INTEGRATION OF PLANAR ANTENNAS AND TWO DIMENSIONAL DEFECT RESONATORS

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INTEGRATION OF PLANAR ANTENNAS AND TWO
DIMENSIONAL DEFECT RESONATORS

• University of Michigan
• Radiation Laboratory
• Bill Chappell
• Matt Little
• Professor Linda P.B. Katehi

Work Supported by the Quasi Optical MURI and the
MURI for Low Power Electronics
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Presentation Overview

• Introduction
• Project Purpose
• Two Dimensional Dielectric Electromagnetic
  Bandgaps (EBG)
• Our Previously Proven Concepts
• Efficient Planar Slot Antenna
• Dielectric Defect Resonators
• Integration of These Concepts
• Defect Coupled Antenna
• Matching
• Simulation Vs. Measurement
• Pattern
• Efficiency
• Multiple Defect Applications
• Conclusion

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Project PurposeHighly Efficient Antenna with
High-Q Planar Resonators on a Single Multipurpose
Substrate

• Integration of Both Antenna and Resonator
• Synthetic (EBG) substrate provides multiple
  functions on the same planar structure
• Benefits of both the high-Q resonator and the
  antenna
• Efficient Planar Antenna on EBG Substrate
• Slot in EBG filled parallel plate
• Measured efficiency 80 percent
• Planar Resonators Defects in EBG Substrate
• 2-D Defect mode has high Q for a planar structure
• Measured unloaded Q 700 to 1000

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Synthetic Substrate Application
Conductor Backed Slot Antenna
Coaxially-fed folded slot
Conductor-backed, folded slot design
In a Traditional Antenna with Homogeneous
Substrate, the Field Couples to a Parallel Plate
Mode and Radiates from Edges Of Substrate With
Periodic Inclusions, the Field Evanesces into
Substrate and Radiates from the Central Slot
Element
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Dielectric Electromagnetic Bandgap

• Eigenvalue solution performed using a plane wave
  expansion (Smith, et al)
• Bandgap is frequency region where no real
  eigenvalue solution exists
• Midband
• Period ?/4 to ?/2

bandgap
Frequency (GHz)
45
0
Propagation Direction
bandgap
S-Parameters (dB)
Frequency (GHz)
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Conductor Backed Slot Antenna
Electric Field Inside Substrate
Evanescent Field Inside Synthetic Substrate
Outwardly Traveling Field Inside Homogeneous
Substrate
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Slot Antenna with Synthetic Substrate

• Synthetic Substrate-backed slot
• BW 7.5
• Gain 3.7?0.2 dB
• Directivity 4.5 dB
• F-B ratio 15 dB
• Low x-pol levels
• Efficiency 81.32.0

Field is Prohibited from Coupling into the
Parallel Plate Mode of the Substrate. Therefore,
Radiation Emanates from the Slot Element instead
of the Edge of the Parallel Plate.
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Slot Antenna with and without EBG

• Slot Backed With Homogeneous Substrate
• 7-8 dB ripple
• er2.2
• Efficiency 30.9 2.0
• (for ? parallel plate)
• Slot Backed By Synthetic-Substrate
• 2-3 dB ripple
• er10.2
• Smoother patterns
• Lower x-pol levels
• Efficiency 81.3 2.0

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What Is a Defect Resonator?

• Periodically spaced rods do not allow wave
  propagation
• Lattice disturbed by removing a single rod or
  series of rods
• Energy is localized and a resonance is created

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Dielectric Defect Resonator
Linear View Field seems to be contained by vias

• Periodic dielectric inclusions block energy
  propagation
• Allowed state created in bandgap

Bandgap
S-parameters (dB)
Frequency (GHz)
Defect
Defect
Bandgap
45
0
Propagation Direction
Frequency (GHz)
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High-Q Quasiplanar Resonators

• Separation of Qs of individual loss factors was
  performed
• Unloaded Qs on the order of 700 to 900
• Dielectric loss was determined to be largest
  contributor to loss
• Simulation and measured results agree well
• 5 percent maximum difference in Q and resonant
  frequency

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Defect Coupled Slot Antenna

• Waveguide Fed Defect
• Slot in parallel plate couples to the defect
• Defect in turn couples to the slot antenna
• Advantages
• Single Sided Planar Slot Antenna
• Highly efficient because of no substrate modes
• Response of antenna controlled by defect

Waveguide Port
Parallel Plate
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Defect Coupled Slot Antenna

• Waveguide Fed Defect
• Slot in parallel port couples to the defect
• Defect in turn couples to the slot antenna
• Advantages
• Single sided planar slot antenna
• Highly efficient because of no substrate modes
• Response of antenna controlled by defect

Defect
Coupling Slot
Radiating Slot
Square Lattice EBG Substrate, D/A .35
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Slot Length Adjusts Coupling to Antenna
Undercoupled Feed Slot 6 mm
Overcoupled Feed Slot 10 mm
Critically Coupled Feed Slot 8 mm
Radiating Slot 22 mm
Waveguide
Free Space
Antenna
Resonator
Feed Slot
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Defect Coupled Slot Antenna
Simulated
Measured
3 dB Bandwidth Measured - 1.1 Simulated - 0.5
Resonant Frequency Measured - 10.815
GHz Simulated - 10.717 GHz Percent Difference -
0.9
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H-Plane Measured Pattern
Measurement Plane
Co Pol E Field
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E-Plane Measured Pattern
Measurement Plane
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Antenna Data

• Directivity 4.29
• Estimated from Pattern
• 41,253/(halfpower angles) 6.33 dB

• Gain 3.37
• Gain Pslot - Pstandard GainStandard
• Measured Data
• Narda Standard Gain Horn
• Received Power -29.17 dBm
• Standard gain 17 dB
• EBG Slot Antenna
• Received Power -40.9 dBm
• Calculated Gain 5.27 dB
• Efficiency 78.3
• Efficiency Directivity/Gain

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Circuit Realization of EBG Substrate Antenna
Other Possibility is two coupled antennas for
Quasi-Optical spatial filtering
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Multiple Defects

• Adjacent defects couple to each other creating
  multiple peaks in transmission
• Coupled Defect Resonators can be used to form
  specific bandwidth and shape filters

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Coupling Between Resonators
3-Periods

• By introducing two defects adjacent to each
  other, two peaks in transmission are created
• Inter-resonator coupling determines the width
  between the peaks
• Coupling controlled by the number of periods
  between defects

2-Periods
1-Period
Transmission (dB)
Frequency (GHz)
k .049
Coupling Coefficient
k .017
k .0049
Period Separation
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Multiple Defect Coupled Antenna
3-Periods
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Conclusions

• Developed Efficient Planar Antenna
• Dielectric EBG substrate blocks substrate mode
• Efficient, single-sided radiator created
• Simulation and measured results agree well
• Synthetic Substrate with Defect used to Couple to
  Antenna
• Antenna matching controlled by adjusting external
  coupling to defect
• Coupled defects alter the resonant response of
  the slot to create multiple radiating frequencies
• Wide range of coupling coefficients available by
  adjusting number of periods separating defects
• Preselect Filtering Possible with the Use of
  Artificial Substrate and Defect Technology