Topic outline

  • After studying single microwave components, such as transmission lines, impedance matching networks and analysis of passive and active microwave networks, in this topic we arrange those components to perform as complete radio systems. Especially, we concentrate on microwave communication systems. Other typical radio systems would include radars, transponders and sensors but they are handled more in other courses. A crucial part of radio systems is the antenna which is a component that in transmission converts a guided wave coming from the transmission line into a free-space spherical wave and in reception vice versa. The power density (unit W/m2) of a spherical wave obey the inverse-square law 1/r2. We assume that our students master the basic concepts and parameters of antennas, such as far-field region, radiation/directional pattern, directivity, gain, efficiency, effective aperture etc. In this topic, we will first discuss transmitter and receiver architectures, especially mixers and superheterodyne receivers. One specific concern in all radio systems is noise which deteriorates the quality of any radio link. A fundamental source of noise is thermal vibrations in any material in a temperature above 0 K. All radio systems receive noise by the antenna (external noise from nature, space and man-made devices) and generate additional noise in all passive and active components inside the system. Noise defines the minimum acceptable level of received signal when a particular radio system can still reliably detect the signal. Very important concepts  studied in this topic are: equivalent noise temperature, antenna noise temperature, noise figure, noise bandwidth, signal-to-noise ratio (SNR), and link margin. We will also learn some methods how to manage with noise.   

    This part of the course addresses the following learning outcomes:

    • The student is able to explain the operational principles of basic microwave systems, such as mixing phenomenon and superheterodyne transceivers.
    • He/she can also calculate the relevant radio system parameters, such as signal-to-noise ratio, equivalent noise temperature, noise figure and link budget analytically.

    In this topic one should command the following subjects of the course book (given according to Edition 4, the chapter numbers may be different in Editions 2 and 3):

    • 10.1 Noise in microwave circuits
    • 10.2 Noise figure
    • 13.5 Mixers (Mixer characterics only)
    • 14.1 System aspects of antennas
    • 14.2 Wireless communication

    In addition, we recommend Chapter 14 "Radio systems" of the book Räisänen - Lehto: Radio engineering for wireless communication and sensor applications. This book is fully available electronically in