Spiral Slot Patch Antenna and Circular Disc Monopole Antenna for 3.1-10.6 GHz Ultra Wideband

Johnna PowellAnantha Chandrakasan

Massachusetts Institute of TechnologyMicrosystems Technology Laboratory (MTL)anantha, johnna@mtl.mit.edu

ISAP 2004August 18, 2004

Outline and Goals

IntroductionSpecifications 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 Design

Impedance Matching RequirementsBandwidth +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

Antenna Designs

Diamond DipoleElliptical Planar Antennas

CDMSpiral

Diamond Dipole

A B C

A

B

C

1.18 GHz

1.24 GHz

2.9 GHz

Time Domain Diamond Dipole

Single Ended and Differential Elliptical Antennas

30 0.24L

cf GHzL rλ∗

= =+

b

a

0.9”

1.5”

IC location

J. Powell and A. Chandrakasan, “Differential and Single ended Elliptical Antennas for 3.1-10.6 GHz Ultra Wideband”, AP-S 2004.

Circular Disc Monopole

Circular Disc Monopole1

1. 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%30 0.24

Lcf GHz

L rλ∗

= =+

2.3 cm

Spiral Equiangular Slot Patch

Equiangular Spiral Slot PatchVSWR=2

Antenna Feed

0.5 cm

Expansion rate = .38Total Arm Length = 6 cmOuter Radius = 2.25 cm

Designed in Remcom’s XFDTD

Back plane allows for use with PEDs

Fabricated with Omax waterjet and PCB milling router

VSWR and Group Delay

-6

-4

-2

0

2

4

6

8

10

3 4 5 6 7 8 9 10

Del

ay (n

s)

HornCDMSpiral

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10

Horn

CDM

Spiral

VSWR vs. Frequency (GHz)

Group Delay vs. Frequency (GHz)VSWR=2

Pulse Fidelity Time Domain Plot

Rx Pulse- Red

Tx Pulse- green

500 ps/div

Taken from TDS 8000 Digitizing Oscilloscope

Antenna Results- Chamber

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

Photos courtesy Lincoln Labs

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Antenna Results- Chamber

Lincoln Laboratory Measured Pattern: Azimuth =Blue, Elevation = Red

3.5 GHz

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

Gain vs. Frequency

-20-18-16-14-12-10

-8-6-4-20

3.5 4.5 5.5 6.5 7.5 8.5 9.5

-20-18-16-14-12-10

-8-6-4-20

3 4 5 6 7 8 9 10

Horizontal Polarization

Frequency (GHz)

Vertical Polarization

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3.5 GHz 4 GHz 5 GHz

7 GHz 9 GHz 10 GHz

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Radiation Patterns for Varying Frequency- Vertical Polarization

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3.5 GHz 4 GHz 5 GHz

7 GHz 9 GHz 10 GHz

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Radiation Patterns for Varying Frequency- Horizontal Polarization

Summary

UWB Antenna DesignsVSWR < 2 for 3.1- 10.6 GHzPhysically Small SizeGood Pulse FidelityConsistent gain patterns

Discrete System ImplementationFuture Work: System Considerations