antenna design genesys ver4

7/28/2019 Antenna Design GENESYS Ver4

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4G MIMO ANTENNADESIGN & Verification

Using Genesys And

Momentum GX To Develop

MIMO Antennas

Copyright 2008 Agilent Technologies, Inc.


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Agenda

4G Wireless Technology

Review Of Patch Technology

Review Of Antenna Terminology Design Procedure In Genesys

Verifying Antenna Performance

-


Verifying Method With Momentum GX

Conclusion


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4G Wireless: LTE, WiMAX, Mobile WiMAX, 802.11n

Fourth Generation WirelessInfrastructure:

Higher Data Rates

Up to 150 Mbs downlink, 50Mbs uplink


- Edge, GSM, FTE, UMTS etc.

Speedy Mobiles 100 km/hr


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Selection criteria for antenna type:

Beam pattern

Gain

Power handling capability

Antenna Parameters


rect v ty Bandwidth

Manufacturability

Cost


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Patch antenna topologies:

Advantages

Ease of manufacture

Form complicated antenna patterns

Flexible substrates

Patch Antenna Characteristics


Weight

Cost

Disadvantages

Substrate material limits efficiency Lossy, lower radiation efficiency means increased transmit power

Power limited


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There is an almost endless number of antenna feed topologies:

Rectangular, Circular, Arrays

Shapes affect bandwidth, radiation patterns and polarization

Spacing and phase affect directivity, gain and radiation pattern

Patch Antenna Shapes


Patch Patterns

Series Feed

Parallel Feed


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E

Radiation Patterns

Fields defined by E-theta and E-phi

Etotal is the vector sum of both components

Etheta sweeps from the North Pole 0o to 90o

Ephi sweeps from 0o to 180o around the North Pole


E

Note relationship of the field to theX and Y axis of the circuit board


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Orientation In Antenna Patterns

Patch antennas Rarely Have Symmetrical Pattern

Due to current distribution on patch(s)


Phi=0o Phi=90o


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Antenna Design Procedure

Use linear analysis to evaluate physical dimensions

Verify design with Momentum GX

Determine additional matching circuitry using MATCH

Examine prototype with far field analysis


Design and verify a steer-able beam array

Develop a mathematical model of the far field pattern

Apply procedure to dual antenna pattern

Verify multi-element pattern with Momentum


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20 + h11

Start with a rectangular design

Resonance is determined by length along the feed axis

Length is approximately Width is loosely equal to length, however maximum efficiency is given for width

by (1)

2

Patch Design


12 +

=rrf

=

Weff

22

( )

( )

+

++

=

8.0258.0

264.03.0

412.0

hW

h

W

h

L

eff

eff

Fringe Effect

L

f

L

effr

= 2

2

0

L LL

W


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Patch Design

Frequency requirements for LTE band II

Approximately 7.5% bandwidth

Transmit band is 60 MHz wide, 1850-1910 MHz

Receive band is 60 MHz wide, 1930-1990 MHz


The design will then center at 1920 MHz Start a patch Length =1440 mils, with a Width =1860 mils

Substrate is FR4 Er=4.5, height = .059 inches


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Using Linear Modeling

Start with simple transmission line model to verify the length



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Using Momentum GX

First simulation establishes resonant frequency


Of course transmission line does not model radiation

Markers show band edges for the transmit and receive bands


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Reducing Patch Width And Optimizing Length

Reducing patch width has small effect on response but reducesfootprint

Length =1434.5 mils

Width =1200 mils



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Evaluating Matching Structures

Using Genesys MATCH we can determine the optimummatching structure

Start with settings dialog we set the frequency band of match The settings represent the full band 1850-1990 MHz with 50 pts



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Using Antenna Data For Match

In Sections Tab We Point MATCH To The Momentum Data Set As TheTerminating Impedance

The Type Of Matching Structure Is Selected Next We will try to use distributed matching for incorporation into the layout



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Stepped Impedance Network

Stepped impedance provides a good match at band center butthe band edges are not improved



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Quarter Wave Matching Line

A simple quarter wave provides improvement at band center butagain the band edges are not improved



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Match For Transmit Band

The patch antenna chosen is inherently narrow band

Focus on matching for the transmit frequencies since a poor match canresult in watts of power loss

Re-center resonant frequency for transmit band center 1880 Mhz


Slight increase in antenna length decreases center frequency


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Synthesize Matching Network

Using MATCH Again To Find Best Structure

In this case a simple quarter wave transmission provides an adequatematch at band center and edges

Length =1434.5 mils



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Final Momentum Analysis

Final analysis places center frequency at ~1880 MHz

Quarter wave matching line gives us -36 dB return loss at ~1880

Transmit band edges provide ~-10 dB return loss

Receive band has the worst match of -6.5 -> -3 db, possible secondantenna



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Plotting Field Patterns

We must have performed a Momentum simulation first!



