PPT《部分作业答案》

部分作业答案 Homework-1 1.

The fields of a traveling TEM wave inside the coaxial line shown left can be expressed aswhere ? is the propagation constant of the line. The conductors are assumed to have a surface resistivity Rs, and the material filling the space between the conductors is assumed to have a complex permittivity ? = ?' - j?" and a permeability μ = μ0μr. Determine the transmission line parameters (L,C,R,G). x y a ρ φ b μ,? Solutions: 2. For the parallel plate line shown left, derive the R, L, G, and C parameters. Assume w >> d. d ?r ? y z x w Solutions: For TEM mode: Homework-2 3. A lossless transmission line of electrical length l = 0.3?, is terminated with a complex load impedance as shown below. Find the reflection coefficient at the load, the SWR on the line, the reflection coefficient at the input of the line, and the input impedance to the line. ZL =

30 Cj20 ? ZL l = 0.3 ? Zin Z0=

75 ? Solutions: 4. A radio transmitter is connected to an antenna having an impedance

80 + j40 ? with a

50 ? coaxial cable. If the

50 ? transmitter can deliver

30 W when connected to a

50 ? load. How much power is delivered to the antenna? Solutions: Match at source.But mismatch at load Match at source.But mismatch at load Homework-3 (optional) 1. An attenuator can be made using a section of waveguide operating below cutoff, as shown below. If a =2.286 cm and the operating frequency is

12 GHz, determine the required length of the below cutoff section of waveguide to achieve an attenuation of

100 dB between the input and output guides. Ignore the effect of reflections at the step discontinuities. Solutions: TE10

2 Design a microstrip transmission line for a

100 ? characteristic impedance. The substrate thickness is 0.158 cm, with ?r = 2.20. What is the guide wavelength on this transmission line if the frequency is 4.0 GHz? Solutions: For W/d < 2, For W/d >2,