Appendix A: K Values of Different Topologies
These tables provide a simple method of deriving the cut-off frequency for a defined filter structure and number of poles. Use of the tables is as follows.
Using Table A.2 select the topology such as a double π. Look down the dB column to find the loss in dB required. For example, a loss of 40 dB is required. The value close to 40 dB is listed as 40.98. Follow over to the left hand column where the K value = 4. Assume that the frequency requiring this loss is, for the purposes of example, 160 kHz and divide this by 4.
In this example, 160 kHz/4 = 40 kHz. Therefore, 40 kHz is the −3-dB cutoff, or pole-Q frequency, and the values of L and C can be calculated as follows:
where R
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