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Etotal Compared To Phi

Select antenna graph measurement then select phi cut

Radiation pattern is dependent upon rotation around phi axis



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Antenna Patterns

Field pattern is a function of

90=

0=


00=

0

90=


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Standards affect antennas for base stations and mobilesdevices

Base stations need to provide data to multiple users whilecompensating for multi-path and delay

Mobiles also need to compensate for multi-path and fading

MIMO Networks Require Agile Antennas



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Networks Require Agile Antennas

Variety of antenna function and types

Omni Directional

Steer-able Array

Diversity


Switched or Multi-Beam

Patch Antenna Types


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MIMO- Steerable Antenna

Use Genesys to develop MIMO Antennas

Design and evaluation of steerable MIMO Antennas

We use the results of our antenna design to predict the contributionsfrom an array

If the patch antennas are reasonably isolated Smn~ 0, then linear


superpos t on can e use to p ot t e ar e contr ut ons 2


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Determining Far Fields

Far Field value is the superposition of each radiator

22 ))cos(*())sin(*(1 dRRFp +=

FAR FIELD

FAR FIELD


4/=d

R

Fp1 Fp2

R )sin(* R

dR )cos(*

dR +)cos(*

22

))cos(*())sin(*(2 dRRFp ++=

A B


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Mathematically Generated Pattern

v2k

Antk

B cos k( ) B sin k( ) i+( ):=

v1k

Antk

A cos k( ) A sin k( ) i+( ):=

k 2 Fk:=

k 2 Ek:=

Fk

R cos k

2

K

2

R sin k

2

2

+:=Ek

R cos k

2

K+

2

R sin k

2

2

+:=

Antk

.5 cos k ( )( )1.0

.5cos k ( ):= 0deg:= 0deg:=

D 2 K:=K n

4:=R 100:=n 1:= 1:=

B .5:=A .5:=k k 180:=k 0 360..:=

Superposition of Fields


0

15

30

45

607590105

120

135

150

165

180

195

210

225

240255 270 285

300

315

330

345

0.8

0.6

0.4

0.2

0Vk

k

0

15

30

45

607590105

120

135

150

165

180

195

210

225

240255 270 285

300

315

330

345

0.8

0.6

0.4

0.2

0Ant k

k

Vk

v1k

v2k

+:=


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30

45

607590105

120

135

150

0.8

0.6 30

45

607590105

120

135

150

0.8

0.6

Far Field plot of two omni-directional antennas

Driven with equal amplitude and in phase

Note the new directionality

Superposition Of A Two Element Array


0

15165

180

195

210

225

240255 270 285

300

315

330

345

0.4

0.2

0Ant k

k

0

15165

180

195

210

225

240255 270 285

300

315

330

345

0.4

0.2

0Vk

k

Single Antenna Pattern Result Of Far Field Superposition


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Antenna Interference

An intuitive look at interference vs. spacing

Like colors or phases add while unlike colors or phases

subtract


+

+

++

B


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Front Sided Antenna

45

607590105

120

135 0.8 45

607590105

120

135 0.8

Little or no backward radiation

Pattern becomes narrower with little side lobe radiation

Typical of patch antenna


0

15

30150

165

180

195

210

225

240255 270 285

300

315

330

345

0.6

0.4

0.2

0Ant k

k

0

15

30150

165

180

195

210

225

240255 270 285

300

315

330

345

0.6

0.4

0.2

0Vk

k


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Changing The Feed Phase

15

30

45

60

7590105

120

135

150

165

0.8

0.6

0.4

0.2Vk

Varying the phase and amplitude of the elements

Results in controlling the tilt or angle of maximum radiation


0

15

30

45

60

7590105

120

135

150

165

180

195

210

225

240255 270 285

300

315

330

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0.8

0.6

0.4

0.2

0Vk

k

60 deg:=

195

210

225

240255 270 285

300

315

330

345

k

90 deg:=

0

15

30

4560

7590105

120135

150

165

180

195

210

225

240255 270 285

300

315

330

345

0.8

0.6

0.4

0.2

0Vk

k

180 deg:=


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Pattern Array

Field patterns for an array of antenna elements can be analyzedor synthesized by*.

1) Knowing the single element radiation pattern2) The amplitude and phase of the sources driving each element

3) Knowing the spacing or separation between elements


Method may be extended to multiple elements

*Interference or coupling between elements is zero or nearly zero

d d d

A B C D


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Array Design In Genesys

Applying the same trigonometry within Genesys

We start with the single patch antenna from before

Using Momentum far field data we obtain the element pattern Genesys rich set of math functions allows us to project far field data from

the captured single element pattern


The ability to tune parameters such as feed amplitude and phase as wellas antenna distance gives full control over the far field

When applied to a large number of elements, optimization reduces the timeand effort


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Extracting The Element Pattern

Run a Momentum GX analysis of the proposed antenna

Extract Momentum E-field dataset values for single element


New Data VectorWith Field Values


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Using Genesys Math Functions

