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A leapfrog filter is a type of active circuit electronic filter that simulates a passive electronic filter. Other names for this type of filter are active-ladder or multiple feedback filter. The arrangement of feedback loops in the signal flow-graph of the simulated ladder filter inspired the name ''leapfrog filter''.〔 The leapfrog filter maintains the low component sensitivity of the passive ladder filter that it simulates.〔"Hence, the low sensitivity property of the doubly loaded LC ladder is preserved."〕 ==Synthesis== The definition and synthesis of leapfrog filters is described by Temes & LaPatra,〔 Chen and Wait, Huelsman & Korn. Synthesis of leapfrog filters typically includes the following steps: :1. Determine a prototype passive ladder filter that has the desired frequency response. Usually a double terminated prototype is used. :2. Write the equations relating element current to voltage across the element in a form suitable for expression as a signal-flow graph. :3. Draw the signal-flow graph. The nodes of the signal-flow graph will include both voltages and currents. The branch gains will include impedances and admittances. :4. Convert all nodes of the signal-flow graph to voltages and all impedances to dimensionless transmittances. This is accomplished by dividing all impedance elements by R, an arbitrary resistance and multiplying all admittance elements by R. This scaling does not change the frequency response. :5. Manipulate the of the signal-flow graph so that the gains feeding each summing node have the same signs. This is done as an implementation convenience. At the completion of this step, typically, all the feedback gains in the signal-flow graph will be +1 and the signs of the gain blocks in the forward path will alternate. As a result, some of the nodes, including the main output, may have a 180° phase inversion. This is usually of no consequence.〔 :6. The gain blocks are implemented with active filters and interconnected as indicated by the signal-flow graph. Often, state variable filters are used for the gain blocks. :7. The final circuit usually has more components than the prototype passive filter. This means the final circuit has degrees of freedom which can be chosen to optimize the circuit for dynamic range〔 and for practical component values. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Leapfrog filter」の詳細全文を読む スポンサード リンク
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