# ELT-47206 Basics of RF Engineering, 5 cr

#### Person responsible

Mikko Valkama, Olli-Pekka Lunden

#### Lessons

Implementation | Period | Person responsible | Requirements |

ELT-47206 2019-01 | 4 |
Toni Björninen Jari Kangas |
Student must pass the exam or alternatively a set of tasks. A compass and a set square with degrees scale (harppi ja kulmaviivain in Finnish) may be needed in the exam. |

#### Learning Outcomes

Upon completion of this course, students are able to solve theoretical problems that relate to practical applications of RF engineering, transmission line theory, and high-frequency circuit analysis. Students are able to make meaningful use of the core contents, (the RF concepts, tools, and definitions listed below), both in conventional and new situations. Students are not expected to memorize anything by heart. The competence this course provides is general and valid in and applicable to all sub-diciplines in RF engineering, be it wireless communication, RFID, RFIC, IoT, high-speed mixed signal design, automotive applications, radar, EMC, medical applications etc. It is not restricted strictly to any frequency ranges, or end user applications either. It is impossible to exactly and in detail list all the things students are expected to master in order to pass the course. However, an EXAMPLE that follows should help understand the nature of the requirements: After completing the course, students are able to find the input impedance of a 100-ohm transmission line (with given electrical length) that is terminated to an antenna whose feed point impedance is, say 15 + j25 ohms. In addition, students are able to design lossless impedance matching networks for the antenna that allow maximum power transfer at a given frequency. Further, given some basic properties of the generator that feeds the system, students are able to calculate how much of the generator's available power is actually delivered to the antenna, with and without the impedance matching network. This was just an example of ONE AREA of topics.

#### Content

Content |
Core content |
Complementary knowledge |
Specialist knowledge |

1. |
TRANSMISSION LINE THEORY. Transmission lines: typical use and practical cables and planar structures. Lumped element model of a infinitesimally short segment of a transmission line. Telegrapher's equations and their solutions plus their physical interpretation. Basic concepts: propagation constant, forward and reverse direction waves, characteristic impedance, phase velocity, wavelength, load reflection coefficient, reflection coefficient along the line and line input reflection coefficient, input impedance. Properties of quarter wave and half wave lines. Replacing inductors and capacitors with transmission line elements. Their effective capacitance and inductance, respectively. VSWR. Return loss and reflection (mismatch) loss. Reflection at impedance discontinuity. Voltage transmission coefficient. Transmission of voltage and power at the discontinuity. Generator properties: Thévenin equivalent and available power. Properties of lossy transmission lines. | Wave trap (bandstop filter). Transmission line filters in general. Effective dielectric constant of microstrip line and its relation to the wavelength in this media. | Multiple reflections. |

2. |
SMITH CHART (SC). Normalized impedance. Drawing and reading impedances and reflection coefficients and other related parameters on the SC. Normalized admittance. Impedance locus as a function of frequency. | How the Smith chart is made? Mathematics behind it. | |

3. |
IMPEDANCE MATCHING. The advantages of impedance matching. Simple ipedance matching techniques: lumped element matching, distributed element matching, resistive vs. reactive matching. | Bandwidth of impedance matching. Free-ware design tools. | The relationship between RF/microwave filters and impedance matching networks. |

4. |
SCATTERING (S) PARAMETERS AND GAIN CONCEPTS. Definition of S-parameters as based on the forward and reverse voltage waves on transmission lines that are connected to each port of a linear two-port network. The reasons for and advantages of using S-parameters instead of other equivalent representations such as the y-, z- and h-parameters. Applications of S-parameters. Input impedance of a two-port as a function of its S-parameters and load impedance. Determination of S-parameters of simple (and arbitrary) S-networks. Polular gain definitions: power gain, available power gain, transducer power gain; and their relation to S-parameters. | Unilateral transducer power gain (Gtu), maximum Gtu. | Unilateral figure if merit. |

#### Instructions for students on how to achieve the learning outcomes

- Try to relate all the "new stuff" to what you have previously accepted and understood. - Do not try to memorize anything. Try to understand. Understand the derivations and definitions. See the examples and solve problems. Ask for help when things do not make sense. The course instructor is more than happy to help! - Anyone may have gaps in their prerequisite knowledge. If this is the case, then go back to your previous materials, recap, talk to peers and teacher. Seek for help. Fill the gaps. - Luckily the contents of this course are based on a relatively narrow piece of theory (network theory). There is just a small number of "rules". And they all make sense! Its like chess: few rules, many games. We re-use the old rules in RF circuits. Develop them a little further. - The more you study the more you enjoy it. You start feeling stronger and stroger, as you master this new exciting realm. - Practice, practice, and practice. It may take blood, sweat and tears, but it shall also be rewarding. - If you pursue a succesful career in RF engineering, you have to be good at the basics!

#### Assessment scale:

Numerical evaluation scale (0-5)

#### Prerequisites

Course | Mandatory/Advisable | Description |

ELT-21051 Transistorit ja vahvistinpiirit | Advisable | 1 |

DEE-10100 Piiriteoria | Mandatory | 2 |

ELT-41711 Johdatus suurtaajuustekniikkaan | Advisable | 3 |

ELT-47426 Transmission Lines and Waveguides | Advisable |

1 . For foreign students: A basic course in analogue electronics.

2 . For foreign students: A basic course in network analysis.

3 . ELT-41727 Pract. RF Electron.: 1st Principles Appl

#### Correspondence of content

Course | Corresponds course | Description |

ELT-47206 Basics of RF Engineering, 5 cr | ELE-6057 Basics of RF Engineering, 5 cr |