Which characteristic distinguishes a Butterworth filter?

Get ready for the FCC General Radiotelephone Operator License (GROL) exam. Study with flashcards and multiple choice questions, each with hints and detailed explanations. Prepare effectively for your licensing test!

Multiple Choice

Which characteristic distinguishes a Butterworth filter?

Butterworth filters are designed to have a magnitude response in the passband that is as flat as possible, with no ripple. This maximally flat passband means the gain stays essentially constant up to the cutoff frequency, then falls smoothly and monotonically into the stopband. The level of flatness is what distinguishes this type of filter from others that intentionally introduce ripple in the passband or stopband to achieve a steeper transition. In practice, realizing a Butterworth response requires a ladder network that uses both inductors and capacitors; it is not built from capacitors alone or inductors alone. The idea of a constant product of the series- and shunt-element impedances across all frequencies doesn’t describe how a Butterworth filter achieves its flat passband—the impedances vary with frequency to produce the desired response. So the defining trait is the maximally flat response over the passband.

Butterworth filters are designed to have a magnitude response in the passband that is as flat as possible, with no ripple. This maximally flat passband means the gain stays essentially constant up to the cutoff frequency, then falls smoothly and monotonically into the stopband. The level of flatness is what distinguishes this type of filter from others that intentionally introduce ripple in the passband or stopband to achieve a steeper transition.

In practice, realizing a Butterworth response requires a ladder network that uses both inductors and capacitors; it is not built from capacitors alone or inductors alone. The idea of a constant product of the series- and shunt-element impedances across all frequencies doesn’t describe how a Butterworth filter achieves its flat passband—the impedances vary with frequency to produce the desired response.

So the defining trait is the maximally flat response over the passband.

More practice questions