High Pass LC Filters:

A highpass filter is a frequency inversion of a lowpass filter. A highpass filter provides good transmission at frequencies above the cut-off frequency (Fc) and suppresses transmission at lower frequencies. An abrupt change from the “pass” to “stop” condition is not feasible for real filters. Therefore, a reasonable “guardband” is provided by specifying a stopband frequency Fr which a specific level of attenuation Ar is to be mainained.

The highpass filter is often the most difficult to realize in practice, particularly to maintain a flat response to an indefinitely high frequency. Therefore, highpass filter are used in practice than any other type of filter. The highpass filter retains the same transmission and selectivity characteristics of the low pass filter. Good passband quality may be defined as low reflection, low insertion loss and flat time delay. In general, increasing selectivity results in decreasing passband quality.

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