TECHNOLOGY FOCUS
Whether used for radar or communications, microwave and millimetre wave radio systems and the signals within them are becoming increasingly complex, with the boundary between digital and analog processing moving ever closer to the antenna.
This course will help you to design and piece together the elemental building blocks of wireless RF systems for optimal performance. Using powerful system simulation tools, you will gain insight into signals in microwave communications systems, how they behave and can become corrupted, and how this impacts overall performance.
In doing this, we will explore both circuits and systems. RF circuits are typically designed to meet power, efficiency, gain, linearity and noise specifications; whereas the Radio System itself is driven by complex modulated signals and must be designed to meet specifications like bit error rate, dynamic range, and minimum detectable signal in the presence of interferers. Between two such radios, the communications link itself must achieve a given bit rate, consume minimal bandwidth, not interfere with other systems, and cover a certain distance.
Through understanding the interactions between circuits, and through detailed simulation of both circuits and systems, and modelling the link, we will understand how to design circuits and systems to meet all levels of performance specification.
COURSE CONTENT
This 5-day course starts with a review of basic communications theory, and from the top down gradually builds the picture of how a radio (or radar) receiver and transmitter system can be designed to achieve wireless communications.
At the communications link level, we will see how link distance, antenna gain, and signal thresholds can be traded off against each other; and how channel bandwidth improves the link capacity in spite of elevating the receiver noise floor.
We will focus on examining trade-offs in the design of wireless systems themselves, and show how to seamlessly move between both the circuit and system level in radio transceivers and other RF systems. We do this by looking at typical radio architectures, exploring the design compromises, and simulating at both the circuit and system level. The course treats digitally coded signals in RF and IF components, and explores the compromises that are inherent in the design of a radio transceiver. For example, a receiver needs to minimize interference from nearby unwanted stronger signals and allow detection of a desired signal in noise. For the transmitter, avoiding corruption of other signals sharing adjacent spectrum is critical. Filtering might seem to provide the best solution, but we look in more detail at what other complications this creates.
In wireless LAN for instance, we will see how tradeoffs in signal modulation and multiplexing (i.e. OFDM) made to improve performance in some parts of the system, such as multipath reception, have placed tight constraints on other parts of the system, such as the linearity and efficiency of the transmitter. We will interactively simulate a double super-heterodyne, dual-band radio receiver, a direct conversion receiver, and an I-Q modulator and transmitter, as well as various components that make up these systems. This provides the opportunity to explore 'what if?' scenarios. We will also get "inside" the circuits themselves for a greater understanding of how each component works, and contributes to overall system performance.
To benefit most, bring your own laptop computer and, prior to attending, obtain a free trial license of the Visual Systems Simulator (VSS) from AWR at www.awrcorp.com.
On completion of the course, you will be:
- Able to choose a system architecture and specify the best types of circuits to meet given system requirements
- Fully conversant with how RF system architectures work, how they are implemented, and the challenges to watch for
- Able to simulate various types of RF and IF systems and circuits, and model component interactions
- Familiar with microwave and RF subsystems such as amplifiers, mixers, and oscillators
- Familiar with the physical layer specifications of an RF wireless system, and understand how the key system parameters relate to RF hardware and the communications link itself
- Able to understand and write critical RF specifications for wireless communications systems
- Comfortable with reading integrated circuit data sheets for wireless systems, their architecture, and specifications
WHO SHOULD ATTEND
This course begins with a revision of communications and is suitable even for those new to system design. It will be most helpful for engineers with some background in electronic circuits already, but who may be wishing to move into microwave system design, or for those who wish to become systems engineers.
The course is suitable for engineering managers, design engineers, and experienced test and production engineers. Course participants will most likely work for systems integrators, prime contractors, telcos, defence organisations, or in emerging ‘new space’ industries.
Past participants who have benefitted most are those who arrive with an area of detailed expertise and leave with a much broader appreciation of microwave systems.
Day 1
Radio Systems and Digital Communications
We start at the top, by reviewing digital wireless communications and a variety of modulation formats, and the tradeoffs between capacity, bandwidth, signal power, and noise.
- Revision of Communication and Information Theory Principles
- Coding and Modulation Formats
- Baseband Filtering and Impact on Signal Constellation
We then look at the elemental building blocks that make up a system – amplification; frequency generation; frequency translation; and filtering, and see how these can be assembled in typical receiver and transmitter architectures to achieve communications functionality.
