image impedance&m-derived filter

I feel confused about some concept: image impedance, m-derived filter

Could someone give me some guide?

The image impedance concept is that the input impedance of the filter is equal to thee load impedance when the sections are cascaded. The m-derived aspect is putting a zero in the stop band. This makes the input impedance more constant over the pass band. there is also a double m with two zeros but it is rarely used.