Filter classification: When a continuous band of frequencies around a center frequency is allowed to pass to the output while others are attenuated, what type of resonant filter is this?

Introduction:
Filters are categorized by how they treat frequency components. A band of frequencies centered around a resonant frequency is characteristic of a bandpass response, widely used in communication receivers, instrumentation, and audio crossovers to select desired signals while rejecting out-of-band noise.

Given Data / Assumptions:

• We want a range (band) of frequencies to pass
• Out-of-band frequencies are attenuated
• Realizable with RLC resonators or active filter topologies

Concept / Approach:

A bandpass filter exhibits low attenuation within its passband (between f1 and f2) and increased attenuation below f1 and above f2. It can be implemented using series-parallel RLC combinations or active op-amp stages (e.g., multiple-feedback or state-variable filters). The resonator sets the center frequency f0, and Q controls bandwidth.

Step-by-Step Solution:

Verification / Alternative check:

Sketching the ideal magnitude response confirms a pass window between f1 and f2 with roll-offs on either side, matching a bandpass filter’s behavior.

Why Other Options Are Wrong:

• low-pass filter: Passes only low frequencies below fc.
• high-pass filter: Passes only high frequencies above fc.
• band-stop filter: Rejects a band around f0 instead of passing it.
• notch-pass filter: Not a standard category; usually “notch” means a narrow band-stop.

Common Pitfalls:

• Confusing bandpass with band-stop because both involve two corner frequencies.
• Ignoring Q, which sets bandwidth and selectivity.

Final Answer:

bandpass filter