 19.7608 9.2119 30.2224 http://www.ets-lindgren.com/page/specs.cfm?i=31600.416497 0.15 0.075 2.31293 7.58826 4.62586 15.1765 http://www.ets-lindgren.com/page/specs.cfm?i=31610.31218 0.125 0.12 1.5593 5.11576 1.62427 5.32891 http://www.l-com.com/item.aspx?id=216940.63906 0.125 0.12 6.53436 21.4379 6.80663 22.3312 http://www.l-com.com/item.aspx?id=21706

0.143 0.125 0.12 0.32718 1.07343 0.34082 1.11815 http://www.l-com.com/item.aspx?id=205930.641405 0.34483 0.3125 2.38612 9.54449 2.63296 8.63822 http://www.l-com.com/item.aspx?id=22371

0.66 0.33708 0.3125 2.58456 8.47942 2.78784 9.14635 http://www.l-com.com/item.aspx?id=324510.594916 0.36408 0.3125 1.94423 6.37862 2.26512 7.43141 http://www.l-com.com/item.aspx?id=33983

3.2808meter to feet conversion

m

Far Field Distance

f1 f2

FF=2*D^2/λλ=c/f

λ

Far-Field / Angular Bounce Calculation

The far-field region is the region where the measurements for the chamber will be taken. To be in

the far-field, the distance between the receive antenna and the transmit antenna must be greater than 2D2

λ, where D is the largest length of the antenna. For a horn antenna, D is the diagonal length of the front face. This length is found using Pythagorean’s Theorem with the given height and width of the antenna face. For a parabolic grid antenna, the effective area is found to be 0.55 times the actual area. Using this fact, the smaller length side is multiplied by 0.55, and Pythagorean’s Theorem is again applied. For a circular dish antenna, the diameter is the length needed and this is scaled as well by 0.55. To find the wavelength, the largest frequency in the given range is taken to make λ as small as possible to achieve the largest far-field possible. This gives you the maximum far-field difference for this antenna at the given

frequency range. Lambda is found by λ=cf . The far-field distance is found in meters then converted to

feet using the 3.2808ft : 1m conversion factor. For a chamber to give accurate measurements, the distance between the face of the antennas must be greater than the far-field distance.

The regions where the signal will bounce within the chamber are then calculated. On the transmit side, the depth of the antenna is taken out of the total length. On the receive side, the length of the absorber is taken out of the total length. This leaves you with the distance between the two antennas. The Half Power Beam Width angle is divided in half for simplicity. Using the tangent definition, the third side of the triangle is found using the angle and total length as the other side. The resulting length is the distance from the center of the box that the antenna signal will hit the back wall. This will allow you to determine if the Quiet Zone will be upheld with the given antenna. This also allows you to see how many times, if any, the signal will be bouncing inside the box. If it is calculated that there is a bounce in a certain area, more absorber will be added there to try to minimize reflections.


Selected Antenna Data Sheet



Control System Overview


Motor Arm Design


Motor Control Overview


Microcontroller Pseudo Code Initialize

o Configure ports p3,4,6o Enable interrupts on labview portso Rotate home and rotate measurement set to read onlyo Reply port set to write onlyo Configure timer Ao Calculate and save time to make a single tick

Maino Wait for interrupt

Rotate to home interrupto Disable interruptso Retrieve current locationo Calculate time needed to rotate home-ROTATEo Configure timer A for required acceleration profileo Run timer A to rotate armo Save new arm locationo Clear flagso Enable interruptso Return to main

Rotate for measurement interrupto Disable interruptso LabView reply port = 0vo Retrieve current locationo Configure timer A using saved data from initializeo Run timer A to rotate one ticko Save new arm locationo LabView reply port = 5vo Clear flagso Enable interruptso Return to main


Motor Selection

Stepper in Current Chamber Geared Stepper DC Motor<0.1 degree/ increment no yes yes

can be controlled by microcontroller yes yes yes

Does not Require rotational motion calculations yes yes no

able to handle axial loading no yes no

high precision/repeatability of increments yes yes yes

skill set required in regular EE course path yes yes yesopen system yes yes no

Inexpensive (<100$) yes no yes

Totalsyes 6 7 5no 2 1 3

ManufacturerRIT Preferred

Vendor's List?

Frame Size

Rotation Angle Rated Torque Weight Height Cost

LSG35012E88P Hurst no 35 mm 0.06º 963.9 mN*m 243.8 g 43 mm $74.39-$90.80*

17YPG001S-LW4 Anaheim Automation no 43mm **981.5 mN*m-8826.5mN*m

340.2 g-1440.7 g

56.9 mm- 82.8 mm based on gearbox

* Vendor's website wound not work for the desired motor, these are prices for a motor with a too small step angle and a motor with a two large step angle

** vendor does not display base angle of stepper motor to be reduced, therefore final gearbox can not be selected yet


Motor #1 Spec Sheet








Motor #2 Spec Sheet



LabVIEW Overview


LabVIEW Measurement Program



LabVIEW Calibration Program



LabVIEW Functional Blocks





Documents

MSD I: WKS 8-10 Preliminary TEST plan Sub …edge.rit.edu/edge/P12311/public/P12311 Detailed Design... · Web viewNext the angle of incidence from the normal, that the wave will impact