antennas: the key to your wireless application harald naumann round solutions

www.roundsolutions.com 2 / Harald Naumann / 07.04.2009© Round Solutions GmbH & Co. KG

Dipole or monopole?Dipole or monopole?

Monopole with "mirror" on ground plane

Dipole shows that antenna has two rods

To transmitter(GSM module)

half wave length


Benefits of embedded monopolesBenefits of embedded monopoles

Small size

Size interferred by of half wave length only

Assembling direct on PCB

Cost savings by automatic pick and place

Cost savings, because no costs for coaxial cables needed by using of micro strip lines

Higher reliability by bypassing coaxial connectors

Q: When to select a monopole? A: If small size is needed, integration inside the enclosure

or just for cost reduction.


Drawbacks of embedded monopolesDrawbacks of embedded monopoles

Reasonable ground plane of 3500 to 4500 mm in square needed

Components in the near will interfere and detune the antenna

Even Epsilon R of plastic enclosure will have an impact on centre frequency

Antenna could interfere with micro controller, power supply or any other component on PCB

Q: How to minimize the risk on embedded monopoles? A: Select a partner that will help with modules, antennas,

references and GSM testers for final design check.


Practical use of interferencePractical use of interference

A good example for radio waves and interference is the musical instrument Theremin.

The Theremin creates sound by changing the position of your hands in the electromagnetic field

In same style components in the near will interfere and detune your antenna

Q: How to tune the embedded monopole antenna? A: There are several options. Please take care and follow the

guideline on free space, distance to ground and place formatching circuit. Please show steps in between to yourantenna partner and ask for their advice.


Examples for embedded monopoles Examples for embedded monopoles

Q: Which antenna to select? A: This depends on cellular bands to by covered and ground

plane you can offer.

Tri band GSM

Dimensionsin mm:20.5 x 7 x 3.2

Antenna GXE477

Quad band GSM + UMTS 2100

Dimensionin mm:24 x 4.4 x 5.6

Antenna GXE472

Tri band GSM

Dimensionsin mm:30 x 6 x 5

Antenna GXE475


Voltage Standing Wave Ratio VSWR Voltage Standing Wave Ratio VSWR

Practical not possible

Nothing will be reflected

VSWR =1

Already not that nice

A lot of energy is not feed to the antenna

VSWR = 3

Q: Why VSWR is important? A: Any energy that is not feed to antenna never has a chance

to be radiated.

Reasonable practical value

Part of wavewill be reflected

VSWR = 2


Antenna EfficiencyAntenna Efficiency

The efficiency of an antenna relates the power delivered to it and the power radiated or dissipated within the antenna.

A high efficiency antenna has most of the power present at the antenna's input radiated away.

A low efficiency antenna has most of the power absorbed as losses within the antenna.

Q: Why and when antennaefficiency is important?

A: If efficiency is low, thenpower consumption ishigher. The stand by timeof your product will be

less.

You will spend more money

for bigger batteries.

The products of competition

with better antennas will work at locations, whereyour product has already

topass.

input

radiated


Impact of a reduced ground plane Impact of a reduced ground plane

DUT antenna ANT-GXE477

Lenght of ground plane

Good VSWR on GSM 900 and GSM 1800 MHz band

Optimised ground plane


Impact of 15 cm smaller ground plane Impact of 15 cm smaller ground plane


Lenght of ground plane cut by 15 cm

Centre frequency on GSM 900 and GSM 1800 MHz band still ok

VSWR on GSM 900 is already less

VSWR on GSM 1800 has not changed


Q: Why is there no change on GSM 1800?

A: Because wave length is only the half.


Impact of 30 cm smaller ground plane Impact of 30 cm smaller ground plane


Lenght of ground plane cut by 30 cm

Centre frequency on GSM 900 and GSM 1800 MHz band still ok

VSWR on GSM 900 is already poor

VSWR on GSM 1800 is still close the same


Q: Do you know options on optimization?

A: Yes, often we can help with hints and tipps.


Ground plane in praxisGround plane in praxis

Q: Why does my GSM antenna radiates, but my GPS antennadoes not work?

A: Why didn’t your supplier sell you a starter kit;why didn’t they recommend to take care on ground

plane?

