Applied RF Techniques I

Course 001

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Switching from traditional circuit definitions based on voltages and currents, to power-flow concepts and scattering parameters, this course offers a smooth transition into the wireless domain. We review S-parameter measurements and applications for both single-ended (unbalanced) and balanced circuits and have a brief introduction to RF systems and their components.
Impedance matching is vitally important in RF systems and we use both graphical (Smith Chart ) and analytical techniques throughout the course. We also examine discrete and monolithic component models in their physical forms, discussing parasitic effects and losses, revealing reasons why circuit elements behave in surprising manners at RF.
Filters, resonant circuits and their applications are reviewed through filter tables and modern synthesis techniques, leading into matching networks and matching filter structures. Since wires and printed circuit conductors may behave as transmission line elements, we also cover microstrip and stripline realizations. 2D and 2,5D electromagnetic field simulators are used in the course to illustrate transmission line behavior and component coupling effects. Also included is a discussion on mmWave ( mmW ) transmission line techniques.
In the area of active circuits, we first examine fundamental limitations posed by noise and distortion. The next topic is small-signal linear amplifier design, based on scattering parameter techniques, considering input/output match and gain flatness RF stability is examined both with S-parameters and also with the Nyquist test using nonlinear device models. Since DC biasing affects RF performance, we review active and passive bias circuits and see how they can be combined with impedance matching circuits. Another important consideration is circuit layout, therefore we look at problems caused by coupling, grounding and parasitic resistance. Narrow- and broadband designs are compared, using lossless and lossy impedance matching as well as feedback circuits. Low-noise amplifier design is illustrated, discussing trade-offs among gain flatness, noise, RF stability, and impedance match. Harmonic and inter-modulation performance is also examined. Performance trade-offs of balanced amplifiers are viewed. The course concludes by examining large-signal and ultra wideband feedback amplifiers.

Students are encouraged to bring their laptop computers to class. The design software available for use in this public course is from NI (formerly AWR).

Learning objectives

Upon completing the course you will be able to:

  • Describe RF circuit parameters and terminology.
  • State the effects of parasitics on circuit performance at RF.
  • Use graphical design techniques and the Smith Chart.
  • Match impedances and perform transformations.
  • Design filters with lumped and distributed components.
  • Perform statistical analysis: design centering, yield optimization.
  • Predict RF circuit stability and stabilize circuits.
  • Design various RF amplifiers: small-signal, low-noise, and feedback.

Target Audience

The course is designed for practicing engineers who are involved with the production, test, and development of RF/Wireless components, circuits, sub-systems, and systems, from HF to mmWave. It is equally useful to new engineers and to those who may have practical experience but have not had the opportunity of getting a thorough foundation in modern RF circuit and component integration techniques..

Engineering degree or at least three years applicable practical experience is recommended.


Day One

Introduction to RF Circuits
 • Linear circuit analysis in RF systems • Frequency range of coverage • Log conversion, dB and dBm scales • Complex numbers in rectangular and polar form • Component Qs • Importance of Impedance Matching • Normalization • RF component related issues
CAE/CAD Applications
 • Computer Aided Design Methods • Major Optimization Methods in Microwave CAD • Network Synthesis Procedure • Physical Limitation on Broadband Impedance Matching • Electromagnetic (EM) Simulation • Reliability and Yield Considerations • Monte Carlo Simulation
RF/MW Fundamentals
 • Complex impedance and admittance systems • Resonance effects • One-port impedance and admittance • Series and parallel circuit conversions • Lumped vs. distributed element representation • Characteristic impedance and electrical length • Signal transmission/reflection and directional couplers • Key parameters - Gamma - mismatch loss - return loss - SWR • Impedance transformation and matching • Illustrative exercise
The Smith Chart and Its Applications
 • Polar Gamma vs. Rectangular Z plots • Impedance and Admittance Smith Charts • Normalized Smith Charts • Lumped series/parallel element manipulations • Constant Q circles • Expanded and compressed Smith Charts • Impedance and admittance transformations • Transmission line manipulations • Illustrative examples
Scattering Parameters
 • Review of one-port parameters • Two-port Z-, Y-, and T-parameters • Cascade connections and de-embedding • S-parameters of commonly used two-ports • Generalized S-parameters • Illustrative examples • Mixed-mode S-parameters

Day Two

Impedance Matching Techniques
 • Power-flow in two-port networks • Transmission zeros, LC network order • Maximum power transfer from Z1 to Z2 • Single LC-section impedance matching • Bandwidth and parasitic considerations • Wideband match -- low circuit-Q • Narrowband match -- high circuit-Q • Illustrative examples
Lumped RF Component Models
 • Resistors • Inductors • Effective Inductance and Q Variations • Capacitors • Effective Capacitance and Q Variations • Primary self-resonance variations • Definitions of Magnetic Properties • Magnetic Core Applications • Ferrite Bead Impedance • Exercise: Complex Impedance Matching

Day Three

Transmission Lines and Ground Parasitics
 • Via-Hole and Wrap-Around Ground Inductance • Parasitic Inductance and Capacitance Effects at RF • Multilayer PC-Board Parasitics • PCB/Interconnects • Open Stub Effects in Differential Vias • PC Board Materials • Transmission Line Realizations - RF to mmWave • Transmission Line Discontinuities • Converting an Electrical Circuit to Physical Form
Filters and Resonant Circuits
 • Introduction • Recipes for lumped-element filters • Parasitic loss and Q factor • Impedance inverters • Band pass filters with resonant structures • Piezoelectric filters

Day Four

Active Circuit Fundamentals
 • Linear circuit definition • Amplifier Performance Limitations • Thermal Noise Definition • Harmonic Distortion Definitions • Gain Compression • Intermodulation Distortion • Spurious-Free Dynamic Range • Error Vector Magnitude • Various Power Gain Definitions • Testing for RF Stability • Causes of RF Oscillation • Typical Stability Circles for an RF Transistor • RF Stabilization Techniques • Nyquist Stability Analysis
Small Signal Amplifier Design
 • Transducer Gain Expression • Simultaneous Conjugate Match for Maximum Gain • Class Exercise • Two-stage Amplifier Design for Gmax • Gain Definition - Block Diagram • Operating Gain Definitions • Operating Gain Circle Application • Maximizing Output Power • Available Gain Definitions • Available Gain Circles

Day Five

Low Noise Amplifier Design
 • Sources of RF noise • Noise Factor and Noise Figure definitions • Noise of cascaded stages • Two-port noise parameters • Low-noise design procedure • Illustrative example
Broadband Amplifiers
 • Broadband Concepts • Wideband Amplifier Design Overview • Voltage Gain Phase Shift • Gain Control and Impedance Matching in Feedback Amplifiers • Series and Parallel Feedback Applications • 10-4000 MHz Feedback Amplifier Design • Equivalent Circuit for Microwave FET • Lumped Transmission Line and Distributed Amplifier • Mitigating Cdg: the Cascode