Wide Band Antenna Array for Synthetic Aperture Radar Applications

Table of Contents

Chapter 1 :Introduction

1.1. An Overview

1.2 Organization of the Thesis

Chapter 2: Antenna Arrays for Land-Imaging SAR Systems Application Requirements and Methods of Beam Shaping

2.1 Introduction

2.2 Electromagnetic Wave Polarization

2.2.1 Elliptically Polarized Fields

2.2.1.1 Polarization Ellipse

2.2.2 Linearly Polarized Fields

2.2.3 Vertical and Horizontal Polarizations for Polarimetric SAR Systems

2.2.4 Circularly Polarized Fields

2.2.4.1 Simple Method to Produce Circular Polarization

2.3 Atmospheric Propagation Impairments of Land-Imaging SAR

2.3.1 Effect of the Ionosphere

2.3.2 Effect of the Troposphere

2.4 Operation of the Side-Looking SAR System

2.4.1. Range Resolution in Case of Uncompressed Pulse

2.4.2. Azimuth Resolution

2.4.3 Simplified Calculation Of The Pulse Reptition Interval

2.4.4. Pulse Compression using Linear Frequency Modulation (LFM)

2.5. Requirements of Polarimetric SAR Antenna Arrays

2.5.1. Operational Frequency Bands for Commercial Land-Imaging SAR Systems

2.5.2 Requirements of Antenna Arrays for Land Imaging

2.5.3 Requirements of Antenna Arrays for Image Download to Ground Stations

2.6. Antenna Arrays for Commercial Space-Borne Land-Imaging SAR Systems

2.6.1 Antenna Array of the Spaceborne ‘RADARSAT-2’ SAR System

2.6.2 Antenna Array of the Spaceborne ‘SEOSAR/PAZ’ SAR System

2.6.3. Circularly Polarized PolSAR Antenna Arrays Proposed for Land Imaging

2.6.4. Antenna Arrays for PolSAR Image Data Download to Ground Stations

2.7 Beam Shapes for Spaceborne SAR and Satellite communications

2.7.1 Beam Shape for Isoflux Radiation from LEO Satellites

2.7.2 Cosecant-Squared Beam

2.7.3 Flat-Topped Beam

2.8 Optimization Techniques for Antenna Array Pattern Synthesis

2.8.1 PSO for Antenna Array Pattern Synthesis

2.8.1.1 Iterative Algorithm for the PSO

Chapter 3: Microstrip Patch Antennas for SAR Arrays and Satellite Communications

3.1. Introduction

3.2 Design of Rectangular Microstrip Patch Antenna

3.2.1 Linearly Polarized Microstrip Patch Antenna

3.2.2 Circularly Polarized Microstrip Patch Antenna

3.3 Wide Band U-Slotted Rectangular Patch Antenna for Linear Polarization

3.3.1 U-Slotted Patch Antenna Fed by Straight Probe

3.3.2 U-Slotted Patch Antenna fed by an L-shaped Probe

3.4 Truncated-Corner Microstrip Square Patch Antenna for Circular Polarization

3.4.1 Mechanism of Producing Circular Polarization for truncated corner

3.4.2 Controlling the sense of polarization

3.5 Corner-Slotted Microstrip Square Patch Antenna for Circular Polarization

3.5.1 The Mechanism of Producing Circular Polarization for the corner slotted

3.6 Compact Dual Band Dual Polarized Square Microstrip Antenna

3.7 Mutual Coupling between Microstrip Patch Antennas

3.7.1 Mutual Coupling between U-Slotted Patch Antennas

3.7.2 Mutual Coupling between Truncated-Corner Patch Antennas

3.8 Results and Discussions

3.8.1 U-Slotted Patch Antenna over Foam Substrate

3.8.1.1 U-Slotted patch antenna over foam substrate fed by a straight probe

3.8.1.2 U-Slotted patch antenna over foam substrate fed by the L-shaped probe

3.8.2 U-Slotted patch Antenna over FR4 Substrate

3.8.3 Truncated-Corners Microstrip Patch Antenna

3.8.3.1 Current distribution on the surface of a microstrip patch

3.8.3.2 Frequency band of the truncated-corners patch antenna

3.8.3.3 Experimental assessment of the truncated-corners patch antenna

3.8.3.4 Radiation patterns of the circularly polarized fields for the truncated corners patch

3.8.4 Corner-Slotted Microstrip Patch Antenna

3.8.4.1 Frequency band of operation of the corner-slotted patch antenna

3.8.4.2 Radiation patterns of the circularly polarized fields for the corner-slotted patch antenna

3.8.4.3 Dimensional parametric studies for the corner-slotted antenna

A. Effect of varying the length Ls of the axial slots

B. Effect of varying the length Lsc of the L-shaped corner slots

