fication. tions required in a radio receiver, and also the main ad- In a typical direct broadcast satellite receiver, the first vantages and disadvantages of three basic radio receiver r.f. amplifier section operates in the band 11.6-12.4 types, namely the TRF, superhet and double superhet GHz. The first local oscillator (fx) is operated at a fixed receivers. The first type is used in very simple receivers, frequency of 10.650 GHz. The resultant first i.f. band- the second type is used extensively in domestic receivers width range is 950 to 1750 MHz and is really the r.f. band and the last type is used for direct broadcast reception translated to a lower frequency band. This intermediate from satellites. frequency is then amplified by the first set of 1st i.f. You have now been provided with an overview of amplifiers. All the foregoing action takes place in a basic radio communication system. This page intentionally left blank Chapter 2.2 Transmission lines Ed da Silva 2.2.1 Introduction to explain and derive expressions for standing wave ratios; At this stage, I would like to prepare you for the use of to explain and derive the propagation characteristics the software program called PUFF. PUFF (Version 2.2.1) of transmission lines; is very useful for matching circuits, and the design of to provide an understanding of signal distortion, couplers, filters, line transformers, amplifiers and oscil- phase velocity and group delay; lators. Figure 2.2-1 shows what you see when you first to show how transmission lines can be used as open the PUFF program. Figure 2.2-2 shows you how the inductors; program can be used in the design of a filter. In to show how transmission lines can be used as Figure 2.2-1 you can see for yourself that to understand capacitors; and use the program, you must be familiar with to show how transmission lines can be used as Smith charts (top right hand corner) and scattering or transformers. 's-parameters' (top left hand corner), transmission lines and the methods of entering data (F3 box) into