Advanced Array Antennas: Conformal Arrays and Digital Beamforming

We recommend you to submit your preliminary or firm registration at least 4 weeks before course start to ensure a seat on the course.

TECHNOLOGY FOCUS
The demand for evermore-sophisticated information from communication and radar systems leads to concomitant requirements on antenna performance. Conformal array antennas and digital beamforming are emerging technologies that can meet these demands.
Conformal arrays, i.e. array antennas on curved surfaces, are suitable for integration on various vehicles: cars, aircraft, satellite bodies, etc. They can provide wide angular coverage, which makes them attractive for several communication and surveillance applications. With modern high-density packaging of microelectronic components a complete antenna system can be made as a thin multilayer design, a "smart skin".
Digital beamforming is a powerful technique to enhance antenna performance. DBF arrays digitize the received signals at the element level, thus preserving the total information available at the aperture, and then process these signals in the digital domain to form the desired beams. Microwave ICs, high-speed digital electronics and signal processors are now making DBF practical in many applications such as fast adaptive interference rejection, high resolution direction finding, ultra-low sidelobes, and various forms of adaptive space-time processing, both for communication and radar (incl. MIMO systems).

COURSE CONTENT
This course spans a range of technologies significant for the development of advanced antenna systems. Arrays on curved surfaces are compared with traditional planar arrays. Practical conformal array configurations are presented taking examples from base stations, radar, and satellite communication applications. Basic DBF systems are contrasted with analog beamforming systems. Typical DBF applications, their components and system architectures, are reviewed. We discuss applications where both DBF and conformal antenna technology are likely to be combined in future antenna systems.

WHO SHOULD ATTEND
This course is aimed at engineers, scientists and managers involved in design, planning or use of array antennas and antenna systems. The focus is on advanced and new concepts with antenna elements on non-planar surfaces and modern antenna related signal processing. Some knowledge of traditional antenna technology is expected. However, key aspects of electromagnetic theory, conventional (planar) array antennas, and signal processing will be reviewed in order to introduce important concepts and notations.

Monday - JOSEFSSON/PERSSON
Conformal Array Antennas 
Basic concepts are reviewed to establish a common understanding of important characteristics and definitions. Array antennas in general are discussed, starting with linear and planar arrays.

• Radiation Mechanisms, Antenna Impedance
• Mutual Coupling Effects, Bandwidth, Beam Steering Performance
• Applications

Circular Array Antennas
The circular array can be seen as a building block of many conformal antennas, e.g. arrays on cones and cylinders. We give examples of typical pattern performance and bandwidth limitations.

• Design Rules
• Phase Modes and Pattern Characteristics
• Suppression of Harmonic Radiation

Computational Methods for Conformal Antennas 
We discuss commonly used methods for analyzing conformal antennas to get a physical understanding rather than specific details of the different methods. Canonical examples are given.

• Modal Solutions, MoM, FEM, and FDTD
• Asymptotic and Hybrid Methods
• Geodesics

Tuesday - PERSSON /JOSEFSSON 
Conformal Array Characteristics 
General characteristics of conformal array antennas are reviewed. Canonical array designs and expected performances are discussed.

• Mechanical Aspects, Active Surface Definition
• Phase Scanning, Commutating
• Grating Lobes, Tapering, Element Impedance Variations

Singly Curved Array Antennas 
Their characteristics are discussed, using wave-guide-fed apertures and microstrip-patches as examples. The focus is on mutual coupling and its effect on radiation characteristics.

• Mutual Coupling vs. Surface Shape
• Embedded Element Patterns
• Dielectric Radome Effects

Doubly Curved Array Antennas

• Polarization and Element Distribution
• Mutual Coupling and Radiation Properties

Polarization

• Cross Polarization Effects, Definitions
• Sources of Cross Polarization in Curved Arrays
• Controlling Cross Polarization

Analog Beamforming (ABF) 
ABF and beam scanning principles for conformal array antennas are presented. Analog solutions for beam steering, multiple beam generation, and commutating the active sector are discussed.

• Feed Networks, Matrix Feed Systems
• Quasi-Optical Feeds

Wednesday - PERSSON /JOSEFSSON/STEYSKAL 
Conformal Array Synthesis and Design
Pattern synthesis is just the starting point in a design problem.

• Conformal Array Shape Optimization
• Pattern Synthesis: Linear vs. circular arrays
• Accounting for Mutual Coupling

Conformal Array Antenna Scattering 
Radar Cross Section (RCS) characteristics of conformal antennas are presented, incl. scattering vs. radiation performance trade-off.

• Scattering Cross Section
• Impedance Load Effects and Curvature Effects

Demonstration of Analysis and Design

• Theoretical Design Using Software Tools
• Practical Design Examples

Digital Beamforming (DBF): System and Components
A generic DBF receiver system and the effects of the subsystems on overall system performance will be discussed. Basic system parameters are defined and present commercial component performance indicated.

• Review of Sampling Theory and Channel Capacity
• Receivers, A/D Converters, Digital Beam Former, Beam Controller, Calibration Networks
• DBF in the Transmit Mode, Direct Digital Synthesis (DDS)

Typical DBF Applications 
Several of the unique capabilities of DBF will be discussed.

• Review of Matrix Algebra
• Signal Processing Approach to Array Calibration
• Spatial Multiplexing

Thursday - STEYSKAL 
Typical DBF Applications (cont´d)

• Array Element Decoupling
• Open- Loop Adaptive Interference Suppression
• Direction of Arrival Estimation
• Basics of Multiple Input, Multiple Output (MIMO) Systems

Partial DBF and Sub-arraying Architectures, DBF Systems 
Trade-offs between DBF system performance and cost.

• Periodic and Random Sub-Arrays, Thinned and Wideband Arrays
• Experimental DBF Systems with Planar and Conformal Arrays

Said about the course from previous participants:
"Very skilled instructors."
"Well-organized, interesting topic, good ratio teachers/students."
"Very good illustrative examples and situations."
"The material is well updated and latest development was covered and mentions."
"Complete overview of conformal antennas including design, math, hardware and signal control"