Trigonometric equations relating far-field value to elementpattern characteristics

Antk

.5 cos k ( )( )1.0

.5cos k ( ):=R 100 :=K n

4:=n 1:= 1:=

0deg:= 0deg:=D 2 K:=B .5:=A .5:=k k

180:=k 0 360..:=

SUPER POSITION OF FIELDS


Vk

v1k

v2k

+:=

v2k

Antk

B cos k( ) B sin k( ) i+( ):=

v1k

Antk

A cos k( ) A sin k( ) i+( ):=

k 2 Fk:=

k 2 Ek:=

Fk

R cos k

2

K

2R sin k

2

2+:=E

kR cos k

2

K+

2R sin k

2

2+:=


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Tuning For Phase And Levels

Antenna parameters are made tunable

Instant visualization on far field pattern


Antenna A level

Antenna B level

Phase Difference

Antenna spacing in half wavelengths

0o

Phase


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Result Of Phase Offsets

Antenna beam steers, side-lobes and beam width change

~28o~42o


90o Phase

60o Phase


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Additional Degrees Of Freedom

Pattern is influenced by drive levels and element separation

Added elements offer improved control over beam


Element spacing 1.3 half wavelengths Element spacing 3 half wavelengths


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Verifying Predicted Pattern

Layout two element patch antenna modeled after single element previouslydesigned and simulated

Use Momentum to generate the combined far-field with appropriate voltages

and phase

Review the far-field pattern to verify the predicted performance


V if i I l i


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Verifying Isolation

At band center, 1880 MHz isolation is -43 dB


-43 dB=50 millionths

S tti S V l


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Setting Source Values

Under Momentums far-field options

The source levels and relative phase


Note that the phase is set at 180o Why?

M F t F M t GX


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More Features For Momentum GX

3D Field Viewer


Comparing Predicted Field


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Comparing Predicted Field

Comparison of far-field predicted and Momentum GX

Both show a half power beam width of 290

PREDICTED Momentum Momentum 3D ViewSingle Element Pattern


Adding Phase Shift At Ports


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Adding Phase Shift At Ports

28 DegreesPREDICTED Momentum

Result of 28o difference in phase between sources

Note identical beam values at -3dB of 38O from beam center


Note: The current version of Momentum plots half beam

Using Two Evaluations


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Using Two Evaluations

Plotting both halves of Momentum field requires two phaseevaluations

Note values are equal between predicted and Momentum!

60 De rees

PREDICTED Momentum


Elements Driven Opposite


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Elements Driven Opposite

The extreme for two element antenna is 180 phase difference

180 Degrees

PREDICTED Momentum

Difference in magnitude due to re-normalizing in Momentum


Orientation Of Beam Relative To Board


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Orientation Of Beam Relative To Board

Major cut was through phi = 0

Swept pattern steers along X-axis


00=

Field Pattern In Genesys


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Field Pattern In Genesys

Extending the equations to four elements a narrow beam isachieved


Optimization Of Beam Pattern


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Optimization Of Beam Pattern

Beyond two elements selecting the correct feed-phase isburdening

We use the optimization features of Genesys to aide in finding the best setof feed amplitude and phases


Goal = 30 deg

Beam Amplitude Optimization


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Beam Amplitude Optimization

Additionally we optimize the feed amplitudes to compensate forbeam power as a result of steering

688.2271.0

374.268.0

139.1268.0

=

=

=

c

b

a

Angles in radians


.. =

Other Sources Of Antenna Data


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Other Sources Of Antenna Data

Single antenna element information can be measured and imported viaTestLink


Conclusion


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Conclusion

An antenna design procedure was presented

A rectangular patch was designed and verified with Momentum 3D-PlanarEM Field Simulator

A modified antenna was optimized for a LTE band and matching networkincorporated

The single patch field pattern was then used to model or predict the effect


o an array o two or more e ements

Verification of this technique was established with Momentum field solver

Optimization aides in extending this procedure to larger arrays


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Agilent Genesys product bundles start at about $4K USD

The modules used to complete the synthesis, design andverification of MIMO antenna system presented in this

-


(W1426L) for about $16.6K USD

References


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Antenna Theory Analysis and Design, Constantine Balanis, Wiley, second edition,Pgs 727-736

Ibid, Pgs 249-261

Fundamentals of Applied Electromagnetics, Fawwaz Ulaby, Prentice Hall,1997, Pgs316-365

Agilent AN note 3GPP Long Term Evolution, doc 5989-8139EN


Agilent AN Mobile WiMAX PHY Layer Operation and Measurement, doc 5989-

8309EN

Agilent AN MIMO Channel Modeling and Emulation Test Challenges, doc 5989-8973EN

Agilent AN MIMO Wireless LAN PHY Layer RF Operation & Measurement, doc

5989-3443EN

antenna design genesys ver4

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