Design Keven Lockwood Advisor: Dr. Prasad Shastry 1 Outline - - PowerPoint PPT Presentation

SDARS: Front End Antenna Design

Keven Lockwood Advisor: Dr. Prasad Shastry

1

Outline

• Project Overview
• Antenna Characteristics
• Feeding Techniques
• Performance Specifications
• Design Process
• Expected results
• Design Dependencies
• Equipment
• Schedule

2

Project Overview

• Patch Antenna for receiving SDARS

– Compact size

• Idea from “A Circularly Polarized

Microstrip Antenna using Singly-Fed Proximity Coupled Feed” by Iwasaki, Sawada, Kawabata – Not previously designed at BU

• Past Projects

– Greg Zomchek and Erik Zeliasz

• Probe feed antenna
• Aperture coupled feed antenna

– Sasidhar Vajha

• Proximity coupled, linearly polarized, 1.9

GHz patch antenna

Source: H. Iwasaki, H. Sawada, K. Kawabata. “A Circularly Polarized Microstrip Antenna Using Singly-Fed Proximity Coupled Feed.” Institute

• f Electronics, Information and Communication Engineers. September
• 1992. pp. 797-800.

3

Circular Polarization

Above: Illustration of a right-hand circularly polarized wave. Right: Circularly polarized waves travelling in the +Z direction (out of page). Source (both figures): Ulaby, Fawwaz T. Fundamentals of Applied Electromagnetics. Pearson Education, Inc.

• 2007. p. 298

4

System Block Diagram

Antenna Low-Noise Amplifier Sirius Radio Receiver Mixer Band pass filter IF amplifier Local Oscillator Active Antenna Down Converter Intermediate frequency ready for decoding

5

Antenna Characteristics

• Gain
• VSWR, input

impedance

• Polarization
• 3-dB

beamwidth

• Axial Ratio

Representative plots of the normalized radiation pattern of a microwave antenna in (a) polar form and (b) rectangular form. Source: Ulaby, Fawwaz T. Fundamentals of Applied

• Electromagnetics. Pearson Education, Inc. 2007. p. 382

6

Feeding Mechanism

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd ed. John Wiley & Sons, Inc. 1997. p. 725.

7

Feeding Mechanism: Microstrip

• Simple to fabricate / model
• Simple to match with inset position
• Prone to spurious feed radiation, limiting

bandwidth

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd ed. John Wiley & Sons, Inc.

• 1997. p. 725.

8

Feeding Mechanism: Coaxial

• Easy to fabricate, difficult to model
• Narrow bandwidth
• Low spurious radiation

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd ed. John Wiley & Sons, Inc. 1997.

• p. 725.

9

Feed: Aperture Coupled

• Independent
• ptimization of

patch and feed

• Difficult to

fabricate

• Narrow bandwidth
• Easier to model

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd ed. John Wiley & Sons, Inc. 1997. p. 725. 10

Feed: Proximity Coupled

• Wide bandwidth
• Easy to model
• Low spurious radiation

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd ed. John Wiley & Sons, Inc. 1997. p. 725. 11

Performance Specifications

• 2320 MHz to 2332.5 MHz (BW = 12.5

MHz)

– 100 channels, 125 kHz per channel

• VSWRmax = 2:1
• Left-hand circular polarization
• Total active gain 28.5 dB - 32.5 dB

12

Antenna Design Process

Paper Design Simulation Optimization Fabrication Physical Testing

13

Paper Design

• Substrate selection

– Thick, with low dielectric constant for better radiation efficiency, larger bandwidth (top layer) – Same dielectric constant, thin bottom layer

• Patch Dimensions

– Influenced by

• Operating frequency
• Collective height and dielectric constants of the substrates
• Transmission line model equations
• Feed line dimensions

– Calculated using “MSTRIP” with Zo = 50 Ohms, dielectric constant, height of bottom substrate

14

Design Dependencies

15

• ɛr eff depends on h, t, and ɛr of each
• Wp and Leff are inversely proportional to fr and the ɛr eff
• Leff = L + 2*(∆L)
• ∆L is proportional to h+t
• Ws depends on h and ɛr of bottom layer

Source: Balanis, Constantine A. Antenna Theory: Analysis and Design. 2nd

• ed. John Wiley & Sons, Inc. 1997. p. 729.

Simulations

• Momentum

– Uses Maxwell’s equations – Measures and graphs

• S11 (reflection

coefficient)

• VSWR,
• input impedance
• Radiation pattern

– Optimization through variable sweeps

16

Fabrication

• Create a template using final

simulation dimensions (out-source)

• Use template and substrate boards

to fabricate individual layers

• Carefully glue layers together
• Solder on the packaged LNA and

add SMA port (include picture of where LNA sits / what final product looks like

17

Physical Testing

• Network analyzer

– Graphs S11,VSWR, return loss – Gain of LNA, Noise Figure

• Anechoic chamber

– Beam pattern – Gain

18

Expected Results: VSWR

Image taken from: Erik Zeliasz, Greg Zomcheck. “SDARS Front-End Receiver: Senior Capstone Project Report.” Bradley University Department of Electrical Engineering, May 13, 2001. p.

Simulated VSWR of a linearly polarized patch antenna. VSWR measures the degree of input impedance match to 50 Ohms 19

Expected Results: S11

• Measures return loss at a

center frequency of 1.9 GHz

20

Graph taken from source: Vajha, Sashidar. “A Proximity Coupled Active Integrated Antenna.” Bradley University, 2000. p.26

Expected Results: Input Impedance

21

Graph taken from source: Vajha, Sashidar. “A Proximity Coupled Active Integrated Antenna.” Bradley University, 2000. p.26

• No matching circuitry

Equipment

• Anechoic Chamber
• HP 8722C Network Analyzer
• RF fabrication machines
• CAD with Momentum
• Spectrum Analyzer

22

Schedule

1/23 – 1/26 1/27 – 2/2 2/3 – 2/9 2/10 – 2/16 2/17 – 2/23 2/24 – 3/1 3/2 – 3/8 3/9 – 3/15 3/16 – 3/22 3/23 – 3/29 3/30 – 4/5 4/6 – 4/12 4/13 – 4/19 4/20 – 4/26 4/27 – 5/3 Design Simulation/optimization (linearly polarized antenna) Simulation/optimization (circularly polarized antenna) Fabricate Antenna and testing Fabricate LNA board and testing Incorporate both the antenna and LNA and test integrate with commercial receiver and test Presentation and Final Project Report

23

Questions

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