C. Effect of varying the width of the axial slot ws

D. Effect of varying the width of the L-shaped corner slot wsc

E. Effect of varying distance ts of the corner slots from the edge

3.8.5 Compact Dual Band Dual Polarized Square Microstrip Antenna

3.8.5.1 Frequency band of operation of the corner-slotted dual band dual polarized patch antenna

3.8.5.2 Radiation patterns of the dual polarized fields for the dual-fed corner slotted patch antenna

3.8.5.3 Dimensional Parametric study for the dual-polarized patch antenna

3.8.6 Mutual Coupling between Microstrip Patch Antennas

3.8.6.1 Mutual coupling between adjacent U-slotted patch antennas

A. Mutual Coupling between Straight-Probe Fed U-slotted patches over Foam Substrate

B. Mutual coupling between L-probe Fed U-slotted Patches over foam substrate

C. Mutual coupling between straight probe U-slotted Patches over FR4 substrate

A. Radiation Patterns of Two-Element Array of U-Slotted patches over Foam Substrate

B. Radiation Patterns of Two-Element Array of U-Slotted Patches over FR4 Substrate

3.8.6.2 Investigation of adjacent Circularly Polarized Truncated-Corners Patch Antennas

A. Mutual Coupling between two adjacent patches

B. The axial ratio of the radiated fields for two-element arrays of truncated corners patch antenna

C. Radiation Patterns of Two-Element Array of Truncated-Corners Patch Antennas

Chapter 4: Shaped Beam Linear Arrays for High Resolution SAR and Satellite Communications

4.1. Introduction

4.2 Radiation Pattern of the Linear Array

4.3 PSO Algorithm for Beam Shaping using Linear Arrays of Point Sources

4.4 Numerical Results and Discussions

4.4.1 Application of PSO to Synthesize Beams for SAR and Satellite Communications

4.4.1.1 Flat-topped Beam Synthesized by Linear Arrays of Point Sources

A. Beam Steering

B. Beam Shaping

4.4.1.2 Isoflux Beam Synthesized by Linear Arrays of Point Sources

A. Isoflux Beam for GEO Satellite Antenna

B. Isoflux Beam for LEO Satellite Antenna

4.4.1.3 Cosecant-Squared Beam Synthesized by Linear Arrays of Point Sources

4.4.1.4 Summary of the excitation coefficients distributed over the linear array elements to produce flat-topped, isoflux and cosecant-squared beams

4.4.2 Effect of the Linear Array Dimensions and Optimization Parameters on the Accuracy of the Synthesized Beam

4.4.2.1 Effect of the Inter-Element Separation

4.4.2.2 Effect of the Number of Elements

4.4.2.3 Effect of the Weighting Coefficients of the Cost Function

4.4.4 Beam Shaping using Linear Arrays of U-Slotted Microstrip Patches

4.4.4.1 Isoflux beam for uniform coverage by GEO satellite using a linear array of U-slotted patches on foam substrate

A. The linear array of U-Slotted patches with straight-probe feeding for GEO satellite

B. Linear array of U-slotted patches with L-probe feeding for GEO satellite

4.4.4.2 Isoflux beam for uniform coverage by LEO satellite using a linear array of U-slotted patches on foam substrate

A. A linear array of U-slotted patches with straight-probe feeding for LEO satellite

B. A linear array of U-slotted patches with L-probe feeding for LEO satellite

A. Linear array of U-slotted patches on foam substrate with straight-probe feeding

B. Linear array of U-slotted patches on foam substrate with L-probe feeding

C. Linear array of U-Slotted patches on FR4 substrate with straight-probe feeding

4.4.4.4 Linear Arrays of U-Slotted Patches for Cosecant-Squared Beam

A. A linear array of U-slotted patches on foam substrate with straight-probe feeding

B. Linear array of U-Slotted patches on foam substrate with L-probe feeding

C. A linear array of U-Slotted patches on FR4 substrate with straight-probe feeding

4.4.5 Beam Shaping Using Linear Arrays of Circularly Polarized Patch Antennas

4.4.5.1 Cosecant-squared shaped beam

4.4.5.2 Flat-top shaped radiation pattern

Chapter 5: Shaped Beam Planar Arrays for High Resolution Land-Imaging SAR Systems

