RF Power Amplifier Design Techniques

Course 222

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Online version available - See Course #289

Summary

Power amplifiers are crucially important in determining a communications system cost, efficiency, size, and weight. Designing high power / high efficiency amplifiers that satisfy the system requirements (bandwidth, linearity, spectral mask, etc.) is challenging. It involves difficult trade-offs, proper understanding of the theory, and careful attention to details. Additionally, designing, building, and testing power amplifiers usually pushes test equipment and lab components to their limits and frequently results in damage to the circuit or lab equipment. This course will examine the different aspects of this challenge with emphasis on practical tips to build power amplifiers successfully. This 4-day course will include thorough information on GaN power amplifiers. Differences between GaN pHEMT, Si LDMOS,GaAs MESFETs, and SiGe will be discussed.

The instructor uses CAD software to simulate design examples and presents them to the students.

Learning objectives

Upon completing the course you will be able to:

Learn the advantages and limitations of various technologies.
Gain an understanding of the pros and cons of various classes operations.
Learn how to characterize device for power amplifier design.
Acquire design know-how of high efficiency amplifiers.
Attain practical knowledge on the design of linear amplifiers.
Calculate the lifetime of power amplifiers in packaged and unpackaged assemblies.

Target Audience

Microwave engineers who want to design, fabricate, and test power amplifiers, in the 1-50 GHz frequency range, will benefit from this comprehensive design course. Basic knowledge of microwave measurements and transmission line (Smith Chart) theory is assumed.

Outline

Session 1 and 2 (Day 1)

Power amplifier Fundamentals

• Power basics: power factor, effect of match quality on output power and standing waves • Device technologies (GaN, GaAs, InP, Si, SiGe) and leading commercial/defense suppliers. • Device stuctures: MESFET, pHMET, HEMT, HBT, LDMOS. • Small signal model generation, frequency limits (ft, and fmax); theoretical and practical. • Power Amplifier Stability detection (even mode, odd mode); Freitag detection approach. • Optimum power load estimation, calculation, and simulation. • Load-pull characterization of devices (static, dynamic). • Device characteristics and non-idealities. • Dependence of transistor parameters on drive level. • Large signal models. • Power Amplifier biasing methods. • Bode-Fano limit. • Example: small signal model generation.

Session 3 and 4 (Day 2)

Conventional and High Efficiency Amplifier Design

• Power amplifier classes A, B, AB, C, and D; concepts, designs, and examples. • Waveform engineering for maximum efficiency. • Class E Switching mode power amplifiers: Concept, Design, Limitations, Maximum Frequency, Exercises, and Examples. • Class F (and F-1) power amplifiers: Concept, Design, Limitations, and Examples. • Comparison of various classes: efficiency, output power, and frequency limitations. • Effects of knee voltage, harmonic terminations, and nonlinearities. • Example: High efficiency power amplifier design.

Session 5 and 6 (Day 3)

Linearization Techniques and Signal Modulations

• Classical Modulation schemes: AM, FM, PM. • Modern Modulation: FSK, PSK, MSK, BPSK, QPSK, p/4-DQPSK, OQPSK, QAM, etc. • Distortions in power amplifiers. • Harmonic balance and time domain simulations. • Linear/Non-linear Memory effects; electrical and thermal memory effects. • Measures of Distortion: Third order intermodulation, ACPR, NPR, M-IMR, X-parameters. • Linearization techniques: Feed Forward, Predistortion, LINC, Cartesian Feedback, Reflect Forward, Envelope Elimination and Restoration, Cross Cancellation. • Comparison of Linearization Techniques. • Envelope tracking, Polar transmitters. • Real world design examples, challenges, and solutions.

Session 7 and 8 (Day 4)

Power Combing, Packaging, and Reliability

• Multistage amplifiers, inter-stage matching. • Push-pull, Balanced amplifiers, and Traveling Wave Combiners. • Power combining techniques (Corporate, Current, Wilkinson, Lange, Branch Line, Serial, Darwish, HiFET). • Package design (ceramic, plastic, PCB, metal composites and alloys). • Thermal management and reliability calculations. • Biasing and transient considerations. • Example: calculating required biasing for 20+ year lifetime. • Example: Design of a power combiner. • Example: Design of a high efficiency power amplifier class F.

Subject Areas:

RF Power Amplifier Design

Really enjoyed the course and the hands-on software work. Printed take home materials will be a good reference guide. K.K.

-Best Besser course so far (I have attended three). - Great material, very thorough and easy to refer to. - Technical details, examples, topics covered. - A semester in 3 days! V.G.H.

I liked the balance between lecture and hands-on exercises. He was fully knowledgeable to cover all course material and answered questions from the course.

Very methodical instructor and not a lot of emphasis on derivations/math. He provided numerous practical insights. He made sure the class was attentive at all times.

In general, a lot of effort is dedicated by the instructor towards developing this excellent course. A lot of technical information, experience, and literature review are clearly stated through the presentation. Very impressed by the broad knowledge of the instructor in covering almost all areas with regards to RF power amplifiers. M.A.

The instructor is equipped with great knowledge and showed full respect to us. He also provides his past experience tips, pitfalls and wisdom. It certainly was an awesome lecture. I have learned so much within a short period of time and I would recommend others to take this course as well. F.B.