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m-Derived Sections

Structures known as m-derived sections have good impedance characteristics and sharp cutoff frequencies. In Fig. 42 are shown T, or mid-series, sections, and as explained in the preceding section m-derived and constant-k sections are used together to make composite filters.

These m-derived sections have attenuation characteristics shown in Fig. 43. It will be noted that both m and a are shown on these curves, the relation between these two quantities being as follows

Figure 43. Variations of attenuation with frequency ratios for m-derived and constant-k sections (m = 1.0).


In this relation f is the frequency at which the attenuation of the m-derived section reaches a theoretical value of infinity (Fig. 43), and fc is the cutoff frequency of the constant-k prototype, that is, the constant-k section to which the m-derived section is related by the factor m. Referring to Fig. 42, if m = 1.0, the derived sections become the constant-k prototype.

Last Update: 2011-05-30