5.1 Introduction

5.2 Application of the PSO Algorithm to Planar Arrays

5.3 Results and Discussions

5.3.1 Three-Dimensional Beam Synthesis using Planar Arrays for side-looking SAR systems

5.3.2 Planar Arrays of Linearly Polarized Patch Antennas for Side-Looking SAR System

5.3.3 Planar Arrays of Circularly Polarized Patch Antennas for Side-Looking SAR System

5.3.4 Planar Arrays of Dual-polarized Patch Antennas for Side-Looking SAR System

Chapter 6

6.1. Introduction

6.2 Turnstile Antennas for Circular Polarization

6.2.1 Four-Dipole Turnstile Antenna in Free Space

6.2.2 Four-Dipole Turnstile Antenna above Ground Plane

6.2.3 Four patch Turnstile Antenna for Circular Polarization

6.3 Linear Arrays of Overlapped Turnstiles for Shaped Beam with Circular Polarization

6.3.1 The Linear Array of Two Overlapped Four-Dipole Turnstiles in Free Space

6.3.2 Linear Array of Four-Dipole Turnstiles in Free Space

6.3.3 Linear Arrays of Four-Dipole Turnstiles above Conducting Plate

6.3.4 Two Overlapped Turnstiles of Four U-slot patches

6.3.5 Linear Arrays of Overlapped Turnstiles of U-slotted patches

6.4 Planar Arrays of Turnstile Subarrays for Shaped Beam with Circular Polarization

6.5 Results and Discussions

6.5.1 Four-Dipole Turnstile Antenna

6.5.2 Effect of The Turnstile Array Radius on the Radiation Characteristics

6.5.3 Four-Dipole Turnstile above a Conducting Plate

6.5.4 Turnstile of Four U-slotted Patch Antennas

6.5.5 Two-Element Array of overlapped Four Dipole Turnstiles

6.5.6 Two-Element Array of Overlapped Turnstiles of Four U-slotted patches

6.5.7 Linear Array of Overlapped Four Dipole Turnstiles

6.5.8 Linear Array of Four-Dipole Turnstile Subarrays above a Conducting Reflector

6.5.9 Linear Arrays of overlapped Turnstiles of U-slotted patches

6.6 Planar Array of overlapped Turnstiles of Four Dipoles for Circular Polarization

6.6.1 Isoflux Shaped Beam

6.6.2 Cosecant Squared/Flat-topped Beam for Side looking SAR

6.7 Planar Arrays of overlapped Turnstiles of U-slotted Patches for Shaped Beam with Circular Polarization

Chapter 7: Shaped Beam Antenna Arrays with Circular Polarization for Land- Imaging SAR

7.1. Introduction

7.2 Circular Arrays of Printed Antennas

7.3 Radiation Pattern of Concentric Circular Arrays

7.3.1 Radiation Pattern of A Circular Array

7.3.2 Radiation Pattern of Multiple Concentric Circular Arrays

7.3.3 Concentric Circular Arrays for Circularly Symmetric Radiation Pattern

7.4 Application of PSO for Shaping the Beam of Circular Arrays

7.4.1 Application of the PSO to A Circular Array

7.4.2 Application of the PSO to Multiple Concentric Circular Arrays

A. Computational Improvement of the PSO Algorithm

7.5 Results and Discussions

7.5.1 Circular Array of Truncated-Corner Microstrip Patches for Directive Beam with Circular Polarization

7.5.1.1 Circular Arrays of Truncated–Corner Patch Antenna Elements for High Gain and Circular Polarization

A. Four-element circular array

B. Eight-element circular array

C. Sixteen-element circular array

7.5.1.2 Beamforming using A Circular Array

A. Flat-topped beam by a circular array of isotropic point sources

B. Flat-topped beam by a circular array of truncated-corner patches for circular polarization

7.5.2 Concentric Circular Arrays for Flat-Topped Beam with Circular Polarization

7.5.2.1 Flat-Topped Beam by Concentric Circular Arrays of Isotropic Point Sources

7.5.2.2 Concentric Circular Arrays of Truncated-Corners Microstrip Patches for Flat-Topped Beam with Circular Polarization

7.6.3 Concentric Circular Arrays for Isoflux Beam with Circular Polarization

7.6.3.1 Isoflux Beam Synthesized by Concentric Circular Arrays of Point Source Elements

7.6.3.2 Concentric Circular Arrays of Corner-Slotted Microstrip Patches for Isoflux Beam with Circular Polarization

Chapter 8: Conclusions and Suggestions for Future Work

8.1 Conclusions

8.2 Future Work

Research Goals and Topics

This work focuses on the development and optimization of wideband antenna arrays intended for Synthetic Aperture Radar (SAR) systems and satellite communications. The primary goal is to synthesize specific radiation patterns — such as flat-topped, isoflux, and cosecant-squared beams — to meet the high resolution and uniform coverage requirements of modern land-imaging SAR and LEO/GEO satellite missions. The research utilizes Particle Swarm Optimization (PSO) to determine optimal excitation coefficients, which are subsequently implemented in practical microstrip patch antenna arrays, including U-slotted, corner-slotted, and turnstile configurations.