- Typical Receiver System Architectures - Direct Conversion, Superheterodyne, Dual Conversion Superheterodyne
Day 2
Today we consider a simplified form of the air-interface specification for a common RF system. This describes the overall radio system requirements and enables multiple system operators to co-exist and interoperate. We will define and examine the key system parameters that have to be measured - parameters such as noise, distortion, sensitivity, selectivity, and interference. We also examine how the IF frequency is chosen.
Characterization of Receivers
- Noise in Receivers
- Selectivity, Sensitivity and Minimum Detectable Signal
- Nonlinearities and Third-Order Intermodulation Distortion
- Reception in the Presence of Interferers
- Dynamic Range and How to Improve It with AGC
Characterization of Transmitters
- Power and Harmonic Distortion
- Spurious Products
- ACPR, Spectral Regrowth and Linearity with Different Modulation Formats
- Efficiency
Frequency Selection
- The Image Frequency
- Choosing the Correct Intermediate Frequency
Day 3
Today we will see how system performance parameters can be met by assembling a number of components. We will turn to their data sheets to discover how each is characterized, and examine the tradeoffs involved in selecting them. We will extract key defining features that describe the behaviour of each circuit, and then simulate both the component and the system in the systems simulator.
Systems Simulation - Behavioral Modeling
Simulation of a Dual-band CDMA Superhet Radio Receiver
- Spreadsheet-based Linear Systems Analysis
- Calculation of Sensitivity and Dynamic Range
- Systems Simulation to Compare with Linear Analysis
- Using AGC to Increase the Dynamic Range
- Effect of Changing the Gain, Intercept Point, and Filtering
We now start to explore how the key RF functions of amplification, frequency synthesis (oscillation), and frequency translation (mixing) are achieved at the circuit level. We begin with various ways to change frequencies.
Mixers
- Spurious Analysis
- Image Reject and Single Sideband Mixers
- I-Q Modulators and the Importance of Quadrature
- Basics of Mixer Design and typical mixer problems
Day 4
Today we continue the detailed design process and explore some of the key tradeoffs in design, for example, between the power, efficiency, and linearity in a transmitter, and how to model these tradeoffs. We will focus on discrete design and review some IC designs of frequency generators (oscillators) and signal amplifers.
Oscillators
- Basic Concepts of Oscillator Design
- Deriving the VCO Tuning Curve and Explaining Mode Hopping
- Phase Noise in Oscillators and its Impact on Communications Systems
- Calculating Allowable Phase Noise from System Specifications
Power Amplifiers
- Design Tradeoffs between Linearity, Power, and Efficiency
- Classes of Amplifier Operation
- Simulation of Spectral Regrowth with Different Modulation Formats
Day 5
Finally, we look at putting everything together, including the modelling of a complete communications link. We will consider a variety of challenges facing the systems designer; we examine some 'real' air interface specifications, and we work an example of the complete design process, from air interface specification through to circuit design.
The Link Budget
- Modelling a communications link and understanding the tradeoffs
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Characterising a receiver by G/T and a transmitter by its EIRP – and understanding why these measures are useful
Noise in more detail
- Reconciling the treatment of noise – terrestrial communications and space communications
Simulation of a Direct Conversion Receiver
- Trade-off between Modulation Scheme, Data Rate, RF Bandwidth, Channel Filter, Power, Noise, Phase Noise, and Bit-Error Rate
Interpreting Air Interface Specifications
- CDMA Air Interface Specifications (Narrowband and Wideband) (if time permits)
Review of some technical papers
- Design Considerations of Typical Wireless GaAs and CMOS Chip Sets
Said about the course from previous participants:
"Interactive teaching, good with simulations examples."
"Simulations and workshops are refreshing to have."
"Very good mix between system point of view and circuit / schematic point of view - very useful for my daily work."
"Very good notes for reference after the course."
Dr Rowan Gilmore and his colleague Dr Les Besser have written two books that they recommend, however, the books are not compulsory for the course:
Publisher: Artech House
Title: Practical RF Circuit Design for Modern Wireless Systems
Volume I: Passive Circuits and Systems
ISBN 1-58053-521-6 (2003)
Title: Practical RF Circuit Design for Modern Wireless Systems
Volume II: Active Circuits and Systems
ISBN 1-58053-522-4 (2003)
Students may order the books over the Artech House website, http://www.artechhouse.com and receive a 15% discount by entering the promotion code "CEI" in the online order form.