Please do not follow the upper example Please do not follow the upper example


Do's and Dont's during development Do's and Dont's during development

Never place ground plane or tracks underneath the antenna Never place the antenna very close to metallic objects Be careful about the wiring in the finalized product, not too

close to the antenna A monopole antenna should have a reasonable ground plane to

be efficient Do the final tuning in the end product, not in free air Never install a chip antenna in a vastly different layout than the

reference design, and expect it to work without tuning Do not use a metallic enclosure or metallized plastic for the

antenna Test the plastic casing for high RF losses, preferably before

production Never do a cut and paste antenna design and expect it to work

without testing Do not use very thin PCB tracks, the tracks should be fairly

wide


International success storiesInternational success stories

Medical Intelligence,Canada

Eureka,Italy for

e-foxx,Germany bplan,

Germany


Customised external antennasCustomised external antennas

Q: Can you help us with antennas that will pass PTCRB? A: Yes, we can help with standard and customised antennas.

GSM 850/1900 antenna GSM 850/1900 antenna with American PTCRB with American PTCRB approvelapprovel

Narrow band GSM-RNarrow band GSM-R antenna on top of antenna on top of information terminalinformation terminal

Top and back viewTop and back view of GSM-R antenna of GSM-R antenna


Embedded antenna GSM 900/1800 Embedded antenna GSM 900/1800 and ISM 868 for electricity meterand ISM 868 for electricity meter

Result after customisation:The VSWR for GSM 900 is always better than 1.9 and in GSM 1800 MHz band the VSWR is always better than 1.6.

Before After


Enhanced servicesEnhanced servicesDesign in aid for embedded antennas Design in aid for embedded antennas Tuning and

customisationof antennas

Developmentof matchingcircuit

Development of new customisedantennas

Mount standard part on board and check for shift in characteristics Select an item from the frequency and impedance series to correct

the shift in characteristics Mount the new part on the board and check characteristics

Repeat steps 2 and 3 if necessary to get the best results

Receipt of Customers Board

Measure the radiation pattern in the company's anechoic chamberCheck the center frequency, upper and lower band limits as well asverify the gain.

Send a technical report of the test results and a recommendation for the part to use to the customer.

CustomerCustomer

TuningTuning

Standard MeasurementsStandard Measurements

Make Technical ReportMake Technical Report

CustomerCustomer


Q: How to find the best partner?

A: Just divide the number of listed components on line cardby support engineers

Where to buy my antennas?Where to buy my antennas?

Wireless Solution supplier

300 components

You get all parts you need and it fits always together

Best support, becausethe team has to serve minimum lines

Special distributor

3000 components

You get a fewmore parts

Good support, because the team has to serve a few lines

Broadline distributor

30000 components

You get a few parts for your project

Poor support, becausethe team has to serve several lines


Do not burn your moneyDo not burn your money

Be careful when selecting your antenna supplier

First plane the size of PCB and antenna

Doing the other way around can force enormous costs

Better spending money for feasibility study, then loosing the chance to get GSM operator approval

Take care that GSM operators like Cingular and Vodafone are looking for antenna efficiency of at least of 40%

Our European wireless paradise will shrink, as soon operators will use close the same rules than the Americans

Hire resources as soon you run in trouble with your RF design

The best RF amplifier is a good antenna

The best antenna you get by selecting a high position


Tools and services to play with Tools and services to play with

Q: Where to get all thetools and services?

A: Please feel free to askfor measurement equip-ment, consulting,

studies and development with us.

Please note that we offer the loaning of GSM testers and other equip-ment for premium customers free of charge.


Why not to use services like Why not to use services like rapid prototyping of enclosures?rapid prototyping of enclosures?

Robust material Polyamide

Very detailed by usingfiles in format STL

Minimum edge lengthof polygons 0,01 mm

Only Euro 350 to 400for handheld enclosure

Delivery after 2 - 3 workingdays

Final enclosure

Prototype


Why not being a part of a huge Why not being a part of a huge community?community? World's biggest forum for wireless

applications

5.000+ members

Support and information24 hours/7 days a week


Round Solutions GmbH & Co. KGHans-Boeckler-Straße 1663263 Neu-Isenburg, Germany

Parliamo italiano +49 6102 79928-220

Kundtjänst på Svenska +49 6102 79928-210

Hablamos el espanol +49 6102 79928-230

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Fax +49 6102 79928-199

[email protected]

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