Filter Design Basics

1. Center Frequency, Fo
2. Stopband Cutoff Frequency, Fs
3. Selectivity Factor, Q
4. Shape Factor, SF
5. Insertion Loss
6. VSWR and Return Loss
7. Phase Linearity and Group Delay
8. Filter Impedance

 Types of Filters

The two classical approaches in the design of filters are

• Image-parameter
• Network method

Image-parameter method 

        - treats the filter as a transmission line and uses lumped components.

• Constant k filter
• m-derived filter - is a modification of the constant k filter in order to vary the impedance (constant) and the shape factor (steeper).

Network method

     - based on frequency response curve or transfer function.

Other common filter design methods are

• Top-coupled resonator
• Varactor-tuned BPF (Band Pass Filter)