Lesson 4 : Section 3 : Second Attempt

Section 3: Second Attempt at Improving the Quarter-Wave Transformer

We will attempt to frequency shift the circuit in Figure 4.3 by adjusting the line lengths. We are now using multiple quarter-wave elements, rather than playing with two quarter wave elements. We will also adjust the simulation frequency.

Circuit check list:

• • Start from the circuit in the previous section

  • Change the frequency limits to “500 MHz” to “2 GHz”

Figure 4.3: Second attempt at widening the bandwidth

Figure 4.4: Wider bandwidth using multiple quarter-wave elements

Main Point

The bandwidth is improved (by defining bandwidth as better than -20dB return loss), but the circuit is now twice as long and the nulls are no longer as deep. These are typical design trades that have to be made in engineering.

Questions:

4.2.1: Can you improve the values by hand?

4.2.2: What does the simulation look like if you run from 500MHz to 4GHz? Why might this be the case?

Copyright 2010, Gregory Kiesel