Transmission lines with open or short-circuited ends are frequently

Transmission lines with open or short-circuited ends are frequently used as resonantcircuits in the UHF and microwave range. We consider such networks in this section.Since the quality factor is an important parameter of these circuits, we need toinclude the finite (even though small) loss in the line. There are four basic types ofthese networks as illustrated in Figure 4.16. It can be easily found de1104 by analyzing the input impedance characteristics around theresonant wavelength, /l.r, that the circuits of Figure 4.16(a) and (d) behave like aseries R-L-C circuit. On the other hand, the other two transmission lines possess thecharacteristics of a parallel resonant circuit. A quantitative analysis of these circuitsis presented below for n as unity. For a series resonant circuit, Zin≈ R + j2 6(c) /. Hence,de1121 a half-wavelength-longtransmission line with short-circuit termination is similar to a series resonant circuit.The equivalent circuit parameters are found as follows (assuming that losses in theline are small such that the characteristic impedance.
Example 4.5: Design a de11 half-wavelength-long coaxial line resonator that is short-circuited at its ends. Its inner conductor radius is 0.455 mm and the inner radius ofthe outer conductor is l.499 mm. The conductors are made of copper. Compare theQ of an air-filled to that of a Teflon-filled resonator operating at SGHz. Thedielectric constant of de1105 Teflon is 2.08 and its loss tangent is 0.0004.From the relations for coaxial lines given in the appendix