lot lines, twin lines and finally connected across the loads presented at ports 3 and 4. coupled microstrip lines. For centre frequency operation, these stubs appear as In Section 2.2.4, you were shown how the character- open circuits. Similarly, the transmission line lengths istic impedance of the coaxial, twin line and microstrip between ports 3 and 1, and ports 4 and 1, transform the line can be calculated from its physical parameters. The 50 S load impedances at ports 3 and 4 to 100 S (2Zo) at information demonstrated what properties you should port 1. When combined at port 1, these transformed look for if the characteristic impedance of a line does not impedances produce the 50 S impedance at port 1 (see behave as expected. Figures 2.2-20(a) and (b)). Sections 2.2.5 and 2.2.6 demonstrated how the A similar analysis can be applied at each port, showing characteristic impedance can be calculated and measured that the hybrid exhibits a matched impedance of 50 S or from primary constants of the line. Section 2.2.7 men- Z at all nodes. It should be noted that when port 1 is tions some of the more common impedances associated driven, the outputs at ports 3 and 4 are equal and in with commercial transmission lines but it also brought to phase, while ideally there is no signal at port 2. However, your attention that there are many types of lines with the when port 2 is driven, the output signals appearing at same impedance. ports 3 and 4 are equal but exactly out of phase. Also Section 2.2.8 explained how propagation delay, at- there is no signal at port 1. Hence ports 1 and 2 are tenuation and frequency dispersion affect waveforms as isolated. This is very useful especially in signal mixing they travel along transmission lines. This was followed by circuits because it enables two slightly different fre- more discussions on the effects of these properties in quencies, for example f1 at port 1 and f2 at port 2, to be Section 2.2.9. applied to a balanced mixer whose diodes may be In Section 2.2.10, we introduced the c