Problem 1

For certain wireless application (IEEE 802.11a), assume a company uses a special microstrip patch antenna with an input impedance of 150Ω. Design a circuit to match the 50Ω transmission line impedance to the antenna at f=5.8GHz, using a 150Ω resistor to simulate the antenna. In your ADS circuit layout, include a square metal pad for the via hole contact, and a space where the processing engineers will solder a surface mount resistor.

Problem 2 (30pts): A double stub tuner has the disadvantage that it cannot match all load impedances. For this reason, RF/microwave designers use a triple stub tuner (See Figure 2). Using smith chart, design a triple stub tuner with d=λ/8 . match ZL=150+j150Ω to a 50Ω transmission line. Then, using ADS software optimize this design for a frequency of 20GHz. You can use either short or open stubs. In addition, provide a design with radial stubs. For both cases (straight and radial stubs) optimize the design for maximum compactness (i.e. smallest size) and minimum reflection.

Design Considerations: Assume that all circuits will be fabricated using FR-4 copper clad PC board: εr=4.7, tanδ=0.02, h=711.2 µm and t=25.4 µm. When generating circuit layouts, do not exceed the maximum circuit board side of 60mm. Check to makes sure that ADS gives you practical circuit dimensions. For example, avoid using microstrip lines with w/h>10, and for resonant stubs keep w/l<0.4.

Solution(design and calculations)