Antenna Design GENESYS Ver4
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Transcript of 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
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Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
- 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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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)
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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Using Momentum GX
First simulation establishes resonant frequency
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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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
Copyright 2008 Agilent Technologies, Inc.
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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
Copyright 2008 Agilent Technologies, Inc.
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Stepped Impedance Network
Stepped impedance provides a good match at band center butthe band edges are not improved
Copyright 2008 Agilent Technologies, Inc.
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Quarter Wave Matching Line
A simple quarter wave provides improvement at band center butagain the band edges are not improved
Copyright 2008 Agilent Technologies, Inc.
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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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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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
Copyright 2008 Agilent Technologies, Inc.
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Plotting Field Patterns
We must have performed a Momentum simulation first!
Copyright 2008 Agilent Technologies, Inc.
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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
Copyright 2008 Agilent Technologies, Inc.
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Antenna Patterns
Field pattern is a function of
90=
0=
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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Networks Require Agile Antennas
Variety of antenna function and types
Omni Directional
Steer-able Array
Diversity
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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0Ant k
k
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v1k
v2k
+:=
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0.6 30
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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
Copyright 2008 Agilent Technologies, Inc.
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0.2
0Ant k
k
0
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0.4
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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
Copyright 2008 Agilent Technologies, Inc.
+
+
++
B
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Front Sided Antenna
45
607590105
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135 0.8 45
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135 0.8
Little or no backward radiation
Pattern becomes narrower with little side lobe radiation
Typical of patch antenna
Copyright 2008 Agilent Technologies, Inc.
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0Vk
k
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Changing The Feed Phase
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0.6
0.4
0.2Vk
Varying the phase and amplitude of the elements
Results in controlling the tilt or angle of maximum radiation
Copyright 2008 Agilent Technologies, Inc.
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60 deg:=
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90 deg:=
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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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
V if i I l i
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Verifying Isolation
At band center, 1880 MHz isolation is -43 dB
Copyright 2008 Agilent Technologies, Inc.
-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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
00=
Field Pattern In Genesys
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Field Pattern In Genesys
Extending the equations to four elements a narrow beam isachieved
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
.. =
Other Sources Of Antenna Data
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Other Sources Of Antenna Data
Single antenna element information can be measured and imported viaTestLink
Copyright 2008 Agilent Technologies, Inc.
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
Copyright 2008 Agilent Technologies, Inc.
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
-
Copyright 2008 Agilent Technologies, Inc.
(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
Copyright 2008 Agilent Technologies, Inc.
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