Purpose:
To use the insertion loss method to design a filter allows us to have a high degree of control over the passband and stopband amplitude and phase and to synthesize a desired response. For this project, we used an equal-ripple low-pass filter prototype to achieve a minimum insertion loss and satisfy a requirement for the sharpest cut-off frequency of 2.0GHz with > 30dB loss at 3.5GHz with 0.5dB ripple.
Microstrip filter:
For this project, we implemented a low pass filter in microstrip line by using alternating sections of very high and very low characteristic impedance lines that are called stepped impedance or hi-Z low-Z filters. We first find the equivalent circuits of a short length of transmission line by having a very large or very small impedance. The ABCD parameters of a transmission line with length l and 𝑍"are found from figure 1 shown below:
Design Procedure:
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