sociated with their equipment. A VSWR of |1 shows that this occurs when | = 0. With this condition, is the optimum condition and indicates that a perfect there is no reflection, optimum power is transferred to the match is possible and that there will be no reflections when load and there are no standing wave patterns on the line to the equipment is matched to a perfect transmission line. cause excessive insulation breakdown or electrical dis- VSWR can be calculated from the reflection coefficients by charges to surrounding conductors and there are no 'hot spots' or excessive currents on sections of the conductors. VSWR = Example 2.2.11 A manufacturer quotes a maximum VSWR of 1.07 for The return loss is a way of specifying the power reflected a resistive load when it is used to terminate a 50 O from a load and is equal to - 10 log r2. The mismatch loss Transmission lines CHAPTER 2.2 or reflection loss specifies the fraction of incident power not reaching the load and is equal to -10 log (1 - r2. The current I splits into two parts: I2 and a part going through Z2. By the current divider rule, the split is 2.2.12 Propagation constant (y) of transmission lines giving 2.2.12.1 Introduction In Section 2.2.8, we saw that signals on transmission lines 12-14-2020 suffer attenuation, phase or time delay, and often fre- quency distortion. In this section, we will show the re- Substituting the definitions for Z1 and Z2 and the formula lationships between these properties and the primary for Z derived above gives constants (R, G, L and C ) of a transmission line. 2.2.12.2 The propagation constant (y) in terms of the primary constants To find the propagation constant (r) we start with the same equivalent circuit (Figure 2.2-8) used for the der- ivation of Z. It is re-drawn in Figure 2.2-13 with the voltage and current phasors indicated. The propagation constant, as defined, relates V2 and Also I1/I2 = evol To use these two expressions for I1/I2 V1 by to find Y we must first expand e ard into a Taylor series. Since (2.2.39) wh