differential and single ended elliptical antennas for 3.1 ......spiral equiangular slot patch 1....
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Differential and Single Ended Elliptical Antennas for 3.1-10.6 GHz Ultra
Wideband Communication
Johnna PowellAnantha Chandrakasan
Massachusetts Institute of TechnologyMicrosystems Technology Laboratory (MTL)
IEEE AP-S/URSI 2004June 23, 2004
Outline and GoalsIntroductionSpecifications and ConsiderationsDiscrete System ImplementationAntenna DesignsAntenna Results
FrequencyTime DomainAnechoic Chamber
IntroductionMotivation for UWB?
Revolutionary approach to wireless communicationPulse based waveforms compressed in time3.1-10.6 GHz, -41.3 dBm/MHzLow power levels allow for coexistence
Frequency
Time
UWB Impact on Antenna DesignImpedance Matching Requirements
Bandwidth +100% of fc|Γ|=|S11| < 1/3 VSWR < 2-10log|S11
2|= Return Loss > 10 dB
Wave ReceptionLinear PhaseHigh Radiation EfficiencyOmnidirectional Radiation PatternTime Domain Pulse Fidelity
Physical ConstraintsCompatible with Portable DevicesSmall, Compact, Planar
Power Loss < 10%
Discrete System Implementation
System Modeled after design by E. Green, Manny, B., “Ultra Wideband: A Disruptive RF Technology,” Intel Developer Conference, February 28, 2002.
Signal Generator
ImpulseGenerator
HPF
PowerAmp
WidebandAntenna
SwitchDriver
+-
RFSwitch
Splitter
PulseInverter
9.6”11”
HPF
Pulse Generator
LNA Splitter
Pulse Inverter
RF Switch
Switch Driver
Discrete System ImplementationTransmit Pulse Power Density
Power Spectrum vs. Frequency
FCC Spectral Mask
3.1 GHz 10.6 GHz
Frequency (GHz)
Discrete System Implementation
Transmit Pulse (red)Received Pulse (green)
Horn Antenna
Narrowband Monopole(Wire Antenna)
A wideband impedance match indicates optimal reception for a
wideband pulse
VSWR Wire
VSWR HornVSWR =2
Spiral Equiangular Slot Patch
1. Johnna Powell, Anantha P. Chandrakasan, “Spiral Slot Patch Antenna and Circular Disc Monopole for 3.1-10.6 GHz Ultra Wideband Communication", Int. Symp. Antennas and Propagation, August 2004
Equiangular Spiral Slot Patch1
Time Domain Plot
Transmit
Receive
VSWR=2
Diamond Dipole
A B C
A
B
C
1.18 GHz
1.24 GHz
2.9 GHz
Time Domain Diamond Dipole
Circular Disc Monopole
Circular Disc Monopole1
Agrawall N. P. ,Kumar G.,Ray. K.P., “Wideband planar monopole antennas”, IEEE Transactions on Antennas and Propagation
VSWR =2
VSWR < 1.5 Power loss < 4%
Single Ended and Differential Elliptical Antennas
30 0.24L
cf GHzL rλ∗
= =+
b
a
0.9”
1.5”
IC location
Antenna Results- Frequency
VSWR =2
Phase and Group Delay Comparison
Antenna Results- Time Domain
10 mV/div 500 ps/div 500 ps/div
Tx pulse (Red)Rx pulse (Blue)
Single Ended Elliptical Antenna Differential Antenna
Positive Terminal (Red)Negative Terminal (Yellow)
Absolute Value of Differential Pulses
-40 -30 -20 -10 0 10
0
30
60
90
120
150
180
-150
-120
90
-60
-30
Antenna Results- Chamber
Spherical Coordinates:Azimuth = Rotation in φElevation = Rotation in θ
Photos courtesy Lincoln Labs
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0
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-120
-90
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60
90
120
150180
-150
-120
90
-60
-30
0
Max Gain 2.11 dB
Antenna Results- Chamber
Lincoln Laboratory Measured Azimuth Pattern Measured Elevation Pattern
4 GHz
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0
Max Gain 2.7 dB
HPBW =73°
Spherical Coordinates:Azimuth = Rotation in φElevation = Rotation in θ
-15
-10
-5
0
5
10
3.5 4.5 5.5 6.5 7.5 8.5 9.5
Ga
in (
dB
i)
Gain vs. Frequency for Azimuth and Elevation Planes
-15
-10
-5
0
5
10
3.5 4.5 5.5 6.5 7.5 8.5 9.5
Ga
in (
dB
i)
Azimuth
Elevation
Frequency (GHz)
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0
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-90
-60
-30
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0
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3.5 GHz 4 GHz
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0
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-90
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-30
5 GHz
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0
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-30
7 GHz 9 GHz 10 GHz
Radiation Patterns for Varying Frequency- Elevation Co-polarized
3.5 GHz 4 GHz 5 GHz
7 GHz 9 GHz 10 GHz
Radiation Patterns for Varying Frequency- Azimuth Co-Polarized
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3-D Radiation PatternFarfield Simulated
MeasurementFrequency = 4 GHz
Radiation Efficiency = 99.58%Total Efficiency = 92.90%
Gain = 3.22 dB
MeasuredFrequency = 4 GHz
Radiation Efficiency = 93%Impedance Efficiency = 99.3%
Total Efficiency = 92.3%HPBW = 73°
Summary
UWB Antenna DesignsVSWR < 2 for 3.1- 10.6 GHzNear Omnidirectional PatternHigh Radiation EfficiencyPhysically Small Size
Discrete System ImplementationFuture Work: System Considerations