Differential and Single Ended Elliptical Antennas for GHz Ultra Wideband Communication

Transcription

1 Differential and Single Ended Elliptical Antennas for GHz Ultra Wideband Communication Johnna Powell Anantha Chandrakasan Massachusetts Institute of Technology Microsystems Technology Laboratory (MTL) IEEE AP-S/URSI 24 June 23, 24

2 Outline and Goals Introduction Specifications and Considerations Discrete System Implementation Antenna Designs Antenna Results Frequency Time Domain Anechoic Chamber

3 Introduction Motivation for UWB? Revolutionary approach to wireless communication Pulse based waveforms compressed in time GHz, dbm/mhz Low power levels allow for coexistence Frequency Time

4 UWB Impact on Antenna Design Impedance Matching Requirements Bandwidth +1% of f c Γ = S 11 < 1/3 VSWR < 2-1log S 112 = Return Loss > 1 db Wave Reception Linear Phase High Radiation Efficiency Omnidirectional Radiation Pattern Time Domain Pulse Fidelity Physical Constraints Compatible with Portable Devices Small, Compact, Planar Power Loss < 1%

5 Discrete System Implementation Signal Generator Pulse Generator Impulse Generator + - RF Switch Switch Driver Splitter Switch Driver RF Switch Pulse Inverter 11 HPF Power Amp Wideband Antenna 9.6 LNA Splitter Pulse Inverter HPF System Modeled after design by E. Green, Manny, B., Ultra Wideband: A Disruptive RF Technology, Intel Developer Conference, February 28, 22.

6 Discrete System Implementation Transmit Pulse Power Density Power Spectrum vs. Frequency 3.1 GHz 1.6 GHz FCC Spectral Mask Frequency (GHz)

7 Discrete System Implementation Horn Antenna Narrowband Monopole (Wire Antenna) Transmit Pulse (red) Received Pulse (green) VSWR Wire A wideband impedance match indicates optimal reception for a wideband pulse VSWR =2 VSWR Horn

8 Spiral Equiangular Slot Patch VSWR=2 Time Domain Plot Equiangular Spiral Slot Patch 1 Receive Transmit 1. Johnna Powell, Anantha P. Chandrakasan, Spiral Slot Patch Antenna and Circular Disc Monopole for GHz Ultra Wideband Communication", Int. Symp. Antennas and Propagation, August 24

9 Diamond Dipole 1.18 GHz A 1.24 GHz B A B C Time Domain Diamond Dipole 2.9 GHz C

10 Circular Disc Monopole VSWR =2 Circular Disc Monopole 1 VSWR < 1.5 Power loss < 4% Agrawall N. P.,Kumar G.,Ray. K.P., Wideband planar monopole antennas, IEEE Transactions on Antennas and Propagation

11 Single Ended and Differential Elliptical Antennas 1.5 a b IC location.9 f L c = = λ 3.24 L+ r GHz

12 Antenna Results- Frequency VSWR =2

13 Phase and Group Delay Comparison

14 1 mv/div 5 ps/div 5 ps/div Antenna Results- Time Domain Single Ended Elliptical Antenna Differential Antenna Tx pulse (Red) Rx pulse (Blue) Negative Terminal (Yellow) Positive Terminal (Red)

15 Absolute Value of Differential Pulses

16 Antenna Results- Chamber Spherical Coordinates: Azimuth = Rotation in φ Elevation = Rotation in θ Photos courtesy Lincoln Labs

17 Antenna Results- Chamber Spherical Coordinates: Azimuth = Rotation in φ Elevation = Rotation in θ 4 GHz Max Gain 2.11 db Max Gain 2.7 db HPBW = Lincoln Laboratory Measured Azimuth Pattern Measured Elevation Pattern

18 Gain vs. Frequency for Azimuth and Elevation Planes 1 5 Gain (dbi) Gain (dbi) Azimuth Elevation -15 Frequency (GHz)

19 Radiation Patterns for Varying Frequency- Elevation Co-polarized GHz 4 GHz 18 5 GHz GHz 9 GHz 1 GHz 18

20 Radiation Patterns for Varying Frequency- Azimuth Co-Polarized GHz 4 GHz 5 GHz GHz 9 GHz 1 GHz 18

21 3-D Radiation Pattern Farfield Simulated Measurement Frequency = 4 GHz Radiation Efficiency = 99.58% Total Efficiency = 92.9% Gain = 3.22 db Measured Frequency = 4 GHz Radiation Efficiency = 93% Impedance Efficiency = 99.3% Total Efficiency = 92.3% HPBW = 73

22 Summary UWB Antenna Designs VSWR < 2 for GHz Near Omnidirectional Pattern High Radiation Efficiency Physically Small Size Discrete System Implementation Future Work: System Considerations