Page 311 - Complete Wireless Design

Filter Design

310 Chapter Six

Figure 6.58 The tuning range capacitance of the varactor circuits (a) without C and (b) with C .
s s

Over its entire tuning range, this type of filter cannot be expected to main-
tain its bandwidth, insertion loss, or return loss, but it should be quite accept-
able for most variable-filtering applications.
A top-coupled inductor type tunable filter can likewise be built as a base for
this tunable filter if upper frequency attenuation is more important than the
superior, low-frequency attenuation of a top capacitor-coupled filter.

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