• Application of Particle Swarm Optimization (PSO) for efficient beam shaping and steering.
• Design and performance assessment of various linearly, circularly, and dual-polarized microstrip patch antennas.
• Synthesis of three-dimensional radiation patterns using planar rectangular and circular arrays.
• Mitigation of mutual coupling effects in dense antenna array configurations through innovative feeding and overlap techniques.
• Experimental validation of fabricated prototypes for C-band and X-band radar and satellite communication systems.

Excerpt from the Book

Summary of Chapters

Chapter 1 :Introduction: This chapter provides an overview of the role of Synthetic Aperture Radar (SAR) in remote sensing and outlines the thesis structure and research objectives.

Chapter 2: Antenna Arrays for Land-Imaging SAR Systems Application Requirements and Methods of Beam Shaping: This chapter introduces the theoretical requirements for SAR antenna arrays and discusses atmospheric propagation impairments and methods for beam shaping.

Chapter 3: Microstrip Patch Antennas for SAR Arrays and Satellite Communications: The chapter details the design, fabrication, and performance of various microstrip patch antenna elements, including U-slotted and corner-slotted designs, focusing on impedance matching and bandwidth optimization.

Chapter 4: Shaped Beam Linear Arrays for High Resolution SAR and Satellite Communications: This chapter applies the Particle Swarm Optimization (PSO) algorithm to linear arrays of point sources and patch elements to synthesize specific radiation beams for SAR applications.

Chapter 5: Shaped Beam Planar Arrays for High Resolution Land-Imaging SAR Systems: This chapter extends the beam synthesis optimization techniques to planar arrays to achieve targeted 3D radiation patterns suitable for high-resolution side-looking SAR.

Chapter 6: This chapter explores turnstile antenna arrays and describes the methodology for creating planar arrays of overlapped turnstiles to achieve shaped beams with precise circular polarization.

Chapter 7: Shaped Beam Antenna Arrays with Circular Polarization for Land-Imaging SAR: This chapter addresses circular array configurations, detailing the synthesis of circularly symmetric beams and providing experimental validation results.

Chapter 8:Conclusions and Suggestions for Future Work: This chapter summarizes the key findings of the research and provides recommendations for prospective further investigations in the field of antenna array optimization.

Keywords

Synthetic Aperture Radar, SAR, Antenna Arrays, Microstrip Patch Antennas, Particle Swarm Optimization, PSO, Beam Shaping, Circular Polarization, Cosecant-Squared Beam, Isoflux Beam, Mutual Coupling, Satellite Communications, Turnstile Antennas, Land-Imaging.

Frequently Asked Questions

What is the primary focus of this thesis?

The thesis focuses on designing and optimizing wideband antenna arrays for Synthetic Aperture Radar (SAR) systems and satellite communication platforms to achieve specific radiation patterns.

What are the key thematic areas addressed in this work?

The key themes include antenna element design (U-slot, L-slot, turnstile), optimization algorithms for beam shaping (PSO), and the development of efficient planar and circular array configurations.

What is the main objective or research question?

The research aims to develop computationally efficient techniques using the Particle Swarm Optimization (PSO) algorithm to synthesize radiation patterns that satisfy the stringent requirement of high-resolution land-imaging SAR and continuous satellite communication coverage.

Which scientific methodology is primarily employed?

The work employs a multi-stage methodology involving electromagnetic simulation (using CST Microwave Studio and HFSS), combined with the Particle Swarm Optimization (PSO) algorithm, and culminating in the fabrication and testing of antenna prototypes.

What topics are covered in the main body of the work?

The main body covers the theoretical basis of polarization, the design of various microstrip patch elements, the application of PSO for beam synthesis in linear and planar arrays, and the development of turnstile arrays for circular polarization.

What are the characterizing keywords for this research?

Essential keywords include SAR, Antenna Arrays, Particle Swarm Optimization (PSO), Beam Shaping, Circular Polarization, and Microstrip Patch Antennas.

How does the PSO algorithm contribute to the computational efficiency of the array design?

The proposed method decomposes planar array optimization into linear array optimizations, which reduces computational complexity from proportional to N² parameters to only 2N parameters, significantly saving memory and time.

What practical improvements are suggested for future implementations?

Future work is suggested to involve the design of complex feeding networks to realize the calculated excitation amplitudes/phases and extending the PSO application to handle non-planar (cylindrical or spherical) array surfaces.