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

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Antenna Results- Chamber

Spherical Coordinates:Azimuth = Rotation in φElevation = Rotation in θ

Photos courtesy Lincoln Labs

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Max Gain 2.11 dB

Antenna Results- Chamber

Lincoln Laboratory Measured Azimuth Pattern Measured Elevation Pattern

4 GHz

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Max Gain 2.7 dB

HPBW =73°

Spherical Coordinates:Azimuth = Rotation in φElevation = Rotation in θ

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3.5 4.5 5.5 6.5 7.5 8.5 9.5

Ga

in (

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i)

Gain vs. Frequency for Azimuth and Elevation Planes

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Elevation

Frequency (GHz)

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3.5 GHz 4 GHz

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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