What type of filter passes high frequencies and attenuates low frequencies?

What type of filter passes high frequencies and attenuates low frequencies?

• A. Low-pass
• B. Crystal-controlled Oscillator
• C. Hartley Oscillator
• D. High-pass

Answer: (D)

A high-pass filter lets signals with frequencies above a certain cutoff pass through with little attenuation, while reducing the amplitude of lower-frequency signals. This happens because the filter’s reactive elements are arranged so that the impedance favors high frequencies and blocks or attenuates low ones. In practice, a capacitor in series with a load blocks DC and very low frequencies (high impedance at low frequencies) but becomes a near-short at higher frequencies, allowing those signals to pass. The description “passes high frequencies and attenuates low frequencies” matches this behavior exactly, so that is the correct type of filter. The other options aren’t filters: one is a low-pass filter but it passes low frequencies rather than high; the remaining two are oscillator circuits used to generate stable RF signals, not to filter a frequency spectrum.

A high-pass filter lets signals with frequencies above a certain cutoff pass through with little attenuation, while reducing the amplitude of lower-frequency signals. This happens because the filter’s reactive elements are arranged so that the impedance favors high frequencies and blocks or attenuates low ones. In practice, a capacitor in series with a load blocks DC and very low frequencies (high impedance at low frequencies) but becomes a near-short at higher frequencies, allowing those signals to pass.

The description “passes high frequencies and attenuates low frequencies” matches this behavior exactly, so that is the correct type of filter. The other options aren’t filters: one is a low-pass filter but it passes low frequencies rather than high; the remaining two are oscillator circuits used to generate stable RF signals, not to filter a frequency spectrum.